Wikipedia:Reference desk/Archives/Science/2012 August 13

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

August 13

When you have a cold and feel weak, what exactly is happening to your body？

Monday I am healthy, Tuesday I have a cold. Tuesday I feel weak. But I cannot possibly be physically weaker than I was on Monday, can I? The muscle fibers are all still there. Am I really weaker? I've never bothered to try a strength and conditioning comparion, but I certainly have less energy... what's the biological situation here? Do my muscles have less ATP? Is my digestive tract temporarily absorbing nutrients less efficiently? What is the source of the weakness? Or is it just psychosomatic? This has been fascinating me for years and I only just remembered to finally ask... The Masked Booby (talk) 00:42, 13 August 2012 (UTC)

That's an interesting question.. Our article for Common cold says that fatigue and muscle ache are common symptoms of a cold, as well as loss of apetite, but it doesn't really get into the mechanics of how that happens. My guess is that, broadly speaking, your body is using up resources fighting the infection. I dare say a more complete answer would be quite complicated. Vespine (talk) 01:00, 13 August 2012 (UTC)

Having just said that, I just noticed the Pathophysiology section in the cold article, it points to inflammatory mediators as the cause of the symptoms (at least in some cases). Vespine (talk) 01:03, 13 August 2012 (UTC)

Note that interferons cause fatigue in most persons taking them.[1] Interferon 2-alfa treatment for influenza is well known, having been developed in the Soviet Union in the 1960s and used in Russia to this day (Influenza_treatment#Interferons), but like so many Soviet technologies it remains ever just out of reach of Western science more than fifty years later.[2] Response to RNA virus infection by interferons, including interferon alpha, by lung macrophages (and IFN-gamma by epithelial cells) is an important immediate response by the lungs to the infection. (See [3] and references therein for review) The fatigue effect can be reduced by the use of L-carnitine,[4] a common OTC supplement which also has longer-term effects on anemia/etc. caused by interferon treatment.[5] Note however that this is pretty recent research and I did not immediately see any study to prove that taking carnitine doesn't achieve these effects by somehow reducing the effectiveness of interferon, which would be counterproductive, and I don't intend this as a recommendation. I'll mention that I've myself noticed considerable fatigue 15 minutes to 1-2 hours after flu shots (some more so than others) which apparently is not an uncommon side effect.

I haven't tried to nail down the situation so well with common cold viruses because they're a pretty large assortment of entities which are not typically well diagnosed, though one of my references cites "promising" results from 1973.[6] Wnt (talk) 11:48, 13 August 2012 (UTC)

With an infection such as the common cold, the immune system may trigger sickness behavior, which includes physical weakness and hyperalgesia (increased sensitivity to pain). Modocc (talk) 18:51, 13 August 2012 (UTC)

There would seem to be three factors, the immune response, with the effects of factors such as interferon and pyrogens, toxins produced by the infecting agent, and low blood sugar due to lack of eating as mentioned above in sickness behavior, which is a quite interesting article. μηδείς (talk) 20:16, 13 August 2012 (UTC)

E=mc²

Is E=mc² and E=mcc same thing ? I am thinking about squaring of "c" and multiplying it by itself isn't the same ? With later the equation would be more simple (if they are same thing)...

I would also like to know why the same question was removed from this page yesterday ?124.253.184.205 (talk) 03:41, 13 August 2012 (UTC)

It was removed as part of an automated archiving system. It has already been answered as yes, it is the same. Plasmic Physics (talk) 04:05, 13 August 2012 (UTC)

The question was archived normally. All questions are archived after a few days. Nimur (talk) 04:06, 13 August 2012 (UTC)

Well. I asked that because...you see the advantage of squaring c is that it gets multiplied by itself before being multiplied with m. In case of E=mcc the c gets multiplied with m and then their product gets multiplied by c again. Won't that make a difference ? — Preceding unsigned comment added by 124.253.95.62 (talk) 04:52, 13 August 2012 (UTC)

Multiplication of real numbers is associative. That means that a * b * c = (a * b) * c = a * (b * c). So in this case, (m c) * c = m * (c * c). --Amble (talk) 05:00, 13 August 2012 (UTC)

(4 * 9) * 16 = 36 * 16 = 576

4 * (9 * 16) = 4 * 144 = 576

(m * c) * c = mc * c = mc²

m * (c * c) = m * c² = mc² Plasmic Physics (talk) 05:15, 13 August 2012 (UTC)

As a note: It's unlikely that any of us would say "yes, it is the same" when we mean "no, its not the same", so feel free to believe us. Plasmic Physics (talk) 05:24, 13 August 2012 (UTC)

