Revision as of 16:08, 19 October 2007

Misplaced Pages:Reference desk/headercfg

October 13

Robotic Arms

Has anyone come up with a way to make robotic tentacles? That is, long, everywhere-articluated arms like an octopus or snake? Black Carrot 01:56, 13 October 2007 (UTC)

Yes. Did you even try to Google for robotic tentacle? -- kainaw™ 02:47, 13 October 2007 (UTC)

I knew I'd forgotten something. I did check Misplaced Pages itself for it (and ran into some serious stubs). Thanks. 76.185.123.122 03:04, 13 October 2007 (UTC)

Make that an image-search and you get some intriguing ideas of what one could do with such tentacles. DirkvdM 10:11, 13 October 2007 (UTC)

On Saturday (in fact, on the very day this question was posed - how curious!) I was at a convention where they had a "satellite link-up" with Stan Lee, and one of the people lined up to ask him a question actually offered to make him a set of Dr Octopus arms. Confusing Manifestation 22:35, 14 October 2007 (UTC)

Runaway Global Warming

What evidence is there for and against runaway global warming? Don't talk about related, but different, stuff such as the existence of global warming and the effects of humanity on it. Please state weather the evidence is about existentially dangerous or merely catastrophic runaway global warming, or both. Site sources if possible. — Daniel 03:12, 13 October 2007 (UTC)

We shall have proof of Runaway Global Warming after the fact and never before. 211.28.129.8 09:47, 13 October 2007 (UTC)

He asked for evidence, not proof. Alas, this sort of thing was not included in the IPCC report because of the low probability (or even inability to calculate a probability). Which is stupid, of course, because risk is a function of probability and seriousness. You're asking about both (good on you). I don't know about the probability, but I can give some considerations concerning the existential risk (the chances that mankind will become extinct, I understand). Such events have taken place many times in Earth's history, and the consequences have indeed been catastrophic. Even to the point that almost all life on Earth died. But with rapid change, it's the least adaptable species that die out. It just happens that mankind's strongest point is adaptability. I think no other (land) species is as widely spread across the globe, so we've already got experience with all sorts of climates. And if we encounter a climate that we're not familiar with, we'll learn. We do that like no other species. Basically, species adapt through evolution, so they need many generations. We can do the same thing within one generation. So mankind will almost certainly not die out. Maybe some 90% will die, but even then there will be 500 million left (more than is normal for a species our size, which is the cause of the problem, but that's a different issue, which you didn't want to hear about :) ). And it won't be any fun for the survivors, but their will to survive will ensure mankind will not die out. DirkvdM 10:31, 13 October 2007 (UTC)

The effects that might cause "runaway" global warming are the ones that have an element of positive feedback to them, there are three that I can immediately think of:

1. Increasing global temperatures cause the ice caps and glaciers to melt. Shrinking polar/glacial ice reduces the area of the earth's surface that is white and increases the area that is dark. This in turn reduces the earth's albedo - which causes more absorption of sunlight - and more global warming - and more ice melting. This effect could potentially runaway until there is no more surface ice year-round.
2. In a similar vein...as the climate warms up, the oceans get warmer. As water warms up, it expands (except at temperatures very close to freezing) - and that causes a rise in sea levels. This inundates some lighter coloured land areas with darker coloured sea water - which also causes the earths albedo to drop - increasing the absorption of sunlight and adding to global temperatures - causing the sea levels to rise still further.
3. In deep parts of the ocean, there are large deposits of frozen methane. If the ocean temperatures rise too high, these will start to melt. The resulting methane gas will bubble to the surface. Unfortunately, methane is an even more virulent greenhouse gas than CO₂ - so releasing more methane traps more sunlight which raises temperatures and in turn releases more methane.

You can argue about other effects such as the disruption of certain ocean currents - but these are more about affecting the weather in certain regions than they are about global warming - they aren't any less devastating - but they aren't likely to make global temperatures change much UNLESS they cause warm water to be carried to places where more ice or methane can melt.

The nasty thing about effects with positive feedback is that even if mankind mended it's ways overnight, if we've inadvertently triggered one of these feedback loops, we may not be able to prevent ultimate catastrophy (although we ought to be able to slow it down). The tricky part is to know at what global temperature each effect will kick in. The fact that the northern polar cap and the glaciers are all melting MUCH faster than we had formerly predicted means that we've almost certainly triggered that problem in the Northern hemisphere. Fortunately, the majority of the ice is at the South pole which doesn't seem to be in a runaway situation yet.

SteveBaker 11:32, 13 October 2007 (UTC)

Follow up question: I never heard about methane clathrate back in the dark ages when I was in school. Is it technically correct to talk in terms of natural sources of "frozen methane" on Earth? Methane says the melting point is -296.5 °F. --JWSchmidt 15:27, 13 October 2007 (UTC)

The stuff was only discovered 'in the wild' fairly recently. Technically, it's not "frozen methane" it's methane dissolved in water ice. However, when the water melts and turns back into liquid water it releases the methane as bubbles - so the effect is the same. This is fairly exotic stuff and it generally only forms at great depths - which explains why we only recently discovered these deposits. Our article suggests that there is a heck of a lot of this stuff out there - and it could even (theoretically) be mined as a source of fossil fuels (except that we're trying to use LESS fossil fuels - not more!) —Preceding unsigned comment added by SteveBaker (talk • contribs) 17:26, 13 October 2007 (UTC)

Steve, the southern polar cap is also shrinking in size - that is, at the sides, where the ice is on water, so there is the same feedback effect. This is in a way compensated by the fact that the ice gets thicker in the central parts, due to heavier snowfall, so the total amount of ice remains more or less the same. But that's not what counts here. In this case, surface size matters.

Concerning the slowing down of the first two effects (both albedo related), I suggested in a previous thread that we could scatter some reflective stuff like polystyrene on the oceans to replace the ice. That would reflect the light. An alternative would be to capture it with solar panels. These would not only prevent the seas from warming up, but would also provide us with energy, for which we would then not need to burn fossil fuels, so that would give a double positive effect. For the first effect, the panels would not need to be very efficient, so we can use the technology we have now. This would give a big boost to the solar panel industry, which would then have more of the money they lack so much now to develop more efficient and cheap solar panels. A very postiive feedback indeed, I dare say. :)

The third cause, the sudden release of methane, could be truly catastrophic. Methane is a greenhouse gas that is 62 times stronger than CO₂, but it has a shorter lifetime. I don't know what the most important of these two factors would be, but it is theorised to be have been a factor in the Permian-Triassic extinction event, which killed off almost all life on Earth. If this release were to take place in our lifetime, then it would not be mainly a problem for later generations. A sudden rise in temperature by several degrees (global average!) would likely cause massive crop failures the world over. Which of course would lead to war the world over. Not WWIII, because alliances will likely break down, but smaller continuous wars all over the world (a worldwide Darfur, so to say), which would probably be a whole lot worse. DirkvdM 08:14, 14 October 2007 (UTC)

The short lifetime of methane in the upper atmosphere is only partially comforting. When it breaks down you get CO2 and water vapour. Water vapour (at those altitudes) is another gas that's a stronger greenhouse gas than CO2. The amount of these methane clathrate deposits is estimated to be equal to the total amounts of underground natural gas deposits - so even after the stuff decomposes, it would be like putting 500 years worth of CO2 from fossil fuel usage into the upper atmosphere. SteveBaker 15:35, 14 October 2007 (UTC)

There are many positive and negative feedback loops. Theoretically, you could use them to construct an accurate model, but I very much doubt we know enough to make a very complete one, and thus any we make will probably only be accurate for a short time after it is made, if at all. By studying the Earth's history, it may be possible to find evidence for catastrophic runaway global warming. Specifically, how often have circumstances similar to what we are currently in led to it. Has anyone done so? Whether we can use our own planet as evidence against existentially risky runaway global warming is closely related to the Sleeping Beauty problem. Personally, I think we can. If so, a similar study to the one I mentioned for catastrophic runaway global warming can be done for it. Again, has anyone done so? By the way, DirkvdM, solar panels absorb much of the light that hits them as heat. This could be helped by making a coating that reflects light too low of a wavelength for the panels to use. AFAIK the painting the roof of houses in warm climates white saves more energy than solar panels make, and reflects more light into the atmosphere. — Daniel 21:49, 14 October 2007 (UTC)

Interesting idea. But how much ground do human settlements cover? Looking at the Netherlands on Google maps I'd say less than 10%. And the Netherlands is one of the most densely populated countries on Earth. If you zoom in about 2/3 of the way at a random location in the US, you need to search around quite a bit until you find any buildings. And even in densely populated India the buildings cover just a few percent of the ground. The total land surface on Earth is about 150 million km. So let's assume we're talking about 1 million km, where maybe 30% extra is reflected. Polar ice cap says "The area covered by sea ice ranges between 9 and 12 million km²". And the albedo difference between ice and water is more like 90%. So painting all (!) houses all over the planet white (yes, that includes your house plus all other buildings in your city) will have a compensating effect of just 1/30 of the melting of all sea ice, which is likely to happen much sooner than this paint job, given the slowness of politics (voters, really). Of course two more factors are that polar caps receive less sunlight and that roof tops cover less than half of a city's surface, which probably balance out against each other.

But any bit helps. There is no single all-encompassing solution, so we have to implement anything that might help. And this seems a very simple and cheap thing to do. So I'm all for it.

In what other ways can we change the albedo? Asphalt has an albedo of almost zero, and streets cover about as much ground as buildings in cities, so those could also be painted white. In cities they're not always in the sun, but in the tropics, the ones that run east-west are. But there are also the streets outside the cities. How much ground do they cover (literally)?

Btw, at first I thought you meant that if you cool a building with paint you need less airco. That'd largely be the southern US then because in most tropical countries most people can't afford airco, although shopping centres in most tropical countries do often have it. I think it would make more of a difference if they didn't turn it up so ridiculously high. What's the radiative forcing effect of cooling a 100,000 m building down 5C, compared to the extra energy reflected by the same building if it got a fresh paint job? DirkvdM 07:59, 15 October 2007 (UTC)

That wasn't supposed to be a way to stop global warming. I'm more saying solar panels wouldn't do a very good job. 67.182.172.17 23:28, 16 October 2007 (UTC)

Where? Did you forget to log in? DirkvdM 06:09, 18 October 2007 (UTC)

Human birth defects???

Any and all text related to the subject of human birth defects. 1 Abnormalities related to but not limited to the following, herniated diaphram, herniated stomach. 2 Formentioned organ and conective tissue missplaced within torso cavity resulting in underdeveloped lung or heart tissue. All other information on human birth defects welcome. —Preceding unsigned comment added by Terrynisely (talk • contribs) 04:15, 13 October 2007 (UTC)

See situs inversus, teratology, diaphragmatic hernia, hypoplasia, hypoplastic left heart syndrome, congenital disorder, dextrocardia, congenital heart disease, congenital heart defect, and articles that they link to, for a start. - Nunh-huh 07:48, 13 October 2007 (UTC)

Category:Congenital heart disease has a bunch of them. Category:Congenital disorders has a lot more, and there is also List of congenital disorders. SteveBaker 11:14, 13 October 2007 (UTC)

Other things then what's been mentioned, e.g. Polydactyly. There are so many possibilities I'm not sure if you'd really want to study them all. It depends also on your definition of a Congenital disorder. For example I noticed Huntington's disease in one of the lists. While I'm not disagreeing, as far as I'm aware it's very rare or never that symptoms are present at birth even if the disorder is. Therefore should we also include any inherited genetic disorder (which would be present at birth)? But of course even this isn't a clear cut issue since there is no boundary between 'normal' and 'disorder'. Nil Einne 11:53, 13 October 2007 (UTC)

fixed point calculation by utilisation of non stressed axial expansion joints

i would like to know how the force is calculated on the anchor points in a vertical chill water risers used in high rise buildings. all the steps in detail. these risers have expansion joints to take on the expansion and how to calculate on to where these joints can be installed on the pipe. how much should the distance be between the expansion joint and the fixed anchow point at the top and bottom fixed points. —Preceding unsigned comment added by Mohdbilal123 (talk • contribs) 13:17, 13 October 2007 (UTC)

Well, from first principles, I guess you need to consider the hottest and coldest temperatures of the water in the pipe - look up the thermal expansion coefficient of whatever the pipe is made of - and from that calculate the total amount of expansion that has to be allowed for - then (adding a safety factor) divide that by the number of pipe segments you have. However, I would assume there were standards set for such things - and if such standards exist, those are what you should follow. SteveBaker 13:26, 13 October 2007 (UTC)

I'd guess that since there are expansion joints - you would want no force on the anchor points (common sense) - therefor you want to know how much expansion the expansion joints need - to get this you need the length between anchors, the thermal expansitivity of the pipe, and the expected temperature range. For safety include extra expansion in the expansion joints for extreme conditions etc.

You can work this out in reverse as well - for a expansion joint that can expand x - calculate how much pipe it can allow to expand under given temperature ranges - so for a total pipe length you can work out how many expansion joints you need.. (Was this relevent?)83.100.254.51 13:33, 13 October 2007 (UTC)

gdfghdrg

tr RTAWT —Preceding unsigned comment added by Mohdbilal123 (talk • contribs) 13:37, 13 October 2007 (UTC)

Pardon me? —Keenan Pepper 13:58, 13 October 2007 (UTC)

You are hereby pardoned. DirkvdM 10:06, 14 October 2007 (UTC)

AYYLU. --JWSchmidt 14:50, 13 October 2007 (UTC)

¡Atención! ¡Atención!. Markovian Parallax Denigrate. Resurrect dead on Planet Jupiter. 12 Galaxies Guiltied to Omegalogical Exortations. GeeJo ⁄_(c) • 00:25, 14 October 2007 (UTC)

Google search on gdfghdrg and tr RTAWT neither of which seem promising. I suggest trying the wikipedia sandbox instead. 71.226.56.79 22:18, 14 October 2007 (UTC)

Oh great, another genius. And how many of those do we have here? *rolls eyes* But anyway, have you tried combining the two terms into one google search? NASCAR Fan24 22:21, 14 October 2007 (UTC)

The only non-nonsensical google hit I get is thus: (Saporin and ricin A chain follow different intracellular routes to enter the cytosol of intoxicated cells). Though I think the more likely answer is that Mohdbilal123 was using a public computer to ask the above question and forgot to log out, leaving the door open for some random person to come along and type in gibberish. --VectorPotential 12:45, 15 October 2007 (UTC)

Raising metabolism

In theory, how high could the metabolic rate in humans be raised as a percentage of the average human metabolic rate?

My interest in this comes from an article I read about the powers of characters in the TV show Heroes. One character has rapid spontaneous regeneration ability and the article I read said that she would need an incrediably high metabolism to achive this. I'm aware that the ability to heal this quickly would be physically impossible (it would require constant eating and cardiovascular exercise, leading to indigestion) but I'm curious about how fast human metabolism could be raised.

-- _{Escape Artist Swyer Articles touched by my noodly appendage} 14:41, 13 October 2007 (UTC)

One problem with any significant amount of increase would be that metabolism produces heat. Increasing heat production would push up your body temperature - and taken to superhero extremes that would not be a healthy thing. This probably explains the skimpy costumes that those guys wear! :-) (Although, not in Heroes).

Oxygen is a rate limiting factor for human energy throughput. There are some numbers at VO2 max suggesting that it is rare for the best athletes to be able to sustain more than 3 times the oxygen uptake of the average person. I guess "in theory" might include genetically engineered humans. According to this dogs can do 3 times better than the best humans, so it might be possible to modify humans genetically and increase the maximum aerobic capacity. --JWSchmidt 15:14, 13 October 2007 (UTC)

And to back up my earlier point, dogs have a significantly higher body temperature than humans. There is also (across all mammals) a strong correlation between lifespan and body temperature - so increasing your metabolic rate will also (on the average) result in you dying sooner. SteveBaker 17:15, 13 October 2007 (UTC)

I've been thinking about healing and cell division and even noticed that Misplaced Pages has "healing factor". I've never seen Heroes, but I've had a chance to consult with my kids and they claim that on that show a character was shown regenerating a toe in a few seconds. For a relatively small amount of tissue repair/regeneration such as this, I do not think that "metabolic rate" is really the issue. There are limits on how quickly individual cells can reproduce and organize themselves. To get around these physical limitations, I think rapid regeneration would require special stores of cells and some kind of special cell migration process. After injury, pre-formed bone, muscle and other cell types would have to be quickly released from storage sites and transported (in the blood?) to the wound where they would have to efficiently assemble into tissues. There is no known mechanism for such assembly of differentiated cells into complex organs and limbs. As described at regeneration, animals that can regenerate structures form stem cell masses that must slowly differentiate and organize into new tissues using the kinds of cell-cell interactions used during normal embryogenesis. So I think you would have to say that some kind of shapeshifting is required, maybe involving some kind of nanorobotics (functional and structural components that are not conventional cells). I'm not an engineer, but it seems to me that if you can imagine some type of sophisticated self-organizing nanobots that can quickly shape themselves into a toe, then I do not see why we would have to assume that such self-assembly would require large amounts of energy....someone with the ability to design such nanobots would probably be able to make their assembly efficient. If you get into needing to rapidly produce (from conventional organic molecular building blocks?) a large mass of such nanobots in a short period of time using conventional metabolic energy sources, then in addition to energy concerns for synthesizing the nanobots, you might have a problem related to limitations on the rate at which storage molecules like glycogen and protein can be broken down and their molecular components released from cells. I end up thinking that it is unrealistic to imagine that "metabolic rate" is the only limiting factor. --JWSchmidt 18:39, 13 October 2007 (UTC)

I can't quantify how much metabolic rates could be increased as I'm not an expert in biochemistry. What I do know from my limited knowledge in biochemistry is that many (if not most) enzymes that we have operate close to the maximum rate that nature allows. A way to increase the rate in metabolism is to have all metabolic enzymes run at their most optimal rate. Another way to raise metabolic rates is to have more efficient pathways. Metabolic pathways are very complex; for a particular biological function, some organisms have more efficient pathways in completing that function. (For example, instead of requiring two steps and enzymes to synthesize a product, only one is needed. There are many sorts of evidence of this in nature. Evolutionary mechanisms have forced certain species to develop better pathways.) And as the questioner mentioned, quick regeneration is impossible without constant eating. With the two things I mentioned about increasing metabolic rates, none of them would matter if there is no increased intake of molecules that contain consumable energy.128.163.113.152 17:50, 16 October 2007 (UTC)

What is the chemical composition of a typical computer?

Hey. I understand that my question might look pretty weird, but what I want to know is what elements a typical computer would be made out of- specifically, would it contain a majority of organic compounds, or inorganic ones? Any help would be appreciated. Thanks in advance! 68.54.42.126

First, make sure you know the difference between element and compound. Here is a guess at the most common elements a computer is made of: carbon, oxygen, hydrogen, chlorine, aluminum, iron, copper, silicon.

Plenty of other trace ones after these.

Because of the housing, circuit board, and wire insulation, I bet organic compounds would be most prevalent Delmlsfan 17:21, 13 October 2007 (UTC)

Iron (steel) for the case and transformer, a lesser but similar amount of copper for the wires.

There's some silicon in the chips but also in the glass fibre in the printed circuit board.

Very Small amounts of other elements in the chips eg germanium etc (tiny).

Relatively small amounts of other metals - gold/silver/tantalum etc in wires/contacts/capacitors

The remainder will be 'plastic' - almost certainly hydrocarbons eg polystyrene, ABS, polypropylene etc - a quite large perentage of the mass of the plastic will be filler - this can be chalk, gypsum, silica, feldspar, titania (any inert mineral) or even carbon fibres or other exotic materials.83.100.254.51 17:20, 13 October 2007 (UTC)

If PVC is used in plastic shielding of cables this means that chlorine will also be present, anything made of teflon (not unknown in cableing and insulation) would introduce fluorine

And the heat sinks are likely to be made of aluminium

Any paint will be carbon based - though the pigment might contain other elements

By mass I'd expect iron to be the major component - next copper, then carbon as plastics, then silicon and oxygen (not sure which is most) plus a similar amount of aluminium if you have large heat sinks (may also be present in filler), followed by hydrogen (in the plastic) and then all the trace elements (gold, boron etc)83.100.254.51 17:27, 13 October 2007 (UTC)

According to a number of computer recycling websites, there are about 5 pounds of heavy metals like cadmium, arsenic, and mercury in the computer motherboard and CRT monitor. --24.147.86.187 17:28, 13 October 2007 (UTC)

That sounds wrong - were would these elements be found?83.100.254.51 18:23, 13 October 2007 (UTC)

If you're including the CRT then you have a lot of glass (Silicon, Oxygen) and Phosphorous in the face-plate - plus a bunch more copper, etc from the circuitry and plastic in the case. I'm not qualified to guess what an LCD panel includes - certainly more plastics, copper and glass - but what is the liquid crystal made from? A plasma display presumably has some of the novel gasses in it...dunno, my knowledge just ran out! SteveBaker 17:37, 13 October 2007 (UTC)

The plasma gases are xenon or krypton according to plasma display

The phosphors are not phosphorus - they are rare earth oxides typically, or Zinc sulphide or... see the article for more details

Liquid crystals are organic compounds - C,O,H are certainties here.83.100.254.51 18:21, 13 October 2007 (UTC)

The greatest use of Indium is in thin films including flat-panel displays. Cheers Geologyguy 18:16, 13 October 2007 (UTC)

Don't forget laptop batteries - typically add lithium and cobalt to the elements83.100.254.51 18:22, 13 October 2007 (UTC)

Electronic waste might be useful.

Forgot to mention all that lead and tin in the solder - quite a lot of this...83.100.254.51 18:28, 13 October 2007 (UTC)

Plus a disk drive or cd rom (as well as hard disk) will most likely have a cast metal base - these are made out of aluminium/zinc/(possibly magnesium) alloys.83.100.254.51 18:43, 13 October 2007 (UTC)

Wow, there are quite a few responses! Thanks for the help! 68.54.42.126 —Preceding signed but undated comment was added at 20:07, 13 October 2007 (UTC)

All those elements just to download porn. Delmlsfan 21:59, 13 October 2007 (UTC)

For older (pre 2005) computers, there is a fair amount of lead in the solder. Newer computers comply with ROHS and do not have lead in the solder. Quite a bit of tin either way. For CRTs, there is a fair amount of lead in the glass. -Arch dude 00:27, 14 October 2007 (UTC)

That's an EU law, not a worldwide one, however. Rmhermen 13:44, 15 October 2007 (UTC)

True, but since the computer market is a worldwide one, it's usually cheaper to make computer parts RoHS-compliant than it is to make different products for the EU and the rest of the world. --Carnildo 21:39, 15 October 2007 (UTC)

infrared

What is the reason that (absorption of?) wavelengths surrounding 3μm causes the temperature of atoms and molecules to rise? In particular, can you tell me if it is due to a correspondence between wavelength and the dimensions of an atom or molecule? Clem 16:50, 13 October 2007 (UTC)

Absorption of light of any wavelength causes the temperature to rise - it's just energy. Perhaps your question should be "Why do materials absorb more light in the 10,000nm band than elsewhere in the electromagnetic spectrum?" (I'm not sure that's true either - but it's a better question!) SteveBaker 17:03, 13 October 2007 (UTC)

Infrared spectroscopy may be of some use here, though it is of some middling quality. Essentially, molecules (not atoms!) have specific vibrational and rotational frequencies, some of which just happen to match the IR band. These "resonant frequencies" explain why the molecules absorb EM radiation of those particular wavelengths. As the energy of the molecules is increased by doing this, the average energy of the system (temperature) increases. Note though that there are many vibrational frequencies outside of the IR range (which is why UV-vis spectroscopy works). GeeJo ⁄_(c) • 17:11, 13 October 2007 (UTC)

Is there a graph of resonant frequencies showing various molecules which might reveal how they are grouped or more closely distributed around 10,000nm? And for that matter a graph showing temperature rise on a black body surface for different wavelengths of radiation at the same intensity? Clem 21:25, 13 October 2007 (UTC)

For the first question, I'm not sure anyone's really looked that deeply into absorptions around that region for the simple reason that everything in the lab is going to be emitting radiation in that band, making it impossible to get any decent resolution. For the second question, a black body absorbs all radiation by definition, so it'd be a fairly dull graph, with E=hv determining the change in energy contribution from the various wavelengths. GeeJo ⁄_(c) • 22:41, 13 October 2007 (UTC)

In general any absorbsion of any light wavelength will cause an increase in temperature - the more light - the more the temp rises - 10,000nm isn't particularily special here. —Preceding unsigned comment added by 83.100.254.51 (talk) 17:13, 13 October 2007 (UTC)

That contradicts visible light having a higher energy level than IR yet not producing the same rise in temperature as IR of the same intensity. Clem 21:28, 13 October 2007 (UTC)

You seem to be under the misapprehension that IR wavelengths are somehow "more heating" than those of visible light. If you pointed lasers with beams in the visible and IR bands at a black body, I guarantee you that the visible will heat it more quickly. GeeJo ⁄_(c) • 22:55, 13 October 2007 (UTC)

ee assay

Does anyone know what an ee assay is? It is simply any assay used to determine the mixture of enantiomers, or is it something more subtle or completely different?

Thanks,

Aaadddaaammm 22:19, 13 October 2007 (UTC)

Enantiomeric excess mentions some specific methods for assay of "ee". --JWSchmidt 16:00, 14 October 2007 (UTC)

Thank you very much! I don't know how I missed that when I searched. Cheers! Aaadddaaammm 22:22, 14 October 2007 (UTC)

becoming an alcoholic without alcohol.

How might someone become an alcoholic, if you don't include alcohol or anything that breaks down or combines etc into alcohol. Can you substitute alcohol with something else (non-alcohol) and cause someone to become alcoholic over extended, high-volume ingestion? (This is just one example, another source of alcoholism, such as a pill that affects neural structure or something jsut taken once, would also fit my request). Thank you! —Preceding unsigned comment added by 81.182.100.153 (talk) 22:21, 13 October 2007 (UTC)

Some research on alcoholism has suggested that there could be specific neurotransmitters involved in alcohol addiction. For example, endorphin activity might be enhanced by ethanol, allowing a receptor antagonist such as naltrexone to possibly inhibit addiction to alcohol (See). Hypothetically, there might be some drug that could be chronically administered which would cause a person to become addicted to that drug and would at the same time predispose the person to alcohol addiction. If you are creating a plot element for a science fiction story, it might be more trendy to invent a polynucleotide analog or a viral vector that would genetically predispose someone to alcoholism. See also: Wikipediholic. --JWSchmidt 15:40, 14 October 2007 (UTC)

Some people lack the genes to make enzymes needed to break down alcohol. This makes them predisposed to NOT be alcoholics, I suppose. This is documented in Alcohol flush reaction. Personally, I don't believe that alcoholism is a strictly phisiological condition, though. I'm not sure if what you're asking is possible. --Mdwyer 15:54, 14 October 2007 (UTC)

You'd have to convince them that whatever they're drinking is alcoholic. If they know it isn't, they'll have no way of knowing alcohol will satisfy their craving, and thus they couldn't be considered alcoholic. — Daniel 21:53, 14 October 2007 (UTC)

Resonant frequencies

Where might one find a list of resonant frequencies for various molecules? Clem 22:35, 13 October 2007 (UTC)

Any good spectroscopy textbook will carry table upon table of the things. The only one I can find on Misplaced Pages itself is for a few organic bonds in the near-IR range at Infrared spectroscopy correlation table. GeeJo ⁄_(c) • 23:04, 13 October 2007 (UTC)

There must also then be a graph showing the distribution of molecules across these and other wavelengths such as Different regions in the infrared. Do you know of any others aside from Summary of absorptions of bonds in organic molecules? Clem 23:14, 13 October 2007 (UTC)

There are more detailed versions of the graph you mention out there - were you thinking of organic molecules specifically or anything? - a search for "IR absorbtion bands table" or "ir functional group" turns up thousands (try image search)

For example here is one for nitrogen functional groups http://www.vidrine.com/vcorr3.htm

And here is a paper containing a spectra for silicates (scroll down) http://www.aanda.org/index.php?option=article&access=standard&Itemid=129&url=/articles/aa/full/2002/31/aah3549/aah3549.right.html

There probably are millions - if you need more help please ask.87.102.19.106 04:39, 14 October 2007 (UTC)

Yes, this seems to be what I'm looking for, one question though, are absorption frequency and resonant frequency the same or do they refer to different phenomenon, and if not, are there graphs for resonant frequency? Clem 14:01, 14 October 2007 (UTC)

Yes - in terms of IR the absorbtions cause physical vibrations of the molecules at the resonance frequency of the bond - so the absorbance frequency is the same as the natural resonance frequency of a bond. they have the same origin/meaning/frequency87.102.82.26 17:54, 14 October 2007 (UTC)

OK, then things now add up. A microwave oven works because it operates at whatever the absorbency/resonance frequency of food is so the food heats up. What I'm locking for then is an online graph that extends all the way from zero to the highest frequency known that shows the frequencies at which something (everything from atoms to kettle drum) resonates. Clem 18:30, 14 October 2007 (UTC)

Yes, that's right - though typically the microwave oven is 'tuned' to water's frequency - or OH (hydroxyl) groups - microwave ovens don't heat up fat as well as water for this reason (though they melt butter well because butter has water in)

No, 2.5GHz microwave ovens aren't tuned to water resonance which is up above 10GHz. Also, while water gas (vapor) does have sharp resonance frequencies, liquid water does not. If a microwave oven was actually tuned to a sharp frequency for water, then the food would be opaque to the radiation, and only a tiny outer layer of the food would be heated. Because the oven's operating frequency is far from any absorption peak, the RF energy passes deep into the food before being absorbed. --128.95.172.173 01:24, 16 October 2007 (UTC)

second question - I've never seen but would like to see too such a graph.. Can't find one.87.102.82.26 20:44, 14 October 2007 (UTC)

reduction of multiple state logical equations

If “… we're overrun by really efficient algorithms. “ (SteveBaker 13:40, 8 October 2007 (UTC)) to reduce logical equations to minimum form, which of these algorithms is capable of reducing multiple state equations to minimum form? Clem 22:53, 13 October 2007 (UTC)

October 14

Maximum limit of kinetic energy?

Hey guys! So i was daydreaming today and i thought if absolute zero exists is there an upper limit to the amount of energy a particle can have? Thank you very much for your time!

