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January 16

Bigger, better, faster, Moore?

I got interested in this with the earlier question about Moore's law. For a long time I've noticed CPU speeds have been about constant in the 2-3 GHz range. Why do they not get faster? Here's just one example of a not-too-cheap laptop that only has 2.4 GHz. If Moore's law still applies, why is it about the same as my 5 year old laptop (2.1GHz)? I know the law is about number of processors, and the article says that this is not linearly related to speed, but it does say that "There are cases where a roughly 45% increase in processor transistors has translated to roughly 10–20% increase in processing power." That should still mean a lot of speed, so more processors = faster and better, one would think. What's been happening, and is a 2.4GHz machine today that much better than a 2.1GHz machine from 5 or 6 years ago? I'm asking on the science desk because the other question was posted here, but I also feel it's a more general science issue, and not just for techies (it is after all a consumer-type question). IBE (talk) 05:39, 16 January 2015 (UTC)

http://www.tomshardware.com/forum/336310-28-processor-speeds-increasing Greglocock (talk) 06:05, 16 January 2015 (UTC)

Moore's law is about transistor density. CPU speed is peaked for level-0 SRAM single cycle reads. Up until 8-10 years ago (90 nm), Vt (MOS threshold voltage) and operating voltage was scaling with process. Leakage, cell stability, transistor drive, and the bitline development rate all hit a tradeoff wall at about 1 volt and 2 GHz. Normally, when we used to compare frequency, architecture and pipelining were the drivers. When it became SRAM, all single cycle reads were limited by the same cell so that's why ARM and x86 and all the various other architectures seem to peak at the same frequency. The performance gained is that the SRAM still shrinks so SRAM size increases but it isn't getting much faster. Each technology node has Vt/leakage tradeoff but the current consumed is exponential. This causes power delivery and heat issues that are not as good a tradeoff as more SRAM or processors. --DHeyward (talk) 06:33, 16 January 2015 (UTC)

Heat is an issue, but it's less problematic than you might think. Heat is removable with sufficiently-giant heat sinks or liquid nitrogen coolant; if it were the real problem, you'd see at least certain performance-crazed segments of the market running 10 GHz CPUs with cryo-coolers attached. In reality, the limiting factors for the last decade or so has been signal integrity, not thermal load. If you want to really know why we don't build 5 GHz VLSI circuits with today's technology, here are two books you should read:

• Planar Microwave Engineering: a practical guide to theory, measurements, and circuits. CPUs that run digital logic at 3 GHz are really operating their analog parts in the microwave regime. You need to know how the analog electronics actually behave when you build them on silicon with modern processes. At 3 GHz, with the parasitic capacitances that are inherent to real transistors that we can actually build, square-waves look pretty not-square, and ones look an awful lot like zeros. Things get worse when signals have to cross clock domains, or worse yet, leave the substrate across a wire bond.
• Computer Architecture: A Quantitative Approach. No punches pulled, this book runs the numbers on practical and theoretical computer architectures, so that you can understand whether the performance limitations are due to pipeline depth, cache strategy, data hazards, and so on.

Nimur (talk) 07:19, 16 January 2015 (UTC)

No, heat, power density and IR drop really becomes intractable (and a poorly scaled) problem at the die level. 1 volt @ 130 Watts is 130 amps. Put that into a square centimeter chip with IR drop and inductance and power delivery (and heat removal) become huge, expensive issues. These high-performance CPU's are all flip-chip and die size has to be large when power is high so they have enough power delivery bumps. Wire-bond is out of the question due to inductance and the di/dt requirements. Because frequency is a function of voltage and power is V^2, the resulting increase in power with the increased frequency is effectively a V^3 scaling. So linear increase in frequency comes with cubic increase in power. --DHeyward (talk) 09:19, 16 January 2015 (UTC)

The Core i7-4700MQ CPU in that laptop actually runs at up to 3.4 GHz, temperature permitting. It also has 4 cores supporting 8 logical threads, while your older laptop most likely has 1 or 2 cores supporting 1 or 2 threads. Each core has a sustained maximum throughput of 4 micro-ops per cycle versus earlier generations' 3, and the execution units support 256-bit SIMD registers (AVX) versus your laptop's 128-bit SIMD (SSE). There's probably substantially more on-die cache RAM, and Intel has made various incremental improvements to other aspects of the internal architecture. Putting all of that together, it could easily be twice as fast as your laptop or more on realistic computing tasks. That's not very impressive for 5 years by historical standards, but CPU performance hasn't completely flatlined. (Source for some of the above: Agner Fog's microarchitecture manual.) -- BenRG (talk) 09:44, 16 January 2015 (UTC)

should you mix water back into sour cream, or drain it?

If you open a package of sour cream and there's some water inside, should you drain it (since it's water) or mix it together (on the theory that it was supposed to all be together, that's how much water should have been inside anyway)? — Preceding unsigned comment added by 212.96.61.236 (talk) 07:38, 16 January 2015 (UTC)

I usually drain it, but it's just water. Won't hurt or help much. Can always replace it later if you want, but it'll go rancid before it ever dries out in a fridge. Emulsifiers make sure of that. InedibleHulk (talk) 08:08, January 16, 2015 (UTC)

First, check the expiration date. ←Baseball Bugs carrots→ 08:19, 16 January 2015 (UTC)

I just realized my sour cream company also sells the ingredients. Yours might, too. I'd never thought of sour cream as something to repair instead of replace, but if you're feeling frugal, you might be able to save the mixture, well beyond the best before date. InedibleHulk (talk) 08:30, January 16, 2015 (UTC)

My sour cream company also doesn't believe in real milk. InedibleHulk (talk) 08:38, January 16, 2015 (UTC)

Under that first link under "Flavour" it says, hilariously, "Bland flavour with a hint of dairy." 212.96.61.236 (talk) 08:45, 16 January 2015 (UTC)

The honesty's refreshing. I can't count how many times corn-based ingredient-based products have implicitly promised to blow my face off. According to a guy on the Internet, the missing "amazing explosion" ingredient (and they aren't missing many) is plain old sour cream. Keep it real, Doritos. InedibleHulk (talk) 03:52, January 17, 2015 (UTC)

Watch for the new nitrogen triiodide flavor.  :) (Though of course it is more practical for use in a jawbreaker) Wnt (talk) 19:31, 17 January 2015 (UTC)

Mmmm...legitimately destructive. Those would also give a nice zing to Pop Rocks. InedibleHulk (talk) 22:18, January 17, 2015 (UTC)

Subterranean rivers

Do subterranean rivers generally end up discharging into the sea like most other rivers? I always assumed so but the article doesn't say. If so, do we know where any of these "mouths" are?--Shantavira| 12:37, 16 January 2015 (UTC)

The article names many of the mouths. The water has to go somewhere, after all. However, in some cases like the Mojave River that destination may be an inland delta on a salty lake, or even just to dry up as an intermittent river. Wnt (talk) 15:34, 16 January 2015 (UTC)

Ending at an Endorheic_basin would be another option. SemanticMantis (talk) 15:41, 16 January 2015 (UTC)

Hmmm...this is a very good question!

Surely it can't be just like above-ground rivers draining into above-ground seas because in that case, evaporation from the oceans forms clouds which causes the water to rain on hilltops and mountains to keep the rivers flowing and to stop the seas from eventually overflowing.

Below-ground, what is the mechanism to lift the water from subterranean lakes/seas back up to the source of the water for the subterranean rivers? I presume that some water makes it back to the surface from geysers and such - and water flows into the subterranean rivers from the surface to keep them flowing...but it's hard to believe that enough water is lifted to the surface to keep the levels of large underground aquifers from just filling up and causing the underground rivers to stop flowing.

Obviously, for shallow underground water, it can arrive back onto the surface from a spring - but that's not going to work for rivers that are further below ground than the lowest point in the local topography.

SteveBaker (talk) 16:09, 16 January 2015 (UTC)

It all gets cycled (eventually) of course, e.g. subsurface flow, groundwater flow, water cycle, etc. If you want to know how long water stays in a given system, you can look up estimates for Baseflow_residence_time. SemanticMantis (talk) 16:31, 16 January 2015 (UTC)

I can't say for all caves, but for one of the major ones, Mammoth Cave National Park, whose profile looks like this, its underground river flows downhill at a shallow angle and then opens out into the Green River, a tributary of the Ohio. ←Baseball Bugs carrots→ 17:22, 16 January 2015 (UTC)

Some of those underground streams (fountains of the deep) come up under the sea and are known as vruljas, eg at Bay of Mali Ston, Ngaruroro River, Chekka Wonky hole and Pisak. Graeme Bartlett (talk) 02:10, 17 January 2015 (UTC)

Thanks. "Vrulja"! We like that word! And wonky holes, which could only be Australian! Thanks!--Shantavira| 08:50, 17 January 2015 (UTC)

Raspberry Ketone B.Half life

How could I know the Biological Half life of Raspberry ketones?, I wouldn't mind import it from a source you guys consider reliable, to the article. Thx, Ben-Natan (talk) 16:29, 16 January 2015 (UTC)

A quick search of raspberry ketone urine on PubMed turns up PMID 7113261, which compares its metabolism in rats, guinea pigs and rabbits, saying that 90% is excreted within 24 hours and listing metabolites (sounds like the usual: molecule meets oxygen, molecule loses). But it's in a really obscure journal, so a PITA to look up. You could take the log₂10 and suppose that the half-life is 24/3.32 = 7.2 hours, but that's a fraught assumption since there could be many sequential steps the molecule goes through that impose various delays so that it doesn't pee out according to a log table. (I suppose even saying "half-life" already wades into these issues, come to think of it) In any case it would be OR; stick to what the paper says. :) Wnt (talk) 13:34, 17 January 2015 (UTC)

Kg to lunar lb

How much does 22kg weigh on the moon? Apollo_11#Lunar_ascent_and_return says that the astronauts lifted two sample boxes containing more than 22 kilograms (49 lb) of lunar surface material, but because of the moon's lesser gravity, 22kg weighs a lot less than 49lb. 65.210.65.16 (talk) 19:25, 16 January 2015 (UTC)

The Moon's gravity is 0.1654 of Earth's, so a mass of 49lb would "weigh" 49 times 0.1654 on the Moon. Note that the mass remains unchanged, so extra care has to be taken when the mass is moving because it has the same momentum as on Earth. Dbfirs 19:48, 16 January 2015 (UTC)

(ec) Both kg and lb are used here as units of mass. Although the Pound (mass) can be used as a unit of weight, this is also true of the kilogram. See Mass versus weight. Weight is not a very useful quantity when talking about the contents of a sample. However, if you used a spring-based or electronic scale, 22 kg on Earth weighs 0.1654 * 22 = 3.64 kg on the moon, which is equal to 8.02 lb. - Lindert (talk) 19:49, 16 January 2015 (UTC)

Actually Lb is always weight but in standard gravity, it's a constant relation to mass. The term for mass is Slug --DHeyward (talk) 21:22, 16 January 2015 (UTC)

That's not what I was taught! A slug is a rarely-used unit of mass, along with the Pound (mass). Dbfirs 21:27, 16 January 2015 (UTC)

Whether one is taught about pounds as a unit of weight depends on where one studies and what discipline. As a physics student in Canada, we were taught that pounds were strictly a unit of weight, and slugs are the appropriate "imperial" unit of mass. American engineering students, on the other hand, seem to be taught how to work with pounds as a unit of both mass and weight. I have run across kg as a unit of force in the U.S., which to me is an abomination.--Srleffler (talk) 03:25, 18 January 2015 (UTC)

In the UK in the 60s/70s, we were taught that a pound is a unit of mass, and its associated force is a poundal.--Phil Holmes (talk) 11:43, 18 January 2015 (UTC)

Yes, I remember meeting the slug as an amusing aside in the 1960s, but the poundal was much more common as a unit of force in the Foot–pound–second system (where the pound has to be mass). It seems that Canada used a different system which our Template:GravEngAbs calls a "British Gravitational System", but the link is circular and the text says that it is used by American engineers. I'm baffled! Dbfirs 13:32, 18 January 2015 (UTC)

The kilogram is a unit of mass. A mass of 22 kg will still have a mass of 22 kg if it is relocated from the Earth to the Moon. The force of gravity, at the surface of the Earth, is the mass times the acceleration due to gravity, 22 × 9.807 ≈ 215.8 newtons. On the moon the force on the object due to gravity is 22 × 1.622 ≈ 35.68 newtons.

It would be foolish to further contaminate the Moon with US customary units so I will not do so. Jc3s5h (talk) 21:51, 16 January 2015 (UTC)

If you're suggesting that the metric system is the realm of lunacy, I won't argue. Now, here's a poser: How many newtons does one fig newton weigh? ←Baseball Bugs carrots→ 22:12, 16 January 2015 (UTC)

If ever I visit the Moon, I shall make a point of taking some Imperial units with me, especially a 100-year-old pound mass that I happen to own. Fortunately for Jc3s5h, I'm not likely to make that journey. Dbfirs 22:22, 16 January 2015 (UTC)

What software would you use to model something spreading in water (river, lake, sea)?