Perhaps the OP is confusing E=mc² with E=(mc)² (which are not the same, of course). Dbfirs 14:20, 13 August 2012 (UTC)

I think the OP should peruse our article on the order of operations. There are fairly strict conventions about this sort of thing. --Mr.98 (talk) 15:33, 13 August 2012 (UTC)

I'd rather the OP didn't read that article because it's largely bunk. There's no "order of operations" in mathematics. There is operator precedence, which can be overridden by explicit parentheses, but after applying the precedence rules you can reduce the expression to a value in any order you want. 1 × 2 + 3 + 4 means (1 × 2) + 3 + 4 because of the precedence rules, but beyond that there are no restrictions: you can perfectly well reduce to (1 × 2) + 7, doing an addition before a multiplication.

Equally wrong is the idea that operations are done from left to right. In real mathematics, A − B + C is a shorthand for A + (−B) + C, and those additions can be done in either order. For multiplication and division there's no left to right rule because there's no division operator. "A / B × C" is just a vertically compressed form of either ${\tfrac {A}{B}}\times C$ or ${\tfrac {A}{B\times C}}$. Since it's ambiguous, a mathematician wouldn't ordinarily write it unless the correct interpretation was obvious from context. For that matter, "1 / x+1" is very likely to mean ${\tfrac {1}{x+1}}$. Of course, a mathematician would never write A ÷ B × C or 1 ÷ x + 1, since the ÷ symbol doesn't exist outside of grade-school arithmetic.

I wish I could fix the article, but changes seem unlikely to stick. -- BenRG (talk) 16:50, 13 August 2012 (UTC)

Related rant: "Order of operations" and other oddities in school mathematics by Hung-Hsi Wu. -- BenRG (talk) 20:41, 13 August 2012 (UTC)

Since we use a system of Arabic numerals wouldn't it be more logical for operations to be done from right to left? I understand your point that operations don't inherently go in either direction, but still... 203.27.72.5 (talk) 21:39, 13 August 2012 (UTC)

Stacked exponents do go from right to left, so that e^-x2 = exp(-(x*x)). But I always assumed that the left-to-right rule is there to ensure that expressions like 5 ÷ 2 ÷ 3 are parsed as (5 / 2) / 3 instead of 5 / (2 / 3). I think the arguments above are reasonable if you assume that the only goal of mathematics education is to prepare students for more advanced math and give them an appreciation of math in its own right. In reality, it's at least as important that students be taught what they need to know to practically use everyday or professional math. Reading an accounting formula or using a calculator would be impossible without knowing the appropriate order of operations. Similarly, a language arts class may teach students rules of grammar that would be irrelevant to academic research in linguistics. Those same rules are, however, important for correctly understanding income tax instructions or writing a job application. --Amble (talk) 22:12, 13 August 2012 (UTC)

antifungal

if psoriasis is simply a skin shedding disorder why do doctors commonly prescribe antifungal medicine for scalp psoriasis?--Wrk678 (talk) 05:06, 13 August 2012 (UTC)

Because fungus often irritates the skin, especially on the scalp (see seborrhoeic dermatitis). We don't have anything about it in our own article on psoriasis, but I'm assuming it's because when you have an inflammatory skin disorder, removing other sources of irritation is probably a good thing. Psoriasis-afflicted skin may also be prone to fungal infections [7]. Someguy1221 (talk) 05:30, 13 August 2012 (UTC)

Height and sexual satisfaction

Is there any study that correlates height and sexual satisfaction as in, for example, taller women reach an orgasm easier than shorter ones or viceversa?--79.144.246.216 (talk) 10:07, 13 August 2012 (UTC)

The French are all shorties, so I don't think your theory works. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:53, 13 August 2012 (UTC)

Really Bugs? Did you ever go to France? Have you seen a shot of Charles de Gaulle? The shortest member of the French national basketball team is 6ft 2ins, so not all then. ;-) Richard Avery (talk) 07:35, 14 August 2012 (UTC)

Not in hetero men (PMID 22378712) or gay men (PMID 20813600) but apparently nobody has yet looked at height and sexual satisfaction in women. But since the studies about women show a correspondence to cultural body image, I predict a bimodal peak a couple standard deviations on each side of the mean height. 75.166.207.214 (talk) 08:23, 14 August 2012 (UTC)