24.88.103.234 02:42, 14 October 2007 (UTC)Timothy

A greatly simplified way to think of it is that absolute zero is all mass and no energy. The speed of light is all energy and no mass. So, those are your two opposites. From there, you can get into the particulars that break down the simplicity into a muddy mess of conflicting areas of science. -- kainaw™ 02:51, 14 October 2007 (UTC)

That's a level of simplification even I would never go to...In short, no. Someguy1221 04:13, 14 October 2007 (UTC)

But it is true that the speed of light sets an upper limit to kinetic energy, right? DirkvdM 10:11, 14 October 2007 (UTC)

Short answer, no. And that's exactly the reason for the odd mass increase of the accelerated particle when it approaches the speed of light. You 'add' energy to the particle, since it can't store the extra energy as speed, it stores it as extra mass. --Taraborn 14:21, 14 October 2007 (UTC)

Not really. Kinetic energy = 1/2mv, so (ignoring common sense) if you had a mass travelling at c, you could simply have another mass slightly greater than double that of the first travelling at half the speed and you'll have a higher kinetic energy. You can set a maximum theoretical kinetic energy for any specific object, but the maximum possible kinetic energy would be the entire mass of the universe travelling at the speed of light, which is a ridiculously large and pointless number. GeeJo ⁄_(c) • 10:37, 14 October 2007 (UTC)

Firstly, it's 1/2mv, secondly, that is a formula of classical mechanics, false in special relativity, and so is invalid for large speeds. In SR, the kinetic energy of a body of rest mass m and speed v is given by

${\displaystyle E_{k}=m\gamma c^{2}-mc^{2}={\frac {mc^{2}}{\sqrt {1-v^{2}/c^{2}}}}-mc^{2}}$

And so, as the speed of a massive body approaches c, its kinetic energy approaches infinity. Thus c does not provide a very interesting upper bound. (note this does not apply for photons, which actually travel at c but have zero rest mass). Algebraist 10:54, 14 October 2007 (UTC)

<after ec, before seeing Algebraist's response>The relativistic kinetic energy of an object with rest mass m traveling at velocity v (in a given inertial frame of reference) is

${\displaystyle E_{k}=m\gamma c^{2}-mc^{2}={\frac {mc^{2}}{\sqrt {1-v^{2}/c^{2}}}}-mc^{2}}$

This is approximately ${\displaystyle {\frac {1}{2}}mv^{2}}$ when v is small compared to c. However, as v approaches c, E_k is unbounded - it has no upper limit. What this means in practice is that no matter how much energy you pump into an object, it will never reach the speed of light. This is sometimes expressed by saying that the energy increases the object's relativistic mass or inertial mass ${\displaystyle m\gamma }$, and so makes it "harder to accelerate". Gandalf61 11:00, 14 October 2007 (UTC)

Uh oh, I just thought of something. If photons are all energy and no mass, what is their temperature? I mean, if more photons in an area means more energy (and thus higher temperature), what if you could measure the temperature in a photon? Since temperature depends on the amount of photons (particularily heat) in a certain amount of space, what would be the temperature of one photon? If there is no upper limit, would it be infinity? What if you could squueze a huge amount of photons (just photons) into an extremely tiny space, is it possible for the photons to be so crammed that they create their own mass and gravity? Also, if they had no mass, why don't they float away from gravitation? Is there such thing as an antimatter photon? If there was, if one touched a matter photon, wouldn't it create either no energy at all, or only the amount of energy already in the photons, because E=MC2 relies on mass of the object? Thanks. ~AH1 20:30, 17 October 2007 (UTC)

Wow, that's a lot of misconceptions in a row. I'll see how many of them I can dispel. First of all, temperature is a concept of thermodynamics and statistical mechanics, which only makes sense if there are a large number of particles with a certain statistical distribution of energy. One particle does not have a temperature, only an energy. So one photon does not have a temperature, but a large number of photons can have a temperature if they follow a special distribution called Planck's law. For example, the light from an incandescent light bulb has a temperature (it is equal to the temperature of the filament), but the light from a fluorescent lamp does not (because the spectrum is quite different, having discrete spikes for the different phosphors rather than a smooth curve). The light from a fluorescent lamp has a non-thermal distribution, because it is not in thermal equilibrium with itself (which is possible because the photons don't exchange energy with each other).

The thing you describe next is called a geon. It's unknown whether they are stable in theory, and they certainly haven't been observed.

I'm confused why you ask "why don't they float away from gravitation?". If you shine a flashlight into the night sky, the light does "float away from gravitation". Perhaps you're asking why light follows a curved path in a gravitational field? Well, that's not true either. Light follows a geodesic, which is the straightest possible path in the curved spacetime of general relativity.

The photon is its own antiparticle, which simply means the total number of photons is not a conserved quantity. Anyway, photons can't "touch" because light doesn't interact with other light, only with electrically charged particles (photons are uncharged). So photons cannot annihilate with each other. —Keenan Pepper 14:30, 18 October 2007 (UTC)

Redox reactions

I know that oxidation is loss of electrons and reduction is gain of electrons. I also know that an oxidant gains electrons whilst a reductant loses electrons.

Yet I am a bit confused about the terms (1)"oxidising strength", (2)"reducing strength", when something is (3)"oxidised", when a molecule (4)"oxidises" something else, when something is (5)"reduced" and when something (6)"reduces" something else.

I think that "oxidising strength" refers to the ability for something to act as an oxidant whilst "reducing strength" refers to the ability for something to act as a reductant. Yet I'm not completely certain.

Could somebody please define clearly the 6 above terms. (You can refer to the words oxidant, reductant, oxidation and reduction in the definition as I am confident with these terms.)

Thank you very much. —Preceding unsigned comment added by D3av (talk • contribs) 09:28, 14 October 2007 (UTC)

The oxidising strength is the tendency to oxidise - a very strong oxidant may oxidise a weaker oxidant that would usually be reduced in a reaction and not oxidised - the same goes for a concept of reducing strength - you already have the meaning of 3,4,5,687.102.82.26 17:51, 14 October 2007 (UTC)

The Redox page might be useful…besides being "yet another explanation of the ideas" (sometimes one wording just sinks in better than another), it puts them in context and explains the reactions. Memorizing terms is pretty useless without knowing what they really mean and how they work in the real world. DMacks 18:57, 14 October 2007 (UTC)

Thanks for the reference. I found what I needed on the Redox page. D3av 11:31, 15 October 2007 (UTC)

Cyanide Vs. CO

Though Cyanide and CO are both strong ligand, why is there a difference in their mechanism of toxicising the human body? —Preceding unsigned comment added by Curieous (talk • contribs) 13:51, 14 October 2007 (UTC)

See Cyanide: Mechanism of toxicity and Carbon monoxide poisoning. Xn4 18:52, 14 October 2007 (UTC)

cyanide would almost certainly poison in the same manner as CO, but there is (according to the experts) yet another way in which CN can poison.. If this pathway wasn't available to CN, then cyanide would still be poisonous in the same manner that CO is. (The two compounds CN- and CO are isoelectronic and would be expected to have very similar behaviour

A side question that arises is why doesn't CO poison in the same way in which CN- poisons87.102.82.26 20:35, 14 October 2007 (UTC)

The short answer is that their chemistry is different, so they affect certain vital systems more effectively than others. Even if the substance affects several vital systems it is the one that causes you to die the fastest that is officially the cause of death. For example, if your head gets cut off, it is lack of oxygen to the brain that kills you the fastest (in seconds) rather than lack of glucose, so the cause of death is lack of oxygen although both separately would have killed you.

The long answer is that the "cause of toxicity" is a combination of which cellular process reaches the failing point the soonest after the substance is introduced to the body (usually one with a low concentration of the substance needed to cause critical failure) coupled with the time it takes to die from that failure. Carbon monoxide and cyanide have sufficient chemical difference so that they affect different vital cellular processes much more effectively thus causing the difference in mechanism of toxicity witnessed. Although the compounds are isoelectronic, the overall charge and the distribution of charge are not identical.

• Carbon monoxide is an overall neutral molecule with a slight negative charge on the carbon and a partial positive on the oxygen.
• The cyanide ion is overall negatively charged with the Electrostatic potential surface model on the cyanide page suggesting the negative charge is spread around to both atoms of the cyanide with the more-electronegative nitrogen hogging more of the negative charge.
• These compounds have different bond lengths and atom sizes.

Enzymes are "finely tuned" for their normal mode of operation, with the side effect that small differences in the chemistry of potential inhibitors can drastically change the magnitude of the inhibition.

Now, to get to the nitty gritty. For the sake of this question I will assume a large fatal concentration of the compounds are being inhaled continuously.

• Carbon monoxide poisoning

CO binds to hemoglobin very effectively, so most of it getting into the body will probably stick to hemoglobin and less will be available to muck around with other enzymes. Even if carbon monoxide is binding to many different enzymes in various life supporting pathways, the first pathway that will reach its failure point is the oxygen transport system due to carbon monoxide outcompeting oxygen on the binding site of hemoglobin. Death by lack of oxygen occurs in several minutes so the time until death after the failure point is fairly quick, making it the primary cause of toxicity.

• Cyanide poisoning

Cyanide doesn't bind to hemoglobin as efficiently as CO does, so more of it will be available to muck about with other vital enzymes. Cyanide happens to bind very efficiently to the enzyme cytochrome c oxidase, vital to the production of ATP (which is in high demand in the heart and nervous system). It takes much less cyanide to bind to bind a fatal amount of cytochrome c oxidase than a fatal amount of hemoglobin, so even if the majority of cyanide is stuck to the hemoglobin, the system that reaches it's "fatal concentration" first will be the ATP pathway. Death by lack of ATP to the heart/central nervous system is also fairly quick; the article cyanide says several minutes for high doses, similar to the time to death caused by lack of oxygen. Therefore the cause of death and primary means of toxicity for cyanide poisoning is binding to cytochrome c oxidase and causing a failure of the ATP pathway in the heart and nervous system.

Hoped that helped. If anyone has anything to add please do so. Sifaka 05:32, 15 October 2007 (UTC)

If possible I'd like to see equilibrium constants for CN/CO Haemoglobin - it the bit about "Cyanide doesn't bind to hemoglobin as efficiently as CO does" - as having a little chemistry I'd find that suprising - but I was never expert in biological systems..83.100.255.190 10:04, 15 October 2007 (UTC)

Also at Cytochrome c oxidase ref 1 - says CO also inhibits the enzyme - is it possible that the CO page is wrong/out of date?83.100.255.190 10:07, 15 October 2007 (UTC)

Would it be truer to say that CO/CN poisoning is in fact due to both pathways? (I'm no biochemist - it's a question.not my 'theory')83.100.255.190 10:27, 15 October 2007 (UTC)

• • Just have a look at this excerpt from the CO article:-

Toxic mechanism:- The precise mechanisms by which toxic effects are induced by CO are not fully understood.

Carbon monoxide binds to hemoglobin (reducing oxygen transportation), myoglobin(decreasing its oxygen storage capacity), and mitochondrial cytochrome oxidase (inhibiting cellular respiration)#

So,may be it justifies the above discussion that though multiple paths are available,the declared path will be the one which is the fastest.

However,the above excerpt says that the mechanism is not fully understood...could someone mention the complications involved in it? --Curieous 08:52, 16 October 2007 (UTC)

microscopy

when the slide is moved down in what direction does the image move —Preceding unsigned comment added by 99.226.126.42 (talk) 14:43, 14 October 2007 (UTC)

Think: Which way is the lens moving relative to items on the slide? --Mdwyer 15:49, 14 October 2007 (UTC)

It depends on the type of microscope.... TenOfAllTrades(talk) 16:20, 14 October 2007 (UTC)

For the type of microscope often used in school teaching labs, the image is inverted, see this manual, page 26. --JWSchmidt 20:02, 14 October 2007 (UTC)

When light enters a microscope's objective lens, light from the lower part of the slide will hit the upper part of the lens, travelling upwards. Light from the upper part of the slide will do the same and hit the lens' lower portion. Of course, the same is true of light from all other directions; it will strike the lens in a position opposite to the object's direction.

This will cause the image to be inverted. So, in which direction will an inverted image move if the slide is moved down? --Bowlhover 04:45, 16 October 2007 (UTC)

Effects of long term usage of asthma medication

I'm just wondering if there are any known adverse effects to long term usage of asthma medication. In particular inhalers such as Duovent. Thanks :) 84.197.59.250 15:16, 14 October 2007 (UTC)

Take a look at the page for the active ingredients: fenoterol and Ipratropium. Both of those articles are kind of short, so you may want to then feed those names into Google. --Mdwyer 15:47, 14 October 2007 (UTC)

Long term inhaled steroid use has risks of glaucoma and cataract formation.

Atlant 16:18, 15 October 2007 (UTC)

Transport Phenomena

While browsing today in WIKIPEDIA, I came across the entry TRANSPORT PHENOMENA. I notice that our book TRANSPORT PHENOMENA, by Bird, Stewart, and Lightfoot (Wiley, 1960) has been cited. Actually there is a 2002 edition as well as a 2007 "Revised Edition." These later revisions should really be cited, since the 1960 edition is now 47 years out of date! R. B. Bird, University of Wisconsin —Preceding unsigned comment added by 128.104.178.123 (talk) 18:03, 14 October 2007 (UTC)

First of all, this is not the place to grovel about out-of-date information. Secondly, the most likely cause of the 1960 ed. being cited is that no one who contributed to the article has the 2002 or 2007 editions. NASCAR Fan24 18:16, 14 October 2007 (UTC)

Be nice. And nobody "groveled". I copied the original message to the article's talk page. --Milkbreath 18:19, 14 October 2007 (UTC)

Guess I did bite them there. I just get mad when people don't use things for their intended functions. To Professor Bird: You may change any out-of-date information in the article. You may want to read WP:CITE to learn how to cite a book. NASCAR Fan24 18:22, 14 October 2007 (UTC)

Some people in academia are too busy to edit, feel they have a conflict of interest or they are just unfamiliar with the wiki concept. I've had people send me email about page content problems in Misplaced Pages when they could have just taken a minute and fixed the problem by editing the page. "when people don't use things for their intended functions" <-- See Murphy's law. --JWSchmidt 19:45, 14 October 2007 (UTC)

There would be an air of impropriety with the author of a book citing his own work on Misplaced Pages (although in this case, I doubt anyone would object). It makes sense to have someone who is already an active editor of the article make the change. So the best procedure would be to post this kind of note to the talk page of the article (which Milkbreath took care of)...and if that doesn't produce a result, look at the edit history of the article and ask some of the most active editors directly via their talk pages (or email addresses if they provided them). SteveBaker 21:41, 14 October 2007 (UTC)

• Dr. Bird, I would like to apologize on behalf of polite Wikipedians everywhere for the unmerited incivility you were shown above. It's absurd that an obviously-qualified editor offering input should be treated so rudely. --Sean 15:35, 15 October 2007 (UTC)

  I second this apology. Dr. Bird deserves a more detailed explanation and I have a request, so here goes: anyone can edit, but must cite sources. The original editor had access to the earlier edition, but not to the later one, and therefore could cite it: you must not cite a work unless you actually read it and used it. If another editor (such as Dr. Bird himself) has access to the newer edition and is willing to verify that facts in the article are supported by the newer edition, then that editor is welcome to change the article to use the newer edition. Please help us. Thanks. -Arch dude 15:54, 15 October 2007 (UTC)

Spectroscopy of elements

If spectroscopy of molecules reveals the frequency at which their bonds resonate what is it the spectroscopy of the elements represents, the resonance of the subatomic particles, i.e., protons and neutrons and electrons, within the atom? Clem 18:35, 14 October 2007 (UTC)

NMR and EPR are types of spectra that analyze resonance of nuclei and electrons, respectively. Careful though…"resonance" applies to a particular kind of interaction, not a particular kind of particle. Ultraviolet-visible spectroscopy is another kind that analyzes resonance of electrons, but it's not related to EPR. DMacks —Preceding signed but undated comment was added at 18:52, 14 October 2007 (UTC)

exlcuding nmr - all these resonances are at frequencies above that of visible light - the difference between 'resonance' frequencies of electrons is electronic spectroscopy (the term resonance is possible debateable here - depending on what theory you have), the differences between energy states in nuclei is in the x-ray or gamma ray region - again it's debateable whether or not the nuclei are actaully resonating - and depends on what theory you are using..

Note that electronic spectoscopy (the electrons) also depends on the type of molecule the electrons are in - there's also (for lower down electrons) mossbauer spectroscopy and X-ray photoelectron spectroscopy amongst others,not all these spectrosopy are interpreted as being directly from resonances..87.102.82.26 20:50, 14 October 2007 (UTC)

And you can get crazy and do Raman spectroscopy, which is a measurement of electronic transitions that indicates bond vibrations. This is similar to using IR, which only examines vibrational modes, to see the effect of rotational modes on those vibrations, instead of using Microwave spectroscopy to probe rotational modes more directly. DMacks 22:10, 14 October 2007 (UTC)

CLASSIFICATION

What would a scientist have to prove to show that the organisim they had discovered was a new species?

What would you expect to see in the organisms within groups that get smaller and smaller. 88.110.21.169 18:38, 14 October 2007 (UTC) Alex McAdam

I suggest checking out the Species and Species problem articles. As for the organisms in groups that get smaller and smaller -- fortunately, there are a finite number of organisms on Earth, so if you kept dividing organisms into group, you'd at least hit the limit once you created a new group for each organism. -- JSBillings 18:59, 14 October 2007 (UTC)

Usually a lack of cross breeding with other similar species of organisms is what you need to prove that an organism is a new species. How exactly this is determined may vary between different organisms. 71.226.56.79 22:13, 14 October 2007 (UTC)

I posted this in a question below but it seems to be important to this one as well. Sometimes the line between species are drawn for reasons other than "can two species interbreed". Even if two organisms can interbreed they may still be considered separate species based on the fact they wouldn't likely interbreed in the wild because they are separated geographically, or because their behaviors are suitably different, etc... See the hybrid page for some examples. Taxonomy has all manner of inconsistencies and politicking. A cross between a Bullock's Oriole and a Baltimore Oriole produces fertile offspring, but the two may be considered separate species or the same species called the Northern Oriole depending on who you talk to. Animal taxonomy is arguably the most straight forward. Plants are probably next but can be a nightmare taxonomically because many "species" can cross rampantly. Fungal taxonomy is all over the place and still developing. Many fungal species have multiple nomenclature synonyms simply because the various reproductive stages of fungi appeared different only to be found to be the same thing later. I don't know enough about protista and bacteria, but I can guess they probably can get rather messy as well. Sifaka 02:13, 15 October 2007 (UTC)

Absolute zero

I just want some input on my reasoning about this topic, or any other speculations that are floating around out there.

Absolute zero is the lack of all energy, right? So if you managed to get an atom down to absolute zero, what would happen to it? Don't electrons have potential energy based on their orbital position? In order to reach absolute zero, would they have to fall into the nucleus? What would happen then?

For curiosity's sake... justice 18:41, 14 October 2007 (UTC)

Thermodynamicists say it isn't possible to reach absolute zero. Xn4 18:48, 14 October 2007 (UTC)

Our absolute zero page has info about this topic. One important issue is that "Absolute zero is the lack of all energy" is a convenient and short explanation for the general public, but it's not the precise and correct definition. As you note, there is a non-zero minimum for various potential energy components. DMacks 18:49, 14 October 2007 (UTC)

Theoretically though, for you to reach absolute zero the electrons couldn't stay in their orbitals because of potential energy. If they hit the nucleus, what would happen? Also, I'm assuming that in real life, if we can never reach absolute zero, it's an like an exponential function- always getting closer to whatever number, but never quite reaching it? justice 19:08, 14 October 2007 (UTC)

Again, I point you to the absolute zero page, which states "It is the point at which particles have a minimum energy, determined by quantum mechanical effects, which is called the zero-point energy.". They don't stop moving and they don't have zero potential energy. DMacks 19:12, 14 October 2007 (UTC)

Yes, a necessary result of quantum mechanics is that you can never get rid of zero-point energy. Someguy1221 19:19, 14 October 2007 (UTC)

There is a certain elegant symmetry here - Einstein says we can't reach infinite kinetic energy - and the third law of thermodynamics says that we can't reach zero kinetic energy either. Nature seems to love having exponential tails to avoid having mathematical discontinuities. SteveBaker 21:31, 14 October 2007 (UTC)

The third law applies to statistical ensembles of particles. Individual particles within an ensemble may well obtain a state of minimum possible kinetic energy, such as happens to the majority of particles in a Bose-Einstein condensate. Dragons flight 23:15, 14 October 2007 (UTC)

It's also worth noting that ending up with zero energy could have weird implications for what it means for fundamental particles to "exist". What happens to light if it has no energy? Light is defined (in part) by its wave-like properties — would it even make sense to talk about it as existing if it had no energy, no motion? I'm no physicist but I imagine similar issues come up when you are talking about matter as well, given the deep connection between energy and matter. --24.147.86.187 22:25, 14 October 2007 (UTC)

I was going to ask about that. So nothing, as best we understand it, would exist without energy? If it had no energy, the matter would be... destroyed? justice 22:55, 14 October 2007 (UTC)

No, no, no! Not "Zero Energy" - we're talking about temperature - which is "Kinetic Energy" - mass times velocity squared. When the velocity of an atom drops to zero (so you get absolute zero temperature), it still has mass - so it still has energy of the E=m.c variety - it's just kinetic energy that hit zero because that's mass multiplied by velocity and when velocity is zero, the kinetic energy is zero no matter what the mass is. I agree with User:Dragons flight too - single atoms can have zero kinetic energy. SteveBaker 15:06, 15 October 2007 (UTC)

question on Sexually transmitted disease--why aren't there more of them?

Why there are apparently relatively few STDs? I think there "ought" to be hundreds of well known STDs. I mean, fluid exchange during sex is a jackpot for microcritters to evolve to take advantage of. Could it be that these missing STDs are really there but are wrongly presumed to be genetically heritable diseases, defects,(or even advantageous traits!?) since they would commonly run in families?-Rich Peterson —Preceding unsigned comment added by 130.86.14.86 (talk) 20:53, 30 September 2007 (UTC) (I put this on the STD discussion page a while back, but that isn't the right place for it, according to Misplaced Pages policy)130.86.14.90 20:02, 14 October 2007 (UTC)

You're running on some pretty strong assumptions there. Genetic defects are not diseases, as they are... well, not diseases. They're flaws in the DNA that cause abnormal conditions in the body's development, not body parts being attacked by a specific organism. Second, why should there be "hundreds of well known STDs." Sexual fluids are actually a less efficient method of spreading disease than blood or airborne transmission. There's nothing inherently special about sexual fluids that should be a "jackpot" for diseases. -- Kesh 20:09, 14 October 2007 (UTC)

I know what a genetic defect is.What I'm proposing is that some things thought to be genetic defects are actually diseases transmitted semen.I am interested in what you say about sexual fluids not being as efficient, perhaps you're right. Can you explain your reasoning or refer me to a source? Thanks, Rich Peterson—Preceding unsigned comment added by 130.86.14.90 (talk • contribs) 22:56, October 14, 2007

Please read disease. A disease is a foreign organism that enters the body and damages it in some way. Genetic defects are inherent in the DNA of the child. How are you proposing that a disease could A) stick around in the mother's body long enough to infect the fetus, yet B) be undetected in the mother OR the fetus, C) not harm the mother and D) continue to affect the child throughout its development? -- Kesh 23:03, 14 October 2007 (UTC)

I think you may be inadvertently defining a possibility out of existence, by use of the word "disease". In answer to A and B and C, it's not too different to what most parasites struggle and adapt to do over time, though some may not be hidden but are perceived to be genetic defects, rather than stowaways in fluids for gene transmission. Thanks for your comments.--Rich Peterson

At this point, I'm not even sure what you're proposing. The causes of genetic defects are in the DNA of the child, inherited from the parent. An STD is a disease, a microorganism. The two are not even similar. The mechanics behind both are rather well understood, so I don't see how a disease can "masquerade" as an inherited defect. -- Kesh 23:35, 14 October 2007 (UTC)

I agree with part of what you say if you mean a disease's strategy is to 'masquerade" as a genetic defect--that surely wouldn't happen as often. I mean perceived by us in our ignorance, not an intentional masquerade. What "is rather well understood" may or not be just a portion which is "rather well understood." For example, there is no telling for sure that the the two that "are not even similar" don't have a large, and unknown, range of intermediates.--Thanks, thats's all for today for me.-Rich Peterson —Preceding unsigned comment added by 130.86.14.90 (talk) 00:13, 15 October 2007 (UTC)

At that point though, you're venturing into philosophy territory. That there may be things we do not know is obvious. However, going from that to saying "diseases are causing these defects" is a huge leap of faith. There's nothing whatsoever to support it in science. -- Kesh 00:19, 15 October 2007 (UTC)

I don't think sex is a good way for a disease to transmit itself at all. Humans are relatively monogamous and typically have sex just a few times a week - mostly with the same partner. A common cold virus is transmitted between complete strangers via nothing more than a handshake, a cough or a sneeze - with an opportunity to transmit itself dozens and dozens of times per day. SteveBaker 21:27, 14 October 2007 (UTC)

Careful Steve, humans are not that monogamous. If you've ever had a partner who has had at least one other partner, you are part of the great sexual network. I do agree though, airborne is the best way for a pathogen to go. Returning to the original question, STDs aren't super easy to pass to your kids (it depends on the STD of course, but AIDs for example, is preventable to about a 15%-25% transmission rate in the West), and mistaking them for genetic defects seems pretty far fetched. Also, remember that diseases "should" evolve to become less noticeable and less virulent, so there are probably "STDs" that we don't even classify as diseases anymore. --Cody Pope 21:39, 14 October 2007 (UTC)

--I think "so there are probably ""STDs" that we don't even classify as diseases anymore" supports my proposal. I did suggest an STD could even be advantageous as an extreme case of what, as you say, tends to happen-diseases evolve to become less noticeable and less virulent. Thanks for your comments.--Rich Peterson

Sheesh! I said "relatively monogamous" and "typically" - just how careful do I have to be? The point is that it's pretty much impossible to have sex with someone without passing on a cold. So it's pretty much certain that a disease that can transmit itself through the air is going to have more potential contacts to spread to than an STD. The spread of AIDS is pathetically slow compared to whichever cold or flu strain is unleashed in a given year. Even in the countries where AIDS has spread the furthest, you're only looking at 10 to 20% of the population over 20 or more years. A strong flu strain can spread to a similar percentage of the population in a couple of months. SteveBaker 22:07, 14 October 2007 (UTC)

Hey, I attacked "relatively" not "typically" -- man you do need to be more careful :). But mostly I completely agree with you. --Cody Pope 22:22, 14 October 2007 (UTC)

Compare that to how often you've breathed the same air as someone. I'm not certain, but I'd be willing to bet that most people also share drinks more often then they have sex. In addition, I'm pretty certain that almost all diseases can be transmitted that way, and STDs are the ones that can only be transmitted blood to blood. — Daniel 22:00, 14 October 2007 (UTC)

Hmm, I was agreeing with Steve's observation that airborne is way more common/easy, but disagreeing with him saying that we're all monogamous -- so I'm not sure how we disagreed. Plus, I really just wanted to say "great sexual network" :). Moreover, "almost all diseases can be transmitted that way" is an odd statement (where "that way"=airborne?). Ebola is transmitted through fluid exchange (non-sexual and sexual alike) and it's certainly not classified as an STD. A lot of parasites need a vehicle that isn't air. As well as malaria, non-parasitic dysentery, TB (airborne momentarily, sure but only if someone just sneezed in your face, the bacteria isn't transmissible through sharing water glasses washed dishes though) and others. Take African sleeping sickness, it is usually passed by a fly, but can theotrically be passed via fluid exchange etc. Saying anything transmitted via fluid exchange is an STD doesn't work. --Cody Pope 22:13, 14 October 2007 (UTC) (I would add that people with Ebola almost never have sex). --Cody Pope 22:25, 14 October 2007 (UTC)

I just don't see your point about efficiency or effectiveness of transmission. First, there's quite a lot of different germs that transmit by air etc, far more than the few hundred for sexual transmission I'm proposing. Second, even if very few germs were transmitted by semen, say a few eons ago, there would be lots of time for them to speciate--some adapting to become less virulent, and every once in a while a few "choosing" the greater virulence strategy.-Regards and thanks to all for your thoughtful comments.--Rich Peterson

The point is that it's simply not as effective a method of transmission. Speciation tends to favor the best methods of continuing the species which, for diseases, means they tend to favor the more reliable/easier methods of spreading. Thus, more airborne diseases than fluid-borne ones. -- Kesh 23:44, 14 October 2007 (UTC)

Yes, but I don't mean to suggest there should be more fluid-borne than airborne diseases, I don't know. I only suggest there are MANY fluid-borne ones, more than we suspect. Also, a species transmitted by a fluid would be reasonably likely to have at least some of its daughter species use the fluid route.--Rich Peterson —Preceding unsigned comment added by 130.86.14.90 (talk) 00:00, 15 October 2007 (UTC)

You've still not explained why there should be more than we are currently aware of. -- Kesh 00:03, 15 October 2007 (UTC)

Ok, to summarize, if I understand the conversation so far, Rich argues that there should be more STDs since sex is a good vehicle for transmission and others are saying that sure sex is a great mode, but airborne is way better (where "better" means faster). Now, Rich also argues that it is possible that we have misidentified STDs as Genetic defects, since they could be passed to children by parents and might only present in development. Is that about it? First, airborne is faster and thus ideal for anything that wants to reproduce quickly. Second, sure, I agree that it is possible for us to misidentify a disease as a defect under the conditions that: a. it can be passed from mother to child, b. it is unknown to science, and c. it causes some developmental problem. But, I also contend that given the level of modern medicine this is highly unlikely, since, "a." only happens about 15-25% of the time (for HIV at least), "b." is untestable, and "c." is probably not happening given that many if not most developmental problems have identifiable causes. Tangentially, my problem with the question is more about the limited definition of "STD". Take a look at HPV for example: "of about 13 so-called 'high-risk' sexually transmitted HPVs". There are over 100 HPV forms, and only about 13 are considered STDs. Now all of them can be transmitted by sex (skin contact really). The common cold can be transmitted by sex (kissing and coital fluid exchange). Ebola can be transmitted by sex (any fluid exchange really, touching soars etc). So our working definition of STDs doesn't seem super effective when you're discussing the evolution of diseases and their radiation. We could simple say that Rich's "lost" STDs are all those virus/pathogens/bacteria that can be transmitted via sex but are most often not (or at least not associated with sex in the traditional sense). So to summarize: fluid exchange is not the jackpot it could be, since it is slow. STDs being misidentified as genetic defects is possible but improbable. And if you just change the definition of STD you get a whole bunch of speciation in your new group. --Cody Pope 04:30, 15 October 2007 (UTC)

On HPVs, actually only 13 are "high-risk STDs", that doesn't mean that none of the others are STDs. The article says, "A group of about 30-40 HPVs is typically transmitted through sexual contact", thus about 30-40% are STDs. A "high-risk STD" is one that includes a risk of death, as noted in the Cancer section that says, "About a dozen HPV types are called 'high-risk' types because they can lead to ." The section on HPV caused genital warts (which is an STD) notes that they are not "high risk" because they don't cause cancer. The reason why so few are "high-risk" is not because STDs are hard to contract, but because they increase the odds of killing off the host, which is a maladaptive trait compared to the more benign versions of HPVs. -- HiEv 17:41, 15 October 2007 (UTC)

Actually, this is a pretty good question. To start off with, there are already quite a few STDs, with over 100 species of Human papillomavirus (HPV) identified so far alone. Besides that, the fact is that there are probably many more STDs that we're not aware of, but they're not noticed due to being fairly benign. If a bacteria or virus is transmitted, but there are no symptoms, then people aren't likely to look for it or try to figure out how it was transmitted.
Also, there are diseases that seem to run in families, so we assume that there is a genetic component to the disease, however this could be in error. Researchers are still searching for genes responsible for some apparently genetic diseases. However, what appears to be a genetic condition might actually be due to an environmental cause, such as exposure to a certain germ. If a virus, for example, had evolved to be able to infect a foetus in the womb then it might cause some early developmental changes that affect later growth. For example, while often thought to be genetic, some suspect that one of the causes of schizophrenia could be due to prenatal exposure to infection by the parasitic protozoa Toxoplasma gondii.
Still, there are many problems with this, such as the difficulty in infecting the foetus (as seen above in the AIDS numbers) without killing it, the long dormancy period that would be required from birth to sexual maturity, the fact that negatively affecting the future host reduces its ability to spread, the length of time it would take to evolve to be able to cause a positive adaptation in its future host, and an explanation as to why it would stick to some families and not spread more randomly among the population as other STDs do.
So, yes, there probably are more STDs, but for the most part it's unlikely they're ones worth worrying about, and it's very unlikely, though not impossible, that they're the cause of any apparently heritable conditions. It sounds like it might be worth investigating scientifically, but currently I wouldn't put the odds in favor of it being true. -- HiEv 17:18, 15 October 2007 (UTC)

• It depends how you are defining STD. Is an STD something that is only transmissible by sex (or a sex-like act such as a blood transfusion), or is an STD something that is transmissible by many means, including by sex? By the latter definition, almost every disease is an STD. You can catch flu by having sex with someone -- it's just that you could just as easily have kept your pants on and caught it. --M@rēino 21:02, 17 October 2007 (UTC)

I'd say an STD is something that is primarily transmitted due to sexual contact. After all, there are ways to get any transmissible disease without sex. For example, you can get AIDS from a blood transfusion. So if you say an STD is a disease only transmissible by sex then there are no STDs. -- HiEv 14:06, 18 October 2007 (UTC)

Mitochondrial genome size

Everyone seems to know that the mitochondrial DNA in humans is 16569bp long. This comes from a 1981 paper that sequenced it. My question is: there's gotta be some variation in this number - does anyone know how much give and take there is in humans? Aaadddaaammm 22:19, 14 October 2007 (UTC)

Here is a place to start: Mitochondrial diversity within modern human populations. --JWSchmidt 22:27, 14 October 2007 (UTC)

I didn't know the size of the mitochondrial genome if it makes you feel better. :P I am positive it would vary as is it subject to the same (or more as mitochondrial DNA copying machinery is slightly less fullproof than nuclear DNA copying machinery) random duplication and deletion events as the nuclear DNA. That number is probably good for an average. Sifaka 02:17, 15 October 2007 (UTC)

species

Does the inability of one species to impregnate another species serve as the dividing line for species or does it include the ability to impregnate but with the result of offspring so deformed they are not able to live? Clem 22:32, 14 October 2007 (UTC)

Neither. For instance, horses and donkeys can interbreed, but create infertile mules. They are still considered separate species, as their offspring cannot breed, even though said offspring are not deformed. Most modern biologists look at more than that, though, as genetics and bodily structure play into the definition of species quite a bit. It's not as simple as who they can breed with. -- Kesh 22:35, 14 October 2007 (UTC)

Generally, both genders of any offspring between the two have to be themselves fertile. Mules aren't. Of ligers and tigons, only the females are. Not sure about grolars, but then they're a lot rarer. GeeJo ⁄_(c) • 22:42, 14 October 2007 (UTC)

I don't know about grizzly bears in particular but as Ursid hybrid mentions, some brown bears are more related to polar bears then they are each other which is something I've also read before in scientific papers. It also appears to suggest that both sexes are fertile which isn't surprising although not guaranteed by the DNA studies (polar bears could have some specific difference other then their colour which prevents them successfully interbreeding) Nil Einne 11:52, 15 October 2007 (UTC)

Sometimes the line between species are drawn for reasons other than "can two species interbreed". Even if two organisms can interbreed they may still be considered separate species based on the fact they wouldn't likely interbreed in the wild because they are separated geographically, or because their behaviors are suitably different, etc... See the hybrid page for some examples. Taxonomy has all manner of inconsistencies and politicking. A cross between a Bullock's Oriole and a Baltimore Oriole produces fertile offspring, but the two may be considered separate species or the same species called the Northern Oriole depending on who you talk to. Animal taxonomy is arguably the most straight forward. Plants are probably next but can be a nightmare taxonomically because many "species" can cross rampantly. Fungal taxonomy is all over the place and still developing. Many fungal species have multiple nomenclature synonyms simply because the various reproductive stages of fungi appeared different only to be found to be the same thing later. I don't know enough about protista and bacteria, but I can guess they probably can get rather messy as well. Sifaka 01:54, 15 October 2007 (UTC)

JSBillings suggested checking out the various concepts of species and Species problem articles in a similar question above. Sifaka 01:56, 15 October 2007 (UTC)

Yeah - you can cross a Lion with a Tiger and get a Tigon or a Liger (yes, really!) - but nobody would consider Lions and Tigers to be the same species - we "know" they are different because they look different, they behave totally differently (tigers are lone hunters, lions are pack animals, tigers love to swim, lions don't), they sound quite different (lion roars and tiger roars sound way different) - you can easily tell the difference between a male and female lion by the mane - no such clear difference exists with tigers...stripes...you name it. For sure we don't want to call lions and tigers by the same name. On the other hand, we do want to call all dogs "Dogs" - even though they look/behave/sound more different than lions and tigers do, they actually are closer genetically than lions and tigers.