What software would you use to model something spreading in water (river, lake, sea)? — Preceding unsigned comment added by 31.4.152.13 (talk) 23:45, 16 January 2015 (UTC)

The look of it? Maybe Blender. The actual physics? Maybe Simulink. 75.75.42.89 (talk) 00:38, 17 January 2015 (UTC)

How about reading Schlumberger's Water Services software overview? They sell the world's best aquifer management, monitoring, and simulation software. Nimur (talk) 00:50, 17 January 2015 (UTC)

Thanks you both. I'd take a look at both options for modeling the physical process. My interest is not to make a visual model with tools like Blender, but to understand what will happen next (after an oil spill or other type of contamination of a water resource.--31.4.153.226 (talk) 01:16, 17 January 2015 (UTC)

Here's a full book available at no cost from the Bureau of Ocean Energy Management: Review of the State-Of-The-Art on Modeling Interactions Between Spilled Oil and Shorelines for the Development of Algorithms for Oil Spill Risk Analysis Modeling. Fascinating topic! The software involved in fluid flow simulations pushes the state-of-the-art in scientific computing, so this is not necessarily going to be an easy topic for a hobbyist; the softwares that exist are frequently custom-made, and aimed at a small community of highly-skilled expert users. Nimur (talk) 03:25, 18 January 2015 (UTC)

Note that if you're talking about something biological, like an algal bloom, then quite different software would be needed. StuRat (talk) 06:27, 17 January 2015 (UTC)

It really depends on what your specific goals are. The mathematical analysis will basically be done with a type of Convection–diffusion_equation. The commercial products will still have that at the core. Here is some code and instructions that will let you model various simple cases in MATLAB - . SemanticMantis (talk) 17:27, 18 January 2015 (UTC)

January 17

Tail of comet Lovejoy

Is the tail of C/2014 Q2 (Lovejoy) currently pointing roughly toward the Pliedies? I could see a fuzzy spot and perhaps some tail. Bubba73 00:49, 17 January 2015 (UTC)

I just found the setting while looking for which way the post-1997 Great Comets pointed. You can answer questions like this by going to , setting the table to 27 and reading the numbers. The numbers are the direction the gas and dust tails are pointing (0 points to the NCP (use Polaris), 270 to the direction it's setting or rising), 90 away and 180 to the celestial south pole. If you're 45°N say, then 180 points towards the point that happens to be halfway between down and south. At 30°N it points only 30° down. Sagittarian Milky Way (talk) 01:44, 17 January 2015 (UTC)

I don't see anything there about setting the table to 27. I'm not wondering about the numerical direction - I'm asking if the tail is pointing roughly towards the Pleiades at the present. Bubba73 02:17, 17 January 2015 (UTC)

Ah, you'll have to fill in the time, place, object and table settings links on that page. And leave only "Table Setting" checkbox number 27 active. I'm not too interested in this comet (invisibly dim here) but I'll fill out the forms for you and translate to English if you want. Sagittarian Milky Way (talk) 02:41, 17 January 2015 (UTC)

That seems like an unnecessary amount of work. Someone should know whether or not the tail is pointing roughly toward the Pleiades right now. If it is, then I think I saw some tail. If not, I didn't. Bubba73 03:21, 17 January 2015 (UTC)

I filled in the forms and the gas tail indeed was pointing just like you said. It is close to the Pleiades and moving in space so it won't quite point there tomorrow.

The dust tail though was pointing sideways from the Pleiades direction (down if it's dusk). If you want to try to see it's best when it's highest around 7:30 pm. Sagittarian Milky Way (talk) 03:57, 17 January 2015 (UTC)

Wow, thanks, then I believe I did see some of the tail. My daughter and I saw it tonight about 8PM with 7x50 binoculars. This was the first clear night in several nights and it is going to cloud over again tomorrow. The last time it was clear, the Moon was too close and bright. Bubba73 04:01, 17 January 2015 (UTC)

I guess you could try the day after. And I somehow made a mistake out of laziness so it in fact points the most accurately this weekend and not yesterday. Sagittarian Milky Way (talk) 04:25, 17 January 2015 (UTC)

The forecast is for mostly sunny Monday and clear Wednesday - otherwise cloudy. Bubba73 04:29, 17 January 2015 (UTC)

The gas tail will point 10 and 30 degrees off then. (how far you'd need to rotate it to line up, not how far a line continuing the tail will miss by — that can hardly be 10 degrees when it's only 12 degrees away) Try to look with slight peripheral vision after 30 minutes in the dark (or red light). Make the comet move instead of staring at a fixed spot (as that's what peripheral/night vision is good at detecting). And don't use the temple side blind spot, that makes above and below the only option with binoculars. Let me know if you see the dust tail. Sagittarian Milky Way (talk) 06:20, 17 January 2015 (UTC)

My eyes are 60 years old so they don't adapt to the dark as well as they used to. Also, in '99 I had an eye problem that left me with a lot of blind spots. It is hard for me to recognize constellations that I used to know because some of the stars fall on the blind spots. Also, there is quite a bit of light pollution. Bubba73 07:01, 17 January 2015 (UTC)

No, light pollution is when you can see your fingerprints 4 miles from downtown by cloud light :). Light pollution is when you're almost a hundred kilometres from downtown have only two thin strips of suburbs within 40 miles and the pink around the stars is merely "reduced significantly". Sorry about your eye problem, I sympathize. I guess you could try looking in spirals around the tails, this might make them appear to suddenly pop out of nowhere so having blind spots would make it easier. Sagittarian Milky Way (talk) 17:15, 17 January 2015 (UTC)

How farther apart in wavelengths do two lights have to be in order to appear like two distinct colors to the human eye?

Awkward phrasing, I know. But I am not sure of the term to describe this concept, so I write out the question like so. Anyway, I know that a normal human eye can certainly distinguish orange and yellow on the visible light spectrum, but how close do they have to be to be distinguishable? I mean, in my crayon box, there may be "Lemon", and there may be "Yellow", and they look very similar to each other until I use them to mark the paper and see a slight difference. 71.79.234.132 (talk) 05:40, 17 January 2015 (UTC)

Your phrasing is fine (except "farther" should have just been "far"). We recently had a similar question about how many colors the human eye can distinguish. Let me see if I can find it... StuRat (talk) 05:47, 17 January 2015 (UTC)

...I think this is it: Misplaced Pages:Reference_desk/Archives/Science/2014_April_27#How_much_COLORS_in_the_RAINBOW_do_see:..._.28.3F.3F.3F.29. StuRat (talk) 05:50, 17 January 2015 (UTC)

There is no simple answer to this unless you are colourblind. Humans may have, develope and unfortunately also loose sensual abilities in a wide range. This range is more commonly known in the field of soundwaves, where for example an classical music concert to one person is not much more than "allot of noises" but in that same moment another person may be able to hear one single violin is not played perfect. Its part gift, part training. Graphic artists or printers for example are certainly trained to distince colour much better than average.--Kharon (talk) 14:32, 18 January 2015 (UTC)

Use of DNA to solve crimes

Let's say that we have a hypothetical crime scene. My understanding is that the perpetrator's DNA can be extracted if the perpetrator leaves behind any of the following at the crime scene: his blood, semen, feces, hair, or skin cells. Is my understanding correct on those five items? (I believe so, but I am not 100% sure.) Now, my real question involves two other items: perspiration and urine. Do those items also contain the perpetrator's DNA? Let's assume that the items mentioned above are of sufficient quantity for DNA testing. Thanks. Joseph A. Spadaro (talk) 07:13, 17 January 2015 (UTC)

Accoring to Urinary cast#Cellular casts celluar debris is detectable in urine. (don't forrget salvia and tears) Another reference: http://www.nytimes.com/2010/11/02/science/02qna.html --Digrpat (talk) 08:45, 17 January 2015 (UTC)

DNA is even present in your breath. 2A01:E34:EF5E:4640:5CFF:AF8:B79:73A8 (talk) 10:04, 17 January 2015 (UTC)

It used to be if you murdered a baby, you could frame it on the cat's natural tendency to eat that sort of thing. Not anymore. Well done, science. InedibleHulk (talk) 11:41, January 17, 2015 (UTC)

There has been some work on getting DNA from fingerprints but Google gives many false hits when searching on those terms. Rmhermen (talk) 17:02, 17 January 2015 (UTC)

One thing that always worries me when I hear about a murder being "solved" by finding one hair, etc., is how easily that could be innocently transferred. Anyone who has ever been in your home or met anyone in your family outside the home might very well have left some of their DNA in your home. Possibly even further out, somebody who shook hands with an intermediary, who shook hands with you, might have their DNA on you. So, as the sensitivity of our tests go up, to where we can analyze smaller and smaller samples, we may get more and more false positives.

I would think the first Q any defense attorney should ask the DNA analyst would be "how many unique DNA donors were you able to identify at the murder scene ?". The answer should make it clear if everyone in the neighborhood has left DNA behind there, just how meaningless the presence of any one person's DNA sample there is. StuRat (talk) 17:01, 17 January 2015 (UTC)

Yeah, but they make DNA databases from criminals, i.e. anyone who is ever arrested, whether or not the charges stuck. Since the only hit in the DNA database is a criminal, the only criminal who was on the scene is the person in the DNA database, Q.E.D. he done it. Wnt (talk) 21:54, 17 January 2015 (UTC)

Yes, they have databases for the DNA of criminals. But, they can also compare the DNA profile to any person (for example, a suspect), whether that person is a criminal or not. In other words, they don't only look at the criminal DNA database. They can look at anyone's DNA, even if the person is not in the criminal database. Joseph A. Spadaro (talk) 02:12, 18 January 2015 (UTC)

(I assume the small text is because you're kidding, but others might take you seriously.) StuRat (talk) 22:10, 17 January 2015 (UTC)

I thought it was funny. But then, I've never gone to prison for something the cat dragged in. They may not eat your soul, but they do lick your beard. Another good first question for a defender is "Where'd you find it?" A hair or drop of blood on a carpet or doorknob is far less damning than it is under the victim's fingernails or in her butt. InedibleHulk (talk) 22:22, January 17, 2015 (UTC)

Skink ID

Can anyone identify this species? Someone else uploaded it, so all I know is that it's a skink in Australia: what part of the country, what exact size, etc. I can't tell. All I can suggest is (1) checking the uploader's contributions to see if there's a geographic pattern (i.e. if he has a bunch of Australian photos from a specific region), although I have to run and can't get that now by myself, and (2) perhaps this is in the country's northern regions, as EXIF says that this is taken in late September; it looks like a rather lush environment, not the kind of thing you'd expect to see at the end of winter in a temperate environment. Nyttend (talk) 12:05, 17 January 2015 (UTC)

Eastern blue-tongued lizard. Snow talk 13:12, 17 January 2015 (UTC)

FYI, Nyttend, I've taken the initiative in updating the file description on commons. I think it's a decent quality photo that should probably be added to the article for the lizard as well. Snow talk 23:34, 17 January 2015 (UTC)

genetics (origin of somatic cell chromosomes)

in a human somatic cell, in the autosome pairs, is one of a pair totally from the mother and the other totally from the father? thx.72.183.121.78 (talk) 12:54, 17 January 2015 (UTC)

Not necessarily. Genetic recombination is best known in the context of meiosis, but it can also rarely occur in somatic cells during mitosis. See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3090628/. Looie496 (talk) 15:22, 17 January 2015 (UTC)

thx. that is very interesting. I guess my question should be: is most (or almost all) of one of a pair of autosomes from the mother and most of the other from the father (especially before a lot of cell divisions)?72.183.121.78 (talk) 15:58, 17 January 2015 (UTC)

I don't see how that is different from the original question, so I probably don't understand it. Looie496 (talk) 02:49, 18 January 2015 (UTC)

I really appreciate your patience. if I may: in the first few divisions after the egg is fertilized and absent the rare mitotic recombination, is one of the pair almost totally from the mother and the other almost totally from the father?72.183.121.78 (talk) 03:47, 18 January 2015 (UTC)

Yes, because chromosomal crossover occurs during meiosis, i.e. before the gametes exist. See homologous chromosome though it's not very clear, could use work. This is particularly relevant in genomic imprinting of insects such as mealybugs, where the entire paternal genome can be turned off (heterochromatin) pretty much as a unit. Wnt (talk) 04:07, 18 January 2015 (UTC)

thx much.72.183.121.78 (talk) 12:58, 18 January 2015 (UTC)

How and from what are hormones in pills/medical treatment created?

I've always wondered, with all the hormonal treatment given to lots of people in modern society, where does the hormones in pills etc. come from? Be it testosterone, estrogen or some other hormone, and be it in the form of pills or alcoholic gels etc.

It has to be artificially generated/created before put into pills or gels, right, but from where and how? It just seem so strange to me that they can create and put something like that into pills and the likes, something which are supposed to only be naturally generated inside an individual's body.. When it comes to other types of medicine, it is easier to understand how and from where the key ingredients come, because they are often natural resources that can be gathered.

