Wikipedia:Reference desk/Archives/Science/2016 October 22

= October 22 =

Frozen Virus
With random stories appearing every now and again about Ice melting and releasing some Dinosaur era virus to wipe out humanity was woundering if that was even possible...I understand several species can freeze and come back to life so to speak but long term would have thought the freezing process would destroy the internal workings of life of a sustained period of time; also that it would have to mutate to this environment. With that said would have thought it neigh on impossible for said destruction of humanity. If this is not the case why can we not cryo freeze the human body with out damaging it? — Preceding unsigned comment added by 5.175.72.42 (talk) 05:31, 22 October 2016 (UTC)


 * Viruses do not have a metabolism, some types are able to still be viable after long freezing. There are legitimate concerns about the graves of victims of the 1918 flu pandemic in the permafrost of Arctic regions thawing and releasing the virus. Similar concerns about smallpox have also been raised in scientific literature. -- Roger (Dodger67) (talk) 09:08, 22 October 2016 (UTC)


 * Frozen for a few hundred years might leave a risk - but not from the time of the dinosaurs. Given the movement of tectonic plates and the changes in planetary climate over the millions of years since then I do not believe that there can be anywhere on the planet which has remained consistently frozen over that period. Wymspen (talk) 11:46, 22 October 2016 (UTC)


 * Oh my, we do not have an article on Paleo DNA. This must be remedied.  (Is there something to redirect to that I missed?)  But while Neanderthal DNA has been isolated, it is very difficult to find large intact pieces (how difficult, honestly, I have to look up still).  So the odds of getting a complete viral genome together capable of infecting someone, even from that era, are astronomically low unless some busy beaver is splicing it together and filling in the gaps on his computer.  And of course a virus still has a really hard time infecting someone without its proteins, which in many cases won't survive intact either.
 * The joke though is that a virus much older than that, if deadly, would be very questionable in the first place. If it was deadly enough to select the human population, then modern humans might carry natural immunities that became fixed in the population.  And if it predates humans entirely, there's no telling if it can jump the species barrier at all.  So the viruses we get to actually worry about being intact, like smallpox scabs set aside in an envelope,  are also the ones most likely to be able to kill us.


 * See Ancient DNA. Anything very old is damaged and not viable. The DNA strands become broken or crosslinked. Radiation from cosmic rays or potassium can supply the energy. Graeme Bartlett (talk) 02:32, 23 October 2016 (UTC)


 * Even if somehow an ancient pathogen were to emerge, it would almost certainly be harmless. Our bodies have evolved defense mechanisms from the time life first evolved 4 billion years ago to deal with such threats. The fundamental biochemical mechanisms are actually designed to deal with random threats that could derail it, it's not the case that we can only defend ourselves against a limited number of known threats, this is a misunderstanding based on the way the adaptive immune system works (which only evolved a few hundred million years ago). Here one then focuses only on the limited number of pathogens that our bodies are susceptible to, our immune systems need to deal with those pathogens and one wrongly imagines that all microbes out there are like that. But the dangerous pathogens are the result of an arms race where they try to outsmart our defenses and where our immune systems try to come up with ever more sophisticated defenses. These are the one a billion exception to the random microbes were are subjected to every day.


 * So, a random virus would be extremely unlikely to be do any harm to our bodies, for the same reason why a random person walking toward the entrance of the Pentagon would likely be stopped before he could inadvertently walk in, and if somehow he could walk in, there is no way he would be mistaken for a Ash Carter, and even if somehow that would still happen, there is no way he could actually do some real damage by inadvertently acting like Ash Carter. Obviously a successful impostor would need to have lots of information about the system before it could successfully enter and derail it. That information cannot have come out of thin air, it must have come from the system itself. Now, you can have viruses like the Ebola or HIV virus that are adapted to other animals that can cause deadly infections. But such cases are extremely exceptional, they involve a virus that has adapted to an evolutionarily relative to us. A dormant virus that has never interacted with modern mammals is thus unlikely to do any harm to us. Count Iblis (talk) 18:36, 23 October 2016 (UTC)