I would expect a small correlation with body weight, as estrogen is produced in body fat. (For a long time the medical profession thought that estrogen is only produced in ovaries, but cancer research found that to be not true.) For women of european descent, a minimum body weight of around 55 kg is required for stable hormone levels, regular periods, etc. However the effect of estrogen on ability to reach orgasm is complex. Reaching an orgasm is affected by vaginal health, which is dependent on adequate estrogen, but is also dependent on libido, which is dependent on androgen production and can actually be better with low estrogen levels. Not fogetting that the relationship between estogen and ability to orgasm is not simple, taller women should normally weigh more and have more body fat, so their hormone levels would be a little more reliable. Hence a weak correlation between ability to orgasm and height seems reasonable. Cultural influences, experience, and fondness for her partner, would, I expect, easily overide and probably swamp any such correlation. Wickwack124.178.152.224 (talk) 03:42, 15 August 2012 (UTC)

Unidentified Agama

Could you please help identifying the Agama on the right by its full scientific name? It was found at Tel Arad, Israel. Many thanks, ליאור • Lior (talk) 12:07, 13 August 2012 (UTC)

A starred agama (Laudakia stellio).-- OBSIDIAN†SOUL 13:34, 13 August 2012 (UTC)

Epithelium tissue

While reading a article on epithelium tissue, I find some confusing terms. These terms are-
kidney tubules, uriniferous tubules, intestinal mucosa, primary urine, basal layer, tissue fluid, germinal layer, thyroid vesicles, and genital tracts.
Will you provide me simple meaning of these terms? Sunny Singh (DAV) (talk) 13:29, 13 August 2012 (UTC)

kidney tubules, uriniferous tubules, intestinal mucosa, primary urine, basal layer, tissue fluid, germinal layer, thyroid vesicles, and genital tracts. --TammyMoet (talk) 16:17, 13 August 2012 (UTC)

Strings

So I watched this lecture, http://www.youtube.com/watch?v=25haxRuZQUk given by Leonard Susskind, and he said that particles that manifest in reality like quarks or electrons are actually the "ends" of 1 dimensional strings. So each particle has its own antiparticle and they are joined by a string. So this implies that all the matter and energy that makes up our bodies is actually connected via strings to their anti particle counterparts correct? So where is all this antimatter? Is it in another dimension or universe? 148.168.40.4 (talk) 14:17, 13 August 2012 (UTC)

That video is almost two hours long. Please specify when in the video he says these things.

He may have been talking about string theory's origins as a theory of quarks and gluons, which is different from modern superstring theory. Or it could be something related to Dirac strings. -- BenRG (talk) 17:48, 13 August 2012 (UTC)

He mentions it several times, but one place that I found just now is at 25:00 to about 27:00. He mentions it other times too, I would have to go through it again to find them though. 148.168.40.4 (talk) 14:15, 14 August 2012 (UTC)

Was Richard Feynman a frequentist or a Bayesianist or?

The reason i ask is i vaguely recall that he gave an example of what he regarded as poor probabilistic reasoning.76.218.104.120 (talk) 14:41, 13 August 2012 (UTC)

Do you mean his quote about the license plate? This website attributes the quote to an anecdote in the preface to Six Easy Pieces, though I recall hearing it on some PBS interview. I'll see if I can track the source down.

As far as frequentism or Bayesianism, I can't recall Feynman ever volunteering to subscribe to either school of thought in a direct fashion, though from his other writings, I'd think he may view this as a false dichotomy, in that both models are just ways of interpreting the same universe, which behaves irrespective of our mental conception of it. That's how he described wave-particle duality.. Nimur (talk) 14:58, 13 August 2012 (UTC)

I agree. At a practical level, the difference probably wouldn't have manifested itself greatly in his work. The difference shows up mainly in approaches to hypothesis testing, but in physics, hypothesis-testing experiments are rare -- most experiments come down to making a measurement of some sort, and statistics are used to determine the likely error in the measurement. (The proper term is "Bayesian", not "Bayesianist", by the way.) Looie496 (talk) 15:12, 13 August 2012 (UTC)

Quite correct, Looie496. Personally, I don't find the names "frequentism" or "Bayesianism" for these theories particularly descriptive or useful. With respect to the original: you can know the word for Bayesian statistics in all the languages of the world... but when you're finished, you'll know absolutely nothing whatever about statistics... There's no point in labeling Feynman a Bayesian unless you can deduce some meaningful conclusion from that label. Nimur (talk) 19:11, 13 August 2012 (UTC)

During the Challenger disaster investigation, he without a doubt established a reputation as one of the most influential frequentists. But I'm sure he used Bayesian methods when he had reason to believe they were sound. The two camps aren't a dichotomy in the traditional sense, it's just that the frequentists think the Bayesians overgeneralize in a wide variety of fairly common cases, while the Bayesians often don't dispute the fact, just that it often means only trivial differences in outcomes, like between the population and sample standard deviations for large samples. 75.166.207.214 (talk) 05:27, 14 August 2012 (UTC)