So, to repeat my question; How, from where and from what do they make hormones used in medical treatment? 2A02:FE0:C711:5C41:1CEC:1194:53D:204E (talk) 13:36, 17 January 2015 (UTC)

Some are made by GMO, coping an appropriate set of genes into a suitable bacteria. Insulin is extracted from yeasts, it used to be extracted from pigs, Estradiol (part of the combined oral contraceptive pill is directly synthesised. Progestin (the other part of The Pill) doesn't indicate its synthesis/extraction. Testosterone-like hormones can be synthesised. It really depends on how complex the hormone in question is, and if there is a near-analogue already made by another species. LongHairedFop (talk) 14:38, 17 January 2015 (UTC)

"something which are supposed to only be naturally generated inside an individual's body." is an interesting comment. Chemicals don't know where they come from, they just exist, and have no really intrinsic difference based on their origin. It's something of a marvel of modern science that we can start from a non-biological chemical and make one, but total synthesis isn't a new field of productive research (and vitalism started to be disputed and disproven almost two centuries ago). DMacks (talk) 16:37, 17 January 2015 (UTC)

Thanks for answers. Today's education for me, that is. They say we all learn something every day.. :) I agree by the way that it is "something of a marvel of modern science that we can start from a non-biological chemical and make one." 2A02:FE0:C711:5C41:1CEC:1194:53D:204E (talk) 18:17, 17 January 2015 (UTC)

Premarin is extracted from the urine of pregnant mares. --TammyMoet (talk) 20:09, 17 January 2015 (UTC)

On an interesting historical note, the original source of the precursors for the hormones in birth control pills was yams. See our article. In the 1950s some yam species were found to be abundant sources of steroid compounds that could be converted to sex hormones. And another thing: in the Trobriand Islands, yams are a staple food, and the yams found there contain steroids with contraceptive activity. The regular consumption of these was a factor in the development of sexual mores that are very alien to traditional Western society. --71.104.75.148 (talk) 01:52, 20 January 2015 (UTC)

Main Battle Tank

When I read the information about tanks` maximum range , I noticed an issue which is that the M1 Abrams and all other tanks that use diesel fuel have almost the same range , but once a time I hear that the M1 Abrams refuel each four and a half hours while diesel fuel tanks refuel every 24 hours while watching a documentary film , so how can I understand this contradiction ? 46.185.161.90 (talk) 14:02, 17 January 2015 (UTC)

Simple. They almost certainly mean different things. At a guess, a tank can do 4 or 5 hours of heavy maneuvering before it runs out of fuel (there's your M1 answer -- how long can a tank drive at highway speed). At a guess, an army in combat plans to refuel its tanks daily so that they don't run out in combat the next day, whether or not they've maneuvered heavily the day before (there's your other tanks answer -- what an armored unit's logistics plan is). — Lomn 14:28, 17 January 2015 (UTC)

(ec)You may misremember ;-). The M1 Abrams guzzles fuel, but it also has a much larger tank than e.g. the Leopard 2 - the M1A gets 426 km out of 1900l (for 446l/100km, or about 100 times worse fuel economy than a modern compact car), the Leo 2 gets 550km out if 1200l, for more or less twice the fuel efficiency. How often either needs to refuel depends very much on how they are used. Driving either 420km or 550 km in a tank looks like a full peace-time job for one day to me, so normally you can fuel up in the morning and will run out when you are about to turn in anyways. With the M1A there is a somewhat larger chance that you need to refuel during the day... --Stephan Schulz (talk) 14:46, 17 January 2015 (UTC)

Anecdote alert: During the first Gulf War, the US armour couldn't get to Baghdad because they ran out of fuel. The reason was that they were employing local people to drive the fuel trucks. These people were using them to drive off to visit their families and would disappear for days, plus, even if they didn't do that, they had to pray five times a day, and would always turn up late. This problem was solved in the second Gulf War, by employing Europeans. KägeTorä - (_虎) (Chin Wag) 05:01, 18 January 2015 (UTC)

Or they thought they did. But when they tried it, they found in practice the Europeans were arriving many days later. They found that the problem was the Europeans were demanding 15 minute tea breaks every few hours and similar for smoke breaks, 1 hour lunch breaks and stuff like that. And they would only work 8 hours or if you got lucky, 12 hours. The Iraqis may have prayed for 10 minutes 5 times a day and sometimes disappeared to see family for an hour or two, but otherwise they drove for 18-20 hours straight only taking a few minutes for lunch. Plus you could hire 30 Iraqi drivers for the price of 1 European, so they couldn't hire 3 per truck like they could when someone was concerned about the safety of driving 18 hours. And in any case, long hours aside, the Europeans didn't seem to know how to drive on roads where you may have random camels, motorcycles and whatever else appearing out of nowhere all time. After spending $30 million on several consultants trying to work out what they could do, an intern in the White House suggested they could just use more realistic timetables, and suddenly all was solved. Everyone was happy. The consultants made many many millions more of the years, the tank, fuel truck and other weapon and support system manufacturers billions. Well except may be the intern who went on to teach the children of these consultants and manufacturer CEOs and made about $80k a year until they got fired and blacklisted for saying something innocuous but which made it to the parents who didn't like, and now works at a public school making $30k. Nil Einne (talk) 07:36, 18 January 2015 (UTC)

Actually, as our article states, the U.S. military typically fuels the M1 with JP-8 jet fuel. The U.S. military uses JP-8 for all its ground vehicles as well as aircraft, to simplify logistics. Other users of the M1, like the Australian military, do use diesel. Also interesting is that the M1 is different from most tanks in having a turbine engine, instead of a reciprocating engine like what you would find in a car or truck. --71.104.75.148 (talk) 02:03, 20 January 2015 (UTC)

Mallard ducks in Britain

Do mallard ducks in Britain migrate for the winter, and if so, where?

Also, presuming they do migrate, is there documented behaviour of them returning to the same lakes, year after year? If yes, are these lakes the lakes by which they hatched?--Leon (talk) 16:01, 17 January 2015 (UTC)

The RSPB is your friend.--Phil Holmes (talk) 18:21, 17 January 2015 (UTC)

That article confirms my anecdotal American experience, which is that mallards usually stick around their specific habitat year-round, provided there's sufficient food. ←Baseball Bugs carrots→ 12:34, 18 January 2015 (UTC)

Backing that up with equally anecdotal British experience, it's common to see mallards standing on frozen ponds in winter. AndrewWTaylor (talk) 13:36, 18 January 2015 (UTC)

Road stabilisation

Are all roads stabilised either mechanically, or with a binder? Is it possible to have an unstabilised road other than a dirt road or roads with unbound bases. Can the term stabilisation also be used for the surface course which is normally bound with bitumen? 82.132.239.245 (talk) 18:56, 17 January 2015 (UTC)

1. No, some roads are stabilised with cement, which is not a binder.
2. No, no other public road types may be unstabilised.
3. Not sure.

This is based on New Zealand definitions. Plasmic Physics (talk) 03:10, 18 January 2015 (UTC)

Heat effect on skin: study of blow drier users versus non-users

So, I heard that basically the most damaging things to skin are the sun, and heat. Those who avoid the two (use sun-screen and don't take scalding showers) have fresh skin for longer. I've used this advice to good effect and can easily subtract a quarter of my age and be believed (say 24 at 32).

separately, I've always towel/air dried my hair. I've recently adopted a new look, and was taught to blow-dry for it. (Though not strictly necessary; but if I don't, if I air-dry, then it is wavy/curly instead of straight. I prefer the latter.)

So, here is my question: just how damaging is blow-drying (scalding hot) hair in the mornings, to skin, over a period of years (if I had this look for years)?

Best would be if I could simply see some comparison pictures. For example, here is a picture of someone half of whose face happened to be sunlit over a period of years: http://www.doobybrain.com/2012/06/04/unilateral-dermatoheliosis-the-effect-of-the-sun-on-human-skin/ (and there are many similar ones). It's a dramatic demonstration.

Are there some photos I could see of scalps and faces of blow-drier users versus air-drier users? I'd just like to know how strong the effect is. The blow-drier is scalding hot, but lasts just a couple of minutes. (I don't think drying on the cold setting produces the desired effect with the technique I've learned, and anyway I would catch a cold every morning I wash my hair. Towel/air drying produces totally different hair.)

Also, if you can't find any references, photos, I've thought of another way. If there are actors/actresses who obviously and for years wear a straightened, blow-dried look (that they obvoiusly repeat frequently) I could look at their faces versus ones with shorter/wavier hair or who have gone on record as air-drying. It is easy to follow actors' aging over a period of years (longitudinally) since they're always in the public eye.212.96.61.236 (talk) 22:17, 17 January 2015 (UTC)

I can find nothing on the web about hair driers damaging skin, but having said that we can't give medical advice, so I can't tell you they definitely don't cause skin damage. You may be interested in this and this. I think finding pictures of actors with blow dried hair is a little outside the scope of the science reference desk :-) Richerman (talk) 23:18, 17 January 2015 (UTC)

Yea, this is the first I've heard of hair dryers damaging skin. Are you sure you didn't hear somebody say they damage hair ? To damage skin, they would need to leave a burn, I would think, and that seems more likely with a curling iron than a hair dryer. Of course, a hair dryer might tend to dry out the skin, but that's nothing a little moisturizer won't fix. StuRat (talk) 01:20, 18 January 2015 (UTC)

(OP here). My very strong impression is that the two respondents are wrong and getting blown on by scorching hot air ages skin over time - I would just like to know the magnitude of the effect. The idea that you can blow scorching hot air all over your scalp and delicate facial skin without aging them is obviously wrong on its face and counter to everything I've read or know about keeping from stressing skin. I don't mean to a major extent or anything - just something that visibly ages you and causes wrinkles, etc. If it really does cause no effect, I'd love to see this in a dermatology journal or something. 212.96.61.236 (talk) 02:07, 18 January 2015 (UTC)

Can you provide any sources for this belief ? The top layer of skin is dead, and removing it to get to the "fresh skin" below is what exfoliation is all about. And just how hot is this air if you are actually creating burns on your skin ? Obviously don't do that. Sunlight causes damage by penetrating below the dead skin and damaging the DNA of the live skin below. You can tell it is damaging the skin because excessive sunlight causes sunburns. If excessive hair drying caused similar burns to the skin, then I would agree that you are damaging it, but that shouldn't happen unless the heat is way too high. StuRat (talk) 04:11, 18 January 2015 (UTC)

It's hot enough to scorch my ear if I'm not careful, I have to do it carefully. I guess I could use the next setting down, but the question was in general. I'll provide a source for the belief. Google "heat damages skin" - https://www.google.com/search?q=heat+damages+skin one article on a topic that happens to include heat (http://www.huffingtonpost.com/2010/10/04/warm-laptops-may-cause-sk_n_749049.html) says "Salkey, an assistant dermatology professor at Eastern Virginia Medical School, said that under the microscope, the affected skin resembles skin damaged by long-term sun exposure." So it's not just UV exposure from the sun. That is about laptop heat but heat is heat. A hairdrier is waaaaaay hotter than a laptop. it would be uncomfortable if I held it too close or too long. it's really hot! Here is a whole article on heat-related skin damage: http://en.wikipedia.org/Erythema_ab_igne so I think if you read through the Google search I linked, you can synthesize that there could be something going on here related to heat and heat alone. By the way we're talking about a professional, very hot and very high airspeed blowdrier here. It's extremely hot. 212.96.61.236 (talk) 08:36, 18 January 2015 (UTC)

Turn the heat down dear, turn it down, it ain't rocket science. What kind of ***** uses a hair dryer that burns their ear. You could save the planet and your ear (have you got only one) by turning it down. Richard Avery (talk) 08:49, 18 January 2015 (UTC)

But I don't hold it close to my ear on that setting, I'm just mentioning that it gets hot enough that it would burn me (not literally) if I did. I hold it to my wet hair, obviously. Other than blowing hot across my face for a few minutes, it doesn't bother me. I'm fine with the result and the experience. The only question I have is whether getting blown across the face by very hot dry heat every day or couple of days causes skin damage over the long term or not.... people's impressions were "no, only UV light does that" but my references seem to be "yes." Also, as I mentioned earlier the style of hair I like now is made with very hot blowdrying (and using a round brush). It's just very hot (doesn't bother me per se, unless I weren't careful.) 212.96.61.236 (talk) 09:07, 18 January 2015 (UTC)

On reflection, the references I provided at sturat's request are convincing to me. specifically our ab igne article "Prolonged thermal radiation exposure to the skin can lead to the development of reticulated erythema, hyperpigmentation, scaling and telangiectasias in the affected area". I think I will try to avoid getting hot air on my skin. 212.96.61.236 (talk) 09:29, 18 January 2015 (UTC)

Those sources say the problem comes from elevated skin temps for hours at a time. Presumably it only take you a few minutes to blow dry your hair. But yes, turn the heat down and the fan speed up, if possible, so as to reduce the risk of burns. StuRat (talk) 05:06, 19 January 2015 (UTC)

January 18

Science method: If you want to compare a stock picking algorithm, a stock broker or a fund to a random number generator

