Wikipedia:Reference desk/Archives/Science/2009 July 3

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July 3

Nose-picking in nonhumans

Do all animals that have a nose and the physical capability to pick a nose, in fact pick their noses? YouTube says that parrots do. Just got me wondering... --Kurt Shaped Box (talk) 00:14, 3 July 2009 (UTC)

Many animals, such as cows, have a long tongue which is easy for them to stick up into the nostrils for cleaning purposes. It would be difficult for a cow to pick her nose with her hoof. Edison (talk) 02:27, 3 July 2009 (UTC)

My dogs don't. A Quest For Knowledge (talk) 03:12, 3 July 2009 (UTC)

Animals like people don't get to pick their noses and they have to work with the nose they are given like you know who. Cuddlyable3 (talk) 12:53, 3 July 2009 (UTC)_{Yah! mean cheap shot.}

I've seen chimps and gorillas doing it - and it has been observed (sorry - I can't locate the link) that in many (if not all) primates, the nostrils are the exact same diameter as the index finger. This is unlikely to be an accident. SteveBaker (talk) 14:26, 3 July 2009 (UTC)

Well, Darwin would say it's an accident. Tempshill (talk) 17:37, 3 July 2009 (UTC)

@Tempshill: I don't think that's correct, if you're using "Darwin" as a representative of adherents to evolutionary theory. Just to reduce the risk of confusion, I'm going to hazard a guess: "accident" is being used here (by both SteveBaker and Tempshill) to mean "coincidence" or random chance. Though evolution depends on random variation to generate diversity, it is selection that drives adaptation to specific function (which I think was the point SteveBaker was making). --Scray (talk) 19:49, 3 July 2009 (UTC)

I think SteveBaker used "accident" in the latter sense, and I was using it in the former sense. I don't know that I'd subscribe to the theory that human finger diameter and human nostril diameter have been selected to match each other. Tempshill (talk) 20:39, 3 July 2009 (UTC)

cortisone

What does it mean to get a cortisone shot? —Preceding unsigned comment added by 76.171.21.74 (talk) 01:52, 3 July 2009 (UTC)

It means an injection of cortisone, which is a steroid. --Allen (talk) 03:58, 3 July 2009 (UTC)

What sort of math is being used?

I don't understand how this works or how to stump it? Ideas? --Reticuli88 (talk) 03:57, 3 July 2009 (UTC)

There's nothing very mysterious about it. If we ignore the obfuscating steps that don't involve your number at all, and rearrange the initial grid a bit, then it boils down to being given a 5x5 grid of numbers, choosing one of them, telling someone which row and which column your number is in, and them then working out your number. Algebraist 04:01, 3 July 2009 (UTC)

It looks very simple once you take away all the pointless stuff. First, it asks you the color. That narrows it down to only 4 or 5 numbers. Then, on the step with the houses, the numbers for the colors are split up so that each house contains only one number of each color. Knowing the color from before, that leaves only one possible number. Ta da! --Bennybp (talk) 04:51, 3 July 2009 (UTC)

light propogaton versus particle stability

Is perhaps the only difference between light (as a particle) and other particles is that light is self propagating perhaps due to an inability to become a stable particle whereas other particles are either stable or their instability does not cause self-propagation but self-inhalation instead? -- Taxa (talk) 05:18, 3 July 2009 (UTC)

I would advise you to read the article photon. Photons are pretty stable, you can see them around everywhere. I don't understand what you mean by "self-inhalation", or how you propose that a particle can "self-propagate" if it is unstable. Maybe you mean "annihilation" but that requires two particles - one matter and one which is antimatter. Rkr1991 (talk) 06:36, 3 July 2009 (UTC)

pocket desert

What is a pocket desert? —Preceding unsigned comment added by 89.247.57.20 (talk) 08:07, 3 July 2009 (UTC)

Based on Pocket park and Pocket beach I suspect it is an informal name for a small desert that is surrounded by otherwise non-desert geography. 194.221.133.226 (talk) 09:22, 3 July 2009 (UTC)