The problem is that we have this big pile of taxonomic data with lots and lots of history to it - and we're loath to toss it all out, even though it's evident that the whole thing is a big blurry mess of genetics. The inability to interbreed could be due to just one teeny-tiny genetic incompatibility - or it could be that there are thousands of genetic differences that none-the-less do not prevent interbreeding. Then we have the 'mule' situation where the offspring of two different kinds of animal is infertile, or the situation with tigons and ligars where the female offspring are fertile, but the males are not, or the situation with Great Danes and Shi-Tsu dogs where the offspring are all fertile but will probably have weird health problems of other kinds. Using that 'interbreeding' criteria as a way to name things is an old, outdated idea.

But to come up with an entire new taxonomy based on genetic differences measured directly by number of different genes would require huge amounts of effort, thousands of textbooks been rewritten, endless wrangling over who gets to name what 'new' species with what name and which name to call the result of two sub-species being grouped together. This is a horrible mess - but in the end, it really doesn't matter all that much...it's just a matter of terminology.

SteveBaker 14:20, 15 October 2007 (UTC)

• I bet taxonomists could play a fun six degrees of Kevin Bacon sort of game where you try to link two distant species by breedable species in between, in the style of a ring species. I wonder what the longest such chain among extant creatures is? --Sean 15:26, 15 October 2007 (UTC)

October 15

race

If the distinction between species is so ambiguous how are modern races distinguished, especially with so much inbreeding? Clem 02:19, 15 October 2007 (UTC)

Many scientists feel that race has no scientific basis at all. Dragons flight 02:27, 15 October 2007 (UTC)

The short answer is not easily. There are massive committees dedicated to this sort of thing. For animals it's the International Commission on Zoological Nomenclature (ICZN) which creates the International Code of Zoological Nomenclature, effectively the rules of how to name things when disputes arise. For plants it's the International Code of Botanical Nomenclature. Narrowing the question, for most non-microscopic sexually reproducing animal species the division between species is typically decided based on whether or not the animals frequently interbreed in the wild or not. Mammals may be considered separate species even though they can technically interbreed if they are geographically separated. As a rule of thumb, biological nomenclature for a particular group of organisms is designed so that it can be fairly easy to apply. Dragon flight raised the issue above that labeling a group of organisms a species attempts to impose a black and white concept on the grey world of biology with varying results. While ideally we would like to be able to classify every organism with a consistent definition, we can't at this point. There are tons of cases where it is currently difficult to observe or expensive to exhaustively test whether or not an organism interbreeds with related species or reproduces asexually so the typical criteria don't apply, or whole bunches of other reasons. In these cases, the concept of "species" is based off of observable morphological characteristics which appear to "set apart" a group of organisms from similar organisms. In parts of mycology this method is frequently used; fungal species are determined by differences in spore characteristics, hosts, range, disease symptoms, and whatnot so that populations of very similar organisms are lumped together to form a "species." Sifaka 02:33, 15 October 2007 (UTC)

Note that human races were considered ill-defined even before the species problem really came to a head. You can find discussions about the lack of human races being real biological distinctions going back into the 19th century at least. In any case there is nobody today who thinks that human races are different species. It has occasionally been a belief floated by various scientists in the 19th century but even then it was considered spurious by many (including Darwin). --24.147.86.187 02:50, 15 October 2007 (UTC)

According to the article subspecies the International Code of Zoological Nomenclature calls human races "infrasubspecific entities." Sifaka 03:10, 15 October 2007 (UTC)

Next time I want to piss someone off, I'll call them an infrasubspecific entity. Might be interesting to see how they react. :) Or unhealthy. :( DirkvdM 18:10, 15 October 2007 (UTC)

This is really another one of those "what's in a name?" questions that we shouldn't be too concerned about. It's clear that humans inherit their skin colour and hair type and various other physiological features from their parents. In that sense the races 'breed true'. But on the other hand, we can interbreed between races quite freely and successfully too - so you can't describe the various racial types as separate "species". Between one end of the scale and the other - it's just a matter of what name you decide to use - and that's as much a matter of political correctness as it is science. This is equivalent to asking whether Pluto is a planet or not - biologists need to put a stake in the ground and define their terminology (just as the astronomers did) - but it doesn't "mean" anything in any important way. Sadly, people will make just as big a fuss over whatever they decide as they did over Pluto's demotion to "minor planet" status...and it's just as big a waste of breath to discuss it. SteveBaker 14:02, 15 October 2007 (UTC)

Problem is, if others like to waste their breath so much, the ones who know can't stand by and say nothing. After all, why did you answer this question? :) DirkvdM 18:10, 15 October 2007 (UTC)

Note, I suppose you meant interbreeding, not inbreeding. DirkvdM 18:10, 15 October 2007 (UTC)

Would Interbreeding require that race be acknowledged as a Taxon? If not, is inbreeding between races a better fit? Clem 19:29, 15 October 2007 (UTC)

Breast hormones

Why don't flat-chested women use estrogen to grow larger breasts instead of getting implants? Doesn't estrogen work to grow breasts on males? --124.254.77.148 09:08, 15 October 2007 (UTC)

Well it can cause males to develop breasts but this is different from causing breasts to grow larger. Lanfear's Bane 10:59, 15 October 2007 (UTC)

Hormones are the bio-chemical equivalent of cluster bombs: you can't just apply the œstrogen to one part of the body - it would spread, causing havoc through the rest of the body; it could screw up the menstrual cycle, digestive processes and even induce cancer. Plus, œstrogen can cause the body to burn fat and kill muscle tissue, causing a net reduction in size. Laïka 11:30, 15 October 2007 (UTC)

Pregnant women grow larger breasts (and it's often a permanent change) - I wonder what hormonal brew does that? But as you say - the number of side-effects would be pretty horrific, so it's not something you'd really want to do. SteveBaker 13:53, 15 October 2007 (UTC)

The worst side-effect of that being a parasitic growth that drops out after nine months and then feeds off you for eighteen years or more. Sometimes. Lanfear's Bane 14:52, 15 October 2007 (UTC)

Worst still, the parasite somehow latches onto the father as well. (And 18 years is a severe under-estimate.) SteveBaker 15:42, 15 October 2007 (UTC)

• They do! Many women report that taking birth control pills causes their breasts to get a little bigger. --Sean 15:21, 15 October 2007 (UTC)

As I recall, there are a few published studies of the effect of estrogen supplementation on breast size in women and they do not indicate that estrogen supplements have much effect on breast volume in most normal women. Most women have normal levels of estrogen and adding more estrogen will have little effect to increase breast size. There are probably some doctors who will help normal women try topically applied estrogen for a few months, without promising any results. Rarely, women who have low estrogen (genetically, for example, see aromatase; or otherwise) will have a spectrum of problems and breast size is not likely to be their main concern. During pregnancy there are multiple hormones and growth factors that can influence breast size including progesterone, IGFs, prolactin and poorly-characterized factors that influence weight gain and patterns of adipose tissue growth. Hormone/growth factor levels are not the whole story; there is genetic variation in how tissues respond to these signaling molecules. --JWSchmidt 15:54, 15 October 2007 (UTC)

Oh. Well, maybe when women get on the pill they also start wearing tighter sweaters, which has led to these false reports. :) --Sean 17:16, 15 October 2007 (UTC)

Combined estrogen and progesterone will stimulate mammary gland tissue growth inside the breasts of many women, which is mainly of concern for associate increased risk of breast cancer. Is a possible small increase in breast size worth an increased risk of breast cancer? Orally administered estrogen supplements increase the risk for stroke and other blood clotting problems. I think a doctor who gives women prescriptions for oral estrogen or an orally administered estrogen+progesterone supplement in order to try to increase breast size would be a likely target for legal action. I suspect most doctors feel it is not ethical to give women drugs that have serious side effects while trying to deal with something like small breast size, which is not really a medical problem. --JWSchmidt 17:43, 15 October 2007 (UTC)

• As far as medical ethics go, I note that doctors routinely operate on perfectly healthy women for breast enlargement surgery. Both anesthesia and major surgery carry the risk of serious complications, but are still widely available. --Sean 19:29, 15 October 2007 (UTC)

Medical uses of breast implants, estrogen and progesterone are all regulated by the FDA. Breast implants are approved for breast size augmentation. To my knowledge, estrogen and progesterone supplements have not been approved by the FDA for use in attempts to increase breast size, but I might have missed it. --JWSchmidt 20:14, 15 October 2007 (UTC)

• I didn't mean to imply that they were. I was just noting that doctors are not ethically above doing other potentially risky procedures for something that is, as you say, not really a medical problem. --Sean 21:03, 15 October 2007 (UTC)

I probably should not have left it at "not really a medical problem". In our society there can be psychological problems arising from breast size (even in the normal range), so it has been possible do document psychological benefits for some women from breast size augmentation. In terms of medical ethics, there should be some balance of the benefits against the risks. If there is an FDA-approved medical procedure and a doctor makes sure that the patient knows the available risk/benefit information then they are on fairly safe ground. --JWSchmidt 22:28, 15 October 2007 (UTC)

(outdent) As I understand it, once a medication is approved by the FDA for one purpose, doctors are (as a general rule) free to prescribe it for any purpose. (Do we have an article on off-label prescriptions?) I do seem to recall hearing recently of an exception to this general rule; I don't recall what it was.

Yes, I imagine doctors who do this would be taking risks from a malpractice standpoint. They'd probably want the patient to sign an informed consent form at the very least. --Trovatore 22:34, 15 October 2007 (UTC)

Off-label use would be what you are looking for. Rockpocket 22:55, 15 October 2007 (UTC)

I know some doctors are very comfortable with topically applied estrogen and the breasts are one body location that is sometimes recommended for application of estrogen-containing creams. I'm not aware of FDA approval of estrogen for breast enlargement, but I think some doctors would be comfortable with letting their patients try it for a short time: this would probably qualify as an example of off-label use. --JWSchmidt 23:17, 15 October 2007 (UTC)

This study of topical estrogen therapy for labial fusion had a patient who demonstrated breast enlargement as a side effect (but that was only one out of a cohort of twenty). Rockpocket 23:37, 15 October 2007 (UTC)

Besides all the other points made, not all women want large breasts, nor do all men find them attractive. -- Kesh —Preceding comment was added at 23:38, 16 October 2007 (UTC)

Kinetic energy, part 2

The previous questions about kinetic energy and absolute zero touched on a topic that wasn't specifically answered. If you have an electron - just a plain electron - how much energy can you add to it without changing it? It must remain an electron - just a high energy electron. Is there any limit? If you converted all the mass in the entire universe to energy and applied it to the electron, would it still be an electron? I believe this is what the original kinetic energy question was getting at, but was not answered. -- kainaw™ 12:34, 15 October 2007 (UTC)

Yes as far as I know you can keep adding kinetic energy to an electron - under non-relatavistic thinking as well as under relatavity theories..87.102.47.243 13:12, 15 October 2007 (UTC) The difference between the theories is that as an electron gets approaching infinite energy in relativistic theories it has approaching the c as a velocity (ie 3x10^8m/s), whereas in non relativistic theories it has approachin infinite velocity.

Again as far as I know (and I'm sure someone will take this up) - no electron has ever been found to simply disintegrate due to instrinsic high energys87.102.47.243 13:15, 15 October 2007 (UTC)

Certainly the electron cannot disintegrate due to too much kinetic energy because kinetic energy is a relative thing. Relativity allows us to consider things from the point of view of the electron - and from it's point of view it's dead stationary - why would it spontaneously disintegrate? From our point of view, yes, we can keep pumping energy into it and it will go faster and faster - but even with the entire energy of the universe pumped into that one solitary remaining electron, it'll still only be going 99.99...9% of the speed of light (there would be quite a lot of '9's in that '...' bit - I can't be bothered to work out how many!). This experiment has been done to quite high fractions of 'c' in various high energy physics labs - I don't think any of them have claimed any spontaneous disintegrations in the process - if they did, it would surely be big news. SteveBaker 13:51, 15 October 2007 (UTC)

oops I walked into that one (fun!) - I'm going to pretend that I meant no electron has ever been found to disintergrate due to a high energy collision - actually I'd like to know if this is true? anyone?83.100.252.179 18:20, 15 October 2007 (UTC)

The electron, by my quick calculation, would be moving at ${\displaystyle c(1-4.6\times 10^{-166})}$, so about 160 9s in your ellipsis (and then a 5 after your last 9). --Tardis 23:16, 15 October 2007 (UTC)

Sorry, I should have mentioned that I rounded to 159 places of decimals. I predict we will be using the results of your calculations in future ref desk answers! Thanks! SteveBaker 02:26, 16 October 2007 (UTC)

Thank you for the all the responses, even though i've only had undergrad physics i still found it fascinating! 24.88.103.234Tim

Possibly to make a hybrid/tribrid car that captures wind energy?

Is it possible to make a car with air intakes, that capture wind energy while the car moves? Like the air flow spins a fan inside the intake, which converts that into electricity which is stored in a battery. 64.236.121.129 13:36, 15 October 2007 (UTC)

No - that's definitely not a good idea. The energy you'd extract from the wind would merely show up as increased drag on the car. So the energy your little wind turbines would extract would be dwarfed by the extra drag they'd impose. There is no such thing as a free lunch! If your idea worked then you could build a perpetual motion machine by fixing a windmill onto a cart, and using the windmill (through some gear wheels or something) to drive the wheels of the cart - give it a little push and it would run forever. Since perpetual motion is not allowed (the first law of thermodynamics is a harsh mistress) - we know this can't work. Some older aircraft used little turbine blades out on the wing somewhere to generate electricity - but this was so that they still had a source of electricity if the engine died - they were a net energy loss though, eating kinetic energy (by slowing the aircraft down) at a considerably higher rate than the electrical energy they'd generate. SteveBaker 13:42, 15 October 2007 (UTC)

A vertically mounted turbine (rotate about the vertical) - could capture side winds - but the benefits would be minor - and the downsides (low bridges etc) major..87.102.47.243 13:48, 15 October 2007 (UTC) I don't believe such things can be very efficient easily anyway.87.102.47.243 13:52, 15 October 2007 (UTC)

Sure, you can make a wind-powered vehicle - it's called a 'yacht'! Notice how few yachts use windmills rather than sails! There is a reason for that! However, I have seen things like this A fuel-saving system for ships relies on kites and Giant Sails that could power ships - but they aren't extracting energy from the slipstream air caused by the motion of the vehicle (as our OP suggests) - because that's not possible. SteveBaker 15:31, 15 October 2007 (UTC)

A supercharger pumps cold air into the engine to extract chemical energy by optimizing the fuel-air ratio. This is not usually considered wind energy. It probably adds extra drag, but the energy boost outweighs the drag. Nimur 14:43, 15 October 2007 (UTC)

That's completely the opposite thing! Our OP is talking about extracting energy from the wind using a turbine - you are talking about something that consumes energy to create an air flow (more like a jet engine than a windmill). Superchargers are driven by a belt off the main drive shaft - and turbochargers extract energy from the cars exhaust flow to pump air into the engine. Also, it's not so much that they optimise the air/fuel ratio - a decently designed carburettor can do that without supercharging or turbocharging - the point of a super/turbocharger is that with increased airflow you can inject more fuel and keep the SAME optimum ratio - and thereby either get more power from the same engine - or the same power from a smaller engine. Neither superchargers nor turbochargers directly affect drag - although it is common to add a hood scoop to feed air directly into these beasts, because the pump is sucking air into the duct, it actually creates a small amount of negative drag (but it's pretty negligable!). In the case of a turbocharger, you are actually taking some of the energy out of the exhaust flow to drive the thing - so I suppose you reduce the tiny amount of extra thrust that you car gets from the 'jet' of exhaust fumes being pushed out the back...but again, it's totally negligable compared to the extra power it enables the engine to deliver. As usual though, there is no such thing as a free lunch and these gadgets almost always make the fuel consumption of the car worse, not better. SteveBaker 15:31, 15 October 2007 (UTC)

Commercial aircraft have an emergency generator of this type that deploys if all of the engines fail. It increases the drag, but it provides enough power for the essential flight systems. These units deployed in at least two situations when an airliner flew through a volcanic cloud and lost all engines. -Arch dude 15:41, 15 October 2007 (UTC)

Your comment reminds me of the Gimli Glider story. -- JSBillings 15:55, 15 October 2007 (UTC)

Yes, that plane did use its ram air turbine. --Anonymous, 21:55 UTC, October 15.

Hmmm, I wanted to make a lame joke about how we could interbrid different technologies, but it turns out tribrid is an existing word. (Note how I sneaked in the joke anyway. :) ) Anyway, with a strong sidewind, it might still help if the car had sort of a sail or wing shape. However, given the usual speed of a car, it would have to be a pretty strong side-wind to have a noticeable effect. And if the wind comes from the other side, the car would have to shapeshift. Not a good idea, it seems. DirkvdM 18:21, 15 October 2007 (UTC)

what is the LD50 of...

• vicoden?
• percocet?
• zoloft?

--MKnight9989 14:25, 15 October 2007 (UTC)

• Hydrocodone: 227 mg/kg (rat, oral)
• Sertraline: 419 mg/kg (mouse, female, oral)

Icek 17:16, 15 October 2007 (UTC)

pulse and bleeding

–15:00, 15 October 2007 (UTC)15:00, 15 October 2007 (UTC)~~ca person falls on the ground in front of me,i check his ABC (airway, breething, circulation) and find out that he has no pulse nor breething, hence i start doing CPR trying to revive him. now while i do this can the person start bleeding. basically my question is , can there be bleeding without pulse on?82.148.96.68 15:04, 15 October 2007 (UTC)cuby

If the person still has a decent blood pressure - yes. However, if their blood pressure has fallen too far - then the only blood that'll flow out is under gravity - so maybe yes, maybe no, depending on where the wound is. SteveBaker 15:11, 15 October 2007 (UTC)

Also you are compressing their chest and forcing air into their lungs, pressure may force blood out from any wounds. Lanfear's Bane 15:15, 15 October 2007 (UTC)

Possible to make a Freeze Gun?

Like the gun Mr. Freeze uses? If so, how would it work? 64.236.121.129 15:27, 15 October 2007 (UTC)

Well, the problem with Mr Freeze's gun is where all that water comes from. I suppose you could make a mixture of water and something that would evaporate very quickly when released into the air that would pull the energy out of the water and freeze it. But you'd have to carry a gigantic tank of water around with you - and I can't imagine any way around that. If he were just freezing the water that was already there - then there is no mystery because a CO₂ fire extinguisher or a can of freezer spray can really do that (albeit on a small scale). But he seems to be able to create ice anywhere - even when there is no water around - and there is much more water created than would fit into that tiny gun+backpack. I think the myth is that he's freezing the water vapour in the air - but there isn't anywhere near enough of that to do the job. So basically, "No". SteveBaker 15:39, 15 October 2007 (UTC)

Also see Frozone. Lanfear's Bane 15:48, 15 October 2007 (UTC)

Yep - same problem. It's all very well being able to freeze things - but if there isn't anything there to freeze, you're out of luck! I suppose he might be freezing the air itself - but that's an altogether more difficult proposition! SteveBaker 16:10, 15 October 2007 (UTC)

• .129, I hope these answers haven't left you "COLD"! --Sean 17:25, 15 October 2007 (UTC)

Sometimes you just gotta take the heat. 64.236.121.129 17:37, 15 October 2007 (UTC)

Cool puns, guys. risk 19:28, 15 October 2007 (UTC)

Maybe use hydrogen to power a refrigerator and use the resultant water as the water supply? But then you have to carry hydrogen tanks instead. --antilived 05:01, 16 October 2007 (UTC)

That's funny. But seriously, if you haven't seen the movie Frozone claims to use the moisture in the air, which is why his powers didn't work in that building fire. Besides, what about liquid nitrogen? It worked on the Termintator...and my friend's wart. XD --JDitto 18:56, 17 October 2007 (UTC)

Hydrogen Alpha Images of the Sun

I am a student trying to find hydrogen alpha pictures of the sun. I need to access archives and find one every day for the past week at roughly the same time. I tried the soho website, but their archive section is very confusing. Any help would be greatly appreciated. —Preceding unsigned comment added by 128.255.107.249 (talk) 17:35, 15 October 2007 (UTC)

Why don't you use Google's Image search? Google for "hydrogen alpha sun" and you'll get plenty of nice pics. There is also one here is to the right. 85.127.181.53 21:50, 15 October 2007 (UTC)

This is what you need: Culgoora Observatory H alpha images Graeme Bartlett 01:25, 16 October 2007 (UTC)

Galactic Angling

Out of curiosity only, what's the angle of the Earth's orbit in relation to the galactic plane? GeeJo ⁄_(c) • 17:39, 15 October 2007 (UTC)

Galactic coordinate system; a diagram. There seems to be confusion between various internet sources, some say: "The plane of our Galaxy is titled about 66 degrees relative to the plane of the Earth's orbit around the Sun, which is called the ecliptic". --JWSchmidt 17:53, 15 October 2007 (UTC)

That looks about right according to the two lines in my Atlas of the Heavens. --Milkbreath 18:57, 15 October 2007 (UTC)

According to the formulae found in Ecliptic coordinate system article, and using the position of the North Galactic Pole (NGP) from Galactic coordinate system article (ie. 12h51m26.282s +27°07′42.01″ (J2000)), the position of the NGP is: 179.9768° ecliptic longitude, 29.8115° ecliptic latitude. The galactic plane is perpendicular to the direction to the NGP, at an angle of 90°-29.8115° to the ecliptic. Therefore, to answer the OP's question, the Earth's orbit is tilted at an angle of 60.1885° to the galactic plane. Astronaut 00:10, 21 October 2007 (UTC)

Radio Transmissions

If I had a remote control car, would there be a way to extend the radio transmissions to go very far and for the signal to not have so many interuptions, i.e it could go into a sewer or a cave and still receive my signals from a distance? Could it work off of a satellite or is there a way to strengthen the radio signals? —Preceding unsigned comment added by 63.110.180.29 (talk) 21:08, 15 October 2007 (UTC)

I guess you could hook the radio controller up to a more powerful transmitter with a larger aerial? You'd need one that could transmit the same frequencies, and you'd probably violate several laws doing so. Radio waves don't penetrate solid objects very well, so it's unlikely you could get it to work underground. It's probably conceivable to transmit a signal to a satellite and have it beamed down again, but you'd end up with noticable lag in the cars' response. Exxolon 23:03, 15 October 2007 (UTC)

To get radio signals in tunnels special leaky coax antennas are used to carry the signal into the underground space and make it available all through. You too could use this technology in your sewer or cave, but in fact you may be better off with a roll of optic fibre or wire that unrolls as the car goes forward, and you can drive by wire.

To extend over satellite you will need a fancy antenna on the car, and there is no way to make this work in a cave. Graeme Bartlett —Preceding comment was added at 00:39, 16 October 2007 (UTC)

It's just a matter of power - as a 'thought experiment' - it you really had to, you could equip a satellite with enough power to send a signal that a toy car could pick up 5 feet underground. Soil attenuates radio waves but it's not a sudden cut-off. It would probably have to be a VERY large satellite with one heck of a big transmitter though. But for more sane applications, you can certainly boost the range. When you want to double the effective range of a radio transmitter, you have to quadruple the transmitter power. So let's suppose your car's standard transmitter worked out to maybe a kilometer - to run your car (out in the open) from geostationary orbit (35,786 km) your satellite would have to have a transmitter maybe 35786*35786 times more powerful than the one you have now. That's about 1.3 billion times more powerful! To get through a few feet of dirt afterwards would push the power requirements to truly ridiculous levels. However, that's assuming that (like your regular transmitter) it sends radio waves out in all directions equally. If it only had to send a narrow beam down towards the toy car - it would need a lot less. NASA have used 'ground penetrating radar' systems in satellites that can see down through several meters of martian soil - and in that case they have not only send a radio signal that far - but detect the return 'bounce' too. Those probably don't run on the frequency that your car uses - and that probably makes a difference too. So it's "possible" - but definitely not "easy".

In terms of a practical answer to running your car at longer distances, it's certainly possible to boost the power - but there is a reason they don't do that. Because they sell lots of toy cars (and boats and who-knows-what-else) that use the same range of frequencies, if the signals at the transmitter are too strong, then someone driving one of these things two streets away would interfere with your car - and that would make matters worse, not better. For this reason, radio control transmitters operate at power levels that are strictly limited by law. The best way to get good range from your transmitter is to ensure that the antenna is always fully extended - and if the car has one of those 'dangly wire' antennas - thread it through a drinking straw and hot-glue that onto your car to make that antenna stick up vertically as far as it will go. Don't coil it up! Holding your transmitter antenna vertically will then get you the best possible range. SteveBaker 02:15, 16 October 2007 (UTC)

At some point, the power levels you're using to get the signal through the ground leave the realm of "radio signals" and enter the realm of "directed-energy weapon". The energy in the radio waves doesn't just magically vanish as the signal is attenuated by the ground -- some of it gets reflected, while more of it gets absorbed. --Carnildo 21:34, 16 October 2007 (UTC)

Growing a mushroom on the skin

Don't laugh.

Dermatophytes are fungi, and they are terrible. Amanita muscaria is also a fungus, but it is pretty. Would it be possible to cultivate a fly amanita on one's skin? Would it be safe to do so? HYENASTE 21:59, 15 October 2007 (UTC)

It is not possible, the diet of the fungi is too different. Perhaps you could live off a diet of human skin, but I think you would not survive long on a diet of mulch and tree roots. These different fungi have the same issue. Graeme Bartlett 00:35, 16 October 2007 (UTC)

What's the name of that ancestor of Panoramix in Asterix and Obelix vs Caesar? DirkvdM 08:09, 16 October 2007 (UTC)

There is no way to grow a saprophytic Amanita muscaria on one's living skin because it is not adapted to deal with the human body's defenses. You couldn't even grow it on a decomposed flesh either because Amanitas are adapted towards decaying plant matter. So definitely not. Any fungus growing on your skin is going to be decomposing it, ushering in all manner of infection and putridity, so it wouldn't be safe or the least bit attractive either. Lastly, sorry I did laugh. The mental image of mushroom people I conjured up was way too surreal for me not to. 71.226.56.79 15:43, 16 October 2007 (UTC) (This is User:Sifaka who is unable to sign in)

The moon and stars

In what ways are the stars and moon similar? —Preceding unsigned comment added by 24.126.168.23 (talk) 21:59, 15 October 2007 (UTC)

Um, they appear in the night sky? Have you tried looking at our articles on moon and star? I suspect you'll find more that's different than in common, but if you can ask a more specific question we might be able to help better. Confusing Manifestation 22:32, 15 October 2007 (UTC)

They can be used to tell the time of the year, or in lunar calendars the date in the month. Graeme Bartlett 00:34, 16 October 2007 (UTC)

There is really very little that the stars and the moon have UNIQUELY in common - I mean, they are both made out of atoms (well, except for neutron stars) - they are both kinda-sorta more or less round (but so are golf balls and we don't ask about what makes a golf ball similar to a star). Both stars and moon can be seen in the daylight sky (if you have the right equipment) - and technically, there is one star in particular (the one that we call "the sun") that isn't ever visible at night. The moon isn't even always visible at night - about half the time it's only visible in daylight. And what's wrong with planets, asteroids, comets and dust clouds? Those are a lot more similar to the moon than stars are - why aren't they participating in this arbitary listing of objects? It's really hard to come up with any property that's similar between stars and moon that are not also common with almost everything else in the known universe! "star" and "moon" both have four letters? SteveBaker 01:53, 16 October 2007 (UTC)

They're both christmassy!87.102.12.235 17:33, 16 October 2007 (UTC)

Well, think about it this way, stars are formed from nebula dust. A moon is formed when, a large clump forms in the nebula dust surrounding the new star, and as the clump forms, more nebula dust gathers and rotates and around that clump, and you've got a moon. However, The Earth's moon is believed to have formed when a planetoid struck the Earth, ejecting materiel both from it and the Earth, gathering into a ball. Well, I guess you could say they're both made from nebula dust. Well that's our present theory anyway, but it may have a few bugs. For example, if stars are formed from nebula dust, there wouldn't be that much nebula in the galaxy at any one time, so perhaps some of it was made from galactic dust. Well, I con't really give much of an exact answer here. Hope this helps. ~AH1 20:40, 17 October 2007 (UTC)

See also hearts and clovers. —Tamfang 00:38, 21 October 2007 (UTC)

Pulling wire and the 4th dimension

In a house, if you connect 2 electrical boxes together, you can't hang the wire through the air, but you have to pull through the walls. So if I have 2 boxes that are 10m away, I could be dealing with 1, 2, or 3 dimensions.

Image I made, for reference.

A: I have 1 wall and 1 dimension. I have to make perpendicular turns in 0 nonparallel planes. I use a maximum of sqrt1*10m = 10m of wire.

B: I have 2 walls and 2 dimensions. I have to make perpendicular turns in 1 (nonparallel) plane. I use a maximum of sqrt2*10m = 14.1m of wire.

C: I have 3 planes and 3 dimensions. I have to make perpendicular turns in 2 nonparallel planes. I use a maximum of sqrt3*10m = 17.1m of wire.

E: I have 4 planes and 4 dimensions. I have to make perpendicular turns in 3 nonparallel planes. I use a maximum of sqrt4*10m= 20m of wire.