How would you pick a range for the random numbers? (I suppose that experiment where monkeys thow darts is just a construct and not a thing that really happened).--31.4.154.9 (talk) 00:43, 18 January 2015 (UTC)

I'm not so sure - most fonds seem to work exactly that way. Anyways, there are many ways to set up such an experiment - for each stock in the Dow Jones, throw a die and spend your capital equally on all stocks that come up with a six. Every day, role for all stocks you have and sell the ones that get a one, then repeat the buying procedure with the capital you just got. Or indeed arrange your 36 most interesting stocks in a six-by-six matrix, and role once each for row and column, then put everything in the one stock that comes up (or repeat 10 times and put 10% of your capital into each stock you rolled). --Stephan Schulz (talk) 01:03, 18 January 2015 (UTC)

Put a cow in a flat pen. Draw a 22 x 23 grid at the center. Draw a A outside a corner. Write ZZZZZZ on 6 squares at the opposite corner. Buy the S&P 500 stock the cow poops on first. Sagittarian Milky Way (talk) 01:36, 18 January 2015 (UTC)

No doubt PETA will want to certify that the cows are treated humanely when creating these cow flops, thus the results will be called "petaflops". StuRat (talk) 17:10, 18 January 2015 (UTC)

If you can't come up with anything better, you can use https://www.random.org. But actually, it's very easy nowadays to program a computer to generate numbers that are indistinguishable from random. Looie496 (talk) 02:46, 18 January 2015 (UTC)

The point here is not the random numbers per se, but about the range of the random numbers. For example, given a stock, try to guess its price in 3 months. Should random process pick between -10% and 10%? Or between -20% and 20% or something else? Whatever range we pick, it can make the professional investor win, or the computer program. --31.4.152.90 (talk) 05:03, 18 January 2015 (UTC)

Ah...so you're not asking about picking the best stock from some set (which is generally what stock market people care about) - but rather to estimate the future value of a particular stock at some specific time in the future? I suppose what I'd do would be to pick a random stock from the market from that same amount of time in the past and see how much it gained or lost and assume that the stock you're interested in will do exactly that well. SteveBaker (talk) 05:25, 18 January 2015 (UTC)

I'd make it mores specific than that, by using that same exact stock, and picking a random 3 month time period in it's past, and figure the return there, using that as you estimate for the next 3 months. Thus, if you're following a utility stock in a stable market, you aren't likely to predict wild swings, if it's never done that in the past. StuRat (talk) 05:42, 18 January 2015 (UTC)

The problem is that the more clever statistical tricks you add, the less this is a random prediction - and the closer you get to doing whatever it is that stock market experts actually do. The OP's goal to discover whether pundits get closer to accuracy than chance would predict. The problem is that we can't really say "what chance will predict" without knowing more about the realms of allowed randomness. If you ask that the algorithm picks at random over a linear range from 1,000,000% increase to the stock price hitting zero - then there is no chance in hell that it'll beat the expert. On the other hand, if you guess between 10% increase and 10% decrease, then the chance of beating the expert will obviously be much better. That's because we've applied a bit of knowledge about how the stockmarket works (the likely range of stock price change) - and now the random number generator isn't purely random. As we apply more and more actual knowledge about the market, we would presumably bring the algorithm more and more closely in alignment with a market expert...because, in the end, we'd be using the same algorithm that they use.

So we have a slippery slope. We can say that a truly random number between positive infinity and zero has a zero percent chance of beating an expert. We can say that an algorithm that uses the same tricks as an expert and then randomly adds or subtracts 0.000001% to the prediction will perform (on average) exactly as well as an expert. Somewhere between those two ranges of built-in skill, perhaps the randomness improves over the expert...but that point is unlikely to be a truly random algorithm.

SteveBaker (talk) 06:01, 18 January 2015 (UTC)

This doesn't answer the question, but if the expert is so bad (worse than chance) then why don't you just copy the expert but in reverse? (without telling him). An expert would have to perform as good as chance for there to be no way to time the stock market. So short when he says to buy. And buy when he says sell. This would only work if the prediction industry has made enough predictions that it's very likely that their worse than chance is not because of chance (and that they're even worse than chance at all). I don't know, it's very easy to for a study to exist where random stock picks perform better than experts if the sample size is fairly small. Those get reported on cause they're counterintuitive. Whether this us true over all the known expert stock pick data in history I don't know.

An interesting thing would happen if enough people start doing this. What would happen to the stock prices? The experts' predictions might even suddenly become good if over half the money is betting against them. Sagittarian Milky Way (talk) 07:04, 18 January 2015 (UTC)

I believe the way it typically works out is that, while an expert's predictions are slightly better than random, his stocks actually do worse, because he takes out a management fee that is more than his advice is worth. So, doing the opposite of his advice wouldn't work, unless he also then paid you his management fee. StuRat (talk) 07:36, 18 January 2015 (UTC)

Certainly there is also a Heisenberg-like effect going on here where calculating the value of the stock changes it's value and thereby invalidates that original calculation. If a prominent stock analyst says "This stock is cheap...buy it now!" then that causes a lot of people to do exactly that, which drives up the price of the stock beyond the point where that's a bargain - and possibly beyond the amount that it's really worth. This makes the prediction seem like a very good one to the 'early adopters' that jumped in at the bargain price and sell when the price went beyond the company worth - but a very bad prediction to people who waited a while before following the advice. I suppose this is why people pay stock analysts to work just for them - and why following stock tips on TV shows and such is likely to be a bad idea.

The problem with stock markets is that they have very little to do with what the stocks are really worth and very much to do with what stock buyers and sellers think that they ought to be worth. The gap between perception and reality is where the money is to be made - and that gap is caused by the very people who benefit (or lose) from the gap.

I very much agree with StuRat about management fees. This has been the downfall of many "day traders" because they not only have to make a profit - but find stocks that will earn more than the transaction fees. The classical approach to owning stocks - where you buy them, keep them for many years, and then sell them gives you the scope to achieve much larger gains, which make the transaction fees somewhat negligible. However, that's not a "get rich quick" approach which too many people are looking for these days.

If you stop to think about it - why would a stock suddenly be worth a lot more than it was the day before? What changed about the bricks and mortar, the people and the intellectual property of the company to make it change worth by so much so quickly...and what made that happen more rapidly than other stock market experts had already predicted? Sudden changes aren't changes in real value - they're changes in long-term predicted value...and now you're in the realms of the Heisenberg effect where stocks are changing value because they're changing value, and not for any real reason.

If you take the idea that these aren't real changes in company worth, then the fluctuations in price can only average out to a net zero gain. Now, for every $1 that someone wins by clever trading, someone else lost $1 due to not-so-clever trading. Hence if you average the performance of ALL stock analysts, they can only (on average) do as well as the underlying businesses are (on average) gaining real value. Since the average of all stocks is growing slowly - a random stock picker will (on average) do precisely as well as an average broker.

Hence, there are two ways to gain on the market - pick a stock in a strong company, ride it out for years as the genuine value of the company grows - or bounce around on the random fluctuations in the market caused by everyone else who is doing the exact same thing as you are. In the first case, it's fairly easy to pick winners - but you have to wait a long time to get your winnings - and you might as well bet on the economy as a whole by buying into a financial instrument that is the average of a lot of different stock prices. But in the second case, you're relying on someone who purports to be able to guess how everyone else in his business are guessing - and we know that for every winner, there has to be a loser. That's a zero sum game and averaging all of those experts together will reveal only the underlying growth of the economy. So you can't meaningfully average all of those experts together. You have to ask whether an individual broker does better than chance over time.

SteveBaker (talk) 18:04, 18 January 2015 (UTC)

This has actually already been the subject of considerable study, most famously by Daniel Kahneman. He has won a Noble Prize in economics and lots has been written about his work. Vespine (talk) 04:54, 19 January 2015 (UTC)

What are the most frequently written about species which don't have articles on Misplaced Pages?

Here's my answer:

Animals (chordates only):

1. Girella nigricans - Opaleye or Rudderfish
2. Tor tor - Deep bodied masheer or Tor mahseer (many synonyms including Barbus megalepis)
3. Salpa fusiformis - common salp
4. Embiotoca jacksoni - Black perch or Black surfperch or Butterlips
5. Nandus nandus - Gangetic leaffish
6. Thalia democratica - (appears to have no common name other than salp)
7. Ammodytes americanus - American sand lance
8. Phallusia mammillata = Phallusia mammilata (misspelling) - white sea-squirt or warty sea squirt
9. Epinephelus guttatus - Koon or Red hind

Plants:

1. Nicotiana glutinosa (Solanaceae, Solanales) -- tobacco. Nicotiana
2. Scirpus lacustris (synonym) = Schoenoplectus lacustris (Cyperaceae, Poales) - Scirpus
3. Larrea divaricata (Zygophyllaceae, Zygophyllales) - Larrea
4. Begonia semperflorens (synonym) = Begonia cucullata - clubed begonia (Begoniaceae, Cucurbitales) - Begonia
5. Nicotiana plumbaginifolia - Tex-Mex tobacco (Solanaceae, Solanales) - Nicotiana
6. Pelargonium zonale - Horseshoe geranium (Geraniaceae, Geraniales) - Pelargonium
7. Cola nitida - Großer Kolabaum (Malvaceae, Malvales) - Cola (plant)
8. Sterculia urens (Malvaceae, Malvales) - Sterculia

And here's more chordates and a link to notes and methodology... —Pengo 03:34, 18 January 2015 (UTC)

I think you're in the wrong place -- we can't really answer that, but the attempt could help people improve Misplaced Pages. Recommend you go to WP:WikiProject Zoology, WP:WikiProject Botany, WP:WikiProject Taxonomy etc. and see how you can help out. Wnt (talk) 03:55, 18 January 2015 (UTC)

If what makes these notable is that they're the most commonly written-about species that don't have a wikipedia entry, we have a bit of a catch-22.... --89.133.6.76 (talk) 12:05, 18 January 2015 (UTC)

I get your objection, but the lack of WP articles isn't really a part of the notability. These are just a list of spp that are notable, but not nearly so famous as e.g. C. elegans or E. coli. I agree with Wnt that this list should be shopped around at the appropriate project pages. Good list OP, and thanks for helping! SemanticMantis (talk) 17:20, 18 January 2015 (UTC)

head hair lightening of certain caucasian populations during summer

Why does this happen? Certain other populations do not have this phenomenon.174.3.125.23 (talk) 04:33, 18 January 2015 (UTC)

It's called sunbleaching, but we don't seem to have an article on it under that name, but we do have one for surfer hair, which mentions sunbleaching. (BTW, there's no need to leave a lined out typo in the title, so I removed it for you.) StuRat (talk) 04:38, 18 January 2015 (UTC)

This post at "Ask a Scientist" answers the OP's question directly. This answer to again, almost the exact same question, is more in depth, and discusses the chemistry of sun bleached hair in detail. Sun damages melanin in both skin and hair; skin being alive makes more melanin in response to the damage; sun tanning is a form of "overcompensation": the skin makes more melanin than was initially damaged, resulting in darker skin. Hair, being dead, cannot regenerate the damaged melanin, so it stays damaged. It damages all forms of melanin in all hair, but people with very little melanin anyways (blondes), it shows much more than people with darker hair, where the damage may not be as noticeable because they have so much more melanin in their hair to begin with. At least, that's basically what these sources seem to be saying. If you search for "chemistry of sun bleached hair" in your favorite search engine, you get a lot of hits, which seem to broadly agree with this process. --Jayron32 04:46, 18 January 2015 (UTC)

sane bounds on how much information the human brain can possibly store, and how much computational power it can possibly have

Hi,

I'd like some sane upper bounds on the amount of information that the human brain actually stores (uses), and how much computational power it can possibly have. Here, I'll give some terrible bounds first. If you Google "how many atoms in the human body" Google snippets you this,

> "In summary, for a typical human of 70 kg, there are almost 7*10^27 atoms"

So, clearly 1 atom in the human body does not store 1 terabyte and do 1 teraflop of computation. So the storage limit of the human brain is 7*10^39 bytes (27 plus 12 for tera) and the computational limit is... wait, okay, I don't even know what the general concept is for a certain level of computation (the way we can just call information storage in terms of bytes). You'll have to tell me that too.