Some context would be useful. It could mean someone with empty pockets?! You might like to try the Language desk.--Shantavira|^{feed me} 09:53, 3 July 2009 (UTC)

Typing "pocket desert" into Google turns up articles about a specific place near Oliver, British Columbia. Our article describes it as having a 'pocket desert' nearby. This has more information, as does this. So the term seems to be a generic one for multiple 'pocket deserts' - yet only this specific one ever shows up as an example of such a thing. Perhaps the term is used only in Canada with some other terminology being used elsewhere? SteveBaker (talk) 14:22, 3 July 2009 (UTC)

Searching on "desert pocket", found quite a lot of examples describing areas of local desert conditions as suggested by 194, mainly from the US but also from New Zealand and the Himalayas (cold desert in that case). Mikenorton (talk) 15:32, 3 July 2009 (UTC)

I'm aware of small areas of desert near Lillooet, British Columbia, could it be the same "pocket desert" Steve found on Google?

76.21.37.87 (talk) 04:22, 4 July 2009 (UTC)

What are the strongest and weakest points of gravity on earth?

I'm aware that a number of 'gravitational maps' exist, however, I have heard, in the past, of a place where the phenomena of gravity is noticeably at variance with that of other parts of the world. Where are these places and what, if any, explanation exists for the variance? —Preceding unsigned comment added by 24.234.123.169 (talk) 16:53, 3 July 2009 (UTC)

Our article Gravity anomaly gives the facts, in a sketchy way. It's possible that you're thinking of stories about places like Confusion Hill in northern California, where the layout of the landscape creates an illusion that objects roll uphill. Looie496 (talk) 17:05, 3 July 2009 (UTC)

Due to the shape of the earth, gravity will tend to be strongest at the north and south poles - and weakest around the equator (the earth isn't a perfect sphere). However, you don't feel that difference because the centrifugal forces are zero at the poles and higher at the equator...which is why the earth is that shape to start with and gravity-centrifugal force is pretty much constant everywhere. Aside from that, differences in mineral composition and therefore density can make a tiny difference from place to place - also the presence of mountains or deep valleys. This map [1] gives you a better way to visualise it. ~~

Actually, the effects of oblateness and rotation act in the same direction, both reducing the effective acceleration due to gravity at the equator as compared to at the poles. The difference is about 0.35%, of which about 2/3 is due to the rotation of the Earth and 1/3 is due to the oblateness of the Earth. Definitely a noticeable effect - a pendulum clock on the equator loses about 2.5 minutes a day compared to an identical clock at the poles. See Equatorial bulge#Differences in gravitational acceleration. Gandalf61 (talk) 19:38, 3 July 2009 (UTC)

The story that I heard, was that there was a place where gravity or some other phenomena affected the surface of a lake in Africa. The phenomena supposedly caused the surface to have a noticeable curvature. However, I suppose that this is a legend or myth of some sort.

As an aside, is it possible to obtain the data-set used to generate the map show in [2] ? —Preceding unsigned comment added by 24.234.123.169 (talk) 17:20, 3 July 2009 (UTC)

Yes, check "make data available for download" here. --Sean 13:32, 6 July 2009 (UTC)

As I recall, there's a memorial pool in Boston or Philly which is kept so full of water that it had to be slightly curved to match the Earth's curvature, or else water would spill around the edges. It's huge, but I can't remember the name... Andyo2000 (talk) 18:54, 9 July 2009 (UTC)

Gravity would be lower on the peaks of tall mountains as there is a higher radius from the center of the earth if you are going with a standard physics textbook. 65.121.141.34 (talk) 15:05, 6 July 2009 (UTC)

At what speed do galaxies travel through the universe/space?