But in 4 dimensions, it appears I can end up exactly where I started, although I have to take the time to whip through the 3 planes. Is this correct; does it show that the 4th dimension is time? HYENASTE 23:31, 15 October 2007 (UTC)

In 4 dimensions you are right, you could run the cable there and back. I don't think this has anything to do with time though! just that sqrt(4) = 2.

Graeme Bartlett 23:51, 15 October 2007 (UTC)

This certainly doesn't prove anything special about 4 dimensions. It's just a numerical coincidence. Do the same thought experiment while thinking about the amount of 2D wallpaper you need to cover all of the walls and ceilings - you'll get a completely different set of coincidences. SteveBaker 01:36, 16 October 2007 (UTC)

Sadly, I am very confused by the question. Edison 04:57, 16 October 2007 (UTC)

Simply put - in four dimensions you don't end up were you started - if you start at (0,0,0,0) you end up at (10,10,10,10) - because dimensions are orthogonal ie at right angles (the fourth dimension the same) - you don't end up doubling back on yourself..87.102.12.235 13:15, 16 October 2007 (UTC)

October 16

Why lengthwise instead of widthwise

But even before the A380 takes to the skies on a commercial basis, Airbus chief operating officer John Leahy is talking of stretching the giant lengthways.

My question is why do they want to stretch it lengthwise instead of widthwise. There is a limit of how long you can stretch it lengthwise but no limit on widthwise. 202.168.50.40 00:26, 16 October 2007 (UTC)

There will be many issues, sich as facilities designed for the planes, such as how wide is the runway, the gate space for the plane. A fatter shape will have more air resistance, more so than a longer one, after all an arrow is long and thin. Graeme Bartlett 00:45, 16 October 2007 (UTC)

In terms of redesign, longer is less effort too - just stick in another section identical to the ones you used before. If you make it wider, the wings have to be further apart - the entire cockpit shape changes - the center fuel tank design would change, tha flare down to the tail would block more airflow over the tailplane. There would be issues with how food service could reach through to the new rows of seats...it would be a 'start from scratch' kind of a thing from an engineering perspective. Making it longer is very little engineering effort by comparison. SteveBaker 01:29, 16 October 2007 (UTC)

Indeed. Lengthwise stretching (for ships as well as aircraft) is simple from an engineering perspective - just keep building the hull a little while longer than normal - but widthwise stretching requires new design, new stesting, new machinery... Shimgray | talk | 17:31, 17 October 2007 (UTC)

...and now I've got the picture of a Limousine stuck in my head... by this one is stretched the other way. It seems like a good example, though. Lengthened vehicles work, but I couldn't fit a double-wide vehicle down my driveway, let alone in my garage. --Mdwyer 02:18, 18 October 2007 (UTC)

Body mass index

Where can I find a correlation between BMI, age and death? In other words do people who have a lower BMI live longer and if so how much longer per lower BMI? Clem 02:18, 16 October 2007 (UTC)

The Framingham Heart Study data are fairly famous. Another recent study: Overweight, obesity, and mortality in a large prospective cohort of persons 50 to 71 years old. --JWSchmidt 04:34, 16 October 2007 (UTC)

Is it the case that, sadly, fat people die young? Edison —Preceding comment was added at 04:55, 16 October 2007 (UTC)

Indeed, haven't you heard the famous saying: "Live Fat, Die Young"...(and leave a good-looking, albeit rather heavy, corpse?) Facts and figures from other studies can be found here, damningly, one study quoted found "the risk of mortality increased with increasing BMI at all ages and for all categories of death." Rockpocket 06:55, 16 October 2007 (UTC)

Is homosexuality a STD

Is homosexuality a sexually transmitted disease? Let me explain what I meant. Assume that there is a unknown STD. Let's called it H. Let assume that people with H shows no symptoms.

Now suppose, a woman contracted H from another person. Then the woman became pregnant. Because of the disease H, the fetus is "deprived" of certain chemicals. When the baby is born, the baby becomes a homosexual person.

So scientifically, how should a scientist prove or disproves this assertion?202.168.50.40 05:29, 16 October 2007 (UTC)

I'm no scientist, but I'd say homosexuality - and heterosexuality, for that matter - are STDs only in the same way that life itself is an STD. Homosexuality isn't a disease at all, ergo it isn't an STD. -- JackofOz 05:40, 16 October 2007 (UTC)

Well hypothetically, a scientist with such an hypothesis could test several things:

1. Are mothers that had many sexual partners more likely to have homosexual children?
2. Are mothers that had one homosexual child more likely to have additional homosexual children?
3. Since the prevelance of H would presumably vary across different populations, one could look for large variations in homosexuality across populations, especially for isolated populations. (Though this could be hard to distinguish from cultural variations.)
4. Look for physiological indicators in mother or child that are associated with homosexuality.

For the record, I think it is quite unlikely that homosexuality is a disease. Dragons flight 05:53, 16 October 2007 (UTC)

I am a scientist and your hypothesis doesn't make a much sense. If that were the case, then twins would always be gay or straight, but never one of each. Moreover, parents who had just one sexual partner would never (or rarely) have gay children. It is possible, I suppose, that some form of STD could result in a uterine environment that, in turn, increased the probability one's child is homosexual, but even that would be tractable by statistical analysis. Sexuality, like most aspects of human behaviour, will not be wholely explained by such simple hypotheses. Its clear that a complex interaction of genes and environment (probably both uterine and post partum) are responsible for defining our sexuality. Rockpocket 06:13, 16 October 2007 (UTC)

(edit conflict) Isn't this a matter of definition, and attitude, rather than scientific discovery or statistical analysis? Homosexuality used to be technically classified as a disease in DSM4; nowadays it's not. The only thing that changed was the attitude of the scientific/psychiatric/medical community to homosexuality and to gay people. Which is why psychiatrists etc who claim to be able to "cure the disease" are in some jurisdictions at risk of being disbarred on the grounds of professional malpractice. -- JackofOz 06:22, 16 October 2007 (UTC)

Incidentally, by the same rationale, its equally likely (i.e. not very) that heterosexual children could be the result of an STD. Homosexual children may be the minority among us, born unaffected by the disease... Rockpocket 06:47, 16 October 2007 (UTC)

Life is a sexually transmitted disease. Cyta 06:57, 16 October 2007 (UTC)

With a 100% mortality rate. Cyta 06:58, 16 October 2007 (UTC)

Hmm .. I think I already made that point.  :) -- JackofOz 07:24, 16 October 2007 (UTC)

Shamelessly cut and paste from the web:

First: If one twin is gay, what's the likelihood of the other being gay?

Well, the most widely used numbers are cited from a 1991 study by Northwestern University psychologist Michael Bailey and psychiatrist Richard Pillard of Boston University School of Medicine in which identical and fraternal twins were studied. At least one twin in each pair was gay. The study found that 52 percent of the identical twins were both gay as opposed to only 22 percent for fraternal twins. In other words, there is a 52 percent chance that if one identical twin is gay, both are; and a 22 percent chance both fraternal twins are gay if one is gay.

so if STD H is the cause of homosexuality then we would expect both twins to be gay all the time 211.28.130.81 08:36, 16 October 2007 (UTC)

How many people were investigated in this study. I'd be happy to say that 52% of the identical twins would have the same sexual preference, but if the test subject population is small, drawing any conclusion as to what that preference is would be dangerous. Also, how was homosexual defined by the researchers? - Mgm| 09:22, 16 October 2007 (UTC)

The same findings tend to come out of similar studies. See the discussion at Misplaced Pages:Reference_desk/Science#Gay twin, up there ↑ Rockpocket 16:59, 16 October 2007 (UTC)

"we would expect both twins to be gay all the time" <-- Why? For many genetically-influenced traits there is low penetrance and for many infectious agents there is low infectivity and variability in the course of the infection. --JWSchmidt 14:05, 16 October 2007 (UTC)

Because the OP made the claim that this hypothetical STD would cause homosexuality due to a change in the womb environment. Your suggestion (which is more likely) would be a situation where a STD would increase the probability of having a homosexual child. The difference is key, I think, in attributing "cause" to the development of such characteristics. Rockpocket 16:55, 16 October 2007 (UTC)

photon momentum and mirror .

A mirror is a device that change the momentum of incident photons; but it's own momentum remain unchanged , how is this possible ? —Preceding unsigned comment added by Shamiul (talk • contribs) 06:07, 16 October 2007 (UTC)

False assumption. Momentum is conserved, and the mirror's momentum must change (or at least transfer that impulse to another body), but the magnitude of this change is generally imperceptibly small, just as the momentum of photons is nearly imperceptible in most situations. Dragons flight 06:17, 16 October 2007 (UTC)

In fact, the change of momentum of a mirror struck by photons is how Nichols radiometers and solar sails work. --Spoon! 06:56, 16 October 2007 (UTC)

How non-charged particles are accelerated in particle accelerator .

Charged particles like electron,proton may be accelerated using voltage difference . How non-charged particles like neutrinos or neutron are accelerated in particle accelerator ? —Preceding unsigned comment added by Shamiul (talk • contribs) 06:49, 16 October 2007 (UTC)

They are normally not accelerated. They come from something that already has a source of energy, they may be decay products of an accelerated charged particle, or taken from a nuclear reactor where they are already emitted with some energy, and you just select those in a particular direction. This is tricky, hence why particle accelerators use charged particles. Neutron/neutrin experiments are not normally considered particle accelerators. Maybe see Neutron source and Neutrino#Neutrino_sources. Cyta 07:03, 16 October 2007 (UTC)

An analogy for the fuel cell?

Having read and re-read the entry on the Fuel cell and studied the diagram, I'm still searching for a way to explain - using a widely understandable analogy - how a hydrogen fuel cell works (in a hydrogen car, for example). I need to reduce its function to an explanation that doesn't feature a set of terms that would also require explanation, such as anode, cathode etc. Naturally this is for a lay audience. My problem is that I don't have a background in science and really am only learning about much of this myself.

Any suggestions? Wolfgangus 08:04, 16 October 2007 (UTC)

http://simple.wikipedia.org/Hydrogen says "A fuel cell combines Hydrogen thru a catalyst with an Oxygen molecule releasing an electron as electricity." And http://simple.wikipedia.org/Catalyst says "A catalyst is something that makes a chemical reaction go faster." But I suppose you want more than that. Alas there is no fuel cell article there - hopefully, answers here will lead to one. DirkvdM 08:17, 16 October 2007 (UTC)

Wow, I didn't know that wiki existed. It's like wikipedia for idiots. 64.236.121.129 13:10, 16 October 2007 (UTC)

Alright, here's an attempt.

Water is a molecule that consists of one oxygen atom and two hydrogen atoms. It takes energy to split the two and when they are recombined energy is released. A fuel cell does the latter. Hydrogen (the energy source) and oxygen (which can come in the form of plain air) are fed into it, separated by a membrane that will only let positively charged hydrogen (H+) through to the oxygen (O). At the hydrogen side, a platinum plate helps the electrons of the hydrogen atoms to split off. The now positively charged hydrogen atoms pass through the membrane, while the electrons enter an electric circuit. This produces the electricity required. At the other end of the electrical circuit, it connects to the oxygen side, where the electrons then combine with the positively charged hydrogen and the oxygen to form water (which then comes out the exhaust pipe). These three (H+, O and electrons) 'want' to combine and thus 'pull' the electrons through the electric circuit, thus creating the desired energy.

I'm not sure if that is all strictly correct - I just now learned the workings of a fuel cell through the diagram. But I think it's roughly correct. Is this more like what you were looking for? DirkvdM 08:35, 16 October 2007 (UTC)

Oh, sorry, you were asking for an analogy. I should read questions a bit more carefully in the future. DirkvdM 08:41, 16 October 2007 (UTC)

Actually, DirkvdM, while yes, I was seeking an analogy, I might be able to make one from your explanation - specifically from your word choice, "want". That word might give the process just enough character for me to build on. So I do appreciate your help. Wolfgangus 15:12, 16 October 2007 (UTC)

I don't think there is a suitable analogy - however the hydrogen/oxygen fuel cell is electrolysis of water in reverse - (which is a school topic) - you should be able to find lots of resources on electrolysis of water.. explain that.. then say "the fuel cell instead of using H20 and energy to make O and H uses O and H to make H2O and energy !" ...87.102.12.235 15:43, 16 October 2007 (UTC)

Beta decay .

Beta decay is a phenomenon where a neutron in an unstable atomic nucleus is converted to proton releasing energy(gamma ray) . After beta-decay process is completed the atomic neuclious contain one more proton which should make the atomic nucleus more unstable because protons in an atom repeal each-other , but neutrons in a nucleus do not repeal each-other . So is'nt a neuclious much stable before beta-decay rather than after beta-decay . Please supply me detailed explanation of this confusing topic ; you are wellcome to write down interactive and interesting web address containing this topic . Thank you all . —Preceding unsigned comment added by Shamiul (talk • contribs) 08:55, 16 October 2007 (UTC)

You could start with the semi-empirical mass formula. Icek 10:18, 16 October 2007 (UTC)

I'm not an expert, but I'll try to give you some info. Have a look at the nuclear force which is a force acting at the subatomic level which binds neutrons and protons. From that article "At short distances, the nuclear force is stronger than the Coulomb force; it can overcome the Coulomb repulsion of protons inside the nucleus." Nucleons have energy levels within the nucleus which can be approximately predicted using the Shell model. Just as atoms favor certain electron orbital configurations, nuclei favor certain "nuclear" orbital configurations. Adding a proton might stabilize a nucleus by filling up a "nuclear orbital." You might also be interested in magic numbers, certain numbers of protons an neutrons that tend to stabilize a nucleus greatly. Sifaka 04:20, 17 October 2007 (UTC)

TV animals

Have there been studies on the influence on animal behaviour of watching TV (apes, cats dogs,.)? When offered the opportunity, are apes interested in TV at all? Keria 09:12, 16 October 2007 (UTC)

I've seen many reports of non-human apes watching TV, for example Hiasl. Some dogs and cats can notice things on TV, but not all. A published study with chimps. --JWSchmidt 14:29, 16 October 2007 (UTC)

I did an externship at a pharmaceutical lab when I was in school, and part of the required "enrichment time" for the macaques was TV time. The monkeys seemed to have a preference for cartoons, and they would all sit at the front of their cages watching. The only thing that fascinated them more was the occasional escape. --Joelmills 14:55, 16 October 2007 (UTC)

You didn't let them watch MacGuyver, did you?! --Mdwyer 20:30, 16 October 2007 (UTC)

My dogs certainly notice things on TV. But it's never the pictures - firstly, their eyesight isn't that good - and secondly there is a strong possibility that the colours of TV don't look right to dogs (who can see some colour - contrary to urban legend). They definitely hear the sounds of other dogs though - and they'll sometimes prick up their ears and turn to look in that direction when they hear dog barks or (especially) the whining of a dog or puppy in distress. If I play a home movie, they'll prick up their ears and get VERY excited if they hear voices they recognise or each other's barks coming from the TV.

However, the lack of appropriate smell cues coming from the TV seems to tell them that this is just some weird irrelevence because they rapidly lose interest and ignore subsequent dog noises coming from the TV. Even the sound the TV produces doesn't have the high 'ultrasound' frequencies that dogs can hear (Dogs can hear up to 45kHz - a typical TV set only manages around 15kHz) - so it must sound severely muffled to them.

There is a pattern here. Dogs live in a world primarily perceived through smell, secondarily through sound and only lastly through sight. For them, TV's are pretty hopeless contraptions! No smell, really low quality audio and (possibly) very unrealistic colours. It's not surprising they aren't interested in watching. SteveBaker 22:14, 16 October 2007 (UTC)

Another problem may very well be the lack of 3D information. Remember that dogs, cats and other hunters have stereoscopic vision. There is AFAIK some evidence that even humans can't always initially recognise what's being represented on a TV (I believe some African tribes don't recognise 2D representations of 3D objects although I think this was more related to drawings then pictures but I would suspect the same thing applies). The fact that most animals often show at least initial interest in themselves in the mirror but nothing on the TV even a camera-mirror like setup I think suggests to me this may at least partially be the reason. It would be interesting to know if anyone has ever tested animals with 3D monitors that don't require any sort of glasses. Nil Einne 16:28, 18 October 2007 (UTC)

Declining caffein

Someone told me that the content of caffein decreased if you left tea to brew for too long. Is there any truth in this? Keria 09:14, 16 October 2007 (UTC)

• I think leaving tea to brew for too long would release more tannin which means a lower percentage would be caffein. I'm not sure if caffein degrades if left for too long. The molecule seems pretty sturdy. - Mgm| 09:19, 16 October 2007 (UTC)

• If you leave it brewing too long, the tea tastes terrible. Which means you get less caffiene, as you won't drink it! -- Kesh 23:43, 16 October 2007 (UTC)

Hydrogen sulfide oxidizing enzyme

Which human enzyme catalyzes the oxidation of hydrogen sulfide (the Misplaced Pages article says that there are enzymes doing that)? I cannot find it at OMIM. Icek 09:54, 16 October 2007 (UTC)

A starting point in the research literature. --JWSchmidt 14:48, 16 October 2007 (UTC)

kinetic energy of ideal monatomic gas

I get PV=4/3 E_kinetic (or 3PV/4=E_kinetic) , but the ideal gas page gives the internal energy as 3PV/2.

1.Is PV=4/3 E_kinetic correct

2.If so what's the the extra 3PV/4 in the internal energy of a monatomic gas ( 3PV/2_Internal-3PV/4_kinetic = 3PV/4_extra )

3.If (1.) is wrong - Help!87.102.12.235 13:23, 16 October 2007 (UTC)

Let's just say I spotted my mistake - to those that would have helped - a speculative thanks

And a rhetorical 'You are welcome' to you too. (Actually I couldn't have helped, but lets ignore that fact :P ) Lanfear's Bane 13:47, 16 October 2007 (UTC)

Effect of human population growth on global warming

Hi all,

I have been to the climate change and global warming section of wiki. I didn't see anything about the effect of human population growth on global warming. E.g. more humans = more humans breathing out CO2 = increase in one of the greenhouse gases. Is this contribution by humans so insignificant that it does not warrant a mention?

Also, what about the effect of billions of 36.6 oC people on this planet? Surely all those lovely warm bodies exuding heat should heat up the air around us over time?

Can anyone justify why this is so... or add something regarding this on one of these pages? I have looked on the internet and the only reference I found was way too full of jargon for me to make head or tail of it.

ChantalME 13:32, 16 October 2007 (UTC)

Maybe the amount of carbon dioxide a person breathes out is negligable compared to the amount of carbon dioxide pumped out by transport and powerstations and animal farms to supply the "needs" of that same person. I personally agree that increasing human population increases global warming, but this comes mostly from the actions/consumption of that person, more than their breathing/body heat. --Seans Potato Business 14:20, 16 October 2007 (UTC)

Exactly. Expired CO₂ through respiration or body heat is nothing compared to the amount of greenhouse gases or heat produced for energy and food purposes. --24.147.86.187 16:31, 16 October 2007 (UTC)

As Sean says, it is the knock-on effects of a growing population that significantly influences global warming, rather than the people themselves. For example, more people need more space to live, leading to deforestation. Also, more people need more food. More food mean more crops and livestock. Have a read of Livestock's Long Shadow to understand the effect of that on global warming. Rockpocket 16:47, 16 October 2007 (UTC)

Living creatures have no net effect on the amount of CO2 in the atmosphere. For every molecule of CO2 breathed out by a human or other animal, there is a food plant somewhere that will take that molecule and turn it into sugar and oxygen. --Carnildo 21:41, 16 October 2007 (UTC)

Sorry - but all of the previous respondants (except Carnildo who beat me to it with an edit conflict) have utterly missed the point. (They aren't wrong - they just missed the crucial thing!)

The CO2 you breathe out comes from the breakdown of carbon compounds in your body. The carbon in your body came from the food you've been eating. The carbon in the food either came from a plant - or from the meat or milk or eggs of something that ate a plant (or something that ate something that ate....a plant). So all of that carbon basically came from plants. How did the plant get the carbon? Well, it absorbed it as CO2 through its leaves and used photosynthesis to turn it into sugars and starches. So - in the grand scheme of things, humans (and all other animals) are 'carbon-neutral'. By eating big plants and replacing them with little ones - we're effectively removing CO2 from the air - then cycling it through this big chemistry set and pushing the exact same amount of CO2 out again. Every single microgram of CO2 that every single human produces was fairly recently sucked out of the air by a plant somewhere. The more of us there are, the more plants we eat - the more small plants are growing into big plants and consuming CO2. Everything balances (well...almost...see the bit at the end).

The difference with cars and coal fired power stations and other problematic things is that we fuel them by digging up coal and oil that's been locked away for millions of years. Since the coal and oil isn't being replaced at anything like the rate we're digging it up, we're putting CO2 into the atmosphere WITHOUT locking a corresponding amount away again. A wood-burning power plant - based on renewable/sustainable forestry techniques - or a car that ran on ethanol made from saw-grass that could be grown sustainably - would be no problem at all for global warming.

There is a teeny-tiny caveat that messes up an otherwise beautiful picture. There is no nice way to say this...the problem is: farting. The deal is that some of the carbon we ingest turns into methane - which we fart out. Methane is a much nastier greenhouse gas than CO2. So a very, very tiny percentage of the CO2 that we (indirectly) consume gets turned into a nastier form than CO2 by the time we're done with it. Having said that, there is little or no evidence that the tiny amounts involved are in any way a problem for the planet. However, one big concern for global warming is our farming of cows. Cows fart a LOT more than we do - and we humans have dramatically increased the number of cows in the world. Cow farts are a serious part of global warming - and there are (believe it or not) bunches of scientists out there wondering whether we can genetically engineer cows that don't fart as much - and a bunch of technologists wondering whether we can capture the methane that cows produce and use it to generate electricity - and in the process, turn it back into CO2 so that the grand cycle of CO2-plant-cow-fart-methane-CO2 can be completed.

SteveBaker 21:43, 16 October 2007 (UTC)

Indeed, Steve. You will notice I previously mentioned the effect of livestock on global warming and, hence, did not "utterly miss the point". Rockpocket 01:16, 17 October 2007 (UTC)

The critical point you missed (and to directly answer the OP's question) was to explaining that the human metabolism is carbon-neutral. SteveBaker 14:33, 17 October 2007 (UTC)

As I mentioned in an earlier questions, cow methane farts aren't actually the big problem. They primarily burp it. See Burping, Methanogenesis and Cattle Nil Einne 16:18, 18 October 2007 (UTC)

Don't forget to plug our article on the carbon cycle. TenOfAllTrades(talk) 01:57, 17 October 2007 (UTC)

The question reminds me of the one that goes something like, "How much lighter would the Earth be if humans hadn`t evolved?" lol Dave 64.230.233.222 02:04, 17 October 2007 (UTC)

The problem isn't that the scenarios aren't plausible, the problem is that they are very difficult to quantify. The carbon cycle is dominated by forces much larger than anthropogenic contributions so the effect of man on CO2 is a very small forcing function that acts over decades. Since 1750 the net effect of all the oil we burned and methane we've releases is 1.6 Watts/square metere (IPCC) being retained on the surface. This is slightly more than the 1.3 W/square metre variation in the 11 year sunspot cycle and a small fraction of the 1366 W/sq metre from the sun. Sunspots and global warming are not related, but the order of magnitude is good for comparison of the type of measurement we are trying to make. It is very difficult to extract a forcing effect from such a small effect and predict it's long term behaviour with accuracy especially when our accurate temperature record is so short compared to the multitude of natural cycles of varying duration. We also don't really know how components of the carbon cycle will react to man-made CO2 entering the system with rising temperatures. The ocean and rain forest are complicated and dynamic systems. --DHeyward 07:08, 17 October 2007 (UTC)

Well, one effect is that CO2 is absorbed by the oceans. As a result they become acidic. Notice that this is not future tense - the oceans have already absorbed a large part of the CO2. If they hadn't, the global warming would have been considerably bigger. So so far they've been buying us some time. But they can only absorb a certain amount of CO2, one factor for which is the temperature. So, as the oceans warm up, they can not hold as much CO2 (I think - not entirely sure if I remember this correctly). So somewhere in the future (some of) that CO2 will get released again. So even if we would completely stop pouring still more CO2 into the atmosphere, the concentration is likely to still increase. DirkvdM 06:19, 18 October 2007 (UTC)

What are super metals?

—Preceding unsigned comment added by Safeer 123 (talk • contribs) 14:23, 16 October 2007 (UTC)

Really, really good ones. A metal is a metal is a metal, super is just an adjective. The only references I can find to supermetals (all one word) are proper nouns (company names), in reference to music (super metal), ficticious (Lodestar) or hyperbole (this cheese-fibre biscuit-reinforced steel is supermetal!). Lanfear's Bane 15:00, 16 October 2007 (UTC)

Maybe he is thinking about supersolids? 71.226.56.79 15:51, 16 October 2007 (UTC)

Sometimes titanium is considered to be a super metal...87.102.12.235 15:56, 16 October 2007 (UTC)

Also http://www.future.org.au/news_2006/march/building.html apparently 'bulk glassy alloys' are called supermetals..87.102.12.235 15:58, 16 October 2007 (UTC)

See Amorphous metal this is as near to my guess at your answer87.102.12.235 16:01, 16 October 2007 (UTC)

Supermetals usually refer to metals that excel in one or more particular properties. I've usually heard "superalloys" in the context of the metals from which gas turbine and jet engine turbine blades are fabricated.

Atlant 12:23, 17 October 2007 (UTC)

gas ideal - entropy

Another problem

For a gas (in a piston or something) (ideal monatomic) - at constant temperature - in contact with an infinite resovoir at the same temperature..

If I compress the gas slowly to half it's volume so that it is able to equilibriate with the resevoir then then work done is

(1.) Work(gas) = PVln2 (please comment if wrong)

(P=Pressure, V=Volume, N=number of molecules/atoms , n=number of moles)

And the entropy change (of the gas in the piston) is

(2.) ΔS = -Nk ln2 (since the volume has halved and assuming the number of ways to arrange the gas molecules is proportional to V therfor Ways_after / Ways_before = (V/2)/V = 0.5 and ΔS =k ln Ways_after/Ways_before = k ln 0.5 = kN ln 0.5 = -Nk ln2

(please comment if wrong)

(The entropy change of the resevoir will be infinitely increase - since it is of infinte size and gets some energy)

Assuming I got 1. and 2. right

TΔS_piston = NkT ln2

and N=Ln (L=avogadros constant and n=moles) so

TΔS_piston= nLkT ln2

and kT=R (the gas constant)

TΔS_piston= nLkT ln2 = nRT ln2

I also have Work(gas) = PVln2 (from 1.)

Which means that the TΔS of the piston gas is equivalent to the work that was done - my question is is this supposed to be significant? or is it coincicidence - or is it a definition (in part) of boltzmann entropy?87.102.12.235 14:28, 16 October 2007 (UTC)

Generically, for a reversible isothermal processes, heat flow (Q) = work (W) = TΔS. Dragons flight 22:32, 16 October 2007 (UTC)

The problem is that I get ΔS = ΔEk ln N for the entropy change of a ideal gas increasing in energy by ΔE (with N atoms) - using S=k ln W2/W1 - but this doesn't fit as well with the ΔE=-TΔS formulation - how can I go about reconsiling these two?87.102.12.235 14:38, 16 October 2007 (UTC)

I don't understand what you are trying to say here. Dragons flight 22:32, 16 October 2007 (UTC)

Probably not clear - what I'm asking is more obvious in a question below - I'm trying to use theorectical statistical entropies (ie from non experimental mathematical models) in the thermodynamic definition of entropy - one of the pages states that the two have been shown to be equivalent (using boltzmanns relationship S=k ln W) - but when I try this I only get equivalence on certain cases.. The example of changing the volume of a ideal gas (at constant T) works well. But other cases such as the when the temperature change show no match at all... The equation "ΔS = ΔEk ln N" was statistically obtained - I've clarified my question below relating to the integral S_TdT and whether or not it makes sense to use it..87.102.12.215 14:08, 17 October 2007 (UTC)

require information on CoMFA (Comparative Molecular Field Analysis)

please send the information about CoMFA —Preceding unsigned comment added by Satyaprasad2007 (talk • contribs) 15:18, 16 October 2007 (UTC)

What do you need exactly - that a web search doesn't find? eg http://ww.google.co.uk/search?hl=en&q=CoMFA&meta= ?87.102.12.235 15:23, 16 October 2007 (UTC)

two bodies - different temperatures

If I have two bodies A and B at two different temperatures T_a T_b that are isolated or insulated from everything else.. and then I join them so that they eventually attain the same temperature..

1.What 'measure of energy' should I be using for this process - is it G (gibbs energy)

and

2.What ways are known to calculated the entropy change for the temperature equilibriation process? (assume if you want that it's a very simple system if that help)?87.102.12.235 15:53, 16 October 2007 (UTC)

Can't you just measure the temperatures? Isn't temperature a measure of heat energy? You would just need to know their specific heat values? Don't worry, the real scientists will be with you in a short while :) --Seans Potato Business 16:15, 16 October 2007 (UTC)

What do you know about the system? Do you know the masses? What else? Or are you looking for some sort of general equation? (I struggle with thermodynamics, but I'm sure there'll be others...) Skittle 16:32, 16 October 2007 (UTC)

It's sort of irrelevent to the question but you can assume that the heat capacities are the same and there is the same amount of both... Couldn't you both have not answered? (smiles horribly...)87.102.12.235 17:08, 16 October 2007 (UTC)

I was trying to make sure your answer was sufficiently clear that it could be quickly, thoroughly answered by the first person who could, hopefully getting you your answer quicker. After all, you'd be annoyed if someone who could have answered gave you the answer to a different question to what you had intended, then went offline leaving you waiting hours longer than necessary. Skittle 21:03, 16 October 2007 (UTC)

Assuming no mechanical work is going to be done on the system, you would look at the internal energy, U and find the temperature T such that Ua(Ta) + Ub(Tb) = Ua(T) + Ub(T), where Ua and Ub are internal energy functions for A and B respectively. For simple gases, you often have things like U = 3/2*N*k*T where N is the number of particles, and k is Boltzmann's constant, but for arbitrary materials U can be a more complicated function.