But mostly can you give me some *saner* bounds than the above? I want some more reasonable bounds, likely based on neural count maybe? 212.96.61.236 (talk) 08:19, 18 January 2015 (UTC)

This Scientific American article estimates the memory capacity at around 2.5 petabytes, though some different estimates are given in the comments. It's hard to estimate because (1) the brain isn't a digital computer; and (2) we don't know how memories are stored. AndrewWTaylor (talk) 13:32, 18 January 2015 (UTC)

The calculation in that Scientific American thing is nonsense, as some of the comments point out. That number is quite a bit too high. Most neuroscientists believe that synapses are the brain's main memory elements. The human cerebral cortex is generally estimated to contain around 10 billion neurons, each of which holds around 10,000 synapses. This gives a total of around 10^14 synapses. If each synapse is a binary element capable of holding one bit of memory, we get a total capacity around 10 terabytes. I myself believe that the usable capacity of a single synapse is only a small fraction of a bit, because of the amount of noise in the system: I favor a total memory capacity in the range 100 gigabytes to 1 terabyte. To get a number over 1 petabyte you have to make assumptions about the precision of operations in the brain that don't accord with anything we know about brain structure. Looie496 (talk) 19:15, 18 January 2015 (UTC)

Looie496, did you look much into this? (Because if so I would like to ask follow-up questions - can you tell me how much you know :).) Your numbers overall agree with mine (but are a bit lower). However, one thing that you do not account for that I would have expected is - isn't one of the main sources of information in a neuron the question of WHICH other neurons it has synapses with? It is not like you can just enumerate the neurons and then for each one, store 10,000 binary values without addresses (which is 1 kB per neuron.) You have to account for the addressing, i.e. which other neurons is it in contact with? Don't you? If so it severely impacts the per-neuron size of the data. However, I would also be highly interested in what kind of a connection a single synapse can consist of - how much information can a single synaptic connection represent, really? (Not "on average" but a given one.) You seem to be going for a lower bounds whereas I am trying to think of bounds that are sane but perhaps account for a bit more data. --212.96.61.236 (talk) 22:34, 18 January 2015 (UTC)

What is the mechanism of Morphine on the breathing?

According what I know, Morphine effects on respiratory system and depress it. What is the mechanism of this depressing? 149.78.16.22 (talk) 08:27, 18 January 2015 (UTC)

See Morphine and μ-opioid receptor. According to the latter article, "the physiological and pathological roles of these two distinct mechanisms remain to be clarified", but, unfortunately, it doesn't state what the "two distinct mechanisms" are. This may be an opportunity to improve the article... Tevildo (talk) 11:33, 18 January 2015 (UTC)

Heat discolouration (?)

I've recently arrived in the 20th century, and got a kitchen with a dishwasher. I noticed that one of my ancient but favourite stainless steel pots now shows an interesting and not unattractive discolouration pattern when coming out of the dishwasher - I suspect this is due to the heat, but this is just a guess. Since I'm old, any change is bad, of course ;-). So what causes this change, what mechanism generates the colours (in particular, is this a chemical or a physical change, and if the first, is it just the alloy restructuring itself, or is it a reaction with the detergent?), and how concerned should I be? --Stephan Schulz (talk) 13:32, 18 January 2015 (UTC)

Tempering_(metallurgy)#Tempering_colors. --Kharon (talk) 13:43, 18 January 2015 (UTC)

The colors in Stephan's photo do look like that, but a dishwasher contains water in the liquid state, so its contents can't possibly reach the temperatures mentioned in that article. --65.94.50.4 (talk) 14:31, 18 January 2015 (UTC)

Its a pot. It has been used for cooking most likely. --Kharon (talk) 14:39, 18 January 2015 (UTC) P.S. And in case an metal object is tempered without cleaning its surface very diligently befor, it will likely not result in an evenly Tempering color. Instead it will look like in the picture. --Kharon (talk) 14:48, 18 January 2015 (UTC)

You're very likely seeing iridescence caused by some sort of thin film coating the surface. My guess is a soap film, but it could be some sort of protective coating that has been altered by the heat of the dishwasher. Looie496 (talk) 15:28, 18 January 2015 (UTC)

The thin film coating the surface is oxidation; the color changes are in that oxidized film. It's sometimes called "heat tint". --jpgordon 16:57, 18 January 2015 (UTC)

Yes, it looks very similar to the patterns from a thin film of oil floating on water, in sunlight. StuRat (talk) 16:59, 18 January 2015 (UTC)

If it were tempering, scrubbing wouldn't help at all to remove it, while these stains can generally be removed with stuff like Bon Ami or Bar Keeper's Friend (and a fair amount of elbow grease.) --jpgordon 18:26, 18 January 2015 (UTC)

Thanks all. It's certainly not soap or anything like that, and the pot is not coated. What seems to be most plausible is Jpgordon's suggestion - the dishwasher only reaches 55 °C or so, but maybe the detergent promotes oxidisation. --Stephan Schulz (talk) 21:33, 18 January 2015 (UTC)

Heat transfer

It's quite bad that I can't do this, because I've just graduated with a mech. engineering degree, but someone came to me with this problem, and no one I've asked can give me an answer.

I have a vessel which is hot inside, and cold outside. How long will it take for the temperatures to reach equilibrium?

Say we have a tube - radius 6m; length 15m; wall thickness 0.06m. On one end is a hemisphere - same radius; same wall thickness. On the other end there is no heat transfer in or out. Therefore, the surface area over which heat can be lost is (15*2*pi*6)+(2*pi*36)= 792m^2

Inside the vessel is air at 30C, and outside is water at 3C. Thermal conductivity is 34.3W/mC. Cheating by using this website (http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatcond.html), we get heat conduction to be 12MW.

After that, I don't really know where to go to get the time to thermal equilibrium. I think the heat transfer formula is required - Q = m*C*dT (which is offered here: http://formulas.tutorvista.com/physics/heat-transfer-formula.html)

I see it requires specific heat capacity, which for air at 30C is 1.005 kJ/kgK (I think), and for water at 3C is 2.407 kJ/kgK (I think). The volume of the vessel is 2102 m^3, so the mass of air is 2102000 kg. The mass of water is effectively infinite (it's in the sea)

And at this point I'm totally stuck. Can anyone help? Thanks!! 92.237.191.99 (talk) 15:34, 18 January 2015 (UTC)

If you insist on strict theoretical equilibrium, It will take forever. That dT is the temperature differential, so as the two temperatures equalise, the heat flow goes towards zero. In other words, your hot tube will approach but never reach the temperature of your infinite ocean. I also think some of your numbers are off. The mass of water is 1000 kg per cubic meter, but for air it's only 1.292 kg (for air at 0 °C, 1.164 for 30°C). With those numbers, you need to decide which temperature difference you call "equal" and then integrate heat loss to that point. Sorry, I don't solve even simple differential equations, but the resulting temperature curve should be of the form ${\displaystyle ae^{-kt}+3}$, unless I'm stupider than I hope. --Stephan Schulz (talk) 16:45, 18 January 2015 (UTC)

Agreed. The rate of temperature change is proportional to the difference in temperatures, which results in the temperatures approaching each other asymptotically, whether or not one is considered an infinite temperature sink. StuRat (talk) 16:50, 18 January 2015 (UTC)

(edit conflict)(edit conflict) You need to set up (and solve) the differential equation for heat flow through the material of the vessel. The solution for temperature difference will be an exponential with a negative exponent of time, so in theory the temperatures will never be quite equal, but you can find the time to reach effective equilibrium with perhaps a tenth of a degree difference between inside and outside. Strictly, you also need to set up differential equations for heat flow within the air inside the container, and for the water outside, but you can probably assume that there is sufficient convection in both the latter fluid to be able to ignore the limitations of conduction through the fluids (it depends on how complicated you wish to make the mathematical model). Dbfirs 16:52, 18 January 2015 (UTC)

Lol, physicists. I love these answers. "If you insist on strict theoretical equilibrium, It will take forever. If you're just interested for practical reasons, I'd say you'll be cold by morning." only you didn't even try to estimate that for him - seriously, he said "it's 30C, and outside is water at 3C" - don't you guys want to at least *guess* how long until it's cold in there? 30 degrees is a very hot room, 3 degrees is near freezing, and he's told you how conductive (i.e. how well-insulated) the stuff is as well as the exact dimensions. As helpful as 'forever' is, I think it's a cop-out from actually estimating anything at all - as he was just asked to do, since he's a freshly minted mech engineer :) :) 212.96.61.236 (talk) 17:53, 18 January 2015 (UTC)

No - you could not be more wrong! That is a severe misstatement of the situation. It's a serious consideration for practical engineering as well as for physicists. You simply cannot approximate this one.

If you say that the temperatures have to be equal to within 1 degree, the answer will be VERY different than if you demand a half degree or a tenth of a degree. The rate of cooling depends on the temperature difference so the smaller the difference you require for "equilibrium", the longer it'll take. Halving the amount of allowed temperature difference in your approximation quadruples the amount of time it takes to reach that point. Your completion criterion is not a small irrelevance...the answer can literally be anything from zero to the life of the universe depending on your choice of allowed difference. If anyone tries to tell you that the answer is "about 3 hours" without specifying the final temperature discrepancy - then they are either incompetent or lying. It's not a matter of overly-picky theoretical physicists versus practical engineers.

This kind of failure to specify critical details why you see so much "false" advertising on TV - you say "Our product is two times as good!" is meaningless without saying two times as good as what. So saying "This insulation barrier prevents your house from getting as cold as the outside world for 10 hours after the heating is turned off!!" is entirely meaningless because your competition can say "Well, ours prevents that from happening for 100 hours!!"...since neither of them stated the final temperature difference, these statements tell you nothing whatever about which insulation solution is better.

When you're dealing with a highly non-linear system (such as this one) - details matter a heck of a lot.

SteveBaker (talk) 19:17, 18 January 2015 (UTC)

Did you even read what I wrote? Why would ANYBODY care about equilibrium - in an ocean - to a tenth of a degree or half a degree? Pick a number, such as a couple of degrees, and give him an answer. ("Noo!!!!") The huge difference is whether the thing cools down in a few minutes, an hour or two, or over several hours, or over days. pick some numbers and figure it out, don't just leave the guy hanging with "forever, bro." contextualize. you can give several numbers of course. 22:27, 18 January 2015 (UTC) — Preceding unsigned comment added by 212.96.61.236 (talk)

The OP specified equilibrium, not the replies. This is the sort of question that mathematicians, physicists and engineers could argue over for days. We could have given an accurate "half life" (a second or two) for the temperature difference between the air touching the inside surface and the water outside, but this would ignore the variations in the temperature of the inside air that are more significant than I'd anticipated. Did you read Dragons flight's excellent answer below? Dbfirs 23:09, 18 January 2015 (UTC)

In general, for a simple box model assuming uniform temperature inside and out, you are looking for:

${\displaystyle {dT_{inside} \over dt}={Q \over m_{air}C_{air}}}$

${\displaystyle Q={k_{metal}A_{metal}(T_{outside}-T_{inside}) \over d_{metal}}}$

Which implies:

${\displaystyle {dT_{inside} \over dt}={k_{metal}A_{metal}(T_{outside}-T_{inside}) \over m_{air}C_{air}d_{metal}}}$

${\displaystyle T_{inside}(t)=T_{outside}+(T_{0}-T_{outside})e^{{-k_{metal}A_{metal} \over m_{air}C_{air}d_{metal}}t}}$

In your case, that gives:

${\displaystyle T_{inside}(t)=3+27e^{{-k_{metal}A_{metal} \over m_{air}C_{air}d_{metal}}t}\,{\text{C}}\approx 3+27e^{-t \over 0.5\,{\text{s}}}\,{\text{C}}}$

So, the simple box model says it will take about a few seconds to get cold. If that bothers you, and it should, then it is time to reexamine assumptions. In this case, the issue is with assuming a uniform temperature within. The inside skin of your metal tube will rapidly approach the same temperature as the sea water, but the temperature of your container will primarily be determined by heat transfer through the air (conduction / convection).

For a rough estimate, we can recompute the time constant above, but using values for the thermal conductivity of air. ${\displaystyle {k_{air}A_{surface} \over m_{air}C_{air}r_{tube}}\approx 3.4\,{\text{days}}}$. This considers only conduction and only does so crudely, so should be taken as an upper bound. A somewhat better estimate by replacing ${\displaystyle k_{air}/r_{tube}\rightarrow h_{c}}$ by an effective convective heat transfer coefficient. Let's say 5 W/(m K), which gives a time constant of 4 minutes. That illustrates that there is a very large difference between thermal loss due to conduction and that due to convection. Convection is of course controlled by geometry (including orientation relative to gravity) and temperature differences; however, in most circumstance in air, it is safe to assume convection wins. So in short, I would guess that most of the heat is lost within 30 minutes or so (i.e. several times the estimated convective time constant of 4 minutes). If you want a more precise answer than that, you will need to model the temperature distribution in the air explicitly and probably turn to computer models. (Or you could build the thing and run tests.) However, if you want to keep the inside warm for a long time, then a extra layer of insulation on the interior surface would definitely be a good idea. Dragons flight (talk) 19:40, 18 January 2015 (UTC)

Human evolution

Hello,

I would like help in understanding the followings in simple terms please.

1)

Genetic studies show that primates diverged from other mammals about 85 mya in the Late Cretaceous period, and the earliest fossils appear in the Paleocene, around 55 mya. The evolutionary history of the primates can be traced back 65 million years.

Q: Are they talking about one or two things by dates here? Diverging and evolution here, as its stated, are they not the same thing?

2)

I would like to know, how the evolution occurs? Don’t you need a different gene? How do they, from ‘H. erectus’ to ‘H. heidelbergensis’ are ‘H. antecessor’ and so on at first? I understand that environmental changes could only be a cause of the skeletal changes resulting in different ‘homos’ but after the first migration of H erectus some stayed in Africa and evolved into many other homos. How?