At what speed do galaxies such as the Milky Way and Andromeda travel through space? As a follow-up, what are the speeds of the solar system and earth as well? How are these measured? How does this affect our measurements such as the speed of light, radio waves, etc. Is there a point where the speed of a mass shall decline to 'absolute 0'? Theoretically, is there a way to 'see' a mass traveling faster than the speed of light? —Preceding unsigned comment added by 24.234.123.169 (talk) 17:38, 3 July 2009 (UTC)

As it turns out, the speed of light relative to you will be equal regardless of how fast you're moving. Check out Special_relativity#Lack_of_an_absolute_reference_frame and also Introduction to special relativity. As a result, measurement of the speed of light is not affected by how the earth or the galaxy are moving, and an object can never be observed to travel faster than light. In addition, objects don't have a meaningful absolute velocity since there's no single "preferred" reference frame in which light behave properly; you can only talk about objects' velocities relative to other objects. Here's some info on the Milky Way: Milky_way#Velocity. Rckrone (talk) 18:34, 3 July 2009 (UTC)

The orbital speeds of the planets relative to the Sun are listed in our articles for each of the planets. For example, Earth's is just under 30 km/s. ~AH1^(TCU) 19:12, 3 July 2009 (UTC)

Neoprene wetsuit in chlorinated water

Hi everyone I recently bought a wetsuit made of neoprene and on the label it says do not use in chlorinated water. I intended to use it in chlorinated water. I am wondering if I do go in chlorinated water in this suit will it affect the insulating properties of the material? If chlorine only acts to discolourise/stain the material I don't much care but I want to make sure that going in chlorinated water won't stop the suit doing its job if you know what I mean. Any help would be much appreiciated. Thanks RichYPE (talk) 17:53, 3 July 2009 (UTC)

I was taught, vaguely, that chlorine would somehow destroy the wetsuit. Googling "neoprene chlorine", this result from the first page of results claims that "Neoprene ... contain[s] carbon-carbon double bonds as an essential part of their polymer chains. These bonds are susceptible to oxidative damage from species such as ozone and chlorine." As a layman I'm not exactly sure what "oxidative damage" means, but it sounds like it'd be worse than just staining. Tempshill (talk) 20:10, 3 July 2009 (UTC)

See Halogen addition reaction and ozonolysis for the chemistry behind the reactions you drescribe. --Jayron32.talk.contribs 20:25, 3 July 2009 (UTC)

Thanks for your help but chlorinated water is usually in the form of sodium hypochlorite rather than just actual chlorine. I wonder if this makes a difference and whether or not this would react with the neoprene... RichYPE (talk) 22:17, 3 July 2009 (UTC)

Actually, read the article Bleach. Hypochlorite is really a dynamic equilibrium with chlorine and water, as described here:

Cl₂ + H₂O $\rightleftharpoons$ H⁺ + Cl^- + HClO

With low pH favoring the backwards reaction and high pH favoring the forwards reaction. Still, even under roughly neutral conditions, there may very well be enough Cl₂ present to react with any double bonds via alkene halogenation mechanisms; even if its only a trace amount, Le Chatelier's principle tells us that since the reaction removes chlorine from the system, the hypochlorite-chlorine equilibrium will just generate more chlorine on demand to meet the need. I did some looking, and there does not appear to be any common hypochlorite-alkene reactions directly; however the chlorine is clearly the reactive species here. --Jayron32.talk.contribs 00:39, 4 July 2009 (UTC)

As far as I'm aware, the chlorine addition reaction will not destroy neoprene rubber, but is likely to cause embrittlement over an extended period of time. So, if you frequently use the wetsuit in chlorinated water, it won't come apart the first few times, but you should definitely expect it to wear out sooner than normal. 76.21.37.87 (talk) 04:29, 4 July 2009 (UTC)

Apparently there is an Italian made polyester wetsuit fabric that is chlorine resistant. But as you've already bought your suit, you could try this Wetsuit Shampoo that supposedly removes chlorine. - KoolerStill (talk) 12:00, 4 July 2009 (UTC)

