Wikipedia:Reference desk/Archives/Science/2016 October 19

= October 19 =

Feynman Lectures. Lecture 32. Sec. 32–5 Scattering of light
Quote: Now we can make an experiment that demonstrates this. We can make particles that are very small at first, and then gradually grow in size. We use a solution of sodium thiosulfate (hypo) with sulfuric acid, which precipitates very fine grains of sulfur. As the sulfur precipitates, the grains first start very small, and the scattering is a little bluish. As it precipitates more it gets more intense, and then it will get whitish as the particles get bigger. In addition, the light which goes straight through will have the blue taken out. That is why the sunset is red, of course, because the light that comes through a lot of air, to the eye has had a lot of blue light scattered out, so it is yellow-red. Unquote.

I need advice to check have I correctly understood. The light when is going through the atmosphere is absorbed and re-emitted (scattered ) by atoms' electrons. There is the formula

$$\sigma_s=\frac{8\pi r_0^2}{3}\cdot \frac{\omega^4}{(\omega^2-\omega_0^2)^2}$$

According to it blue light takes 16 times more scattered energy than red light, as the blue has 2 times higher frequency. But frequency ω that enters into the formula is the frequency of scattered light. So (1): where is blue light from incident beam? I've found several demonstrations on youtube (e.g. youtube.com/embed/LSf7iRD5Jws ). And it looks like the light from a lamp loses blue. And (2): even if blue light re-emitted more intensively, last layer of atoms before eye must absorb red light and re-emit white light. So we have the statement that light keeps its frequency and ωincident = ωscattered. (3) When a wave goes through an atom, electrons begin to oscillate and emit: https://s.sender.mobi/u/image/2016/10/19/wl-chKHAa/-.PNG . Electrons emit in all directions in sheet plane whole absorbed energy, but 16/17 of it is blue and 1/17 of it is red light. Then the light from a lamp (which goes form right to left) must lose same amount of blue light as was emitted by electron.

Is it correct?

Username160611000000 (talk) 04:07, 19 October 2016 (UTC)
 * Yes, the light loses mainly blue frequencies as it passes through a scattering medium and becomes redder. Ruslik_ Zero 19:54, 19 October 2016 (UTC)
 * But we know that electric field acts on the charges, not paying attention to the barrier. So oscillating electron emits such a field that the incident waves (490-445 nanometres) is damped. Is it correct?
 * Waves 740-620 nanometres (red) makes the electron oscillate with frequency 400 THz. Waves 490-445 nanometres (blue) makes the electron oscillate with frequency 670 THz. But amplitude of oscillations in second case is higher in (670/400)2 times. Is it correct? But it's unnatural for oscillator. We know that displacement (thereby amplitude) is proportional to force. Or for atom we should use http://www.feynmanlectures.caltech.edu/I_12.html#Ch12-F2 ? Username160611000000 (talk) 16:00, 20 October 2016 (UTC)

Is that true that for increasing testosterone it's good to eat a lot of fats?
Is that true that for increasing testosterone hormone it's good to eat a lot of fats (or food which rich with fats)? I saw a youtuber which said it but I don't believe anything without scientific evidence. I would like to ensure or deny it. thank you 93.126.88.30 (talk) 19:34, 19 October 2016 (UTC)
 * Looking into a general google search for "Dietary effects on testosterone" leads to a lot of sketchy weight building sites with not a lot of hard science. However, using Google Scholar, I was able to find a few interesting published studies.  This one is from an older study (1979) but otherwise looks solid, stating "A lower nocturnal release of prolactin and testosterone occurred in men fed a vegetarian diet" while this one from 2008 states "high-fat fed rats showed significantly lower total values of plasma TSH and testosterone" which would seem to indicate the opposite of what your random YouTuber claimed.  This article from 1987 seems to indicate the controlling factor is not fat at all, but protein/carbohydrate ratios in the diet.  Just some places to research your question.  -- Jayron 32 19:53, 19 October 2016 (UTC)
 * More to the point, why should anyone care? If you have actual androgen deficiency, consult a medical professional. Otherwise, there's no real reason to care about your testosterone level. There are loads of "broscience" passed around in the world of bodybuilding, etc. which is pretty much all bullshit. If you want to maintain good health, eat a well-balanced diet and get regular exercise. --47.138.165.200 (talk) 01:47, 20 October 2016 (UTC)
 * As always, it's horrible to ask here questions regarding to medical science (without any personally aspects). Someone always should make other fear of answering without any reason. I asked my question because the claim felt to me strange.This is the Youtuber in this video. 93.126.88.30 (talk) 02:06, 20 October 2016 (UTC)
 * If you listen to the whole video and put the fat issue in context of everything he says, then it's just the normal advice. The standard advice is to limit saturated fat intake, replace such fats by mono and poly unsaturated fats. Eating nuts such as walnuts as suggested in the video is consistent with the standard advice. One can argue about whether this is really true, because only the Omega-3 and Omega-6 fats are essential fats, our bodies can make all the other fats it needs from eating carbs. But, of course, you do need to eat enough calories and most people will struggle to do so if they don't eat any fat. Count Iblis (talk) 21:02, 20 October 2016 (UTC)

Can dead bodies infect life bodies with hepatitis or HIV?
may dead bodies infect life bodies with hepatitis or HIV? I'm asking it because I have a doubt if this viruses need nutrition or oxygen etc. in order to exist. 19:37, 19 October 2016 (UTC) — Preceding unsigned comment added by 93.126.88.30 (talk)
 * This forum discussion has some excellent references to research on the matter. Here is a more general overview form the World Health Organization, and Here is another source specifically for HIV.  Wikipedia also has an article titled Health risks from dead bodies which has some brief statements to this effect, but also leads to more reading if you follow the references.  -- Jayron 32 19:45, 19 October 2016 (UTC)
 * Just a little grammatical aside &mdash; you mean "can dead bodies infect....". I know the can/may distinction is a little tricky for some non-native speakers, as not every language has it (not sure about Ukranian).  Anyway, you should use may for permission or moral or legal acceptability, can for physical possibility or practical feasibility. --Trovatore (talk) 19:52, 19 October 2016 (UTC)
 * Thank you93.126.88.30 (talk) 01:49, 20 October 2016 (UTC)

Yes it can. Very easy to prove. Just because the person died 10 seconds ago does not mean their body cannot infect your body with hepatitis or HIV if you have unprotected sex with the corpse. 175.45.116.99 (talk) 06:00, 20 October 2016 (UTC)
 * I think the main point of this question remains unaddressed. A virus, according to most definitions, is not even really "alive", it certainly does not require nutrition OR oxygen in order to exist. Most viruses however, including HIV require an alive host and don't survive a long time OUTSIDE of living cells. So a key point here is that "death" is not an instant process, when a person dies, many cell functions continue to operate for at least some length of time. It appears that HIV can take as little as 1-2 days to "inactivate" in a corpse, but can survive much longer (a week or even more) under some circumstances, such as refrigeration. Vespine (talk) 21:59, 20 October 2016 (UTC)

Are there any reports (preferably scientific reports) which talk about the amount of pain that a person with prosthetic balls suffers when he gets kicked in the balls?
Apologies if this is a stupid question; however, I am genuinely curious as to whether or not people with prosthetic balls experience as much pain as people with natural/biological balls experience when they get kicked in the balls.

Anyway, does anyone here have any thoughts and/or data in regards to this? 128.195.178.33 (talk) 22:13, 19 October 2016 (UTC)
 * Here is a discussion forum on prosthetic testicular pain. -- Jayron 32 22:36, 19 October 2016 (UTC)