(Russell.mo (talk) 17:01, 18 January 2015 (UTC))

1) I can't be sure without knowing what you're quoting from, but I suspect the 85 mya divergence is calculated based on studies of genetics, while the 65 mya is talking about actual fossils that can be classified by morphology. Some of the genetic v.s. fossil evidence is described at Human_evolution#Evidence.

2) Natural selection only really needs a pool of different alleles to act upon. Some alleles will change in frequency, and some new alleles will develop through mutation. Speciation can occur sympatric speciation or allopatric speciation (and a few other ways). You also might want to read about gene fixation. Basically all the forms of speciation have to do with some type of (perhaps functional, not physical) reproductive isolation. With early hominids, the reproductive isolation could be in part cultural, e.g. sexual selection. SemanticMantis (talk) 17:16, 18 January 2015 (UTC)

The point of divergence is a very fuzzy line - it could be the smallest change in bone or tooth shape. At the literal instant when the first animal was born that was the ancestor of all humans but the ancestor of no other primate, that animal would have been almost indistinguishable from either of its parents. To be able to examine two fossils and say that because of some tiny bump on this or that bone, this was that point of divergence is impossible. So we have to wait for the divergence to be large enough to be clearly distinct. So examining the fossil record can't ever give you an exact date. Also, fossils are relatively rare - it's quite possible that no animals of that species were ever fossilized - or if they were, that the fossils are embedded in the middle of rock that we'll never excavate.

Worse still, when we find a fossil, we have to assign a date to it. That's tough because the fossil may contain none of the original material that made up the animal, so techniques like carbon-dating don't work. Instead, we have to do tricks like looking at what layer of rock the fossil was found in and use that to get an approximate date...but that too is a somewhat fuzzy measurement. Suppose the animal died by drowning in a river that had cut it's way through the surrounding rocks - that would lead you to think that it was in a layer considerably older than you'd otherwise say.

An alternative way to estimate that date comes from examining the DNA of humans and of species in the same family tree. We can simply count the number of differences in our DNA and use a rule-of-thumb that says "such-and-such number of base pairs change every hundred thousand years" - and use that to calculate the point of divergence...but that's also a very approximate approach.

Since both techniques are inaccurate - it's unlikely that they'll agree very closely.

SteveBaker (talk) 17:39, 18 January 2015 (UTC)

"Since both techniques are inaccurate - it's unlikely that they'll agree very closely." - unlike boolean errors. Which are so close to agreeing, half the time you don't even need to debug them at all! --212.96.61.236 (talk) 17:59, 18 January 2015 (UTC)

I'll read through the articles SemanticMantis, thanks. I don't know where I got it from, my work is mixed up. Thanks for the summary.

@SteveBaker: Are you aware of mtDNA, apperantly it provided satisfactory result (dates things upto 200,000 years)? if so, is this correct? Because your explanation demolished this belief too... -- (Russell.mo (talk) 21:17, 18 January 2015 (UTC))

Sure, but our Mutation rate article says: "Human mitochondrial DNA has been estimated to have mutation rates of ~3× or ~2.7×10−5 per base per 20 year generation (depending on the method of estimation);" - so that's at least a 10% uncertainty over the mutation rate in humans. Worse still, mutation rates vary significantly between species - and humans have only been human for a tiny fraction of the time between the last common ancestor with all primates and today. So the mutation rates get less and less certain as you go back in time. So if you look at the mtDNA of a typical non-human primate and that of a human...count the differences...then divide by the mutation rate, you have at least a 10% error because the mutation rate in humans isn't a definite number - and quite possibly you have a much larger error in your estimation because all of the intermediary species since the last common ancestor and us may have had totally different mutation rates. So it's easy to understand that the estimation over 50 to 80 of millions of years could quite easily differ from reality by several tens of millions...which is plenty enough to explain the discrepency our OP refers to.

So, I agree that they mtDNA studies might provide reasonable rates (with maybe a 10% error) back to 200,000 years (when we were still essentially human) - but when you're talking 55 to 85 million years - the errors compound.

SteveBaker (talk)

I understand. I'll read through the link you stated too. Thank you for taking the time to make me understand in simple terms. Kind regards. -- (Russell.mo (talk) 16:16, 19 January 2015 (UTC))

Atmospheric pressure at the height of the ISS

I've been wondering: is it possible to quantify the ambient air pressure at the level of the ISS in terms of pascals? – Juliancolton |  18:06, 18 January 2015 (UTC)

In our outer space article it says "The Earth's atmospheric pressure drops to about 0.032 Pa at 100 kilometres (62 miles) of altitude", so at 414 km it will be significantly less than that (about 3.6x10 Pa, according to this). Mikenorton (talk) 18:17, 18 January 2015 (UTC)

The ISS orbits roughly 410 km above the earth, in the middle of the thermosphere. According to our article on vacuum, it is hard to interpret the definition of pressure above the Kármán line, because "isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the sun and the dynamic pressure of the solar wind". Not the best answer I'm afraid, but the best I could find =) WegianWarrior (talk) 18:28, 18 January 2015 (UTC)

We could probably come up with a reliable number for the density of the atmosphere at that height - but pressure is tough because it ties in closely with temperature - and both concepts start to lose meaning beyond a certain point. SteveBaker (talk) 19:25, 18 January 2015 (UTC)

At what point does temperature start to lose meaning?--Noopolo (talk) 04:17, 19 January 2015 (UTC)

Temperature loses its conventional meaning once the air becomes ionized. This is the case at the height of the ISS, which is within the F region of the ionosphere. There are different temperatures for the different constituents, e.g., electron temperature and ion temperature. Short Brigade Harvester Boris (talk) 04:36, 19 January 2015 (UTC)

Since pressure and temperature is closely tied to each other and pressure starts to become meaningless above the Kármán line, temperature likely starts becoming difficult to interpret at the same height. That's just a educated guess though =) WegianWarrior (talk) 04:22, 19 January 2015 (UTC)

I've heard 1/1 trillionth that of sea level and 1/100 trillionth atmosphere on the Moon but the ISS was lower then. I don't remember if this was density or pressure. Also, you can define the temperature of a single particle, there are thermal neutrons. And you could calculate the force on the whole 410 km night side and divide by area. Though it's probably not too useful unless your object gets hit by at least 100 particles in the time it takes a particle to move a small percent of the objects size. Sagittarian Milky Way (talk) 06:08, 19 January 2015 (UTC)

measles

If someone has had their measles vaccine when they were a baby but did not get their booster shots, are they immune? and if not, is measles milder in partialy vaccinated people. — Preceding unsigned comment added by 63.247.60.254 (talk) 21:13, 18 January 2015 (UTC)

90% or more will be immune without the booster shot, according to the NHS (other sites suggest an even higher percentage) and 98% or 99% will be immune for life after two doses. The second dose is not a "booster"; it is designed to catch those whose immune system did not respond fully to the first dose. There are recorded cases of mild infection after up to five doses of vaccine, but these are rare. People who were vaccinated with the original killed-virus measles vaccine between 1963 and 1967 often have incomplete immunity and tend to suffer a mild form of measles if exposed to the live virus. Dbfirs 22:08, 18 January 2015 (UTC)

January 19

Handbooks vs. lectures

Some centuries ago, copies of texts were expensive, so, a lector would dictate a text to his students, who would copy it to have access to it. But what is the purpose of lectures today? Why do colleges keep offering them, and still tape them? Shouldn't every college student be able to work his way through a handbook in his field? After all, a handbook is just a simplified, organized view of a field, which is composed by articles as primary source.--Senteni (talk) 00:47, 19 January 2015 (UTC)

I suspect you confuse handbooks (which, at least in my field, typically are collections of survey and method articles, targeted towards advanced researchers) with textbooks (which are aimed at students).I don't think any beginning student has much of a chance of working through e.g. the Handbook of Automated Reasoning without significant help. Even with textbooks, some people find it much easier to learn material under the guidance of a teacher or lecturer. Good lecturers don't just read the text out loud, they motivate, they explain, they reply to questions, and they provide a route through the material. --Stephan Schulz (talk) 01:10, 19 January 2015 (UTC)

Yes, I meant rather textbook than handbook. But textbooks would also accomplish the part of "providing a route through the material." And some lectures are tape these days. Your possibilities of asking a question are the same if you have a textbook or the mp4s.--Senteni (talk) 17:47, 19 January 2015 (UTC)

Indeed, but average lecturers merely repeat the textbooks, and bad ones mangle things up. My final year at uni I attended very few lectures, preferring to work on the problem sets in the library. It's the same with MOOCs, unless the material is exceptionally dense or entertaining then I tend to just do the marked work rather than watch the lecture videos. Greglocock (talk) 01:19, 19 January 2015 (UTC)

I think the key is feedback. A good lecturer will ask his students questions, and answer questions from them, figure out what concepts are unclear from the lecture, and improve them either that day, or maybe during the next lecture, if he has to think about a better strategy overnight. By comparison, if a textbook writer gets any feedback at all from the students, any improvements must wait for the next edition, so the current group of students is out of luck.

A good lecturer might also work with the text, perhaps using parts of it verbatim, where they are well done, but supplementing bad sections of the text with their own material. StuRat (talk) 04:51, 19 January 2015 (UTC)

Gian-Carlo Rota answered this question in his Indiscrete Thoughts, speaking of Alonzo Church, see Fine Hall in its golden age: Remembrances of Princeton in the early fifties. Church "looked like a cross between a panda and a large owl .. His one year course in mathematical logic was one of Princeton University's great offerings. It attracted as many as four students in 1951 ... His lectures hardly needed any preparation. They were a literal repetition of the typewritten text he had written over a period of twenty years, a copy of which was to be found upstairs in the Fine Hall library."

Rota continues: "It may be asked why anyone would bother to sit in a lecture which was the literal repetition of an available text. Such a question would betray an oversimplified view of what goes on in a classroom. What one really learns in class is what one does not know at the time one is learning. The person lecturing to us was logic incarnate. His pauses, hesitations, emphases, his betrayals of emotion (however rare), and sundry other nonverbal phenomena taught us a lot more logic than any written text could. We learned to think in unison with him as he spoke, as if following the demonstration of a calisthenics instructor. Church's course permanently improved the rigor of our reasoning."John Z (talk) 05:08, 19 January 2015 (UTC)

• I think the OP is asking two unrelated questions here, and many people are answering the one and not the other. Question 1 is "What is the benefit of learning by lecture compared to learning by textbook" Question 2 is "What is the benefit to learning from a really shitty lecture." Most people seem to be answering question 2 without addressing question 1 at all, and also they are answering solely from their own personal experiences with shitty lectures, without addressing the research behind the pedagogy of lectures. Self-evidently, shitty lectures are shitty, and so addressing that issue has nothing to do with the OP's question. "I once had a shitty teacher, and they were bad at their job" does not in any way address the pedagogical rationale behind the use of lectures (and textbooks, and any other teaching tool). To actually answer the OP's question, here's some things to consider, presupposing that both the lecture and textbook in question are of sufficient quality.
  • Learning styles: Different students have different ways of learning, and what works for some very well does not work for others as well. While some students learn well by reading, others may be auditory learners (need to hear it to understand it) or need to perform some task to understand it, or need to write it down to understand it (the act of taking notes itself has effects on learning). There's really a variety of ways to teach and learn, and most classes employ multiple methods of doing so, indeed many people need to get the information through several modes (not just one) to get it. This is self-evident: if the textbook were sufficient, we'd not have an education industry at all. We'd just hand our 6-year-olds a pile of textbooks and say "See you in about 16 years, figure it out yourself". Teachers have a role to play in the presentation of information through their lectures. And the fact that people have different learning styles is part of the reason why both the textbook and lecture are necessary elements in the education process.
  • This article does a really good job of addressing the role of a good lecture in education. Again, the lecture has a role in education. The shitty lecture may not, but that's a problem of quality not of appropriateness of the pedagogical tool.
  • This article also does the same.
  • Just in the interest of fairness, this is a really good article showing how lecture matches up against other pedagogical methods, and it DOES show that lecture can be inadequate for certain situations, and shows how lecture can be overused.
• I hope that provides some reading for the OP to help them work through their question. --Jayron32 17:00, 19 January 2015 (UTC)

Indeed, if we were to compare a shitty lecture, for reasons of fairness, we would have to compare it with a shitty textbook. Although I have the impression that shitty lectures are more common than shitty textbooks. But yes, the question was meant in the direction that Jayron pointed at. When it comes down to learning, what is purpose of a lecture still. --Senteni (talk) 17:47, 19 January 2015 (UTC)

Personal research project: histories and uses of "Dwarf Saltwort" or "Small Cordgrass"

Does anyone have any links to good sites that go into deep detail about plants? Particularly the ones in the subject line. I just need to be pointed in the right direction. Any help is appreciated. Thank you in advance.Gosalyn (talk) 04:55, 19 January 2015 (UTC)

Did you look at Saltwort and Small Cordgrass ? StuRat (talk) 05:52, 19 January 2015 (UTC)

(edit conflict) We do have an articles about Dwarf saltwort and Small Cordgrass. I don't know anything about the topics or good external websites for them, but if you find any, might want to add them there (or at least on the talkpage as a reference for someone who might want to expand the article in the future). DMacks (talk) 05:53, 19 January 2015 (UTC)

Spinning 'Rocket' ??