(Good so far thanks 87.102.12.235 18:41, 16 October 2007 (UTC))

The change in entropy calculation is discussed in Entropy (classical thermodynamics). In the simplest case, e.g. equal masses of the same material with constant heat capacity, C, then T = (Ta + Tb)/2 and

${\displaystyle \Delta S=\int _{T_{a}}^{(T_{a}+T_{b})/2}{{C \over T}dT}+\int _{T_{b}}^{(T_{a}+T_{b})/2}{{C \over T}dT}}$

${\displaystyle =C*(Ln({(T_{a}+T_{b})^{2} \over {T_{a}T_{b}}})-2Ln(2))}$

Dragons flight 18:20, 16 October 2007 (UTC)

What about the common formula ΔG=ΔH-TΔS can I use that here in the form ΔG=ΔH-ʃS_TdT ( ΔH=0 ? ) to calculate if ΔG is negative (and hence if the process occurs)

I was really thinking about a theoretical treatment so I'd be using a derived estimate for S (or maybe C) at a given temperature.87.102.12.235 18:29, 16 October 2007 (UTC)

Specifically if I have an equation for S at a given temperature is ΔG=ΔH-ʃS_TdT workable (and if it is wrong please explain why.. thanks) 87.102.12.235 18:41, 16 October 2007 (UTC)

In the above example if T1=T2 then the entropy change is zero - but if the masses are initially separated (thermally) and then allowed to exchange energy (even though T remains the same) by removal of the thermal barrier this causes an increase in entropy (statistically - and possibly depending on your point of view..) (this can be considered like a sort of phase change - depending on your point of view) How does classius's definition of entropy deal with phase changes of the example I gave above in general?87.102.66.248 21:09, 16 October 2007 (UTC)

NOTE: I think I've resolved this - if I make atoms distinguishable but energy indistinguishable as particles then boltzmanns S=k lnW is ok - otherwise not. Anyway if anyone can answer my bolded question above I'd still appreciate it, and if anyoen can tell me more or help out I'd still appreciate that too.87.102.12.215 15:21, 17 October 2007 (UTC)

24 hr urine - checking that we got a full sample

Apparently from creatinine clearance, we can infer whether or not the full 24 hr urine was collected. You can take the concentration of creatine in the blood, the amount in the urine, and divide the amount by the concentration, to determine the GFR necessary to provide this amount in the urine, assuming 100% transfer from glomerulus to urine. Now sure, if you know for a fact that there is nothing wrong with the kidney, an apparently low GFR, could simply be due to a reduced amount of creatinine in urine, directly resulting from the patient not voiding into their container D:< but how is it possible to tell from this test alone, that it is infact, not due to an abnormally low GFR? This whole test seems kinda useless to me, if an actual low GFR could be written off as a failure to collect the full 24 hrs worth of urine. --Seans Potato Business 16:11, 16 October 2007 (UTC)

I haven't thought through this extensively, but it's commonly understood (at least at the hospital I'm training at) that 24-hour urine collections are fraught with errors, including the one you mention. In practice, GFR isn't measured using creatinine clearance; instead, the steady-state plasma concentration of creatinine (along with age, gender, etc.) is plugged into something like the MDRD equation (no page!?). Similar approximations are used in the measurement of urinary protein to avoid having to collect a 24-hour urine sample. In that case, a spot urine test is done and the ratio of urinary protein to urinary creatinine is taken to approximate urinary protein (in grams) per 24 hour period. The point is exactly what you've realized: the utility of the 24-hour urine sample in determining GFR (and other values) is waning. --David Iberri (talk) 21:02, 16 October 2007 (UTC)

Tongue

Is a healthy human tongue supposed to be completely smooth, or would you expect to find bumps towards the back of the tongue? If not, what do the bumps mean? 172.206.176.138 16:21, 16 October 2007 (UTC)

If you're asking for advice about your own health, you should be warned that there's a very good reason why we say "Do not ask for medical advice" (or used to, until we had to make it broader). Anyone with sufficient medical training to give you a good answer to this question will not do so, because they know it would be unethical and dangerous (for example, they can't see or feel what you mean by 'bumps', nor can they see your medical history or examine anything else about you). The only people who will attempt to give you an answer as to what the bumps mean will not be trained or qualified to do so, as well as having all the problems a doctor would have in this situation. So they will offer even worse advice than the doctor would have thought was dangerous and unethical! If this is about yourself, or someone you know, get to a real, physical doctor and show them what you mean :) That's the only way you'll get a reliable answer. Skittle 16:28, 16 October 2007 (UTC)

I'm a biology student and this is part of an assignment of mine. I've tried looking around the web, but as yet I've found nothing written in a level of English that I can understand and so Misplaced Pages now seems like my best option. 172.206.176.138 16:40, 16 October 2007 (UTC)

Notwithstanding what Skittle said, a human tongue is typically not smooth. There are four types of papillae on the human tongue: foliate, filiform, fungiform and, towards the back, circumvallate papillae. Rockpocket 16:40, 16 October 2007 (UTC)

However, when the tongue is infected, (not a common occurence), the condition is called glossitis and is characterised by a smoother than normal tongue. Richard Avery 17:34, 16 October 2007 (UTC)

As purely anecdotal evidence, I have had bumps on the back of my tongue for as long as I can remember, in exactly the way described in circumvallate papillae. --24.147.86.187 18:02, 16 October 2007 (UTC)

Lack of oxygen and sleepiness

Today I had a meeting in a room with "bad air" (no circulation) and we all got very tired and sleepy. However, usual recommendations for a good night's sleep is that the sleeping room is well aired. Wouldn't it be easier for sleepless people to fall asleep in a room that is badly aired? Lova Falk 17:24, 16 October 2007 (UTC)

I imagine it would be easier to fall unconscious, but that doesn't necessarily mean restful sleep. You might get some enlightenment from the article on sleep apnea. --Mdwyer 20:28, 16 October 2007 (UTC)

Not to mention Carbon dioxide. It's unlikely to build up too quickly, but poor circulation can't help. -- Kesh 23:44, 16 October 2007 (UTC)

Technically I think it would be easier to fall asleep in a "badly aired" room. However, I think the point of the advice you cited is not to help people fall asleep, but to make sure nothing happens to them while they are sleeping. You can add a good amount of carbon monoxide to a room, go lay down, and you'll fall asleep within no time, but you also won't wake up.
Mrdeath5493 04:41, 17 October 2007 (UTC)

As Kesh said, carbon dioxide is probably the key, but the general heating of the room and boredom probably provides the rest of the explanation. Next time, may I suggest buzzword bingo as a remedy? Or clandestinely edit Misplaced Pages...

Atlant 12:26, 17 October 2007 (UTC)

:) Thanks! Lova Falk 11:31, 18 October 2007 (UTC)

LASIK

"LASIK" stands for "Laser-assisted in situ keratomileusis". Since they feel it neccessary to mention that the process is in situ, this implies that there is a process where they don't work on your eye in place -- that they pop the eyeball out, reshape the lens, and put it back in. What's this process? --67.185.172.158 18:59, 16 October 2007 (UTC)

Um, just because they point out that they are doing something doesn't mean that the converse exists. Especially when you are talking about a name that happens to make a cool-sounding acronym. In any case, see keratomileusis for discussions of how it was done before lasers. --24.147.86.187 19:44, 16 October 2007 (UTC)

medicine online

Is there any serious university in the US or UK offer medicine online? At least the first two years. —Preceding unsigned comment added by 88.0.101.106 (talk) 19:28, 16 October 2007 (UTC)

Not to my knowledge. What would be the purpose of providing two years of medical school online? Generally speaking, the medical profession is not keen on the idea of many people becoming only half-versed in medicine. Entering medical students are generally warned to not provide medical advice until after completing their degree. The patient experience gained in the clinical years (third and fourth years of a four-year M.D. degree) are crucial. Andrewjuren(talk) 22:03, 16 October 2007 (UTC)

• A study in medicine is also pretty useless if you don't have any practical experience in a laboratory or with patients. - Mgm| 08:52, 17 October 2007 (UTC)

I just thought that I could do online the two years until the usmed step 1 and then go to the practical experience...Actually there are some 'schools' offering online programs, but they are clearly not serious. —Preceding unsigned comment added by 88.0.101.106 (talk) 12:18, 17 October 2007 (UTC)

How to minimise my exposure to halogens in my food and water?

I no longer wish to be subjected to forced halogenation by government agencies against my individual will. How can I remove all fluourine and chlorine compounds from my water supply and the iodine from my salt, leaving only the untainted product behind? —Preceding unsigned comment added by 62.136.234.82 (talk) 21:44, 16 October 2007 (UTC)

If you can, you could dig a well for your water, it'd probably be easier to just go to the source rather than try to remove fluorine and chlorine. You'll find that Kosher salt is iodine free. -- JSBillings 22:42, 16 October 2007 (UTC)

Buy your water from a difference source, or buy expensive filtering systems that can remove it. The former is probably cheaper than the latter, especially if you are only talking about drinking water. As for salt, simply don't purchase iodized salt—there are lots of non-iodized varieties out there (i.e. sea salt or kosher salt) and purchasing them is surely easier and less expensive than trying to remove the iodine from the salt. Note that I think being paranoid about these sorts of public health measures is a bit silly, but hey, it's your choice, right? --24.147.86.187 22:35, 16 October 2007 (UTC)

Nethertheless you needs chloride and iodine in your diet to survive. Don't try to reduce these to zero. Well water will almost certainly contain chloride, and some fluoride dissolved from the rocks. Graeme Bartlett 23:25, 16 October 2007 (UTC)

Don't worry, if he ever eats out of the house he'd bound to pick up enough. There's a futility to trying to remove things like iodized salt from your diet when almost all salt you consume outside the house is probably going to be iodized anyway. --24.147.86.187 01:02, 17 October 2007 (UTC)

Don't go near the seashore. There are a lot of aerosols that come off the water. There's bound to be iodine in them. And I would guess a few naturally produced chlorinated organics as well. Delmlsfan 02:44, 17 October 2007 (UTC)

Firstly, well water is highly fluorinated. Secondly, avoiding iodine is not a good idea. The reason iodine comes in salt is because long ago iodine deficiency was common; This caused public health issues such as goiters and cretinism. About removing chlorine... That doesn't make sense. Chlorine is one of two atoms that combine to make table salt. So if you buy Kosher salt to avoid iodine (which is stupid in and of itself) then you'll still be ingesting chloride from the salt. My thoughts: Judging by the content and tone of your question, I believe you have a niacin deficiency.
Mrdeath5493 04:37, 17 October 2007 (UTC)

I think the poster was saying that they wanted food products without having any additives - I assume your description of a niacin defficiency was intended as a joke. Mostly though you were a little insulting - what vitamin deficiency to you attribute to that?87.102.12.215 14:24, 17 October 2007 (UTC)

You could always launch an air strike on Russia. Confusing Manifestation 06:43, 17 October 2007 (UTC)

(Assuming you're cocerned about halomethanes and the like,) would an air stripper do the trick? Are they available for home use?

Atlant 12:28, 17 October 2007 (UTC)

In my experience, most table salt in the UK (which is where the OP appears to come from), is not iodized (some shops like Lidl sell iodized salt as default, but this is because it is the same salt they sell in Germany, where it has to be iodized). I would suspect that sea salt would contain significant amounts of iodine, as well as various other impurities (sewage, dead fish, etc) which are not present in the purified rock salt usually sold for table use. However, as the OP wishes to avoid chlorine compounds, then he will not be using any salt at all, and will die a slow and painful death as a result of electrolyte depletion. Water filters aren't that expenxive nowadays (I use one, because the water in Brighton tastes foul, and cannot be used to make a decent cup of tea). OP cold move to an area without fluoridated water if a filter would not be practicable. DuncanHill 12:37, 17 October 2007 (UTC)

In the US, restaurant salt is typically not iodized (because some people have mdeical iodine restrictions), and everywhere sea salt actually contains much less iodine than iodized table salt. Seafood has lots of iodine, but the salt doesn't. --Tardis 19:58, 17 October 2007 (UTC)

If tap water has lots of chlorine, it helps to pour some to a glass or bottle, and wait while it bubbles out. I, however, have only seen water chlorinated in such an amount right after a breakage of water pipes, when they need to fertilize the pipes. – b_jonas 20:33, 18 October 2007 (UTC)

Radio Transmissions and Camera Transmissions

This question relates to the other question previously posted. Is it difficult to get a closed circuit camera signals if it were in a cave or sewer or underground? Would there be a way to boost those signals or does the ground and other interferences cut off the signal? —Preceding unsigned comment added by 67.121.107.157 (talk) 21:49, 16 October 2007 (UTC)

The closed-circuit television system itself is irrelevant to the question. If you have a wire-based transmission (which is the case for most CCTV installations), then the environment is of little consequence. If wireless, then yes, transmission is impeded to various degrees. A more powerful transmitter and a higher-gain antenna are two means of boosting wireless reception. The broadcast frequency is also a significant factor. — Lomn 22:56, 16 October 2007 (UTC)

So, if it is wireless and you boost wireless reception and a more powerful transmitter and a higher gain antenna then it is possible to still get transmissions if it were underground and the receiving end was above ground or down in a sewer, there would still be a way to receive signals? —Preceding unsigned comment added by 67.121.107.157 (talk) 23:23, 16 October 2007 (UTC)

Maybe. There are too many variables to give a definitive answer (e.g. how deep, what material, what transmitter, what antenna...). For instance, FM radio tends to do fine through basic road tunnels and steep valleys and such whereas AM radio doesn't, with the only distinction being frequency. — Lomn 04:14, 17 October 2007 (UTC)

What makes FM car radio work better than AM in tunnels and such is not the frequency but the method of modulation. In AM, the whole carrier is modulated, and in FM, the carrier's frequency is modulated. This means that in AM the strength of the signal available to the audio amplifier in your radio falls off with the strength of the radio wave at the antenna and will get down into the noise pretty quickly. In FM, the audio is more or less encoded in a frequency shift, so that practically any signal at all at the antenna will deliver full audio. This is a simplified version of what really happens, to be sure, but close enough for jazz.

As for underground radio, it seems to me that it can't be done. The ground is, well, ground, and radio waves are produced with respect to ground. There is a ground wave that will run along the surface to an extent, more with lower frequencies, so that if you want to send and receive from inside a cave to a spot at the cave's entrance, you might get something by using a strong low-frequency transmitter at each end.

If you really want to go nuts with it, try ELF. --Milkbreath 13:00, 17 October 2007 (UTC)

Hornworms

Do Hornworms develop under water? —Preceding unsigned comment added by 75.44.152.111 (talk) 22:40, 16 October 2007 (UTC)

It would not appear so. Hornworm. Someguy1221 03:25, 17 October 2007 (UTC)

October 17

silver + potassium nitrate

what happens when i add silver to a solution of potassium nitrate? thanks —Preceding unsigned comment added by Karkaputto (talk • contribs) 00:54, 17 October 2007 (UTC)

The chunk of metal sinks to the bottom, because its density is much greater than the (presumably aqueous) KNO₃ solution? Or is there something you didn't explain clearly here? DMacks 03:19, 17 October 2007 (UTC)

While silver nitrate is quite soluble, potassium is a much stronger reducing agent, and so won't be displaced the silver. In short, nothing. Someguy1221 03:27, 17 October 2007 (UTC)

I am certain that the nitrate will oxidize the silver (but with what results is my question), so that is a moot point--Karkaputto 03:52, 17 October 2007 (UTC)

Make the solution highly acidic and nitrate will dissolve the silver very happily. Someguy1221 04:05, 17 October 2007 (UTC)

unfortunately, that is not my situation--Karkaputto 13:55, 17 October 2007 (UTC)

You need a table of elctrode potentials for nitrate reductions (and adjust to neutral conditions) (Ag > Ag+ -.8V see Table_of_standard_electrode_potentials) then find reductions of nitrate that have potentials at a higher value (note if using standard elecrode potentials the value will be reduced since in your solution << 1 .Does any of that need more explaining?

However I guess that even if a reaction could occur - it will most likely be very slow (acid usually speeds things up) - most reductions of nitrate need H+ to proceed so if a reaction does occur the solution will become basic - further complicating things..87.102.123.108 19:42, 17 October 2007 (UTC)

The barrier for nitrate oxidizing is high because the only way to go is to nitrogen N₂ and this is complicated. You need an relative high activation energy and this is not possible in reasonable time in water at room temperature--Stone 13:54, 17 October 2007 (UTC)

Nitrate can be reduced to ammonia, nitrite as well - what are you on about?87.102.123.108 19:26, 17 October 2007 (UTC)

I cant think of a reaction between Silver and nitrate in the absence of acid, in the presence of acid silver will be oxidised by thee nitric acid formed.87.102.123.108 19:29, 17 October 2007 (UTC)

Light for plants

Can plants grow under normal light bulbs (household lights) or do they need to have sunlight? Hyper Girl 10:14, 17 October 2007 (UTC)

They only use certain frequencies (which couple energy best to the chlorophyll molecules), but they will grow under practically any source of light that we'd deem as "white"; it's just a question of efficiency -- sunlight is free while artificial light costs various amounts depending on its source.

Atlant 12:30, 17 October 2007 (UTC)

Also, sunlight is immensely brighter than artificial light. We tend not to notice that because our vision system is easily able to adjust to the brightness or dimness of the lighting - but plants really do notice that because light is what "powers" them. However, it's certainly possible to grow plants in artificial lighting - people who engage in illicit Indoor Cannabis cultivation use massive amounts of halogen lighting (the article talks about 1000 Watt bulbs) to give the plants what they need. So a typical 40 Watt table lamp isn't going to cut it because the plant is only getting 4% of the energy it needs. (Our coverage of Cannabis (drug) cultivation techniques is truly alarmingly comprehensive! It's a real "How To" kind of a guide with lots of sub-pages and an entire WikiProject all of it's own!) SteveBaker 14:14, 17 October 2007 (UTC)

Cannibis cultivators are reputed to use metal halide lighting, not tungsten-halogen.

Atlant 16:34, 17 October 2007 (UTC)

Actually the old (not warm white - but cool white) fluorescent tubes have sufficient colour temp (enough blue and red light) for some plants to survive. An incadescent bulb won't help much - not enough blue.. Hopefully someone will come along and tell us about plants that have evolved to survive in low light conditions ivy perhaps - anything with very dark leaves is a good sign..87.102.12.215 15:41, 17 October 2007 (UTC)

I guess the plants that live on rainforest floors (where very little sunlight filters through) would be a good choice. Lots of those are carniverous...and I presume there is a reason for that! SteveBaker 20:15, 17 October 2007 (UTC)

I thought being carnivorous (for a plant) was more to do with the lack of nutrients in the soil than the energy? Skittle 23:05, 17 October 2007 (UTC)

Carniverous plants tend to grow in nitrogen-poor environments and have their nitrogen fix delivered to them.

Atlant 12:36, 18 October 2007 (UTC)

• I highly recommend the book How to Grow Fresh Air: 50 House Plants that Purify Your Home or Office --M@rēino 21:32, 17 October 2007 (UTC)

Note that indoor cannabis growing doesn't have to be illicit. I did some of that and of course researched it. Ed Rosenthal's excellent Marijuana Growers Handbook has some quite extensive info on this, but I can't find the book now (probably lent it out to some dopehead :) ). What I can tell you is that two 58 W Fluorescent lamps were enough for two good harvests per year (for a total of about 50 g, precisely enough to cover my 'needs'). This came from about four or five plants (per harvest) on half a square metre of soil. So about 50 W should be enough to let a plant grow. Note, though, that cannabis is a very tough plant and that the lamps were very strategically placed. They weren't used to light the room, so most of the light went to the plants. Also note that I did this because the only alternative I had was the windowsill, which puts to the northwest, so the plants only got some direct sunlight for a few hours in the evening (if any). The lamps did much better. Then again, I didn't put them in as much soil on the sill, so I don't know how big of a factor that was. Ok, the real reason for growing under lamps was that I couldn't look out into the street anymore. Was a shame for the tourists on the boats passing by going "Wow, look at that - marijuana growing in broad daylight." (note the pun). DirkvdM 06:56, 18 October 2007 (UTC)

I can't speak for cannibis growth, but I can assure you that some pretty mighty rubber trees and jade plants grow fine under 4x40W of "cool white" fluorescent lighting; I did that for years.

Atlant 12:36, 18 October 2007 (UTC)

coloring your eyes

In reference to an earlier question about black contact lenses, can one die the color of their eyes? Would something like food coloring be harmful to put into the eye? Obviously pen ink might, but are there any alternatives? Thanks and bunch Picture of a cloud 10:19, 17 October 2007 (UTC)

My mother would tell you not to put anything in your eyes. She would also advise against putting things in your ears or up your nose. Don't run with scissors, either. --Milkbreath 10:57, 17 October 2007 (UTC)

Mums are always out to stop kids having fun. Mine (well my nanna - she brought me up) told me not to play with fire or throw stones at stuff too. Gawd, what else is there to do when you're that age and have no money? :) --Kurt Shaped Box 11:03, 17 October 2007 (UTC)

Please take a seat, remove your contact lenses and I will be with you shortly. Lanfear's Bane 11:47, 17 October 2007 (UTC)

N.B. Nothing in your ears smaller than your elbow please.

Even if there was a dye that would stain the iris but not the lens, how would you get it in there? The coloured part is down underneath the cornea and is washed in the aqueous humor. Any kind of dye that you could inject in there would tend to dissolve in the aqueous humor - and that would really mess up your vision. The answer has got to be a big "No". SteveBaker 14:04, 17 October 2007 (UTC)

I'm reasonably sure that some sort of yellow die is used to test Intraocular pressure, but it apparently wears off pretty quickly. I've never come out of the doctor's office looking like a kidney patient... --Mdwyer 19:04, 17 October 2007 (UTC)

Some treatments for glaucoma, such as prostaglandin analogs, are known to change the eye colour in maybe 10% of patients. These combat glaucoma by increasing drainage of intraocular fluid, thereby lowering pressure. It was thought that prostaglandin acts on eye colour by mimicking a natural hormone that mediates melanin production. However recent research suggests that this hormone does not regulate uveal melanin after all, leaving the mechanism of action a bit of a mystery. Note, however, that this isn't a dye, but a bioactive compound. There are lots of dyes that will stain the eye, including indocyanine green, trypan blue, gentian violet, and methylene blue. However these are temporary, would severely disrupt your vision, and are mainly used for medical purposes during surgery. They are generally also non specific, so would leave you looking very weird for a time. Please don't put any substance in your eye - certainly not a dye - unless instructed to do so by a professional. It would, if you'll excuse the pun, end in tears. Rockpocket 00:31, 18 October 2007 (UTC)

Yes, that sounds familiar. A relative used to have a rabbit that had something wrong with its eyes - some sort of chronic condition. Every couple of weeks, the veterinarian would drip a yellow/orange dye into each of its eyes to see how it was getting on. It would come back with the whites of its eyes stained whatever colour the dye had been. IIRC (it was a long time ago now), it wore off fairly quickly. --Kurt Shaped Box 01:14, 18 October 2007 (UTC)

Consuming melange can color your eyes blue. I wouldn't recommend it for this purpose though, as contact lenses are both cheaper and have less other effects. – b_jonas 20:27, 18 October 2007 (UTC)

Gulls and Botulinum toxin...

I've just been reading this thread over at the misc. desk and it reminded me of something that the local amateur wildlife rehabber once mentioned to me WRT gulls (the large ones, at least). Apparently, they have an *extraordinary* resistance to Botulinum toxin and can tolerate a dose that would kill a human with no apparent ill effects. Even the birds that do come down with botulism paralysis and end up with him are very often save-able (provided that the lungs are not affected), by simply keeping them warm and forcing them to drink enough fluids (his own formula) to flush the toxins out of their systems - then they just get right back up. Next time he gets one brought in, he's going to let me go round to watch the process and help out.

So, anyone have any more info on the mechanism by which gulls have managed to develop such a high tolerance to the bad stuff? I find this kind of thing absolutely fascinating. --Kurt Shaped Box 11:00, 17 October 2007 (UTC)

The mechanism by which they developed it is easy - evolution - gulls that had some kind of resistance to the nasty consequences of their ikky diets survived - those that didn't died. Hence they evolved. What mechanism they developed to do that...I have no clue. According to our article, Botulinum toxin blocks the release of acetylcholine from nerve endings thus arresting their function, and there is an anti-toxin that's "derived from Horses" (how?). Perhaps whatever this natural anti-toxin is - it's produced naturally by Horses...and perhaps also by Gulls? But I really don't know. Another possibility is that somehow the gull doesn't let the toxin reach it's important nerve endings. After all, humans don't get sick from Botox injections - and Botox is just a nice, sanitized shorthand for "BOtulism TOXin". SteveBaker 13:57, 17 October 2007 (UTC)

carbon resistor

1.How can i interpret a carbon resistor with 2 gold bands.plz give one example?Roar2lion 12:06, 17 October 2007 (UTC) 2.how can i interpret a resistor with 5 colour bands.which type is it of?Roar2lion 12:06, 17 October 2007 (UTC)

All your homework questions are answered in the article on resistors. Lanfear's Bane 12:17, 17 October 2007 (UTC)

(edit conflict) Here is a picture that explains color coding for resistors better than any words of mine could. If you still have questions after looking at that, please do ask here. --Milkbreath 12:26, 17 October 2007 (UTC)

In brief, remember that gold is used in two different contexts. It can be the "multiplier" (where it means x0.1) or it can mean the "tolerance" where it means 5%.

Atlant 12:33, 17 October 2007 (UTC)

The strongest material?

If you wanted the strongest material ( for building/construction material, armor, etc), what would you want maximized/minimized ideally? For example, ductility should be maximized, tensile strength should be maximized, brittleness should be minimized, melting point should be high, heat conduction should be low, etc. Those are some I can think of, what else? 64.236.121.129 13:20, 17 October 2007 (UTC)

It's not that simple - the properties you desire depend on what you are using it for. You need a totally different material for (say) the foundations of a bridge pier than you need for the cables holding up the roadway. One needs to be strong in compression - the other strong in tension. Since no material is good at both - you end up with two different sets of needs for two different applications. There are times when high stiffness is required - there are other times when flexibility is needed. I don't think there is a meaningful answer to your question. SteveBaker 13:43, 17 October 2007 (UTC)

Steel is perfectly happy in both tension and compression, it just doesn't tend to be the most economical material for carrying many compressive loads.

Atlant 16:37, 17 October 2007 (UTC)

Hmm, I'm talking hypothetically. I'm not looking for any particular real world examples. Like for example, we use reinforced concrete in buildings because it has high compression strength, low heat conduction, among others. But if there was a material that possessed all those attributes while also having high tension strength, it would be even better.

So I'm talking hypothetically. You mention where high stiffness is needed, and other times flexibility (I'm assuming you mean ductility) is needed. But an ideal material would have a strong resistance to stress before deforming, but when it does deform, it is highly ductile. Ignore the fact that such materials don't exist. Ideally, what should be maximized/minimized. 64.236.121.129 14:36, 17 October 2007 (UTC)

I get that - the answer is - all the measures of strength should be maximise eg tensile strength, yield or breaking strength, compressive strength, and also toughness.. you'll also want high melting point and the effect of temperature on strength should be minimised. Intersetingly ductility isn't a measure of strength - a very ductile material would be very weak.87.102.12.215 14:47, 17 October 2007 (UTC)

Thank you, but I think you are mistaken on a ductile material being weak. Of course you want the material to maximize strength while subjected to stress, but all materials will be unable to hold up against stress at a certain point so at that point it has two options. It can either fracture, or it can deform. Ideally, you want it to deform rather than fracture. If it always fractures past its initial maximum holding strength, that means it's brittle, which is undesireable. A highly ductile material will undergo elastic and plastic deformation before it completely fractures. Ideally, a material should maximize all the strengths you mention, while also being high ductile.

Yes and no. a ductile material will deform though.. not good - that's why I prefer toughness as a measure rather than ductilty.87.102.123.108 17:34, 17 October 2007 (UTC)

ie a material could be tough, non ductile and non brittle..87.102.123.108 17:39, 17 October 2007 (UTC)

Plus if your material is starting to undego plastic deformation - it's broken - and you would need to go back to the drawing board as an engineer!87.102.123.108 17:43, 17 October 2007 (UTC)

These might be useful Elastic modulus Elastic modulus Tensile strength Resilience Yield (engineering) Specific strength Compressive strength

Note Specific strength which requires the material to also be light in weight.87.102.12.215 14:51, 17 October 2007 (UTC)

I suppose you also want this hypothetical material to have minimal weight and minimal cost as well ? I imagine carbon fiber reinforced plastic is going to be a strong contender in all dimensions apart from cost - so if you constructed a whole building from it, it would be enormously expensive, as well as overengineered. For bulk use ECC might be a better choice. Gandalf61 16:07, 17 October 2007 (UTC)

Is this the article you seek? Strength of materials also includes "fatigue strength".87.102.123.108 17:45, 17 October 2007 (UTC)

There also are the articles Fracture_mechanics which may help you reverse engineer a perfect material87.102.123.108 17:48, 17 October 2007 (UTC)

But surely there are lots of conflicting goals. There are bound to be some applications for construction materials where rigidity is valued - and others where flexibility is key. You can't have both - so there can't be a single perfect construction material. To take an extreme example - suppose nanotechnology is someday able to deliver arbitarily large structures made of diamond for the same cost as lumps of coal. This is (virtually) the hardest material known to mankind - it would be cheap, life would be good...until someone wants to hang a shelf inside the building and no drill known to mankind can cut a hole in the darned stuff! So sometimes we WANT a hard material - sometimes that's the last thing we need. You'll always need a range of materials with different properties - so there can never be a single "best" - not even hypothetically. —Preceding unsigned comment added by SteveBaker (talk • contribs) 20:12, 17 October 2007 (UTC)

Glue? DirkvdM 07:03, 18 October 2007 (UTC)

Except I wasn't asking for the "best". What is best, is subjective to what the task is. As for your first point, you CAN have something strong and ductile. There's nothing in physics that doesn't allow this. 64.236.121.129 13:30, 18 October 2007 (UTC)

I'm surprised that in this discussion about material strength no one has considered shear. Often, a material can have a high modulus of elasticity, and its shear modulus can suck. Wood comes to mind about this. Titoxd 09:13, 19 October 2007 (UTC)

Five-Point-Palm Exploding Heart Technique

Is it possible to kill someone with the technique above? --WonderFran 15:09, 17 October 2007 (UTC)

No, as Bill is dead and I doubt Beatrix or Pai Mei will teach you. Lanfear's Bane 15:20, 17 October 2007 (UTC)

Pai Mei is also dead, IIRC. Algebraist 15:49, 17 October 2007 (UTC)

A good point, my bad. Poisoned fish heads. Lanfear's Bane 15:58, 17 October 2007 (UTC)

Beatrix also gave up fighting to live with BB. It dies with her. —Preceding unsigned comment added by 128.101.53.151 (talk) 00:08, 18 October 2007 (UTC)

Use of human excrement as manure in farming

A farm near to where I live in Grafton, Wiltshire has just started to use Human excrement as a manure on two of it's crop fields. Is this a prevalent practice? Does it come from a sewage treatment plant and has it been processed in some way? Is there any difference between the use of human and animal excrement in manure and are there any chemical properties of human excrement that would make it an ideal growing aid? Nanonic 15:09, 17 October 2007 (UTC)

The articles Night soil and humanure should start to answer you. DuncanHill 15:16, 17 October 2007 (UTC)

In my part of the world, it's common to spread the sludge that remains after sewage processing on agricultural fields, but it is not permitted to spread it on crops meant for human consumption. --Sean 17:08, 17 October 2007 (UTC)

I read (and therefore it's Original Research) of a family who spread human manure on their front lawn, only to find that tomatoes began growing there, as the seeds had not been filtered out of the manure. Corvus cornix 20:23, 17 October 2007 (UTC)

Hi. I heard that in some countries, they use human feces or urine (or both) in their crops. however, I've never heard of this being used in farming, as mass-production of human waste is ... eww. However, they might use it in their gardens where they are growing vegetables. As I am not so sure about this, I think you should check with someone else before you start putting human feces in your crops. If I remember correctly, urine contains ammonia, which could be used as an anti-acidizer, which also contains the element nitrogen, which is found in many fertilizers. Again, check with someone else before you actually start doing so. Hope this helps. ~AH1 20:50, 17 October 2007 (UTC)

• If you do this, be careful to keep any pets or livestock away. Human manure is more likely to contain diseases that can infect humans than animal manure is. --M@rēino 21:36, 17 October 2007 (UTC)

• Manure generally wants to be composted before use anyway. --Sean 00:37, 18 October 2007 (UTC)

He isn't planning to do this - his neighbours are doing it.