But, that's just the opinion and interpretation of one guy, Kenneth Hammond - a psychologist, not a physicist or statistician. You can read Feynman's contribution to the Challenger investigation - he contributed to the entire Rogers Commission Report, available in full form from NASA; and Feynman even wrote his own appendix - also available from NASA, expressing his dissenting opinions on certain specific points and certain overall procedures. There's no need to believe a psychologist's opinion of Feynman's views - even if he happens to be credentialed or reputable - because you can read Feynman's own words and decide for yourself. He makes clear how he interprets facts, including statistical evidence - and if you desire to categorize that interpretation in to one of two statistical "schools of thought," you can. It won't change Feynman's actual views. Nimur (talk) 18:31, 14 August 2012 (UTC)

Thanks to everyone.--Rich Peterson76.218.104.120 (talk) 06:45, 16 August 2012 (UTC)

Physicist

Hi. Who is the world's greatest living physicist? --41.178.237.193 (talk) 15:03, 13 August 2012 (UTC)

If by "great," you mean "most massive..." well, there is no registry of physicists by mass, to my knowledge. The question is faulty, because it does not define "greatness" (or "physicist"). Nimur (talk) 15:08, 13 August 2012 (UTC)

We don't do requests for opinions here. The best I advice I can give is start browsing through something like Category:Physicists and see what you find. It a subcategory for 21st century if you're looking for someone new-ish to the field, but it looks pretty sparse. You could also browse through the Nobel laureates subcat and see who is still alive and doing research. As Nimur points out, it all depends on what you think makes a physicist great.209.131.76.183 (talk) 15:10, 13 August 2012 (UTC)

If you took a poll, Stephen Hawking would probably win. Looie496 (talk) 15:14, 13 August 2012 (UTC)

A poll of physicists or a poll of the general public? Hawking would win the general public, but that's because he's one of the few names the general public even knows (which is arguably more about his life story than his actual physics). I don't know if he'd win among physicists. --Mr.98 (talk) 15:21, 13 August 2012 (UTC)

Edward Witten was once called the "world's greatest living theoretical physicist" by Time magazine, for whatever that is worth. He seems like a fairly good candidate for the position if you're looking for one — his influence has been huge and fundamental (if you've heard of string theory, it's probably because of his work on it). Obviously trying to come up with such a thing is going to be a fairly arbitrary operation. --Mr.98 (talk) 15:26, 13 August 2012 (UTC)

I mean by "greatest" the one who "made the most important achievements" in physics. Thank you. --41.178.237.193 (talk) 15:35, 13 August 2012 (UTC)

That's a start at clarification, but all you've done there is kick the can down the road a bit. How does one objectively define "most important achievements in physics"? You need to keep kicking at it until you get to something measurable: most students? most papers? most citations? most prizes? is crowned King of Physics by his or her peers? Even if we handle this just in the 20th century, for example, it'd be hard to know whether, say, Albert Einstein, Enrico Fermi, or John von Neumann would be the "greatest" by those definitions (among many other plausible candidates). --Mr.98 (talk) 15:39, 13 August 2012 (UTC)

Hi, Mr.98. I don't have a defined criteria. I just want to know who do you think is the world's greatest physicist. Thank you. --41.178.237.193 (talk) 15:44, 13 August 2012 (UTC)

As you've already been told, we don't do requests for opinions here. However, you could look at List of Nobel Laureates in Physics for an objectively defined measure of "greatness". --TammyMoet (talk) 16:13, 13 August 2012 (UTC)

Is the claim that the Committee of the Royal Swedish Academy of Sciences can be objectively used to measure physical greatness itself not a subjective valuation of that committee? 203.27.72.5 (talk) 22:08, 13 August 2012 (UTC)

In the OP's defence, they did say living physicist. So Einstein, Fermi and Neumann don't qualify.. I second Edward Witten. Vespine (talk) 22:49, 13 August 2012 (UTC)

I didn't claim they were alive. I was just pointing out that we already have a pretty good idea of what their legacies are, but even then, it wouldn't be clear who you'd call the "greatest." Doing it for people whose legacies are in flux is not going to be any easier. --Mr.98 (talk) 22:54, 13 August 2012 (UTC)

Chen Ning Yang Count Iblis (talk) 23:10, 13 August 2012 (UTC)

I want to second Yang, but even more I'd like to say something about fluid dynamicists instead of particle physicists because, well, it's a hell of a lot harder, really, and that should count even though it's not so earthy-crunchy hidden-mysteryish. But because fluid dynamics is so much harder, I'm not sure anyone stands out recently. The people who do the best work are more likely to be known for what most people would call computer science algorithms, not physics. So, Yang I guess. 75.166.207.214 (talk) 08:16, 14 August 2012 (UTC)

My dad —Tamfang (talk) 07:26, 14 August 2012 (UTC)

How does Slushy Magic work ?