Hi, can somebody give me the name (and maybe a reference to an article ) of this device? How does it stay stable as it climbs, and what sets it spinning? https://www.youtube.com/watch?v=pD_yQZ4iNjY&feature=pla Thanks 122.108.177.30 (talk) 04:56, 19 January 2015 (UTC)

What sets it spinning is the fact that the rockets aren't pointed directly downwards. They're angled. That starts it turning while they are also able to push the whole thing skyward. The fact that it's spinning is what keeps it stable. As the rockets push it around in a circle, it is constantly being pushed to the side due to the angle of the rockets. But by the time it can be pushed off course, the rockets are now in a different position. So at the 12 o'clock position, it's being pushed one way. But there is another set of rockets on the other side, the 6 o'clock position, of the contraption balancing out the sideways forces of the other rockets. Dismas| 05:46, 19 January 2015 (UTC)

The way I'd make it stable is by putting a weight underneath it, at the center. (You could make it something useful, like a camera and transmitter, to send live video, but they'd need to use smokeless powder to get a clear view.) I think the system they used is less stable, and if a rocket or two failed, it might very well have flipped over. StuRat (talk) 05:51, 19 January 2015 (UTC)

How does putting a weight underneath it make it stable? The device in the video uses spin stabilization. Just adding weight doesn't help unless it had some aerodynamic effect. --Bowlhover (talk) 06:42, 19 January 2015 (UTC)

Trying to dredge my memory for the physics of this, I'm fairly sure that rotational inertia is the clue here - the distribution of mass ('dumbell effect') means that slight perturbations of the spin axis get damped down, once it gets spinning. And if I'm right, adding significant mass below the centre would actually make it less stable. No doubt someone better qualified in physics will be able to describe this better - or tell me I've got it all wrong. AndyTheGrump (talk) 07:07, 19 January 2015 (UTC)

Aye, StuRat is regrettably referring to the incorrect pendulum theory of rocket dynamics, which was widely believed until it was discredited by actual experiment. Even Robert Goddard believed this theory. It's an easy error to make, even for a physicist, because when you write the equations that treat a rocket as a simple harmonic oscillator, everything looks correct on cursory evaluation, even though the details are not correct. (The big conceptual gaffe is forgetting that a pendulum solution also contains an un-bespoke constraint force at the pivot point, while a rocket has no such constraint - it's not nailed into a wall - so if you forget to account for this, you neglect an important reaction-force that significantly changes the vehicle dynamics. When a pendulum swings, the pivot pushes back with an equal and opposite reaction... but a free-flying rocket has no fixed pivot on which to exert a reaction-force - hence no restoring force, hence no simple harmonic oscillation). In a perfect world, a rocket with a low center of gravity is exactly as stable as one with a high center of gravity; and in an imperfect world, this configuration amplifies minor perturbations into major aerodynamic instabilities.

Real rockets - including the one in the video - use fins as aerodynamic control surfaces for stability. The rocket in the video looks like its entire outer edge is acting as a large, circular-shaped vertical stabilizer. Rockets also use spin stabilization - a side-effect of the conservation of angular momentum - once spinning, the rocket resists changes to the direction of spinning, preferring to point in the same axis (or to precess in a stable oscillation around its primary spin axis).

Nimur (talk) 07:54, 19 January 2015 (UTC)

Very cool video, thanks for sharing it! It looks like an excellent example of the "because we can" reason for doing things! --Stephan Schulz (talk) 10:06, 19 January 2015 (UTC)

Anion deficient solution

Something I'm reading refers to an anion deficient solution. Based on my admittedly shaky chemistry knowledge I suppose this means acidic (i.e. poor in -ve ions, so rich in H+ ions, so low pH) but am I missing something (or getting it wrong)? Is there a significance to saying "anion deficient" rather than acidic? AlmostReadytoFly (talk) 14:14, 19 January 2015 (UTC)

Do you have a link to the thing you are reading? --Jayron32 16:45, 19 January 2015 (UTC)

Sorry, it's not on the web. It's an aluminium nitrate solution. AlmostReadytoFly (talk) 17:29, 19 January 2015 (UTC)

The anion are the negatively charged ions, in your case the nitrate. I'm not a chemist but I would expect anion deficient to mean that there are fewer nitrate ions than you would expect from the number of aluminium ions, i.e. less than 3 times as many. Ulflund (talk) 19:43, 19 January 2015 (UTC)

Swallowing a long string

What would happen if I swallowed a really long piece of string....And swallowed it slowly and letting it pass through me fishing line style. Would it be possible to have one end of the string hanging out my butt hole and the other end still out my mouth?

That would be cool.

Any medical ramifications? — Preceding unsigned comment added by 106.150.61.164 (talk • contribs) 18:46, 19 January 2015 (UTC)‎

Lol. Might do if you look for it with the other hand. -- (Russell.mo (talk) 18:56, 19 January 2015 (UTC))

Could you get it to come out 'both ends'? Doubtful, Cecil Adams examines this question in this article.

Medical Ramifications? Could be. Ask a doctor. APL (talk) 20:08, 19 January 2015 (UTC)

Hmmm - I was unable to find a solid reference for this. Some random person on Snopes said this: "The reason string can be fatal to animals (or people, for that matter) is that the bowel tries to pass the string along by peristalsis. This results in two peristaltic waves acting as "anchor" points, which eventually causes the string to become taut. Intermediate peristaltic waves then act on the linear foreign body produced by the taut length of string, trying unsuccessfully to move it along. Repeated movement against the string actually saws through the bowel wall, leading to perforation, peritonitis and eventual death."...I have no idea whether (s)he speaks from a position of knowledge - but it certainly sounds plausible, so for 100% sure you shouldn't try this without getting some fairly serious medical guidance...or, preferably, not do it at all!

It's likely that someone here would sooner or later bring up an old story about feeding string to ducks and eventually getting an entire row of ducks strung end to end this way...that can be traced back to a story from the original Baron Münchhausen books...so I think we can probably discount it!

SteveBaker (talk) 20:32, 19 January 2015 (UTC)

• My neighbor's dog did this. They cooked a turkey bound in twine, and he ate the twine out of the trash, leading to dog bloat, for which he survived the surgery. μηδείς (talk) 23:51, 19 January 2015 (UTC)

• Policy says we shouldn't give medical advice, but regardless I'd say... no. Just no. Intestines are amazingly finicky things; we call on them to do so much within their natural range and they comply, but fiddle about with them unnaturally and you tend to just die. All the time surgeons lose patients because of some invisible error with the blood supply after they have done something with them, and you need merely contemplate what happens if you pull the string to see how that might be similar. Wnt (talk) 00:20, 20 January 2015 (UTC)

You might find the tale of Alexis St Martin and William Beaumont interesting. --TammyMoet (talk) 10:14, 20 January 2015 (UTC)

I once pulled four feet of a an inch-wide strip of sweater (punching bag stuffing) from a three-foot iguana. He lived without medical help, but it was bloody and he was lucky. Also wasn't out of his butt. Last week, pulled a thin 8-inch strip of plastic (feed bag weaving) from my cat's butt. No blood or discomfort (or shit on the first few inches, for some reason), but it wasn't out of his mouth. I'll also say "Ask your doctor". InedibleHulk (talk) 10:33, January 20, 2015 (UTC)

Re-posting my answer of 19:15, 19 January 2015 that got deleted: Such a string may causes medical complications due to the action of peristalsis. In other words, the string may abrade the gut lining at a few points and cause complication such as ulcers, possibly leading to Peritonitis etc. But that is just of the top of my head. Parasitic gut-worms can be ever-so long but they have evolved not to kill their host. Your bit of hypothetical string may not be so smart.--Aspro (talk) 14:26, 20 January 2015 (UTC)

Brain neurons

How much/many neurons does a human brain hold, 15-33 or 86? -- (Russell.mo (talk) 18:47, 19 January 2015 (UTC))

An estimated 80 000 000 000 - 100 000 000 000 neurons. Wiki List_of_animals_by_number_of_neurons says 86 000 000 000 neurons, with references. Also, there is a comparable number of macroglial cells, mostly astrocytes. Astrocytes are not neurons, but they do participate in the "computations" carried out by the brain. For a relatively recent discussion of neuron and glia numbers, see e.g. . --Dr Dima (talk) 19:34, 19 January 2015 (UTC)

And bear in mind that the number of interconnections matters - probably more than the number of cells. SteveBaker (talk) 20:19, 19 January 2015 (UTC)

@SteveBaker: I'm guessing that would be the nervous system ('lower' and 'higher'). -- (Russell.mo (talk) 21:02, 19 January 2015 (UTC))

Thanks friends. Astrocytes is new to me. I'll read through...

Onions

What do onions do to your brain?

1. When you smell?
2. When you eat?

Can it affect your consciousness? E.g., a person is sleeping, if he smells a ‘just cut’ onion, will he wake up from sleep?

(Russell.mo (talk) 18:48, 19 January 2015 (UTC))

We have excellent articles on smell and taste. Please read them, and then feel free to ask any additional questions that you may have. --Dr Dima (talk) 19:41, 19 January 2015 (UTC)

If your question is specifically about onion smell and taste, the eye irritation response is caused by sulfenic acid, an irritant, produced when onion bulb is cut or damaged; and the sweet taste is produced by sugars present in the onion. --Dr Dima (talk) 19:46, 19 January 2015 (UTC)

I'm talking about how it effects the brain. I just recalled, the last thing I can remember before getting my sense/consciousness long after I started walking is the onion smell. And the next thing I remember that my mother was showing and explaining it... I'm thinking of what chemical/acid reaction could unlock my brain. - (I could be day dreaming now but this is what I recalled...) -- (Russell.mo (talk) 20:41, 19 January 2015 (UTC))

Ah, I think it's more about a smell, rather than onion smell. Many people's earliest memories have to do with smells. Olfactory_memory has some info. My undergraduate psychology professor told us that scent memories are often the strongest/longest lasting, compared to other types of memory. I don't know if that's mentioned in our article but I don't have time to look for a better reference at present. SemanticMantis (talk) 21:04, 19 January 2015 (UTC)

Its okay, thanks SemanticMantis. I'm going to sleep now after messaging a friend. -- (Russell.mo (talk) 21:11, 19 January 2015 (UTC))

Explaining methods

What is the correct term to define a person who is showing 'with is body movements' as well as 'speaking what he/she is showing' so that you understand? Just like a father/mother tells his/her baby for them to understand… -- (Russell.mo (talk) 18:53, 19 January 2015 (UTC))

Body language? SteveBaker (talk) 20:16, 19 January 2015 (UTC)

Depending on the context, it might also be a gesture or even pantomime. SemanticMantis (talk) 20:19, 19 January 2015 (UTC)

What if you are speaking at the same time by gesturing/using body language? -- (Russell.mo (talk) 20:52, 19 January 2015 (UTC))

I don't think we have a specific word for that. We would just say something like "The fish was this big! he said, gesturing with wide spread hands." SemanticMantis (talk) 21:07, 19 January 2015 (UTC)

Speaking while gesturing would be normal. You could also have the animated speech of Hitler or Mussolini, but that would scare a baby. Gesticulate also works, but this sort of speech is somewhat over the top. You can gesticulate wildly, but not softly. μηδείς (talk) 21:05, 19 January 2015 (UTC)

Your words 'speaking while gesturing' just made me feel like a really dumb person. I'm always in search for formal words that now I forgot the most basic. The two go really well. Thanks. -- (Russell.mo (talk) 21:19, 19 January 2015 (UTC))

• There's no harm in asking. Spanish has at least 4 words, pared, mur, muralla, tapia that all translate as "wall" in English, but distinguish in Spanish whether it's interior, exterior, of a city/castle, or of a garden. On the other hand, English has at least 7 words that translate the Spanish tacaño, "stingy/miserly".