Anyway, three thoughts on this. First, human excrement can carry and thus transmit human diseases (eg cholera spreads this way), so I suppose it would certainly need special treatment for that. The humanure article only briefly mentions this (the article could do with some expansion). Second, what happens to human excrement if it is not recycled like this? Does it all go through the sewers to the oceans, thus slowly depriving the land of nutrients and feeding mass cultures of algae or something in the oceans? Third, excrement is the leftover from food after the body has depleted it of all the stuff that that body needs. So wouldn't human excrement be very bad manure for human foodcrops? DirkvdM 07:15, 18 October 2007 (UTC)

• • Dirk, as to your third question -- there's two factors at work. First off, excrement is the leftover after the body depletes it of most, not all, of the stuff that the body needs. The better-fed the animal, the richer the manure -- I remember reading a fascinating piece a while back (sorry, can't remember the source) claiming that human excrement had become larger in the last century or so b/c we now eat more, and that in particular the protein content had gone way up. Second off, good manure supplies the nutrients that the plant needs. For inorganic material like minerals, that tends to be the same thing as what the human needs because life is very bad at making its own inorganic molecules, but both plants and animals are skilled at chemically converting most organic material into the molecules that they need. --M@rēino 14:00, 18 October 2007 (UTC)

Ok, plants make nutrients that humans need. But what about the required elements? Some are taken from the air, notably carbon, but many are supplied by the soil. If you remove the plants from the field and eat them and then put the excrement and the body after it dies back into the ground, you've got a full circle. But if you let part of that drain away into the oceans and you keep that up long enough, then there will be less and less of the nutrients in the soil. This has been bugging me for years. Is this why we need artificial fertilisers? Btw, why do you bullet your posts? DirkvdM 09:02, 19 October 2007 (UTC)

Activation energy

When two particles collide, in order to react do they both need the actication energy or would it suffice for their combined or average energy to be greater than the activation energy, i.e. if one particle has an energy siginficantly greater than the activation energy and the other has an energy only just below the activation energy? asyndeton 15:29, 17 October 2007 (UTC)

Almost certainly the sum of both energies. (though sometimes the situation can be complex - requiring the 'atom' to be in a specific energy state to react - rather than just having Energy > x )87.102.12.215 15:37, 17 October 2007 (UTC)

Mobile phone on the moon

The earthward face of the moon is in line of sight of mobile phone transmitters. So would a phone work on the moon, or are the signals just way too small? -- SGBailey 15:39, 17 October 2007 (UTC)

Normaly they do not work in airplanes so the moon is simply a few miles too far. They also only collect and transmit horizontally!--Stone 15:51, 17 October 2007 (UTC)

I'd argue that, and agree with it. A GSM phone would NOT work on the moon due to limitations in Timing advance. A CDMA phone would probably not work on the moon due to the low power and antenna limitations. An analog phone might have the power, but the signal from the moon would engage EVERY cell tower it could see, which would just mangle the whole system. (THAT, incidently, it why you can't use a phone in an airplane. It has little to do with safety. Your phone is only licensed to be used on the ground.) Stone's comment about antenna is also apt -- most modern cell towers use antennas that put beams near the groun of the service area. Radio waves going up to space would be wasted, so they are damped. Finally, see EME (communications) to learn about proper ways to reach the moon with radio signals. --Mdwyer 17:30, 17 October 2007 (UTC)

Radio signals drop off in intensity with the square of the range. Your nearest cell tower is usually no more than about 15km away - the moon is 400,000km away - 27,000 times as far. So your cellphone signal would be 730 million times fainter than it would be at your longest distance here on earth. No...it's NOT going to work! SteveBaker 19:59, 17 October 2007 (UTC)

• Follow-up question -- would an Iridium phone work, or are the satellites positioned to only detect earth-based signals? --M@rēino 21:41, 17 October 2007 (UTC)

Same problem - the Iridium satellites are in a very low orbit (just 780km) and there are lots of them - so you're still only going to be a thousand or perhaps two thousand kilometers away from the nearest one. At 400,000km, the moon is still 200 to 400 times as far away as the nearest satellite - which means that (because of that inverse square law problem) you need a transmitter that's 40,000 to 160,000 times more powerful than the one in your Iridium phone. (And of course the transmitter in the satellite would have to be similarly more powerful - and it's not!). There are probably lots and lots of other reasons why it wouldn't work - but signal strength alone is a killer problem - so we need look no further. SteveBaker 22:42, 17 October 2007 (UTC)

Again, take a look at EME (communications). It says that even with current technology, it takes 100 watts and large directional antennas to bounce off the moon. That assumes an out-and-back bounce, of course, but it certainly lends a lot to Steve's explanation. Also, the Iridium sats will have the same antenna-pattern problem as the ground-based stations, except with even tighter patterns. The satellite flare page suggests that the Iridium antennas are "door sized" -- and that just to reach 780km! --Mdwyer 02:12, 18 October 2007 (UTC)

If you do want to communicate cheaply with the moon, a laser is probably your best bet AFAIK Nil Einne 16:08, 18 October 2007 (UTC)

Sacrificing mice

When the time comes, what methods are used to kill laboratory mice? --Seans Potato Business 16:09, 17 October 2007 (UTC)

"Bite they little heads off, nibble on they tiny feet"?

The method doubtless varies depending on what you're hoping to analyze ex-post-mouso. You don't want the killing method to perturb the data (add stress hormones, etc.).

Atlant —Preceding comment was added at 16:42, 17 October 2007 (UTC)

Thoracic puncture, exsanguination, decapitation, cervical dislocation, CO₂…lots of possibilities, which is important as Atlant notes, to avoid interfering with whatever you hope to study after dispatching them. See also . DMacks 16:52, 17 October 2007 (UTC)

I once had a girlfriend who was a biochemist. When I visited her lab, she proudly showed me the guillotine they used for decapitating live mice. In some cases they used the CO2 method instead...it depended on what they wanted to measure. Urgh! SteveBaker 19:54, 17 October 2007 (UTC)

Just curious: How did that relationship end? Well, I take it? :) --Mdwyer 02:05, 18 October 2007 (UTC)

In some countries, the UK for example, the manner in which one kills mice is regulated by law, specifically Schedule 1 of the Animals (Scientific Procedures) Act 1986 . In other countries there is no legal restriction, though local IACUCs may restrict the use of some methods. Other methods include an overdose of anesthetic or, in the case of baby mice, decapitation with a pair of scissors. It can be quite disturbing decapitating newborns in that manner (especially when they keep crawling for a while after their head has been removed). Rockpocket 00:00, 18 October 2007 (UTC)

Other documented methods scientists have used include, "dissolving mice in acid, spinning them in centrifuges, blowing them up in vacuum chambers, and forcing them to navigate exit-free mazes" One scientist "Dr. Thomas Huber, author of the 1996 study Mouse Elasticity And Kinetic Rebound In High-Acceleration Collisions" found a novel method: "...when I have the time, I like to send them flying into walls." (note to ALF, this is a parody and no mice were harmed in its creation) Rockpocket 00:11, 18 October 2007 (UTC)

Homogenizer Delmlsfan 00:24, 18 October 2007 (UTC)

Man - you can see why the animal rights campaigners freak out over things like this. I know that most of it is necessary - but it certainly sounds harsh when taken out of context and listed. Newspeek-like terms such as 'Sacrificing' and 'Homogenizer' probably don't help either... --Kurt Shaped Box 09:53, 18 October 2007 (UTC)

Yeah, but I really have to appreciate DMacks' use of words. "Thoracic puncture, exsanguination, decapitation..." is a pretty neat way of saying "poke holes in 'em, bleed 'em, lop their heads off..." If you get a chance, you've got to hear Henry Rollins talking about his job in a animal lab. It is disturbing, awe-inspiring, and funny all at the same time. --Mdwyer 16:03, 18 October 2007 (UTC)

Rotfl. – b_jonas 20:06, 18 October 2007 (UTC)

Heat-deactivated FCS and deliberate hypotonic lysis

We discussed an article about the involvement of C/EBPa in granulocyte differentiation. In the method, they used 10% heat-deactivated fetal calf serum; since I thought the whole idea behind FCS was that its growth factors can stimulate the growth of cells, what is the point in using heat-deactivated FCS?

They also say that "normal murine marrow cells were obtained from the femurs of mice after hypotonic lysis and enrichment for lineage-negative hematopoetic precursor cells using the standard StemSep protocol" - what is the purpose of the hypotonic lysis? Is this part of the enrichment process? Are certain cells perhaps more susceptible to hypotonic lysis than others? --Seans Potato Business 16:31, 17 October 2007 (UTC)

Can you identify the article? Is it Transcription activation function of C/EBPalpha is required for induction of granulocytic differentiation? People routinely heat inactivate horse serum to remove complement, but I've never heat inactivated fetal calf serum. (see) Maybe there are heat-sensitive growth factors in FCS that influence granulocyte differentiation. They seem to indicate that the lysis step can selectively remove red blood cells and help purification via the StemSep protocol. --JWSchmidt 20:52, 17 October 2007 (UTC)

Why Two LEDs in a remote control.

Most remotes have two Infrared LEDs to transmit the codes to the receiver on the controlled device. Why two instead of just one? —Preceding unsigned comment added by 160.42.234.85 (talk) 17:00, 17 October 2007 (UTC)

I can make a guess: Once would be the pattern. A single led throws a circular spot of light. Two of them would throw a wider oval of light, making it easier to aim. --Mdwyer 17:24, 17 October 2007 (UTC)

I don't think this is right - most I'm aware of only have one LED - see this image ..?87.102.123.108 17:29, 17 October 2007 (UTC)

Most only have one LED, but I have seen ones with multiple LEDs. Here's another theory: A universal remote might need to have two different LEDs to make two different wavelengths of IR light for different receivers. --Mdwyer 18:52, 17 October 2007 (UTC)

I googled this before posting the question here, and couldn't find anything explicitly answering the question, but I got the idea it might be for increased range because two would be brighter, but then why not just use a brighter one to begin with, so I dunno. —Preceding unsigned comment added by 160.42.234.85 (talk) 18:43, 17 October 2007 (UTC)

Mdwyer has it correct: better remote controls use two LEDs for the wider "throw pattern" that is produced. Alternatively, the two LEDs can each be focused more narrowly allowing greater range for the same "pattern width".

Atlant 19:23, 17 October 2007 (UTC)

Thats funny Atlant!. I always thought that more elements produced a narrower, directional beam, as in YAGI antennas or other arrays for instance.--88.109.65.125 01:24, 19 October 2007 (UTC)

Most modern video cameras see far enough into the InfraRed to see the flashes from a TV remote in a darkened room. You could do an experiment to see what's going on. If they are indeed widening the throw pattern (which would certainly be my guess) - then you should be able to aim the thing off to one side of the camera and only see one of them flash when you push a button (use one of the 'continuous' functions like volume because they keep flashing as long as you hold the button down). Then if you aim directly at the camera, it should be possible to see both of them flashing together. (It might be that from off to the side, you see one brightly lit and the other very dimly lit...it's hard to predict) SteveBaker 19:51, 17 October 2007 (UTC)

Cell phone cameras work great for seeing infrared remotes. Sancho 22:26, 17 October 2007 (UTC)

Good advice, both of you! Also, Radio Shack used to sell a cute little "Infrared test strip" that could reveal infrared light and so could also be used to reveal the pattern of infrared light emitted by a remote control. It wasn't strictly a phosphor but instead had to be charged from visible light first; a little infrared than triggered the emission of the stored energy. I don't know the technical name for that effect (but would welcome it if someone else did!) but it was obviously a form of stimulated emission.

Atlant 12:20, 18 October 2007 (UTC)

double hearing

you know how you can see double for whatever reason (maybe a blunt trauma to the head). can the same thing happen with your two ears, to where they aren't coordinated and you hear one sound source as two? Why not?

Also, am I smart or what. Thank you. —Preceding unsigned comment added by 77.234.80.106 (talk) 17:57, 17 October 2007 (UTC)

Ignoring your second question for the moment, the eyes and ears aren't really comparable in this way. You see double because your eye muscles lose coordination, and are unable to correctly do Fixational eye movement. The eyes literally *are* seeing two different images. Problems with the ears usually don't show up as audio problems. They usually show up as balance problems. See Ménière's disease for an example. --Mdwyer 18:58, 17 October 2007 (UTC)

What about some condition that results in somebody hearing a single sound twice, in succession? Has something like this ever been reported? My first guess is that this might happen when taking certain drugs. Sancho 19:08, 17 October 2007 (UTC)

Nitrous oxide causes a flanging effect on inhalation. In my own personal experience, I would call it echoing. —Preceding unsigned comment added by Mdwyer (talk • contribs) 19:25, 17 October 2007 (UTC)

The problem is that your ears are on two sides of the head so what ends up happening is that if there's a problem with hearing, it ends up with the perception of the origin of the sound being incorrect. It would have to be a dramatic difference in processing times for the two ears to give a doubled signal. If it were caused by drugs, it would be something happening in the brain rather than a difference in signals from the ears. Donald Hosek 19:20, 17 October 2007 (UTC)

Yeah, I meant a doubled signal coming from one ear, not from any physical causes at the eardrum, but with the perception in the brain. Sancho 23:51, 17 October 2007 (UTC)

You're definitely not going to get a doubled signal from ONE ear any more than you get a double-image from one eye. If you are seeing double - close one eye and everything will immediately sort itself out. SteveBaker 18:35, 18 October 2007 (UTC)

I don't think it can happen with your ears. With your eyes, you have to point each eye very precisely at the 'target' object so that the two images 'line up' - and your brain calculates the distance to the object by measuring the difference in the angle that the eyes are pointing when everything is properly lined up. When your eyes won't point where they are told to the very great precision needed (perhaps because the muscles are tired) - you see two images.

Your ears don't swivel (you may have noticed that) - you detect the direction the sound is coming from by the relative delay in the sound arriving at the two ears - plus some really complicated stuff to do with how the sound reverberates around inside your skull. There is no way for there to be a 'delay' between the two ears that's consistent with two nearly identical sounds coming from different directions. That's something that it's virtually impossible for us to pick out anyway - let alone by accident. Most hearing 'errors' come down to lack of accurate direction determination.

There was some interesting research done recently that shows that our noses also work in 'stereo' - just like our ears - to enable us to detect where smells are coming from. For the same reason, we don't get double-smelling problems either.

SteveBaker 19:43, 17 October 2007 (UTC)

As to your second question, see IQ test. If you do find an answer please come back and tell us what you find out. :) --S.dedalus 23:36, 17 October 2007 (UTC)

Insect identification

A dull one today. I have one iridescent blue fly, one black housefly-looking one, and one black-and-orange one (second photo of #3). What are they? I'm guessing the last is some form of bee...

All photos taken yesterday morning in South England. (Bonus points if you know what the plant is. I have no idea) Shimgray | talk | 18:09, 17 October 2007 (UTC)

The third is a European dark bee, on examination. Well, one down. Shimgray | talk | 19:09, 17 October 2007 (UTC)

The first one is a Blow-fly. SteveBaker 19:33, 17 October 2007 (UTC)

The insects are on Ivy flowers, probably English Ivy, Hedera helix.--Eriastrum 21:29, 17 October 2007 (UTC)

Er, Shimgray, are you sure the third one is a bee? It looks like a fly to me, though I don't know what kind. Flies have only two wings, which is what it looks like in your photo. Hence the name for the order of flies, Diptera.--Eriastrum 21:37, 17 October 2007 (UTC)

This photo is of a 'dark bee' too - you have to look pretty hard to see that second set of wings! They are a little more obvious in the side-view photo we have at European dark bee - but still - you've gotta agree they aren't exactly prominant. Worse still for the "Not a Bee" theory, the photos clearly orange fur and stripes on the thorax - and I don't think I ever saw a fly that looked like that. I wish we had a photo with a clearer view of the legs - pollen sacs would have clinched the deal. But I have to agree with Shimgray, it's a "European Dark Bee". SteveBaker 22:28, 17 October 2007 (UTC)

Eh, I think it is a bit ambiguous. The "fur" is not very distinct. There are a number of bee-flies that look very similar; the genus Exoprosopa in particular has a lot of very similar look candidates (lots of photos here). (Like this guy or this guy.) Anyway, if it is a bee, it doesn't look much like the European dark bee to me. --24.147.86.187 22:43, 17 October 2007 (UTC)

I'm certainly not wedded to the dark-bee theory, but it did look v. plausible. A slightly sharper photo - with a just-visible foreleg! - is here. I'll see if I can get any more photos of them from slightly closer in the next day or two; I'm curious now, and it certainly doesn't look like the "normal" big fat bees I'm used to seeing. Shimgray | talk | 20:18, 18 October 2007 (UTC)

Shimgray, I think you are right on about the second photo. It does indeed look like a house fly--quite possibly good old Musca domestica.--Eriastrum 21:44, 17 October 2007 (UTC)

The third/fourth pictures are definitely not a bee. The angle of the resting wings are wrong, there is an absence of hair and the abdominal shape is not bee-like. This is a species of hover-fly, (English colloquial name) possibly Rhingia campestris, but it is always difficult to identify exactly from photos and there are many species of hover-flies. Most hover-flies used protective bee or wasp mimicry which naturally can cause some difficulty in initial identification. Very nice photograph. Richard Avery 09:10, 18 October 2007 (UTC)

A photo of the (not-)bee from side-on, this morning - not desperately well-focused, sadly - here. And am I right in assuming A and B are normal, common-or-garden, wasps? Shimgray | talk | 22:37, 18 October 2007 (UTC)

An Interesting Event with a Credit Card

There was a lineup in the mall because someone's card didn't work on the machine. However, after the cashier wrapped it in plastic, it worked! (It was swiped with the plastic on!) Can someone tell me the science behind this? Is it something with electromagnetism? Thanks. --JDitto 18:36, 17 October 2007 (UTC)

I've seen that, too! The reader is using a magnetic tape head to read pulses off the card. The only thing I can think of is that the head is somehow out of alignment with the data track on the card. The plastic might change things just enough to get a good read. Another possibility is that the data on the card is recorded too 'loudly', and the plastic attenuates the signal enough for it to be read. The truth is, I have no idea. :) But I *have* seen it work! --Mdwyer 18:55, 17 October 2007 (UTC)

I can add a bit of data: the cashier who did that to one of my credit cards actually taped over the magnetic stripe with a piece of what you probably call Scotch tape if you live in North America or Sellotape if you live in England. The tape stayed on there until the card expired and never seemed to cause me any problems. --Anonymous, 23:33 UTC, October 17.

Funny that scotch is used in two ways in the US that are not used in England. Do I detect some animosity between the neighbouring countries? DirkvdM 07:33, 18 October 2007 (UTC)

What is the second way ? If you ask for a "Scotch" in an English pub you will get a Scotch whisky. The key point to remember is that the adjective "Scotch" should never be applied to people, who are always "Scottish". Gandalf61 10:06, 18 October 2007 (UTC)

Animosity? The opposite, sort of. The American usage of "Scotch" in "Scotch Tape" is used to mean "cheap". It is offensive to the Scottish people. I imagine if you want to sell Scottish people tape, you're going to want to rename it. In my part of the US, at least, that particular meaning has disappeared. "Scotch" to me means whiskey, tartan-patterned, tape, or something containing butterscotch. --Mdwyer 15:59, 18 October 2007 (UTC)

It could be worse - I'm told that the leading brand of adhesive tape in Australia is 'Durex' - which unfortunately is the leading brand of condom in the UK. I'll leave you to imagine what happens when a Brit goes into an Aussie drug store and asks for "Some Durex" - or what happens when an Aussie tries to buy Durex by the roll in a British chemist shop! Of course if an American goes into a British chemist shop and tries to buy some "Rubbers" he's going to get a surprise too. SteveBaker 18:32, 18 October 2007 (UTC)

Unless the ditch is larger than I think, I doubt that´s true, since I´ve never heard any Aussie talk about ¨Durex¨ while referring to Sellotape. --antilived 05:56, 19 October 2007 (UTC)

Hmmm...Durex says that the adhesive tape of that name is manufactured in Mexico and popular in Brazil. I'd heard it was popular in Australia - but perhaps not. SteveBaker 11:21, 19 October 2007 (UTC)

For another similar story, someone asked for a 'cola' in Colombia. After a very long time he got a dish of 'bull's tail' ('cola' is Spanish for 'tail). I wonder what would have happened if he had specified a brand and asked for a 'coke'. :) DirkvdM 09:11, 19 October 2007 (UTC)

This subthread really belongs more on the Language desk, but... although the story is that "Scotch" was first applied to tape in an insulting way as Mdwyer describes, the company (3M) went on to adopt it as their brand name, presumably implying that a sensibly thrifty person would use their product. It's a stereotype that cuts both ways. In any case, when people speak of "Scotch tape" they're mostly just alluding to the best-known brand name in a false generic way, or else referring explicitly to the brand name, and not using a stereotype at all. --Anon, 23:30 UTC, October 18.

According to (an Australian science presenter) the tape or plastic bag trick works because as credit cards get old or are damaged the magnetic strip can get "noisy", that is spurious data appears. The noise is "quieter" than the data, but the magnetic strip reader can see it and so the data is not clearly readable. If you add some space between the card and the reader, though, the quieter noise becomes unreadable, but the data remains readable. The tape or plastic bag add that space. --203.22.236.14 11:46, 18 October 2007 (UTC)

Thanks! --Anon, 23:30 UTC, October 18.

So it has nothing to do with static? Cool. The website only gives his personal information, could I get the URL for what he actually said about the matter? Or did you hear him at a conference? Thanks. --JDitto 15:15, 18 October 2007 (UTC)

Steam Freezing?

I recently watched a steampunk sci-fi movie,(Memory isn't functioning...) and at a point in the film this machine started blowing steam all over a city, the steam was creazing ice/extremely cold tempuratutes because the steam comes out so hot it sucks in all the cold air into itself and freezes, is this a factual phenomena or fiction? —Preceding unsigned comment added by 72.183.196.100 (talk) 20:39, 17 October 2007 (UTC)

Fiction. The second law of thermodynamics dictates that putting a hot object with a cold object will (with no external intervention) cause the two to equalize temperatures, not further differentiate. — Lomn 21:24, 17 October 2007 (UTC)

In case there's a misunderstanding, though, blowing steam over very cold surfaces can certainly cause it to freeze out as ice. It's not creating the cold temperature, however. — Lomn 21:26, 17 October 2007 (UTC)

• Maybe the steam was not hot water, but evaporating dry ice? That could be quite cold indeed (sublimation of minus 78.5 °C), and it would look a lot like water steam. --M@rēino 21:45, 17 October 2007 (UTC)

To be terribly pedantic, the 'steam' caused by dry ice isn't the CO2 released from the dry ice. It is water vapor. The vapor is nowhere near as cold as the dry ice is. There are some other options, though -- liquid gasses are often terribly cold when they are boiling away. For example, liquid butane and flourocarbons found in air duster cans. --Mdwyer 02:02, 18 October 2007 (UTC)

If by chance the movie was Steamboy, which has great releases of steam freezing parts of London, then the reason, as I understand it, is that the sci-fi "steam ball" was under extreme pressure. Gas released from extreme pressure turns very cold, no? Pfly 07:30, 18 October 2007 (UTC)

Well, it certainly cools down. That's adiabatic expansion. But if heat is the (sole) reason for the pressure then the net effect will be (close to?) zero. If, however, the compressed gas is at ambient temperature (eg room temperature) then releasing it will cause a cooling. Like with an aerosol spray - try spraying on your hand and feel the cold. Do this over a city and you will get something steamy, except it's not steam but mist - same thing, but under different temperatures. The water in the air condenses because its concentration is too high for that new temperature. DirkvdM 07:42, 18 October 2007 (UTC)

If I recall correctly, Michael Faraday did a pneumatic experiment with a spherical copper vessel which involved heating it, probably with water in it turning to steam, and making ice as the pressure was released. Read the original acount a couple of years ago, don't remember all the details. Edison 00:22, 19 October 2007 (UTC)

Virtual Photon

A few questions which my physics teacher wasn't able to answer:
What is the main difference between a virtual photon and a 'real' photon? Does this make any practical difference to how the virtual photon behaves?
Also, when a virtual photon is exchanged in electrostatic repulsion, does this mean that energy is exchanged between the two (in this example, electrons). I have also read somewhere, that there is some way in which the conservation of mass/energy law is broken Is this true?
Thanks, Aiyda 21:47, 17 October 2007 (UTC)

Does virtual particle help with your questions? (I should emphasise that I am not familiar with this topic and have not read the article) Algebraist 22:08, 17 October 2007 (UTC)

A real photon is described as on-shell. It's rest mass is exactly 0. A virtual photon can have a different effective mass, but this means it must be absorbed, it can not travel as a free particle. This is a consequence of a Heisenberg Uncertainty Principle kind of borrowing of energy, but only for a limited time, which in effect limits the range of the force. Energy is exchanged between two electrons if they exchange a photon, yes. The mass/energy relation you refer too is probably that the virtual photon doesn't have 0 mass enforced as in a real photon. Energy is conserved both when the photon is emitted and absorbed, it is not conservation that is broken, but the relation between energy and mass. This is hard to put into words I hope the article does a better job. Cyta 07:47, 18 October 2007 (UTC) Yes looking at it quickly the article seems quite comprehensive, although I am not sure about the stuff in the intro about some scientists not believing in virtual particles, I have never heard that view anywhere before. Cyta 07:49, 18 October 2007 (UTC)

Carbon-oxygen backbone polymer

Does a polymer with an alternating carbon-oxygen backbone exist, for example H-_n-CH₃? If so, what are they called? These are similar to the silicones, but with carbon in place of silicon. Thanks, AxelBoldt 21:52, 17 October 2007 (UTC)

Maybe polyoxymethylene. --JWSchmidt 23:33, 17 October 2007 (UTC)

The Delrin page has a lot of applications for polyoxymethylene, in case you're interested. Delmlsfan 00:28, 18 October 2007 (UTC)

October 18

sharks

Do jellyfish stings effect sharks? If so where can I locate this answer with more info? —Preceding unsigned comment added by 63.3.17.130 (talk) 00:06, 18 October 2007 (UTC)

Kinetic Energy in the Universe

Because all matter in the universe came from the big bang, if we use the velocity of all the mass in the universe just before the bang as a reference frame and all of the matter in the universe, does that mean that the total kinetic energy of the universe is 0? If its true, is this useful to scientists in any way?

Statements like "velocity... just before the Big Bang" hold no meaning, as the laws of physics do not hold at the singularity point. So no, you can't derive "total kinetic energy is zero" from that statement. Besides, "total kinetic energy" is better described as a magnitude than a vector. — Lomn 01:14, 18 October 2007 (UTC)

Right there are at least three things wrong with that statement. Firtstly, there is no "before" when we are talking about the big bang. Secondly, because kinetic energy is mass times velocity SQUARED, it doesn't have vector component to it. Two particles with the same mass, moving at the same speed in opposite directions don't have "opposite" kinetic energy - they have identical kinetic energy (Suppose they both have a mass of 2 units and velocities of -3 and +3, then m.v is 18 for both of them because 3 is 9 and so is -3). Thirdly, kinetic energy isn't conserved - it can be converted back and forth into other forms of energy - so even if there were some sense in which all mass/velocity 'things' summed to zero - it wouldn't still be true now. SteveBaker 04:14, 18 October 2007 (UTC)

I'm sure you know this, and almost sure you were understood, but lest there be confusion, one usually writes ${\displaystyle (-3)^{2}}$: prefix negation has lower precendence (counted as that of multiplication) than exponentiation. --Tardis 20:02, 18 October 2007 (UTC)

Most Popular Health Topics

I am wondering if there is a way to determine which health topics are accessed most frequently on Misplaced Pages. Is there a list available to the public that displays the number of times a health page is accessed. If not, is there a way to access the top ten health issues viewed through Misplaced Pages? —Preceding unsigned comment added by 67.172.250.112 (talk) 00:27, 18 October 2007 (UTC)

I downloaded the 1500 most popular articles, and grepped for "health" in the category. Results:

Rank  Article
359   Sigmund Freud
401   Arnold Schwarzenegger
484   Dog
527   Chernobyl disaster
584   Sexually transmitted disease
590   Pakistan
819   Condom
1064  Heroin
1227  Cancer
1498  Air pollution

--Sean 01:42, 18 October 2007 (UTC)

"Health Topics"...dog, maybe, but Pakistan? Other high ranking pages in June 2007: Rheumatoid arthritis, Malaria, Coital cephalalgia, Necrotizing fasciitis, Breast cancer, Central obesity, Gastroesophageal reflux disease, Genome project, Lupus erythematosus, Blindness (source). --JWSchmidt 02:44, 18 October 2007 (UTC)

Why was Pakistan a grep result if the article has no mention of the word "health"? --Bowlhover 03:30, 18 October 2007 (UTC)

Sean didn't grep the article - he grepped the names of wikipedia categories mentioned inside it (presumably hoping to find all of the articles that were inside categories relating to health). There is a section in the Pakistan article that refers to Category:Healthcare in Pakistan. Hence he also inadvertently included articles that LINK to health-related categories without being in any way about health themselves. That probably explains all of the ones that don't seem like they should be there! I didn't say it was a good technique! SteveBaker 04:03, 18 October 2007 (UTC)

Medicine = poison?

Who was it -- some ancient Greek thinker? - who said all medicines are actually small doses of poison? Thanks, Adambrowne666 00:45, 18 October 2007 (UTC)

Sounds similar to Homeopathy#Law of similars. Some homeopaths think it makes sense to make treatments out of toxins that cause the symptoms found in disease states. --JWSchmidt 00:56, 18 October 2007 (UTC)

Try Paracelsus - a Renaissance alchemist. Delmlsfan 00:57, 18 October 2007 (UTC)

Makes sense in a way. Antibiotics certainly are poison to the bacteria they are supposed to kill. But the toxicity of something basically lies in its quantity or concentration. Lots of things that the human (or whatever) body needs will be lethal if the dosage is too large. I've even heard a story of someone who swallowed some 'household chemical', and rang the doctor, who advised her to drink loads of water while he was on his way to her. In her panic, she drank so much water that that killed her. Don't know if this is an urban myth, though. Anyway, how much of something you ingest has an effect on the 'balance' in your body. Altering the normal pattern of ingestion may thus be used to treat some disease. That said, a lot of medicines are things that the human body hasn't evolved to deal with (eg because they're synthetic), so any amount could be regarded as poison. DirkvdM 07:54, 18 October 2007 (UTC)

In a lecture (actually on psychology, not on medicine) I was told the same thing. For a medicine to work, it must affect the body. Anything that affects the body in any way, can be dangerous to the body when the dosage is not right. Lova Falk 11:26, 18 October 2007 (UTC)

That's bullshit. Something could affect the body in some way, but completely taper off after, say, 1 ounce, so that a pound, or 1,000,000 pounds of it, has the same effect. For example, consider "darknesss" -- having 1 lumen of darkness affects the eyes in a certain way, but going to a million or a billion or a trillion lumens won't adversely affect the body. Likewise, dropping into a pool of water has an affect on the body, but the efffect won't be different if the amount of water in the pool is trillions of gallons. So, just two examples of how it's NOT true that " Anything that affects the body in any way, can be dangerous to the body when the dosage is not right", 1) darkness, 2) external amounts of swimming pool water. —Preceding unsigned comment added by 77.234.80.59 (talk) 12:41, 18 October 2007 (UTC)

I disagree. If someone takes 1,000,000 pounds of anything they'll be dead. There's simply nowhere to store that much mass in their body. Also, a lumen is not a measure of darkness, but a measure of light. Darkness is the absence of light, so you can't have a "lumen of darkness." Furthermore, once you're in complete darkness it just doesn't get any darker than that. Thus a "million or a billion or a trillion lumens" would probably fry you to a crisp instantly.

Similar to your "darkness" example, your water example is comparing apples to oranges. We are talking about dosages here, meaning what you are exposed to, and generally it is taken internally. Even if you're talking about external exposure, how much other water there is is irrelevant, since in both cases the person's body is touching the same amount of water at the same pressure. You could be up to your neck in a swimming pool or an ocean of water, in either case you'd be equally wet.

Simply put, if you drink too much water, you can suffer water intoxication, hyponatremia, or even die. If you breathe too much oxygen, that too can kill you. This goes for anything and is why dosage is important. The "common sense" idea that "if X is good for me then 2X is twice as good" is often simply wrong.

Back to the original question though, I guess whether that's true it depends on how you define "poison." Would a vaccine or aspirin be considered poison? If we define "poison" too broadly then saying "anything = poison" is simply stating the obvious. -- HiEv 14:46, 18 October 2007 (UTC)

Toxicology points to Celsus who said, "All things are poison and nothing is without poison; only the dose makes a thing a poison." --JWSchmidt 15:31, 18 October 2007 (UTC)

Ah, wonderful - all the answers were very interesting - though I wonder if the guy who started with 'that's bullshit' is a bit toxic himself - thanks especially to JWSchmidt; exactly what I wanted. Adambrowne666 20:34, 18 October 2007 (UTC) -- oh, and Delmlsfan too - sorry, I didn't realise Celsus = Paracelsus.

Harnessing biomath

Humans and other animals can innately do some amazing math, such as calculating where a tennis ball coming at you at 100 mph is likely to end up, in a much shorter time than even the Richard Feynmans of the world could calculate it on paper. I'm wondering if there has been any line of research into using that mathematical ability at the conscious level to do equivalent calculations quickly? Thanks. --Sean 00:45, 18 October 2007 (UTC)

I'm not sure what sort of "equivalent calculations" you're going to find. As I see it, "biomath" is either very specific in scope or very approximate in result. That is, the average person knows about where a tennis ball will end up, but about isn't likely to be of sufficient use to spur serious research. On the other hand, while Roger Federer may be very precise about determining where a tennis ball will end up, he's probably no better than average at, say, gaging a baseball hit to deep center. In this case, you might have a viable calculation, but your pool of equivalent calculations will be quite restricted. — Lomn 01:10, 18 October 2007 (UTC)

Sean, what you're talking about isn't calculation. Calculation is something done with digital representations of numbers, like "16 feet + 29 feet = 45 feet". The intuitive estimates you're talking about involve analog operations, like "<-- THIS far --> plus <---- THIS far ----> equals <--------- THIS far --------->". It's a completely different way of thinking.