Their web site: http://slushymagic.com

You freeze 3 "magic cubes", add them to a cold drink, then shake, to make a slushy (a drink with many tiny ice crystals). They don't say how long you have to shake it, so I'm assuming a very long time. I think you just put water in the "magic cubes", but I'm not certain.

So, why don't you just get 3 big ice cubes ? How do you get many tiny ice crystals ? (I'm rather skeptical of this actually working as advertised.) StuRat (talk) 20:11, 13 August 2012 (UTC)

This question has been answered at Yahoo!Answers. The three big ice cubes aren't ice, they're sealed plastic containers that have a high specific heat capacity material in them (possibly saline solution). They just cool the drink to below freezing and since you shake it as that process goes on, large crystals can't form. This is the exact same principle as the store bought slushies that work by constantly mixing the liquid as it freezes to prevent large crystals from forming. 203.27.72.5 (talk) 21:24, 13 August 2012 (UTC)

Thanks. How long do you need to shake it ? StuRat (talk) 21:33, 13 August 2012 (UTC)

Apparently, longer than advertized. 203.27.72.5 (talk) 21:57, 13 August 2012 (UTC)

Curiously, their own website doesn't say how long you have to shake it. The consensus on Amazon customer reviews seems to be >5 minutes. But obviously, you're supposed to shake it for a little over 3 minutes Someguy1221 (talk) 22:01, 13 August 2012 (UTC)

Thanks all. From the reviews it looks like the slush mug is a better alternative: [8]. StuRat (talk) 02:02, 14 August 2012 (UTC)

I remember having Teenage Mutant Ninja Turtle slush mugs growing up. They worked great. They took several minutes as well, but it was easy - just scrape the sides, like the slushy machine mentioned by 203. 209.131.76.183 (talk) 11:51, 14 August 2012 (UTC)

Cool, I'll have to get some on e-bay. StuRat (talk) 07:04, 15 August 2012 (UTC)

Resolved

tsa

do the tsa still molest you?--Wrk678 (talk) 22:20, 13 August 2012 (UTC)

They changed their policy to prevent such incidents, but you can always have the exceptional passenger who will feel molested. Count Iblis (talk) 22:25, 13 August 2012 (UTC)

The TSA very much still uses full body scanners and pat-downs, either of which can be construed as molestation by perfectly reasonable people. However, such judgements of molestation are subjective, and so we likely cannot answer whether you would consider yourself molested by present procedures. Here are TSA pages on scanners and pat-downs. — Lomn 22:44, 13 August 2012 (UTC)

I travel enough, and am distrusting enough of the safety of the scanners (I am not terribly worried about them, but uncertain enough to just avoid them, since the cost to me in terms of time or anything else is low), to voluntarily request the pat-down every time I travel. It's pretty straightforward — they pat you down as you might normally expect, with the only "sensitive" pats being in the groin area (which they do with the back of the hand, and always announce it before doing it) and checking inside the waistband of your pants. The people doing it always seem much more embarrassed about it than I am. Whether you would construe this as "molestation" or not, I don't know. It's not something that otherwise one goes through in one's life, but it is not painful and the guards, at least in my case, never derive any pleasure out of it. --Mr.98 (talk) 22:53, 13 August 2012 (UTC)

Even starship captains are not immune to embarrassing TSA searches.    → Michael J Ⓣ Ⓒ Ⓜ 23:35, 13 August 2012 (UTC)

does the tsa currently still grope your penis and balls if you refuse to go thru the scanners?

For those readers who wonder what this question was all about, Transportation Security Administration, in the United States Department of Homeland Security, has no connection with The Salvation Army, The Scout Association or Trollers Society Anonymous. Dbfirs 19:24, 14 August 2012 (UTC)

If having your balls and penis groped is a concern, and you don't want to be scanned, then you can choose not to fly. No one is forcing you on an airplane. --Jayron32 16:36, 15 August 2012 (UTC)

Or you can write your Congressman, petition for change, etc. --Mr.98 (talk) 20:26, 15 August 2012 (UTC)

They touch the inside of your crotch with the back or sides of their hands. They usually look pretty embarrassed by it. --Mr.98 (talk) 20:26, 15 August 2012 (UTC)