 * That's entirely wrong, Count Iblis. First, our "bodies" do not develop the ability to fight off viruses.  Instead, genes for resistance to viruses by various methods tend to spread when those viruses exert selection pressure on a population.  Once the virus is no longer being spread, there is no pressure in favor of such genes being retained or against them mutating into uselessness.  Your argument makes as much sense as saying humans can't drown since our fish ancestors solved the problem of getting oxygen from the water long ago. μηδείς (talk) 21:56, 24 October 2016 (UTC)
 * "First, our "bodies" do not develop the ability to fight off viruses." Umm, adaptive immune system... ? Whoop whoop pull up Bitching Betty &#124; Averted crashes 01:26, 26 October 2016 (UTC)
 * Yes, but what I mean is that the body cannot easily get compromised by some random agent, an organism is after all a machine that is able to maintain homeostasis, so some random virus that has not evolved to circumvent the defenses of the body that somehow makes its way inside out body won't do any damage. Otherwise, with billions of different types of microbes around us, there is no way we could exist. Count Iblis (talk) 00:27, 25 October 2016 (UTC)
 * It isn't uncommon for a virus to jump a species barrier, e.g. HIV from green monkeys or rinderpest (-> measles) from cattle. If something can jump from a cow to a human then something can jump from a two million year old human ancestor to a human ... if you can get it to survive the trip.  A random virus might fail, but there's no such thing as a random virus; they all exist by virtue of their ability to infect something, and whatever they infect will have some degree of homology to humans. Wnt (talk) 01:33, 25 October 2016 (UTC)

Armpit
Why are amrpits dark compared to the skin of the rest of the body? --IEditEncyclopedia (talk) 05:32, 22 October 2016 (UTC)


 * There are several pictures in the Axilla and Underarm hair articles that seem to show that they aren't. Rojomoke (talk) 10:14, 22 October 2016 (UTC)


 * According to Human skin color, "In some people, the armpits become slightly darker during puberty." This statement is not referenced. Tevildo (talk) 11:33, 22 October 2016 (UTC)


 * In my experience (WP:OR alert), it seems to vary a lot. Besides the axilla, the front of the knees and back of the elbows are also places where this occurs in some people. Then in other people, there's nothing like that. See also linea alba and linea nigra for a special circumstance. Matt Deres (talk) 15:37, 22 October 2016 (UTC)


 * Another possibility is that deodorants/antiperspirants may discolor the skin. StuRat (talk) 22:43, 23 October 2016 (UTC)


 * Not a good selling point. Try another brand! Alansplodge (talk) 19:31, 24 October 2016 (UTC)


 * Also, shaven armpits can develop "five o'clock shadow", too, where the stubble makes the skin appear darker from a distance, if darker hair is averaged by our eyes in with the lighter skin color.  StuRat (talk) 22:43, 23 October 2016 (UTC)

On the falling bodies
In high school a teacher told me that Galileo had shown with a very simple a priori argument (which he actually showed me), without any need for any experiment whatsoever, that Aristotle's position on the falling bodies could logically only be nonsense. In which of his works does Galileo do that? And, if that is so, what need was there to go drop weights from a tower? Basemetal 11:32, 22 October 2016 (UTC) PS: That argument only shows that the speed of fall has to be independent from the mass. You can not actually derive the fact that the acceleration is constant with that simple argument. It is only meant to show that Aristotle could not possibly be correct. I can repeat it here if that seems useful.
 * See Galileo's Leaning Tower of Pisa experiment. The a priori argument appears in Galileo's 1590 book De Motu. Tevildo (talk) 11:39, 22 October 2016 (UTC)
 * A modern form of the argument is that according to Aristotle, a parachutist should fall faster with an unfolded parachute than without, because with it he is heavier. But I feel skeptical that concepts like mass, weight, density, and air resistance were really separated that carefully in speech and writing.  It reminds me of the logic puzzle about whether a hundred pounds of wet cotton weigh more than a hundred pounds of dry cotton.  Any scholar who is too condescending in pointing out about how they weigh the same probably deserves to be sent to go move a few hundred-pound bales of wet cotton and try again. :) Wnt (talk) 13:58, 22 October 2016 (UTC)
 * The fallacy there is of course "hundred pound bale of wet cotton" vs. "hundred pound bale of cotton, wetted". Andy Dingley (talk) 09:53, 23 October 2016 (UTC)


 * If you said here what exactly the argument is, it might help to locate the source. As for if that is so, what need was there to go drop weights from a tower? - well, that is what experimental science is all about. Even if you are convinced your argument is sound, it does not hurt to check; suprises have happened before. There is a lot to be said about that; one essay I like is Newton's flaming laser sword, that can be summed up as "reality is the best argument". A classical example of experiment that turned out with unexpected results is the Michelson-Morley experiment (although to be fair, the aether's existence was already hotly contested at the time). Tigraan Click here to contact me 15:38, 22 October 2016 (UTC)


 * People, Tevildo gave the answer about 7 hours ago, about 10 minutes after I'd posted my query. It's in De Motu and the a priori argument is described at Galileo's Leaning Tower of Pisa experiment, just as it was explained to me by my teacher. Sheesh. Life's short enough and there's enough to do. You do not need to give yourself more work than necessary.