--Anonymous, <--THIS late--->, October 18, 2007.

As I see it, predicting where a ball will end up is based on experience; an experienced tennis player will know what trajectory a ball travelling at a certain speed will follow, after seeing similar situations many times before. I fully agree with Anonymous that this is not math but intuition. A tennis player on the Moon, for example, will not be able to predict trajectories very accurately even if he knows the strength of the Moon's gravity and the effects of a vacuum. --Bowlhover 03:19, 18 October 2007 (UTC)

That is probably the best answer. If you used a simple table based on estimates you would usually be able to find an approximate answer much faster than you could if you calculated it. This is sort of what goes on inside of our heads, and why people get better at these things with experience. Their internal "table" gets more accurate, they can "read" it faster, and they learn how to adjust for other variables and to better cope with errors in the results. Just because things like your tennis ball trajectory scenario could be done using really fast calculations, does not mean that that's the method people are actually using to achieve the result. -- HiEv 15:01, 18 October 2007 (UTC)

There is a sense in which we are innately able to imagine approximate solutions to what would be horribly complex problems if calculated out exactly...but they are very, very approximate. If I ask you to imagine a shelf in your garage or garden shed full of paint cans - and think about what happens if one of the two brackets holding up the shelf were to fail - then in a very tiny fraction of a second - and without any accurate data of any kind - you can envisage the whole business. One end of the shelf slides downwards - the cans start to accellerate down the shelf - they impact the ground one after another - some of the lids come off, paint runs out and forms a big puddle on the floor. You can imagine the sounds of the cans sliding and clanging on the ground - and perhaps even have a reasonable stab at the smell of the paint. That's an AMAZING thing to calculate in such a short time with almost zero data - but is it correct? Does the twisting of the shelf cause the other bracket to fail? Do the paint cans land on top of each other or spread out a little? Do all of the lids come off or just some of them? Exactly how big a puddle does half a litre of a water-based emulsion paint form? You really didn't calculate this - you formed some kind of clever approximate simulation by gluing together bits of past experience. However, it's impressive just how close to reality these things turn out to be. We'd be very hard pressed to write a computer program that could produce such an accurate prediction - even with all of the initial data and all of the physics envolved. And if we did, it might take hours to run. Our brains can do a pretty good job in a small fraction of a second. It's not even that we've seen this exact thing happen before and we remember it. I can make up "what if" thought experiments based on combinations of everyday things you've never seen - and you can come up with a similarly reasonable answer in very short order. SteveBaker 03:53, 18 October 2007 (UTC)

Funny, my very first physics teacher could go on and on about how awful these fraction-of-a-second predictions were, before you took his class, of course ;-) Someguy1221 04:57, 18 October 2007 (UTC)

Anyways, the Amazon Mechanical Turk is trying tor harness peoples ability to do some things better than computers. The idea has been explored to some degree in the novel The Diamond Age by Neal Stephenson. --Stephan Schulz 20:17, 18 October 2007 (UTC)

Cotton buds/Q-tips

Is this just a false memory on my part or were cotton buds (aka Q-tips) at one point specifically sold (in the UK at least) for the purpose of scraping earwax out of the depths of the ear canal? Now, they always make it clear on the packaging that they should *not* be used in this manner. --Kurt Shaped Box 01:24, 18 October 2007 (UTC)

Their original designer Leo Gerstenzang saw his wife wrapping cotton wool around the end of a cocktail stick for the purpose of removing the wax from their babies' ears. Yes. SteveBaker 03:34, 18 October 2007 (UTC)

Funny, that. What else would people buy them for? And why are they perfectly shaped and proportioned for that purpose? I occasionally use them to clean tape heads, but that's not what I primarily buy them for. DirkvdM 08:03, 18 October 2007 (UTC)

Exactly. I look at them and I struggle to think of many other advantages that a cotton bud has over your standard cotton wool in the home environment. --Kurt Shaped Box 09:42, 18 October 2007 (UTC)

All you who answer seem to be men. Cotton buds are perfect for small make-up adjustments. They are also ideal for removing kajal out of your eye (kajal has a nasty habit of slipping into the eye) :) Lova Falk 11:22, 18 October 2007 (UTC)

They are also handy for touching up small nicks in your rooms' paint, especially at corners. But "cleaning tape heads" was the first alternate use I flashed on too; 'guess I'm getting old. ;-)

Atlant 12:28, 18 October 2007 (UTC)

They're also good for cleaning the accumulated fluff and scum from mouse rollers. Still, if it wasn't for people buying them to ream their ears out, I doubt that most shops would even bother stocking them. --Kurt Shaped Box 13:04, 18 October 2007 (UTC)

Come to think of it, I've occasionally used cotton buds to brush eyelashes from my corneas. The loose ones are not so bad - it's the ones that fold down under the eyelid whilst still attached that are the real bastards. --Kurt Shaped Box 13:00, 18 October 2007 (UTC)

So, besides dripping peroxide in our ears, what's the "safe" way to remove wax from the ear canal? Someguy1221 04:54, 18 October 2007 (UTC)

I always used to use them, the idea of it being bad for you is a rather recent one. I spent most of my childhood using them... SGGH 08:37, 18 October 2007 (UTC)

I suspect we can blame that idea on a corporate liability lawyer somewhere.

Atlant 12:29, 18 October 2007 (UTC)

No I'm pretty sure it is ENTs. As an answer to Someguy1221, the general recommendation AFAIK is that you shouldn't need to remove ear wax. Use a tissue to clean the outer ear but that's all. Ear wax is a natural part of the ear and should be left to come out on its own, removing it can often make things worse. While I admit, I usually can't resist cleaning my ears either, it makes sense when you think about it. There is no reason to expect most people would have to clean their ears. It's something that no other animal AFAIK does nor does it seem likely our ancestors would have done it. Nil Einne 15:50, 18 October 2007 (UTC)

TBH, I still do. Scraping out earwax and scratching an itch inside the ear at the same time has got to be one of the best sensations possible - only *just* behind orgasm and the relief you feel when taking a slash after holding it in for three hours. --Kurt Shaped Box 09:36, 18 October 2007 (UTC)

Kurt, take one bobby pin, snap it in half at the join and discard the 'crinkled' half. You now have a smooth end and a rough hooked end to use as you see fit. Never found anything better. This is not medical advice or indeed advice of any sort, if you perforate your eardrum consult a medical professional and don't mention you are silly enough to do what someone off The Internets recommended. But seriously, it's heaven. Lanfear's Bane 10:29, 18 October 2007 (UTC)

I use a paperclip (somewhat straightened). --Psud 11:57, 18 October 2007 (UTC)

I once worked with someone who'd sit at his desk scrubbing out his ear canals with matches (phosphorous end!). That may have been an accident waiting to happen... :) --Kurt Shaped Box 13:06, 18 October 2007 (UTC)

I have a mild form of psoriasis. It doesn't affect me at all, except for the fact that earwax doesn't dry up and fall out of my ears, like normal people. So I end up getting solid earwax plugs after a while. Apparently, it's common enough that any doctor will be willing to squegee out your ears for you. Basically, they use the same kind of drops they use to break up poo to break up your earwax. Then, they use a big snub-nosed needle filled with hopefully warm water to hose it out. You can buy kits from any pharmacy store and do it from home in the shower. Two reasons why this is far better than q-tips: 1. You don't have to worry about sticking it in too far and jamming the earwax back or puncturing an ear drum. 2. You're not scraping against the thinnest, most delicate layer of skin on your body. It's a really easy way to get an ear infection. --JMC —Preceding unsigned comment added by 160.10.98.106 (talk) 18:09, 18 October 2007 (UTC)

Sort of back on track, those cotton bud/Q-tips are also perfect for cleaning dirty laser lenses. Dip one end in a bit of rubbing alcohol (spectacle cleaning solution works), rub over the lens, wait to dry a bit, then use the dry end of the bud to polish it up. I originally learned that to get my Playstation 2 working again, but it works on anything (assuming you can take it apart safely to get to the lens). Neil ☎ 14:16, 18 October 2007 (UTC)

I used to use them to clean 5 1/4 floppies. I had a floppy drive that had been taken apart but which you could attach to a power supply to spin it so with a cotton bud and alcohol you could clean them, just provided you didn't push too hard so your scratched the floppies. Mold build up is a major problem in Malaysia Nil Einne 15:54, 18 October 2007 (UTC)

In art restoration, cotton buds/Q-tips are used in great numbers to clean surfaces over very small areas. I work in a museum where restorers have been cleaning a painted wooden ceiling for years. They have a five-year contract. That said, they make their own cotton buds/Q-tips. Watching them, I wonder how they can stand the tedium! Eriastrum (I forgot to log in)--134.186.103.3 19:34, 18 October 2007 (UTC)

Regarding cleaning tape heads (when magnetic tape was still the primary audio/video recording medium), most equipment manufacturers discouraged using consumer-grade cotton swabs (buds) because small fibers could cling to the heads. Thus were created special so-called "electronic swabs" which were a little bit of foam rubber at the end of a small stick to perform the same purpose. — Michael J 20:14, 18 October 2007 (UTC)

Hey! You should all know that you should not stick anything into your ear that's smaller than your elbow! If you want to clean out the wax, pour some olive oil in there a few times a week and this will dissolve any earwax. If this doesnt shift it, its time to see the nurse/doctor (who will drill it out with a pneumatic drill) —Preceding unsigned comment added by 88.109.65.125 (talk) 01:57, 19 October 2007 (UTC)

Oh yes , just remembered, lots of jaw movements side to side are also recommended for loosening the wax. —Preceding unsigned comment added by 88.109.65.125 (talk) 02:00, 19 October 2007 (UTC)

you can buy drops at any pharmacy for like $10 that will greatly soften wax. If it doesnt come out after a day or so, you simple blow water into the air to get it out. Any doctor will do this. If your years are blocked use the drops for at least 24 hours, then goto a doctor and the wax will come out easily. Most wax build up is caused by people putting things in their ears. Qtips etc. are not recommended to be put in the ear because they don't help. wax will naturally travel and fall out of the air, even when it gets wet. Don't put stuff in your ear ever.--Dacium 02:35, 19 October 2007 (UTC)

Bray-Curtis

What is the Bray-Curtis dendrogram and how does it apply to ecology? —Preceding unsigned comment added by Redrumusic (talk • contribs) 06:17, 18 October 2007 (UTC)

This file describes how to calculate Bray-Curtis distances for use in constructing a Dendrogram. This article makes use of Bray-Curtis calculations to study "Recovery of frog and lizard communities following primary habitat alteration in Mizoram, Northeast India". --JWSchmidt 14:25, 18 October 2007 (UTC)

Hairsplitting

Considering how long the hair of humans can get if it is not cut, I used to wonder if that wasn't inconvenient for our ancient ancestors. My first guess was that their lifestyle would cause the hair to get a 'natural cut'. For example, domesticated animals often need to get their nails or hooves cut, which of course doesn't happen in nature. But a while ago someone remarked that I have split ends. About 15 years ago I stopped using shampoo (as a result of which, as planned, my hair stopped falling out - I was already starting to go bold at the age of 30). At around the same time I stopped having my hair cut. But it didn't grow further than my neck. So might that be the cause? Are having split ends and hair of the length I have the natural state of our hair? Also, do other animals have split ends? The article suggests, as many people do, that it is a bad thing, even a 'medical condition'. I claim the opposite. Split ends are healthy. DirkvdM 10:44, 18 October 2007 (UTC)
ps, I will put a baldness-spell on anyone who whines about this being a medical question. :) DirkvdM

Interesting! How do you keep your hair from looking greasy and dirty? Lova Falk 11:18, 18 October 2007 (UTC)

By not using shampoo. :) When you use it, your follicles or whatever compensate by making it greasy. So when you stop, it gets greasy very fast, but after a while the follicles have 'kicked the habit' so to say, and start producing normal amounts of grease again. Takes about a month. A nasty period you need to go through. DirkvdM 18:15, 18 October 2007 (UTC)

1. Just because 'split ends' have a complicated medical name doesn't make it a medical condition (take my word for it)

2. I've heard about split ends but never been able to see them myself..

3. Is it possible that saying "you have split ends" in another way of saying "go and get a haircut!" - a euphemism - a bit like saying "how do you get your skin so shiny looking" can mean "get a bath you greasy ..." - seriously - look a grizzly bears.. they probably have split ends - but pandas dont87.102.3.9 13:10, 18 October 2007 (UTC)

I don't think I'd want to come close enough to a grizzly to find out. :) It wasn't a euphemism - we don't normally talk like that in the Netherlands, and especially not this guy. DirkvdM 18:15, 18 October 2007 (UTC)

Hair is dead stuff. Aside from social matters of how it looks/smells/feels - you can't do anything bad to the hair itself - so it splits? - big deal. We evolved hair that doesn't need shampoo. Baldness happens down inside the follicules where the hair is formed and it should properly be considered a skin condition. All else is myths and nonsense put about by shampoo manufacturers. They put all sorts of delicious, mouthwatering ingredients into shampoo and tell you that you need to "feed" your hair...what a pile of poop! Really! In reality the only thing shampoo does that actually matters to your hair is to provide some detergent to let the water remove dirt and excess oils...soap in other words. SteveBaker 18:16, 18 October 2007 (UTC)

Split ends are normal (I wouldn't say healthy - just normal)- if they exist at all.. Has anyone got a picture of them - I'm dubious as to whether they really exist?87.102.3.9 18:45, 18 October 2007 (UTC)

With split ends, if you look closely at the ends of the hairs you can see that the shaft forks at the end. It will do so to differing degrees depending on the level of splitting. I usually take it as a sign I'm overdue a haircut. Skittle 00:16, 19 October 2007 (UTC)

As I understand it, the 'natural' state of human hair is dreadlocks - they're not just for Rastamen and hippies. If anyone just leaves their hair to grow without combing or brushing it, it will eventually dread naturally, after a period of being a matted, tangly, uneven mess. I'm trying to let my (3-foot-long) hair do that at the moment. Seems to be going pretty well. At the end of it, I'll never need another haircut in my life. --Kurt Shaped Box 21:52, 18 October 2007 (UTC)

I've heard that each individual hair grows a certain length, stops growing, than falls out. The result is that if you cut your hair, it appears to grow as fast as the growing ones do, but once it reaches a certain length, it stops. — Daniel 22:34, 18 October 2007 (UTC)

That's true, as far as I know. My hairdresser once explained to me that women's hair generally (though not always) grows longer than men's - but that everyone's hair, if left alone will eventually reach a 'maximum length' and stop. I suppose that it's the same with beards. I hardly ever even tidy mine up, yet it's still the same length that it was when I started growing it at the age of 20... --Kurt Shaped Box 22:44, 18 October 2007 (UTC)

Possible to use CGI instead of night vision?

Lets say, we are many many years into the future. 2530 or something. We have super advanced computers, quantum computers perhaps, or better. We have a tank in the middle of the night, and it's pitch black. Is it possible for the tank to send signals (possibly radar or something) to get terrain information, then use that information to generate computer generated images in real time to give the driver detailed information of what is in front of him? Perhaps it can be combined with information from a satelite to give topographical information as well.

So in other words, can an advanced computer generate in real time, what is in front of the tank, and display it as if it were day time, and use that CGI instead of nightvision? 64.236.121.129 13:36, 18 October 2007 (UTC)

500 years into the future? We could do it now, including the combination with known topographic data (aircraft use this all the time). However, sending signals continuously like that is the military equivalent of screaming "I AM A TARGET SHOOT AT ME". Night vision goggles, on the other hand, are passive, granting them an enormous tactical advantage. — Lomn 13:44, 18 October 2007 (UTC)

Well I said 2530 because I wanted the CGI to look very advanced. Close to how you would expect the objects and terrain to look in real life. Hmm, that is true about being a huge target. Maybe such technology would be best on a civilian vehicle then. Something like that could be useful in fog or stormy conditions where lights alone don't help much. 64.236.121.129 13:55, 18 October 2007 (UTC)

For civilian vehicles, I think it far more likely that automated highway systems will be prevalent. A problem with the fog/storm thing is that radars capable of what you want are subject to similar limitations as the human eye. Millimeter-wave radars, for example, suffer heavily from rain fade. — Lomn 14:13, 18 October 2007 (UTC)

Keep in mind that the virtual view will never be completely realistic. For example, radar, sonar, infra-red, and other such things cannot pick up color, only visible light can do that. I suppose a super-sophisticated computer could attempt to colorize it, but those colors will often only be best-guesses. It might see a car driving away, but in complete darkness it would not be able to tell what color the car really was. Fortunately, since you are rarely in complete darkness, light amplifying techniques (like longer exposure) could help determine the approximate colors, but a white car passing near a red light source might still be interpreted by the computer as being red instead of white. "Pinging" an object with a variable wavelength laser could provide color and other information (distance, speed, etc.). Also, computers are better at differentiating shades of black than humans are, so that helps too. Still, the color of moving objects (or other objects while you are moving) would be more difficult to determine in near-darkness than if everything were standing still.

Another problem with an active sensors would be that anything in the shadow of the "lighting" would often be "invisible", unlike under normal lighting. It might seem from the virtual view like you are a light source, since that's effectively what you are when you are actively sending out a radar signal or whatever. Other old data on the area might compensate for such "shadows" or "gaps", but the data might not still be accurate. I don't know how sharp the picture could be either with things like radar and sonar.

To help compensate for the "I AM A TARGET SHOOT AT ME" effect of using active sensors, the "lighting" source might be from a separate drone or drones (much as people sometimes use flares,) or perhaps only brief flashes could be used from a moving zig-zagging vehicle. The latter would have problems with moving objects, however both might end up providing "lighting" for any enemies as well unless there was some way to make it difficult for others to use.

You'd never get a 100% realistic image, but with technology 500 years from now you could probably do a fairly decent job in real time while not moving, with moving objects or seeing things while moving appearing a little less realistic. Hope that helps! -- HiEv 16:09, 18 October 2007 (UTC)

Well - they kinda do that some of the time - but it's actually not as useful as it sounds. For example, some F16 fighter aircraft have already replaced their ground-following radar (which screams "I'M HERE!" to anyone with enough technology to listen) with computer-generated maps that simulate the same kinds of information. (I know for sure that the Dutch F16's that are in actual service are equipped that way because I designed the flight simulators they use to train their pilots to use it.) That's OK for things like not hitting mountains - but the trouble with battlefield conditions is that things change too much. Your computer data will be out of date as the enemy moves around, buildings are destroyed or defensive structures put up. For people running around a battlefield on foot or in vehicles - it's utterly hopeless.

So whatever is generating this synthetic view would have to gather data from the real world in real-time somehow and add that into the synthetic scene. There are only two ways to do that:

• By actively 'probing' the world with Radar, Sonar or Lidar or shining a spotlight on them ...or...
• By passively viewing whatever information is coming from those objects.

The active techniques all suffer from the problem that they give away your position - so those aren't really recommended. So now we're down to passive techniques. This means monitoring the signals the enemy is putting out. But if he's being as careful as you are - he's not going to have lights turned on, he won't have radars and lidars sweeping the world and he's probably trying to be reasonably quiet.

So now you are down to monitoring only those things he absolutely cannot avoid emitting - and which you can measure reasonably well. At night, pretty much the only thing like that is heat. So this hypothetical computer has to look for IR energy. How? With an IR camera of course.

What this boils down to then is that you are suggesting that the computer should get that data with a camera and somehow convert it into a computer graphic that looks as realistic as the data it's recieving...well, yeah - but what's the point? You might just as well have piped the image from the camera straight into the end-users' eyes. Not surprisingly that's exactly what they do. Night Vision goggles and IR sensors are basically just cameras feeding screens in front of the users' eyes. The result is much faster, takes vastly less electronics and is nowhere near so error-prone.

There are systems that use CGI for things like showing the user what's over the next hill (in terms of terrain, lie of the land, that kind of thing) - but they aren't replacements for night vision, you should think of them more as high-tech maps.

SteveBaker 17:32, 18 October 2007 (UTC)

Having trouble understanding how Solar Cells work

I read the article on solar cells, but I'm still not sure if I understand it. So the photons in light strikes silicon and this shakes loose electrons in the silicon and these electrons then travel through a wire into a battery? The electrons are electricity? Can the silicon ever "run out" of electrons? 64.236.121.129 14:35, 18 October 2007 (UTC)

The free electrons are indeed electricity. These same electrons end up going back to the silicon at the other end. --Milkbreath 14:49, 18 October 2007 (UTC)

Technically, the electrons that come back into the battery are very, very unlikely to be the same ones that went out. (Not that you can tell - electrons all look pretty similar!) The actual rate of flow of electrons is very slow indeed. But this need is the entire reason that electricity has to run around a loop. Static electricity is a different matter though. If you do the trick of standing on an insulated block and putting your hand on the shiney chrome ball of a Van de Graaff generator (so your hair stands on end), the electrons only flowed out from the ball and up into your hair - then they stay there until they either leak slowly off into the air - or someone else touches you and a bunch of electrons flow over to them (and they get a short sharp shock in the process). SteveBaker 17:14, 18 October 2007 (UTC)

If it's true they're not the same electrons, I can learn a big thing here. All the electrons in the conductors move, sure, oh. Well, eventually they're the same. --Milkbreath 18:08, 18 October 2007 (UTC)

To further clarify, the reason why electricity works is by having electrons travel in a loop (2nd paragraph in electric circuit). Things powered by electricity are kind of like how a waterwheel works, but electrons are used instead of water. What Milkbreath said is that the electrons never run out because the electrons loop back to where they came from. --JDitto 15:35, 18 October 2007 (UTC)

Water flow is always a nice analogy for electricity. The solar cell is like a pump that's pushing the electrons around the circuit - and the device it's powering is like a water wheel spinning in the flow - you need to take the water out of the water wheel and put it back into the pump or everything runs dry very quickly. Static electricity is more like syphoning the contents of one bucket into another. SteveBaker —Preceding comment was added at 17:59, 18 October 2007 (UTC)

I see. But what about the large solar cell arrays that are used to power homes? How can they complete a circut with something like that? 64.236.121.129 19:40, 18 October 2007 (UTC)

The solar cell array acts as a large battery: two wires run from it to the (rest of the) home, and the current travels down one and back along the other. Within the array, the individual cells are connected (in series or in parallel) with more such wires, and the current flows through the cells as previously discussed. --Tardis 21:09, 18 October 2007 (UTC)

Yea I know that. I was talking about a solar farm. A solar powerplant so to speak. 64.236.121.129 13:14, 19 October 2007 (UTC)

Apart from acting like a battery, solar cells on the roof of a house would almost always actually be connected to a bank of batteries. You wouldn't just be using the electricity that's directly coming out of the solar cell because that would vary greatly depending on how sunny it is and more importantly if it is day or night. The solar cells charge the batteries when it is sunny (pulling the electrons from the positive side to the negative side "against their will" so to speak) and you discharge the batteries using electricity in the house, creating a circuit for the electrons to flow from the negative to the positive side through your appliance hence powering it.Vespine 01:39, 19 October 2007 (UTC)

Solar cells are P-N junctions of silicon. The P side has some boron replacing the silicon. If you look at Boron on the periodic table, you see it has one less electron than silicon in it's outer valance shell. The N side has phosphorous which has an extra electron. These are electrically neutral sections but when they are placed next to each other, the difference in electron concentration in the two sections create a "partial pressure" of electrons and they want to flow from high concentration to low concentration. THis is just like in biology where high saline cells absorb water through a semi-permeable membrane to even out the concentration. It also happens with gasses and gas mixing and partial pressures. As the eletrons move from high concentration N silicon to low concentration P, the two sides start to charge up. The P silicon starts to get a negative charge as it accumulates electrons. The N side gets a positive charge because the electrons are now gone while the protons stayed in the atoms. This charge difference creates an electric field that opposes the diffusion of electrons from high to low concentration until an equilibrium is established. This region of electric field (called the space-charge region) is what is exposed to light. When a photon hits an atom in the high electric field space-charge region, an electron can be excited to leave the atom. It is then swept out of the space charge region. This "unbalances" the equation and an electron will go through the circuit to return to donation site. There are other things to consider but this is the basic mechanism. --DHeyward 04:31, 19 October 2007 (UTC)

So the oppossing charges resist the natural diffusion of the electron. Does that mean the electron is just floating inbetween the two atoms? So is the space-charge region the space in between the two atoms, or does it include the atoms as well? 64.236.121.129 13:26, 19 October 2007 (UTC)

PKC

if you have a Protein kinase C (PKC) inhibitor, and want to inhibit pkc, how would you use it? —Preceding unsigned comment added by Poppynash (talk • contribs) 17:04, 18 October 2007 (UTC)

Historically, such inhibitors have often been used in enzyme assays or on cultured cells where you can add them to the culture medium. Some are starting to be used clinically and administered orally. Example: Enzastaurin (LY317615), a protein kinase Cß inhibitor, inhibits the AKT pathway and induces apoptosis in multiple myeloma cell lines. Note the section of that article called "Enzastaurin Treatment".....it is not unusual to have take special care because of high levels of non-specific binding to surfaces or other components in laboratory PKC assays. --JWSchmidt 22:17, 18 October 2007 (UTC)

When to use the terms proper motion and Improper motion

I think I understand what proper motion and improper motion are -- proper motion is a change in apparent location based on the object's actual motion, and improper motion is change in apparent location based on the observer's actual motion. I'm trying to get a handle on when to use the terms, though. Are they just used for stars? Could one talk about the (im)proper motion of a planet, moon, or artificial satellite? Could one talk about the (im)proper motion of an object on the same body as the observer -- for instance, a jogger as viewed from a moving vehicle? Finally, if (im)proper motion is not the term that is usually used in these instances, what would the correct term(s) be? --M@rēino 17:23, 18 October 2007 (UTC)

Ideal gas law example

It's been a while since I've done Physics and when discussing an ideal gas law question with something came up which I can't remember the answer to. The question was relating to an isobaric process? Specifically, a system where the volume is doubled (pressure remains constant) and with no heat lost or gained by the environment. What is an example of such a system? I know there may not be a perfect example but an approximation. I searched but all I found was examples of Charles' Law setups where they kept the pressure constant but increase the temperature. Cheers Nil Einne 17:41, 18 October 2007 (UTC)

Because PV=nRT for the volume to increase but the pressure stay the same - the temperature must increase.. - and so there must be an increase in energy since E = constant x T

(((I can't think off hand of a real world example - but this system would make a good "gas thermometer" - since the volume is proportional to temperature.)))

One possible example would be a chemical reaction of gases in a isolated or insulated system - if the reaction produces energy then the temperature will rise - causing an increase in volume - for the pressure to remain constant the reaction would have to take place in a piston such that the external pressure on the piston would be constant.. (also note it helps if the reaction is constant in volume eg A+B > C+D and not A+B>C - the second case would complicate things)87.102.3.9 17:49, 18 October 2007 (UTC)

Well yes, the internal temperature would change. In case there was any confusion, my point about the Charles law example was that they were heating the system which was obviously not what the question is referring to (since no heat is lost or gained by the surroundings) Nil Einne 17:53, 18 October 2007 (UTC)

Was my example any good - if the piston is totally thermally insulated? or did I miss something - if so what - I'll keep thinking..87.102.3.9 18:44, 18 October 2007 (UTC)

rubber bands

How far can a rubber band stretch before it bop? —Preceding unsigned comment added by Coco74 (talk • contribs) 19:53, 18 October 2007 (UTC)

Hi. Ok, first you need to understand that how far a rubber band can stretch depends on the size of the rubber band, the texture of the rubber, its stretchiness, etc. I've been able to stretch a single rubber band roughly 1 ft, although it again depends on the rubber band. I'd suggest you read the article rubber band. A rubber band will often rebound violently if stretched enough, for instance it can be used to launch a paper airplane or other projectile at over 70 km/h (roughly 45 mph or 35 kt). If you are conting distance or height, why don't you try it yourself? I've found that a rubber band stretched far enough can go roughly 10 m (~35 ft) forward and 5 m (~15 ft) up. Also, a rubber band that has been dried or repeatedly used and stretched has a higher probability of breaking when stretched before it usually does. Hope this helps. Thanks. ~AH1 20:06, 18 October 2007 (UTC)

it depends on the rubber band. See Bungee jumping. -Arch dude 21:21, 18 October 2007 (UTC)

...and the temperature. Take two identical rubber bands (this works best with the really fat ones) - pop one into the freezer for a while and drop the other into hot water. Now *quickly* grab first one, then the other and give it a stretch. You'll be amazed how different they are! This was the cause of the space shuttle AtlantisChallenger disaster - cold weather impaired the 'stretchiness' of the rubber in the infamous O-ring seals. SteveBaker 23:59, 18 October 2007 (UTC)

Wouldn't that be Space Shuttle Challenger? --Psud 10:05, 19 October 2007 (UTC)

Yeah - sorry - brain-fade. SteveBaker 11:11, 19 October 2007 (UTC)

This question is like asking how fast cars go. It depends on the manufacturer. No one is going to spend a lot of money on a rubber band. Also, ozone really degrades them. That's why they crack after a few months of use. Delmlsfan 01:39, 19 October 2007 (UTC)

Leaky coax antenna?

What is a leaky coax antenna? What does it do exactly? —Preceding unsigned comment added by 67.127.167.238 (talk) 20:09, 18 October 2007 (UTC)

Can you add any context? I assume "coax" means coaxial cable, but the only relevant (I think) items I've found for "leaky antenna" are for getting cell phone and wifi signals in train tunnels, which doesn't seem to relate to coax. — Lomn 20:27, 18 October 2007 (UTC)

Obviously it means that a coax cable is 'leaking' electromagnetic waves and therfor is acting as an antenna. Coax cables aren't supposed to leak though.. Searching for 'leaky coax' turns up a few discussions of this.. So a "leaky coax cable" would be a "leaky coax antenna" I imagine and it's doing what it's not supposed to be doing.. Does that explain?87.102.3.9 20:37, 18 October 2007 (UTC)

see http://lists.contesting.com/pipermail/towertalk/1997-August/008139.html

Alternatively a leaky coax is "A straight length of coaxial cable with regularly-spaced holes cut in the shielding (aka leaky coax) is treated as a Uniform Line Source antenna" from http://www.springerlink.com/content/r7l13900814r1607/ - effectively the coaxcable is converted into a lot of little antennas by cutting through the shielding - was that what you were thinkng of?87.102.3.9 20:40, 18 October 2007 (UTC)

In this example the coax includes lots of small antenna - it's designed for wireless communication - this http://www.hitachi-cable.co.jp/catalog/EW-204.pdf gives a good clue as to a possible use as well as technical info..87.102.3.9 20:44, 18 October 2007 (UTC)

"Leaky Coax" or "leaky line" antennas are used to cover a long skinny area such as a tunnel or the cabin of an airliner, as stated above.-Arch dude 21:16, 18 October 2007 (UTC)

When I was in college, we had a student radio station. Our broadcasting license only allowed us to broadcast within the bounds of the college buildings. The solution was to use leaky coax antennae which allow you to outline the areas where you want the radio to work. I don't understand the detailed technical stuff - but it was really impressive. Anywhere inside the residence building, any old Medium wave AM transistor radio could pick up the station with ease. If you were in your car out in the parking lot with the front of the car up against the building - you could pick up the station on your car radio with plenty of signal strength - but as you reversed out of your parking space, the signal would drop off so fast that by the time you were 15 feet from the wall, all you got was static. SteveBaker 23:54, 18 October 2007 (UTC)

See Leaky feeder 81.79.75.108 11:30, 19 October 2007 (UTC)

Head polish?