I understand and Thank you (whoever you are). Don't forget to use your signature next time -- (Russell.mo (talk) 12:00, 20 January 2015 (UTC))

Thank you all -- (Russell.mo (talk) 12:11, 20 January 2015 (UTC))

Concentrations of antibiotic in Indian rivers

In this report: the CEO of a pharmacutical company claims that "...rivers in India show higher concentrations of active antibiotic than the blood of someone undergoing treatment.". This seems implausible to me...any idea where he's getting his data - and is it likely given flow rates of rivers and antibiotic concentrations in treated patients? SteveBaker (talk) 20:16, 19 January 2015 (UTC)

Sounds like a bit of hyperbole. At the very least the quote should not be about "rivers in India", as they certainly all don't have those high concentrations. Here's a study of one stream in India , that shows a high incidence of antibiotic-resistant alleles in resident bacteria. Downstream of a discharge site for a drug factory, Fig.1 shows up to ~10^3 ug/g of ciprofloxacin measured in the water. I don't know what the therapeutic dose would come out to in a treated human's blood, but this is at least a start. SemanticMantis (talk) 21:01, 19 January 2015 (UTC)

That's 10ug/g of organic material - not per gram of water. Our ciprofloxacin article says that a typical IV dose of ciprofloxacin is 400mg - and an average human has about 5 liters of blood - so around 5000g...so we're looking at something like 80ug/g as a rough therapeutic concentration. So it's close...if more than about 10% of the river is organic material, the guy is right. Wow! SteveBaker (talk) 06:27, 20 January 2015 (UTC)

Hyperbole? Isn't that being held on the 1st? Perhaps he meant the total in the rivers by mass/volume, rather than concentration? In the US, there'd be antibiotic from livestock. There's also the decade-old story about the high levels of cocaine in the rivers of Italy]. μηδείς (talk) 23:30, 19 January 2015 (UTC)

Florida land is worth two extra dollars per acre because one time tens of tons of cocaine was dropped from an plane disposing of evidence or lightening it's load as it was about to crash or something like that. Or at least it would be if the market were totally efficient and everybody was willing and able to sell (the 30,000 houses worth of cocaine). Sagittarian Milky Way (talk) 00:20, 20 January 2015 (UTC)

It sounds unlikely, but bear in mind that a couple of tiny pills provide all the blood concentration you need to start feeling better. Conceivably I can picture a large plant putting out enough waste, in proportion to all those pills for all those people, to contaminate a region of a river near the effluent, especially since some rivers in India have seasonal periods of low flow rate. It's the sort of thing I want a cite before acting on, certainly have doubt about, but can't disprove. Wnt (talk) 00:09, 20 January 2015 (UTC)

Hmmm - so the IV dose of ciprofloxacin is 400mg - and I guess that's diluted into about 5 liters of blood - so around 5000g...so we're looking at one part per 12,500 as a rough theraputic dose. If the river was showing 1mg/g, that's one part per thousand...yikes! I guess the guy was right.

Oops, sorry, good catch. I don't know how much of a "river" is organic material but 10% seems reasonable... SemanticMantis (talk) 15:08, 20 January 2015 (UTC)

The CEO's statement is apparently a (rough) paraphrase of this paper, which showed that the "effluent from a wastewater treatment plant serving about 90 bulk drug manufacturers in Patancheru, near Hyderabad, India-a major production site of generic drugs for the world market" had concentration of ciprofloxacin as high as 31mg/L (= 31ug/ml, which per the above calculations is comparable to the therapeutic blood conc.). Keep in mind though that we are talking about local hotspots (which is concerning enough!), and not "rivers in India". Also, interestingly, as this summary of the PLOS paper linked above points out, the observed antibiotic resistance is quite non-intuitive and somewhat perplexing:

...the relationship to the antibiotics present was not straightforward. For example, the most frequent resistance genes found were for a class of antibiotics called sulphonamides, but the researchers found no evidence of the drugs themselves. They hypothesize that this may be an instance where resistance to one group of drugs could provide resistance to others. And despite detecting high concentrations of fluoroquinolones, a chemical class that includes the heavy-hitting antibiotic ciprofloxacin, the team found less evidence of resistance to these drugs downstream than upstream from the plant. The researchers suggest that the levels of fluoroquinolones in the downstream effluent were so high that they overpowered even the resistant bugs.

Definitely a topic more will be written about. Abecedare (talk) 07:56, 20 January 2015 (UTC)

January 20

After how many hours could you wipe off a butter knife and reuse it?

Wipe very thoroughly (like one more time after no butter is visible on the paper towel anymore), but without washing it. Sagittarian Milky Way (talk) 00:04, 20 January 2015 (UTC)

My butter knife has no crevices or cracks. I don't want an off/rancid taste, though. I always wash it if it's been four hours, I wonder if I could do longer. Sagittarian Milky Way (talk) 00:08, 20 January 2015 (UTC)

Depends on the temperature and personal taste. I often don't even bother refrigerating butter unless the room temperature has been driven up past the usual by the weather. Wnt (talk) 00:14, 20 January 2015 (UTC)

Yes but a thin smear will oxidise somewhat rapidly in warm weather. SM, just because some cupid stunt posts a question every time a breeze blows in one ear and out the other, it doesn't mean you have to. Let's try and make the refdesk better rather than worse? Greglocock (talk) 00:54, 20 January 2015 (UTC)

If you wipe it thoroughly, I can't imagine enough rancid butter would remain to be detectable by taste. StuRat (talk) 05:39, 20 January 2015 (UTC)

Nope. A wipe is as good as a wash. Peanut butter is another story, but even then, a thorough wipe wouldn't be thorough if the knife wasn't clean. Yesterday, I reused the same dirty PB(&B)&J knife for another, six hours later. No wipe. I lived (so far). InedibleHulk (talk) 05:53, January 20, 2015 (UTC)

Species summary format

Hello Misplaced Pages,

Just a question. I very much like the summary boxes that accompany many entries for species of organisms. The 4 features addressed ( 1- Temporal Range, 2- Conservation Status, 3- Classification & 4- Geographic Distribution) are excellent choices. How was format for the boxes arrived at, and is there any incentive to get those boxes that are not quite a complete up to speed?

Many thanks A

Platypus Temporal range: 9–0Ma PreЄЄOSDCPTJKPgN Miocene to Recent Wild Platypus 4.jpg Conservation status

Least Concern (IUCN 3.1) Scientific classification Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Monotremata Family: Ornithorhynchidae Genus: Ornithorhynchus Blumenbach, 1800 Species: O. anatinus Binomial name Ornithorhynchus anatinus (Shaw, 1799) Distribution of the Platypus (Ornithorhynchus anatinus).png Platypus range (red — native, yellow — introduced)AigaBus (talk) 00:50, 20 January 2015 (UTC)

In general, such issues are decided by discussions between editors, leading to WP:CONSENSUS. For this particular example, see Template talk:Taxobox - note that it has 30 pages of archived discussion. If you want to suggest improvements to this sort of thing, you can post a message to the talk page of the template in question. Tevildo (talk) 01:05, 20 January 2015 (UTC)

WikiProject Tree of Life would be the group coordinating such efforts. Rmhermen (talk) 02:29, 20 January 2015 (UTC)

Dregs in Cherry Zero and Vodka

I get a few specks of dregs at the bottom of my glass whenever I mix Coca-Cola Cherry Zero (with Aspartame) and Vodka. I used to drink plain Coke and vodka years ago, and don't remember there being any dregs. Any suggestion as to what might be going on here? Thanks. μηδείς (talk) 01:39, 20 January 2015 (UTC)

This is likely some form of Precipitation (chemistry) due to the change in solvent. The substance coming out ought to be hydrophilic. If you filter some through paper you can see if it's brightly colored, and I predict you can dissolve it again in water (perhaps it will take some time). If that fails we may be back to the drawing board. Presumably it is an ingredient not present in something longstanding like rum and coke, and specifically in the cherry zero formula since I assume the vodka is pretty boring chemically (if it were in the vodka it would redissolve in ethanol, not water). Wnt (talk) 13:28, 20 January 2015 (UTC)

What kind of cat is this?

I saw a cat in the middle of the road, so I stopped and tried to chase it off. It followed me and rubbed and purred, so I picked him up and put him in the car. After all, I don't want to run over a cat. I asked at all the houses within 2 miles, and nobody recognized him. So I took him home. He was filthy and bony, but I gave him a bath and started feeding him. Turns out he's a 6 month old kitten. But other than that, I know nothing about him. So, what kind of cat is he, or what mix, and are there any health issues specific to that breed/breeds I should watch out for? I'm assuming he's a plain DLH, since most strays are, but I just wanted to make sure. He's already been to the vet, but I forgot to ask the breed. http://imgur.com/a/vZdKq/embed#0 --Borat is very nice (talk) 01:09, 20 January 2015 (UTC)

They do have a way of wriggling into your heart, don't they ?

Not sure about the breed, but it looks like a longhair. Longhair cats need extra care, like frequent brushing and occasional trimming, to prevent their fur from becoming matted or causing them fur balls. StuRat (talk) 05:34, 20 January 2015 (UTC)

Like you say, most strays don't care about keeping their lineages pure and their traits by-the-book. No cat likely does, some just go along with their owner's fancies. You have a mutt. Those light splotches aren't going to win him any points in a formal beauty contest, but he's cute, and having unrelated parents is generally a health bonus. Granted, there's a lot about genetic makeup that a picture can't show, but probably safe to assume he just needs regular cat treatment. Some longhairs never get matted, and cough up their hairballs with ease. Brushing's still good if you don't want to clean up the hairball, and most like the contact. InedibleHulk (talk) 07:03, January 20, 2015 (UTC)

Compass poles reversed

Someone broke a rather nice compass by playing around with a magnet and making it spin. Now, north is south and south is north and the owner is quite cross. Is there a way to fix this? Please help. A young child's life hangs in the balance. Anna Frodesiak (talk) 03:49, 20 January 2015 (UTC)

Grab a magnet and move it over this compass. Make sure you are moving along the needle in the same direction each time. See if the compass points to the North again. I'm pretty sure a similar process is exactly what happened to the compass back then when it started pointing in the wrong direction. I hope I saved this poor kid's life. I don't want to live with this weight on my conscience.--Pathnew (talk) 05:07, 20 January 2015 (UTC)

Does the compass have correction marks/magnets? If not, it's not that nice :). Checkout compasses for airplanes for their MEL. --DHeyward (talk) 05:20, 20 January 2015 (UTC)

It worked! (I didn't see correction marks or magnets.) Moving a magnet over the compass just made it spin. So, they held the magnet pole to pole and moved back and forth from the tip of the north arrow to the axis to keep the needle facing one direction. It didn't work and they kept flipping the magnet this way and that. The compass got demagnatized a couple of times and didn't want to point anywhere (which surprised me). Eventually and suddenly, it worked. Nobody knows what they did right. The adults thought it was all terribly interesting. The kid, who was about to trade several allowances for a backward compass was relieved, is now off the hook, and thanks you -- and so do I. :) Anna Frodesiak (talk) 06:12, 20 January 2015 (UTC)

What a tragedy that this child probably doesn't have an old fashioned CRT type TV set to play with. :) Wnt (talk) 13:23, 20 January 2015 (UTC)

Sagittal sutures and scaphocephaly

What is the problem with scaphocephaly, i.e. why would it potentially be important to separate an infantile closed sagittal suture? Facebook friends have just learned that their twins will have to have surgery to remove their skulls' closed sagittal sutures, but the sagittal suture article doesn't seemingly mention any downsides to early closing, other than scaphocephaly, and the scaphocephaly article doesn't seemingly mention anything other than a changed head shape. Is it just an æsthetic thing, because a long, narrow, and wedge-shaped head obviously doesn't look very nice, or are there other reasons why scaphocephaly is a problem? Nyttend (talk) 04:32, 20 January 2015 (UTC)

One thing I can think of right off comes down to safety, namely the ability - or lack thereof - of the individual to wear protective equipment such as hardhats or fire helmets. RegistryKey 05:27, 20 January 2015 (UTC)

Won't it put pressure on the growing brain, if the skull is prevented from spreading apart to accommodate the growth ? StuRat (talk) 05:28, 20 January 2015 (UTC)

About scratching athlete's foot...

Can scratching athlete's foot be more enjoyable than sex?

How?

(Please provide references, if you can). The Transhumanist 10:50, 20 January 2015 (UTC)

I Googled "'athlete's foot' 'more enjoyable' sex" and found Seven Reasons to Get Out More at the top. Might be worth a ponder. InedibleHulk (talk) 11:09, January 20, 2015 (UTC)

Why is NASA hoarding the Dawn data?

I was very disappointed not to find a raw image feed for Dawn as it approaches Ceres , and apparently this is deliberate. Are these images ever being released, or are they being hoarded as a commercial asset, or is NASA afraid that big bright spot really is an alien monolith? In this day and age how can they justify hiding away the data? Wnt (talk) 14:02, 20 January 2015 (UTC)

I think this is just a variant of an Embargo_(academic_publishing) (we don't have a page specific for data embargo but I think you get the point) - the idea is that the NASA researchers should have first claim to publish findings based on the data. We wouldn't want NASA scientists being "scooped" by somebody else! After some time has passed, much of it will probably be made available to the public. Here's a blurb about embargoes at the ESA from the Rosetta mission, which also says

Of course the frustrating thing is that they can embargo some things, let others out immediately, never release some stuff. To my knowledge it's all highly discretionary, either by the PI or some higher level of NASA management. NASA does have a data portal , but while it has a lot of stuff, it is sparse compared to what NASA has collected. Btw, to my understanding this wouldn't be an issue for research funded by the NIH - who now requires all research that they fund be publicly released - though of course that's still after publication, not raw data that has not yet been analyzed. So maybe write to your congresspeople and say you want access to NASA data since you paid for it (assuming you are taxpaying a citizen of USA)? SemanticMantis (talk) 15:00, 20 January 2015 (UTC)

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