Hi thanks for the posts guys. What I will do is get a refund on my suit (still have receipt) and buy one which is chlorine resistant. Cheers RichYPE (talk) 19:05, 4 July 2009 (UTC)

I have been a SCUBA instructor for quite some years,+- 14 Years. We used the local comunity pool as an inland training facilety. The pool water was well clorinated and sometimes to the extend that it could be smelled from outside the water. The cloranation time was more or less the same time as the training schedule. I can realy not say that my wetsuites was damaged in any way other than some fading of the colours and even this was minor. Take note however that we washed and rinsed oue suites well after use in clean fresh water and did not dry them in direct sunlight. My old "outsized suites" was passed on to other guy's and are still in use. 196.25.43.75 (talk) 13:34, 9 July 2009 (UTC)

Minimum Sample Size for a Correlation Study

I know of a formular for determining the minimum sample size for a prevalence study, which most research studies use. Is there any formular to determine minimum sample size for a correlation study, like a correlation between birth weight and fetal cord leptin concentration-a research?Tunmisadej (talk) 19:54, 3 July 2009 (UTC)

I'm not sure there is a general answer to this. For a specified minimum confidence level and correlation value, one can determine the number of samples needed, but since it depends on the strength of the correlation one may not have a good estimate in advance. For example, a perfect correlation can be statistically significant with only a small number of samples. By contrast, a weak correlation (which is much more common in practice), may require a quite large sample to confidently document. Dragons flight (talk) 20:11, 3 July 2009 (UTC)

This is the most common reason for doing power calculations, and our article covers the considerations pretty well. --Scray (talk) 04:47, 4 July 2009 (UTC)

I am sorry, I still find the reference above not clear to answer the question. The one that was mostly discussed was sample size for determining proportion study. If I have correlation coefficients from prevoius research studies, I would like to know if this can help in determining minimum sample size using any formula or otherwiseTunmisadej (talk) 11:30, 4 July 2009 (UTC).

I had a similar question once and although I never really solved it. This may help, but I'm not sure since I haven't formally taken any statistics. Sifaka ^talk 20:40, 4 July 2009 (UTC)

Given correlation coefficient r and number of samples N one can define the t statistic:

$t=r{\sqrt {N-2 \over 1-r^{2}}}$

Which obeys the student's t-distribution characterized by ν = N-2. Using this one can determine the two-tailed probability of r occurring by chance amongst N samples. Most people use a table because the math is messy. To answer your question simply vary N for fixed r and use the table to figure out when the resulting t is associated with the level of confidence you want. Again, since all the factors are interdependent the sample size will dependent strongly on the strength of the relationship, which is general is difficult to know confidently in advance of doing the experiment. Dragons flight (talk) 08:08, 5 July 2009 (UTC)

I am very grateful to Dragons flight, the idea is quite useful. I was trying to have a scientific proof for my sample size in a correlation study.41.219.230.122 (talk) 18:55, 5 July 2009 (UTC)

Blood pressure in cats

Our vet always quotes our cat's blood pressure as a single number whereas human blood pressure is always quoted as two numbers, the systolic and diastolic pressures. Why is only one quoted for cats and which one is it (or is it some other number entirely)? Thanks. --Tango (talk) 22:27, 3 July 2009 (UTC)

The information on this site (http://www.pets.ca/encyclopedia/hypertension_cats.htm) has some details under the 'diagnosis' section and seems to suggest both types of numbers being run against cats. Are these measured separately or together? If they are separate then maybe it is to minimize stress on the animal and perhaps the single piece of information is usually enough. All speculation though, sorry. ny156uk (talk) 23:12, 3 July 2009 (UTC)

I think you have to ask your vet on this one: it's certainly possible to obtain the usual systolic/diastolic readings in cats (normal is ~124/82) using a machine (I think the cat's rapid heartbeat might make it difficult to do by ear). But whether your particular vet is quoting systolic, diastolic, or mean arterial pressure is something only he or she can say. - Nunh-huh 23:16, 3 July 2009 (UTC)