I've heard all the jokes about 'head polish'/'head wax' for bald men (and a quick cursory glance at Google would tell me that such products do seem to exist) but is it actually, *really* a common thing for bald men to buff up their 'domes to a sparkling, shiny finish before they go out in the morning? Is this some sort of really well-kept secret? --Kurt Shaped Box 21:45, 18 October 2007 (UTC)

I have seen my roommate do it, but I don't think it is a daily thing. Just when he wants to go out and impress the ladies. It is like a porch light and moths, they all want rub it for "good luck." 161.222.160.8 22:54, 18 October 2007 (UTC)

Your roomie's not Fabien Barthez, is he? --Kurt Shaped Box 23:41, 18 October 2007 (UTC)

Electromechnical elevator/lift control equipment

Hi there, not sure if anyone can answer this but I've been wondering how the electromechanical equipment that controlled elevators/lifts prior to the invention of integrated circuits/transistors etc works? I can't find anything on this online. The type of equipment I mean includes selectors and relays and contactors and all that sort of stuff but I don't understand how all those components can do the job of controlling a lift, can anyone explain? Here is an image of the type of equipment I mean.

GaryReggae 22:04, 18 October 2007 (UTC)

I guess you understand how a contact on the side of the lift could switch a relay that causes the lift to stop - the real situation will be more complicated than this.

The picture looks like a sort of simple electromechanical computer with possibly some analogue parts

I'd guess that the motion of the lift can be connected to a chain - and then geared down - to a smaller chain - as this smaller chain moves it can cause the lift to stop at certain points (eg floors).. I'm not an expert on this but it doesn't look beyond the capabilities of most people to understand.

Could you split down your question into smaller parts - eg were you interested in how the buttons would cause the lift to stop at certain floors, or how the lift is 'programmed' to stop exactly at a given floor - there's quite a few different things to consider - so splitting the question down might help..87.102.3.9 22:55, 18 October 2007 (UTC)

In the meantime since these things have almost certainly patents applying to them a patent search might be a good source of information on them.87.102.3.9 22:57, 18 October 2007 (UTC)

It's nothing so complicated. There are simply a series of limit switches in the hoistway and as the elevator car passes by them, they indicate to the control logic where the car is in the hoistway and, often, in which direction the car passed the limit switch.

Now, envision the logic that has to exist for each floor. We need a relay that latches when you press the up-going hall-call button, a relay that latches for the down-going hall-call button, and a relay that latches when an occupant of the car presses that floor's destination button. These relays also light the lights in each button and they're cleared when the car stops at that floor going the right way (for the hall-call buttons) or just plain when the car stops on that floor (for the car button). Now, we need a little more logic to record which way the car is presently traveling and make it move to the next "call" in the current direction. When there are no further "calls" in the current direction, reverse direction. If there are no calls in either direction, wait for a call and take that as the new current direction. Finally, we need a block of logic that knows how to do the leveling (fine positioning to line up the car and the floor) and cycle the doors open and then closed.

It all comes down to a block of relays for each floor that is repeated over and over again, the direction control block, and the "leveling" and door control block. Elevator control systems just used pre-assemblies of these logic blocks.

It gets more complicated with more than one car, of course, but the basic principles remain the same. And note that even computerized controls can't schedule cars perfectly because the "hall-call" buttons don't provide enough information to allow perfect scheduling.

Atlant 23:36, 18 October 2007 (UTC)

This seems like the sort of subject that you'll find books on if you visit a university engineering library or a large reference library. For example, I just searched the University of Toronto's online library catalog for subject "elevators". The university's Engineering & Computer Science Library has a 1966 book called Electric lifts: a manual on the current practice in the design, installation, working and maintenance of lifts (5th edition) by Reginald Stanley Phillips. Also, the university's Gerstein Science Information Centre has a 1927 book Electric elevators, their design, construction, operation and maintainance by Fred Anzley Annett: this would presumably be about manual elevators, with simpler control systems. These are just examples of what you might find: try a suitable library near you. --Anonymous, 23:48 UTC, October 18, 2007.

Industrial motor controls and ocmmercial lighting often use electro-mechanical relays as their state elements instead of electronics. If you think of a D latch simply as a level sensitive switch (on when clk is high, off when low), a relay is just a D latch. Another relay completes the state element part. --DHeyward 04:43, 19 October 2007 (UTC)

Thanks for your replies, these help a bit, sorry I should have been a bit more specific with the original question as I understand that the relays basically open and close circuits depending on which buttons are pressed and that the lift 'knows' where it is via the floor selector but it's really the mechanics of how the lift decides which way to go...I understand for example that if somebody has pressed the floor 3 button then this would presumably cause a relay to latch and there would also be relays for the up and down buttons on the landing that tells the lift to stop at that floor only if it is going in that particular direction but it's the starting process I don't quite get. Presumably there are additional relays that act as safety interlocks and don't allow current to flow through the circuit until the doors are closed and there must be some sort of timer that causes the doors to close. Then what happens? How does the lift controller use the state of the relays to decide which way to turn the motor? I will have a look in my local city library but they didn't have a lot of engineering stuff last time I looked but the patents thing is certainly a good idea. Thanks. —Preceding unsigned comment added by GaryReggae (talk • contribs) 08:46, 19 October 2007 (UTC)

My experience of how older lifts decide which way to go suggests pretty simple logic: If they are on a floor, they go in the direction of any floors selected; if none are selected, they wait to be called (perhaps going to a "home" floor) then when called, travel in the direction of the floor calling them; if someone presses a button for a floor in the direction opposite to any already selected floors, it ignores the button press. Buttons in the lift override call buttons, so they never see a choice of directions. --Psud 10:17, 19 October 2007 (UTC)

There must be a relay that 'remembers' which way the lift is going then? Otherwise when it stops, it wouldn't know which way to go? Are there any other relays in the system or just 3 for each floor, a direction state relay and safety interlocks? —Preceding unsigned comment added by GaryReggae (talk • contribs) 10:23, 19 October 2007 (UTC)

In most cases it wouldn't need to remember which way it was going because its direction of travel would be determined by which buttons are lit and which call buttons have been pressed. In fact I can't think of any situation where it would need to remember direction, it seems to me that the lift could work out, with simple logic, which direction to go in any situation where it needs to move.--Psud 13:21, 19 October 2007 (UTC)

You guys are not going back far enough. Elevators originally had a human operator. Elevators with operators persisted well into the 1960's. Thus, the "wired-logic" era was a relatively brief transition from the manual era to the microcontroller era. -Arch dude 13:43, 19 October 2007 (UTC)

I'm sure we're going back exactly far enough. Earlier - Human operator: Boring - human decides up or down or stop. Later - ICs or computers decide up down, stop. Boring. Wired logic - interesting, simple, understandable. --Psud 14:13, 19 October 2007 (UTC)

October 19

Sand

what does sand consist of —Preceding unsigned comment added by 72.179.169.101 (talk) 00:18, 19 October 2007 (UTC)

You could try our article on sand. Andrewjuren(talk) 01:30, 19 October 2007 (UTC)

Most often grains of quartz, but some beaches have other minerals, such as coral fragments, or feldspar. Graeme Bartlett 03:14, 19 October 2007 (UTC)

Trebarwith Strand is made of tiny sea-shell fragments, and is beautifully soft and golden. The sand used to be used to manure acidic soils. DuncanHill 15:31, 19 October 2007 (UTC)

Reflectivity

How do you calculate how much light is reflected off an object? Thanks, —Preceding unsigned comment added by Jeffrey.Kleykamp (talk • contribs) 01:16, 19 October 2007 (UTC)

My first guess would be to use a light meter. Andrewjuren(talk) 01:33, 19 October 2007 (UTC)

Use a reflectometer of course! —Preceding unsigned comment added by 88.109.65.125 (talk) 01:47, 19 October 2007 (UTC)

I mean using math to calculate the reflectivity of an abstract object. Jeffrey.Kleykamp 02:00, 19 October 2007 (UTC)

Hmmm, reflectivity you say. Did you look it up? —Preceding unsigned comment added by 88.109.65.125 (talk) 02:07, 19 October 2007 (UTC)

Given what? —Keenan Pepper 06:00, 19 October 2007 (UTC)

For a mirror-like surface, use the Fresnel equations. For a diffusely reflecting surface, Lambert's cosine law is applicable in most cases. See also diffuse reflection. Simon A. 85.127.182.162 13:19, 19 October 2007 (UTC)

Bass speakers

Why cant they make base speakers that are very small but sound ggod and bassy yet? —Preceding unsigned comment added by 88.109.65.125 (talk) 02:14, 19 October 2007 (UTC)

Try the articles on loudspeakers and woofers. Delmlsfan 03:00, 19 October 2007 (UTC)

One simple way to view it is that low notes or sounds put out by the bass speaker have a long wavelength. They need to move a big volume of air to create a loud sound, so you need a bigger speaker, or transducer to move that air. Also when a speaker cone moves the side moving fowareds pushed the air out of the way, but it will tend to rush around to the other side of the cone, rather than propogating as a sound wave. This will cut the volume especially as you go lower in frequency. THis is alleviated with a large speaker encolsure. Graeme Bartlett 03:13, 19 October 2007 (UTC)

Good sounding bass speakers are much smaller now than they were 40 or 50 years ago, so at least progress has been made. Edison 05:30, 19 October 2007 (UTC)

Also try articles relating to hearing (Equal-loudness contour is one)- human ears are much less sensitive to the same amplitude of bass sounds than higher pitched sounds - so the amplitude of bass sounds has to be bigger to sound 'as loud' - this means the speaker has to move more when vibrating - hence the size - unfortunately this means the answer to you question is no..87.102.7.57 12:07, 19 October 2007 (UTC)

Is there a unit of energy called "Dq"?

I read in a book that ligand field stabilization energy of a transition metal such as manganese can be measured in Dq, for example -20Dq. What is the unit Dq? Misplaced Pages's disambig page for Dq doesn't have it. Shalom (Hello • Peace) 04:38, 19 October 2007 (UTC)

I think it is just kj/mol like any other energy... —Preceding unsigned comment added by Shniken1 (talk • contribs) 08:51, 19 October 2007 (UTC)

Yeah confirmed, kJ/mol :D--Shniken1 08:58, 19 October 2007 (UTC)

Where is it confirmed?87.102.7.57 12:05, 19 October 2007 (UTC)

Please confirm that yoy know what you are talking about before answering.87.102.7.57 12:15, 19 October 2007 (UTC)

A long shot - might you mean Bq, which stands for Becquerel? That's a measure for radiation, and radiation is energy (right?), so it could be taken as a measure of energy. Probably all wrong, what I said here. It's really another way of saying Hz. Or is that all wrong too? DirkvdM 09:41, 19 October 2007 (UTC)

Sorry DirkvdM fully wrong :P.. Bq is number of decays per second, not really Hz (cycles per second). Radiation is not energy, although it has energy... Dq a unit of energy in kJ/mol, don't know what it is called though --Shniken1 09:52, 19 October 2007 (UTC)

Are you sure it's not just a variable like "x" of "Fx" - because a search turns up nothing about Dq as a unit..

Note a unit of energy eg Joules, Calories, Ergs etc have values ie 4.2Calories = 1 Joule or something. A variable doesn't eg if A has f energy in kJ then "f" is not a unit of energy.87.102.7.57 12:04, 19 October 2007 (UTC)

I imagine you read something like this http://butane.chem.uiuc.edu/pshapley/312/Lectures/L25/index.html

Here Dq units are energy, but the amount is not defined. So 1Dq could be anything in kJ etc.

Dq is not (of it self) a measure of energy

Dq ARE NOT units of energy.87.102.7.57 12:13, 19 October 2007 (UTC)

I know less than Sergeant Schultz about all this, but I'm starting to think it's "dQ", delta Q or change in Q. "Q" stands for "charge" a lot of the time. Urk. --Milkbreath 12:15, 19 October 2007 (UTC)

Even though you deleted.. Q can mean energy as well as charge - specifically heat . see First law of thermodynamics - (but not in this context)87.102.7.57 12:45, 19 October 2007 (UTC)

Flu shot

Washing hair

Is it necessary to wash your hair for health of hair and scalp or not? If so how often is best? —Preceding unsigned comment added by 88.109.65.125 (talk) 12:22, 19 October 2007 (UTC)

It's obviously not necessary as humans went hundreds of thousands of years without shampoo. The hair itself is dead so "health" doesn't apply to it, but of course the health of the scalp and that of the person the scalp belongs to is reflected in the hair. I can't think of any problem a bit of grime around the scalp would cause - presuming the grime in question isn't made of the sort of toxins that float around in the air of modern cities. --Psud 13:14, 19 October 2007 (UTC)

Yea, but you don't want it to smell bad dude. 64.236.121.129 13:41, 19 October 2007 (UTC)

People doing fieldwork in remote areas commonly go weeks between hair washes, in fact between washes at all. Your body quite quickly achieves a steady-state, it's not really objectionable, as you get used to your own smell. Still need hand washes for hygeine reasons of course, but otherwise not a problem, as long as someone else isn't downwind. Mikenorton 14:12, 19 October 2007 (UTC)

Biology

What do conjugation and binary fission have in common? —Preceding unsigned comment added by 68.209.98.104 (talk) 13:02, 19 October 2007 (UTC)

They both have wikipedia articles: conjugation & binary fission.--VectorPotential 13:05, 19 October 2007 (UTC)

hint - think about what happens to the DNA. --VectorPotential 13:40, 19 October 2007 (UTC)

• One commonality is that I know a lame joke about each (sort of):

1. Q: What did the sign on the physicist's door say? A: "Gone fission"
2. Q: Why did the grammar teacher enjoy being in prison? A: All the conjugal visits!

Thank you, I'll be here all week. --Sean 13:47, 19 October 2007 (UTC)

heart attack!

"The appearance of some isozymes in the blood is indicative of tissue damage and can be used for clinical diagnosis. For instance, an increase in serum levels of H₄ relative to H₃M is an indication that a myocardial infarction, or heart attack, has occurred"

I got this from an old textbook, the question is how exactly can serum levels be used to indicate a heart attack?--VectorPotential 13:45, 19 October 2007 (UTC)

The enzyme used in this test is lactate dehydrogenase (LDH). LDH is made up of four subunits, each being either an H subunit or an M subunit. Certain tissues have different combinations of subunits in their LDH.

• LDH-1 (4H) - in the heart
• LDH-2 (3H1M) - in the reticuloendothelial system
• LDH-3 (2H2M) - in the lungs
• LDH-4 (1H3M) - in the kidneys
• LDH-5 (4M) - in the liver and striated muscle

When a cell dies, it releases the enzymes that were contained within it. Normally, trace amounts of each of these can be found in the blood as the result of normal cell turn-over. However, following a heart attack, for example, large amounts of heart LDH (the 4H variety) will be released into the blood and can be measured with a laboratory test. This can be used to confirm that a myocardial infarction has occurred, especially if there were atypical symptoms such as a lack of chest pain. Andrewjuren(talk) 14:22, 19 October 2007 (UTC)

Lights at night appearing 'blurred'

I noticed that when i'm out at night, lights tend to appear blurred. When i say 'blurred', i don't mean i can't see the light clearly. I can see the light very clearly, but there're like...'lines' of light coming off it. So a round light (like the light from a street lamp) doesn't look like a round light - it looks like a round light in the middle of a 'star' of light.

It's sort of difficult to describe. But imagine that you get a bit of water in your eyes, and then you look at a bright light and squint. You can still see the light fine, but the 'edges' of the light become blurred and there're these long 'rays' extending from the light.

I'm short sighted, and i noticed that this always happens when i'm out at night.

- It only happens when i look at relatively bright lights at night. Lights look fine during the day, or in artificial light (i.e. the lights in my room don't look blurred) - Lights that are very far away look fine (e.g. from cars far away). It's mostly lights from cars directly in front of beside me, and lights from all the street lamps around me. - it's a *lot* worse when i wear contact lens (as opposed to just glasses)

I've always wondered why this happens. I've heard that seeing bright lights at night as being 'blurred' like this could be a sign of glucoma, or at least high pressure in the eyes. Is this at all true, and if so, should i be worried? I mean...i'm short sighted and have astigmatism, would either of them cause this?

Thanks, --124.191.80.78 13:50, 19 October 2007 (UTC)

Yeah, honestly, this falls under "don't ask medical questions here". Make an appointment with your optomitrist (or, even better, a ophthalmologist, if you have one). If your vision has changed in any way at any point for long periods of time, you really should see a specialist about it. They can tell you if it's something to worry about or if you just need to up your prescription. Nobody on here is going to be able to reliably diagnose you based on just a simple description of symptoms, even if we were qualified to do so. --24.147.86.187 14:00, 19 October 2007 (UTC)

That said - it's a perfectly normal effect...87.102.7.57 14:06, 19 October 2007 (UTC)

Unless it is a recent change. Then it might be a sign of something else. Anytime something has drastically changed (esp. deteriorated) in terms of vision or health, you should get it checked out. Anecdotal evidence doesn't help much there—I'm near-sighted and see halos around lights at night without my glasses, but I've been to an eye doctor since then (that's why they gave me the glasses in the first place), and they confirmed what the cause of it was, and it was nothing to be too worried about. My anecdotal experience doesn't at all inform his experience and he should see a specialist about it. --24.147.86.187 14:49, 19 October 2007 (UTC)

I'm short sighted - I get the same effect.. probably no worries then.. The low general light level will cause the pupil(iris) to dilate - so the localised points of bright light will be 'off the scale' in terms of what your retina can accomodate - I'm 100% certain it's normal to get this - and someone else can probably explain what's happening - I'd guess some internal reflection on the glasses lens is the cause - under normal (overall bright) lighting conditions this effect would be too dim to see.87.102.7.57 14:05, 19 October 2007 (UTC)

I'm not going to give medical advice, but this sometimes happens to me too, especially when I squint or have water in my eyes. I've noticed I can see rays of light from a star, but not when I wear glasses (it just looks like a point). This can expecially happen through a window, etc. I think you should ask someone else, but don't ask for medical advice. I think this happens to some other people too, though. Hope this helps. ~AH1 14:11, 19 October 2007 (UTC)

Basically if it's just started to happen - see an optician/doctor.. If it's always been like that and you where just curious as to why... then someone could give you an answer.87.102.7.57 14:20, 19 October 2007 (UTC)

Also, make sure you've ruled out scratches on your glasses as a cause. Cleaning plastic glasses lenses with paper causes fine scratches that turn them into fair imitations of star filters --Psud 14:27, 19 October 2007 (UTC)

I get this too, especially when squinting a little. I wonder if there is a name for this effect? I assumed it was some of the light defusing in my eyelashes, as if you squint more and move your head from side to side the 'lines' move in unison. I guess you see it at night as if you are tired you are more likely to squint (or if as mentioned above short sighted) and during the day more of the light sources you will come in contact with are larger and 'spread out' (flourescent strips, VDUs) or very small (monitor lights and all sorts of LEDs) as well as coupled with with natural daylight. Or if in the home you very rarely have naked bulbs, everything gets lampshades stuck on it, where are the streetlights are large points of light in a very dark environment which you are relatively close too. Saying that, I am just totally guessing, but it sounds more than plausible. Lanfear's Bane | t 14:34, 19 October 2007 (UTC)

The effect sounds like diffraction in general, but if you are looking through your eyelashes - moire patterns may also be happening.87.102.7.57

The scratched/dirty lens explaination seems to be likely.. In harsh lighting conditions I often have to extensively clean the lens to reduce all manner of relective, diffractive and refractive effects..87.102.7.57 15:04, 19 October 2007 (UTC)

The description given by the original poster is a very good approximation of the effect I see because of my astigmatism. I strongly urge anyone who has any concerns about their eyesight to consult an appropriate professional, as changes in vision can be indicators of a variety of health problems. DuncanHill 15:28, 19 October 2007 (UTC)

It's worth noting that contact lenses are less good than glasses for correcting certain types of defect.. (for various reasons I wont go into because I'm probably wrong) - this would match the posters desscription of it being worse with contacts perhaps..

Maybe they would like to supply a description of their prescription and we could look into the issue more closely - prismatic and astigmatic requirements would seem likely options for a cause..87.102.7.57 15:37, 19 October 2007 (UTC)

You have almost certainly got early cataracts. The symptom that you describe is a classic first sign. My wife has the same effect, she has had for several years a density of cataract to cause this effect but gets no problems during daylight or normal lighting conditions. She first noticed it with approaching car headlights. Many, many people have cataracts and the removal of cataracts is probably the most common surgical intervention of the eye. You need to go to an optometrist or your family doctor for a further opinion about the type, density and treatment of this possible problem. It is not a serious problem at the moment BUT SEEK PROFESSIONAL ADVICE. Richard Avery 15:47, 19 October 2007 (UTC)

Godels constitution loophole

Did anyone ever find out what Godel's aledged loophole in the US constitution was or will it forever stay in the secret of the judge's office? One link from the article offers a few (pedantic) guesses but not more. Keria 13:56, 19 October 2007 (UTC)

According to the links in the article, he didn't even tell the judge. My only problem with Tribe's answer (that you could, hypothetically, amend the Constitution in order to render it null) is that it's not a "logical contradiction" at all by any standard that someone like Godel should find interesting. A document which says "this document can be modified" is not a contradiction; maybe it's a loophole towards dictatorship (albeit a very obvious one and one which is quite hard to exploit, for that exact reason—they realized in the 18th century that if you made modifying the Constitution too easy it would be meaningless), but that's not the same thing as a contradiction. --24.147.86.187 15:04, 19 October 2007 (UTC)

• As the first article cited points out, "It should be remembered that while Gödel was supremely logical, he was also supremely paranoid and not a little naive." The US Constitution contains lots of concerning passages to those who might read it literally and/or mischeviously. The thing is, the judges never read it this way -- even famed literalists like Antonin Scalia actually apply historical precedent and rules of canon about avoiding absurd or abhorrent results. So long as the executive and legislature obey the Constitution enough to let the judges do the interpreting and then respect the judges' results, the little holes (like the President's ability to start an undeclared war, or Congress's power to determine the qualifications of its own membership) never threaten the Republic itself. So I chalk it up to Gödel's paranoia, brought on by the harrowing experience of seeing several of Europe's supposedly stable democracies come crashing down in rapid fashion. A dictatorship could happen in the USA just as in Europe, but it would happen through force or popular revolution, not through sneaky legal channels. --M@rēino 15:07, 19 October 2007 (UTC)

rubber band paper airplane

Hi. I've tried launching paper airplanes by rubber band via a rubber band hook for the last few years. I'm wondering, are there any records for height, distance, speed, etc, in this category? Is there a maximum hypothesical limit for each of the category, assuming that they are built with common household materials? Is there anything that can be done to make them fly better? What makes some of them fly well and others crapily? Would they, at least hypopthesically, fly farther and longer when launched from a mountain, possibly onto a town below, or would they lose energy and stall or crash? Does angle affect distance? What is the best angle to launch one of these if you want more distance? Can such a plane be built to have more lift without increasing as much drag? Are there any real planes launched in this manner? Would a plane fly better with one rubber band, or by stretching a chain of bands linked together? Would it fly farther if the ground ahead of it was lower than the ground from it was launched? Is it possible to use wind to make it gain forward distance or height, and if so, how? Is there a way to retrieve one from a roof without having to physicly climb the roof? Does a card plane fly better than a paper one? Is it better to use a plastic straw or reinforced paper for the fuselage? Is it possible to attatch roaters, propellers, etc, without increasing more drag than thrust? What is the best design to minimize drag but still have enough lift? Could one that has enough thrust fly on the moon, where there is no lift or drag? Does attatching sand to the behind of the plane where it will fly out of it increase thrust or hinder it? Would it fly faster and farther (please, please, DO NOT try this at home or anywhere else) if launched while on a forward-moving object or veichle? How does a curtain manage to slow such a plane to a halt while it will damage a solid object? If such a plane is launched from the exosphere, would it burn up before it reached the ground or would drag prevent it from doing so? If such a plane were able to somehow reach the sound barrier, would it break or burn up? Is it possible to determine the maximum speed from a still object, height and distance from a flat gound, without launching it? Does a flick of the wrist prior to launch cause it to fly further or faster? Does rain during flight slow down the plane? Would it fly farther/faster/higher if it were lighter or heavier? Is it possible for such a plane to stall if launched horizontally? What can be done to prevent the plane or its hook from crashing into the launcher's fingers? Is there a certain speed that paper cannot handle? Does low or high pressure affect the plane's performance? Is it possible to remote-control such a plane if the things were attatched? Is it possible for an animal to mistake one for a bird? Would it pick up speed or slow down if it were launched straight down from say, a cliff? Does this type of plane act more than an arrow than a paper airplane? Thanks. ~AH1 14:04, 19 October 2007 (UTC)

What a huge question. I'll break that up a bit for easier digestion! (my answers interspersed with the questions where I can be bothered after typing all that up)

1. are there any records for height, distance, speed, etc, in this category?

2. Is there a maximum hypothesical limit for each of the category, assuming that they are built with common household materials?

There would be maximum hypothetical limits. Cardboard, paper, balsa wood, etc can only handle certain accelerations. In fact no matter what limits you put on materials, there would be limits on performance - all materials have limits of exposure to acceleration and heat, for example.

3. Is there anything that can be done to make them fly better?

Yes. Careful attention to weight, strength and aerodynamics.

4. What makes some of them fly well and others crapily?

Usually drag and balance. An understanding of aerodynamics is useful.

5. Would they, at least hypothetically, fly farther and longer when launched from a mountain, possibly onto a town below, or would they lose energy and stall or crash?

Certainly would fly further. Whether it would stall and crash would depend on the plane's trim

6. Does angle affect distance?

Probably. Try it out, make a plane that flies well and launch it at different angles. There will be a particular angle where it works best.

7. What is the best angle to launch one of these if you want more distance?

Experiment with different angles until you find one that works best for your plane and your situation. Note that it may be different on a windy day vs a still day.

8. Can such a plane be built to have more lift without increasing as much drag?

It's always a tradeoff. See Lift-induced drag

9. Are there any real planes launched in this manner?

Not really, but Navy aircraft launched from an aircraft carrier are launched with the assistance of a catapault.

10. Would a plane fly better with one rubber band, or by stretching a chain of bands linked together?

Try it and see. Let us know the result.

11. Would it fly farther if the ground ahead of it was lower than the ground from it was launched?

Yes. Just like with the mountain.

12. Is it possible to use wind to make it gain forward distance or height, and if so, how?

Yes. Launch a light, high drag plane with the wind and it will fly much further. I once won a school paper-plane competition like that, made a light plane with large wing area, trimmed the plane to glide slowly and threw it straight up. Wind carried it 200m.

13. Is there a way to retrieve one from a roof without having to physicly climb the roof?

Try a tool with a long handle, a rope. But no really effective ways that don't risk wrecking the toy.

14. Does a card plane fly better than a paper one?

In some situations. Paper planes get better endurance, card planes can fly faster.

15. Is it better to use a plastic straw or reinforced paper for the fuselage?

Try it and see. I'd expect the paper to withstand the forces involved better.

16. Is it possible to attatch rotors, propellers, etc, without increasing more drag than thrust?

Only if the rotors or propellers are powered.

17. What is the best design to minimize drag but still have enough lift?

Depends on what you're trying to achieve. Make different models with different wing length, different wing area. See which works best.

18. Could one that has enough thrust fly on the moon, where there is no lift or drag?

With impossible materials, yes, if you aimed it carefully enough. Practically? No. No rubber bands exist that could deliver that sort of power.

19. Does attatching sand to the behind of the plane where it will fly out of it increase thrust or hinder it?

Hinder. Unless the sand is thrown backwards under power, for example by a rocket engine. Detailed explanations can wait for someone somewhere where it's not 1am.

20. Would it fly faster and farther (please, please, DO NOT try this at home or anywhere else) if launched while on a forward-moving object or veichle?

Yep. Fly faster or fold up. If it was strong enough to handle the airspeed.

21. How does a curtain manage to slow such a plane to a halt while it will damage a solid object?

Curtains flex and spread the impact over time, china vases don't.

22. If such a plane is launched from the exosphere, would it burn up before it reached the ground or would drag prevent it from doing so?

Probably wouldn't burn up. I would expect it to have enough drag, but that depends on its relative velocity when it's released. Hitting the atmosphere at orbital velocity would not be conducive to the survival of the toy. Hitting the atmosphere at relative velocity of a few metres per second would work.

23. If such a plane were able to somehow reach the sound barrier, would it break or burn up?

If you dropped it out the window of a supersonic plane, the toy would break rather than burn.

24. Is it possible to determine the maximum speed from a still object, height and distance from a flat gound, without launching it?

Yes, but it's hard. Easier to make prototypes and test them.

25. Does a flick of the wrist prior to launch cause it to fly further or faster?

Yes, if it imparts more velocity.

26. Does rain during flight slow down the plane?

Yes. The wings will get wet, presuming they are not damaged by the water, the water will make the plane heavier and mess up its balance.

27. Would it fly farther/faster/higher if it were lighter or heavier?

Depends on the state of the relevant part of the world at that moment. Try it and see.

28. Is it possible for such a plane to stall if launched horizontally?

Yes. If it is trimmed to climb, it will stall

29. What can be done to prevent the plane or its hook from crashing into the launcher's fingers?

Practise.

30. Is there a certain speed that paper cannot handle?

Yes. Depends on the paper and the construction of the paper toy.

31. Does low or high pressure affect the plane's performance?

Yes. High pressure is better for duration, low pressure is better for darts that fly like an arrow.

32. Is it possible to remote-control such a plane if the things were attatched?

Remote control gear is available that works with very light indoor planes. Probably possible, certainly very hard to make an RC paper plane.

33. Is it possible for an animal to mistake one for a bird?

Yes.

34. Would it pick up speed or slow down if it were launched straight down from say, a cliff?

It would slow down, a rubber band catapault plane's launch speed is almost always higher than its terminal velocity

35. Does this type of plane act more than an arrow than a paper airplane?

Depends on whether it's shaped more like an arrow or a plane. Try throwing it from your hand, if it flies, it works like a plane, if it follows a parabolic arc to the ground, it's more like an arrow.

--Psud 14:35, 19 October 2007 (UTC)

How can I tell the difference between male and female seagulls just by looking?

Is there a way? --90.242.17.158 15:15, 19 October 2007 (UTC)

earth science

the study of the motion of planet earth and the other planets are called what? —Preceding unsigned comment added by 157.130.162.178 (talk) 15:28, 19 October 2007 (UTC)

Planetary mechanics is a subfield of celestial mechanics. Marco polo 15:49, 19 October 2007 (UTC)

Understanding singularities

I am a person without a strong background in physics. Can someone explain to me in layman's terms how it is possible for the enormous mass of a supermassive black hole to exist within a singularity, or a point without volume? Where do all of the protons, neutrons, and electrons go? Surely they occupy some volume? Or am I wrong that the singularity encompasses the supermassive black hole? Does the black hole actually have some volume? Thank you. Marco polo 15:52, 19 October 2007 (UTC)

Energy, inertia, or force required to cause injury

A non-profit my father works for maintains a number of recycling bins. The bins had large, heavy, bear-proof steel lids. The lid on one closed unexpectedly and injured a person. They've removed the steel lids and want to replace them with plastic. However, local authorities (in a small town, who have nothing better to do) want some analysis to show that the plastic lids won't hurt anybody. I can do the basic physics of the problem, and get the approximate velocities, or kinetic energy, or whatever, of the lids upon closing. But I can't find a source that will tell me how much energy (I think energy might be the way to go?) or inertia is required to injure a person. The scenario we have in mind is a lid falling on a person's hand. Anyone know where I can find out how much energy or force would be required to cause injury? Thanks, moink 15:52, 19 October 2007 (UTC)

wind speeds

Is there a map showing the locations of the average and maimum highest and the lowest wind speeds on the planet? —Preceding unsigned comment added by Kadiddlehopper (talk • contribs) 16:05, 19 October 2007 (UTC)

I have a Steam Engine Powered Automobile circa 1880's

We have a Steam Powered Automobile circa 1888 +-. My interest is in finding authorities of historic Steam Powered Automobiles from the 1800's to determine it's historic significance and also fair market value for sale. It has been kept in immaculate condition. I may be contacted at <contact details removed for protection>. Thank you. Jon Borovay <detail removed for protection> in the United States. —Preceding unsigned comment added by 76.3.30.44 (talk) 16:06, 19 October 2007 (UTC)

Jon, thanks for your question, I've removed your contact details, as any answer will be posted here, and we want to protect you from spam emails or hoax calls. DuncanHill 16:08, 19 October 2007 (UTC)