Wikipedia:Reference desk/Archives/Science/2015 August 10

= August 10 =

How much would an archaeologist know about dinosaurs?
I know that it's a common misconception that archaeologists look for dinosaur bones - but would an archaeologist typically know more about dinosaurs than your average layman? IOW, do their studies include dinosaurs at all? Because they might encounter dinosaur bones in their work... Just thinking about how it's sometimes said that many veterinarians could probably perform surgery on humans, in an emergency and wondering how it compares. --87.114.247.205 (talk) 00:55, 10 August 2015 (UTC)
 * The holder of a B.A. in Archaeology from Stanford might have taken zero classes in paleontology; there are electives offered in zooarchaeology and related scientific areas; but it's up to each individual to choose those optional classes.
 * "Archaeologist" is not a very clearly-defined term; generally, I would not call somebody an archaeologist unless they held at least an accredited undergraduate degree from a major university in the field of archaeology; but a wider definition might include holders of degrees in biology, anthropology, zoology, forensics, any of a variety of liberal arts fields... or even a non-degreed individual.
 * At Stanford, the Anthropology department also grants degrees (in anthropology, not archaeology); the departments are split into cultural anthropology and physical anthropology. Students in the latter department would have more formal scientific training.  The Cultural Anthropology department is less likely to entertain undergraduates who seek specialization in archaeology; but they offer a graduate program.  (Correction - these two departments merged a few years ago, so another important item that determines an archaeologist's formal education is when that person studied to become an archaeologist!)
 * Taking an even broader perspective, some experts in ancient history lack any formal schooling or credentials. A long time ago, I studied archaeology in the Middle East.  Occasionally, I encountered exceptionally knowledgeable experts who were not formally educated at all - they were simply the locals who were enthusiastic enough to stick by the sites of historical interest during some very hard times.  I would feel comfortable calling some of these individuals "archaeologists," irrespective of any formal education.  I doubt they would know the first thing about the paleontology of ancient animals.  Even the professors at the American University Archaeology Department probably did not have a strong background in palaeontology: but they spoke more languages than I could hope to!
 * Moral of the story: in modern times, it's difficult to generalize about a person's expertise, even if you know their credentials. Within the walls of a single institution, there is such a wide spectrum of different pedagogical ideas and formal curricula that it's fairly futile  to speculate about the specific skills and expertise of any individual degree-holder.
 * Nimur (talk) 01:25, 10 August 2015 (UTC)
 * While the above is a good answer, I think it could be pretty much summed up as: "on average, yes". Archaeology states paleontology as a cross discipline. So of course some archeologists would have nothing to do with dinosaurs, but compared to "lay people", the group "archeologists" would, on average, know more about dinosaurs. Vespine (talk) 06:30, 10 August 2015 (UTC)
 * Having watched TV programmes such as Time Team it would appear that most archaeologists tend to specialise in a particular niche and become an expert in that area. So one may be an expert in dating fragments of ancient pottery whilst another may concentrate on a particular period. They then tend to consult someone else when they find something out of their area of expertise. Richerman    (talk) 09:32, 10 August 2015 (UTC)
 * Yes, in two (overlapping) ways. First, as educated people, they likely know a little more about dinosaurs than the general population (though the same could be said for people with degrees in art history, quantum physics, or structural engineering. Second, there are areas where a background in archaeology provides context missing from most lay people's lives (an understanding of geologic time scales, stratigraphy, fossilization, provenience, and the scientific method, among others). However, while obtaining my degree in archaeology we never once mentioned dinosaurs. However (again!), see also some of the writings of Adrienne Mayor for very specific overlaps. 64.235.97.146 (talk) 13:59, 10 August 2015 (UTC)

Not Completely Off-Topic
This discussion reminds me of the periodic comment by Bones (Dr. McCoy) on Star Trek, "Dammit, Jim! I'm a surgeon, not a psychiatrist!" Because he had as much knowledge as he did, he knew the limits of his own knowledge. A competent archeologist should know the limits of her own knowledge of dinosaurs. Some years ago, I, as an information technology engineer with a degree in chemistry, was given the task of classifying various sorts of hazards to American servicemembers to which the system was tracking exposure. Sometimes I discovered that the terminology of industrial hygiene was different from that of chemistry. "Dammit, boss! I'm a chemist, not an industrial hygienist!" Know the limits of our own knowledge, and be aware that sometimes terminology is field-specific. Robert McClenon (talk) 14:55, 10 August 2015 (UTC)
 * Also relevent is the Dunning-Kruger effect (or really the anti-Dunning-Kruger effect here): Your own understanding of your knowledge on a subject means you also know more about how much you DON'T know. -- Jayron 32 16:42, 10 August 2015 (UTC)
 * It is also worth making an emphatic pitch for breadth in education - whether that takes the format of an out-of-field elective during university studies, or an informal hobby educational pursuit. Richard Feynman's chapter, Bringing Culture to the Physicists in his autobiographical work Surely You're Joking, Mr. Feynman, talks all about how he, an amateur (and a physicist) presented a lecture about archaeology on behalf of Otto Neugebauer, and eventually became a reknowned expert on Mayan mathematics.  Someone can choose to specialize in some area - say, physics or computer theory or nuclear weapon design - for a variety of reasons; that primary specialization doesn't preclude the development of knowledge, and even expertise, in other areas.  Nimur (talk) 16:59, 10 August 2015 (UTC)
 * Feynman once took a holiday and spent it working in a Biology lab. He also spent time investigating whether there was some reason that there are six consecutive 9's in the decimal expansion of pi after just 760 digits.  "Common sense" says that this is a suspiciously astounding coincidence.  It turns out that it's not really that unlikely - see: Feynman point.  But, yeah - he definitely excelled outside of his core subject. SteveBaker (talk) 04:15, 12 August 2015 (UTC)

Another Not Completely Off-Topic Point
This is the science board, not the humanities board. But this is vaguely relevant. The Delphic oracle was known to give ambiguous answers to questions. For instance, when King Croesus asked if he should make war on the Persians, he was told that, if he did, he would destroy an empire. He did, and he destroyed his own empire. However, in one case the Delphic oracle made an unambiguous statement, and it may have still been tragic. Someone asked: "Who is wiser than Socrates?" or "Is anyone wiser than Socrates?" The oracle answered, "No one is wiser than Socrates." Socrates didn't think this made sense, because he knew that there were very many things that he did not know. So, in order to contradict the oracle, he went around questioning Athenians who had reputations for wisdom: politicians; poets; craftsmen. He found that at least the craftsmen (of which he had been one before he became a philosopher) knew what they were trying to do. He managed, with his questions, to anger many of the most influential people in Athens. Eventually, as we know, he was condemned in a trial that amounted to a kangaroo court, and was put to death by poison. Socrates knew the limits of his knowledge, and that was true wisdom. But the oracle's statement was the doom of Socrates, because, in testing it, he made enemies. (Whether he would have made enemies without the oracular pronouncement is alternative history.) Knowing the limits of one's knowledge is wisdom, but in this case it had a side effect. Robert McClenon (talk) 18:36, 13 August 2015 (UTC)

Cheapest source of icaridin insect repellent?
Is there are cheaper source of icaridin (it has a few other names listed in the article) in the UK than regular consumer insect repellents? I tried and failed to find a chemical company that stocks/sells it. I just don't want to get ripped off if the same product is available elsewhere at a fairer price. --129.215.47.59 (talk) 12:28, 10 August 2015 (UTC)
 * Well, you can buy 100% picaridin from a Chinese company called Simagchem. Their minimum order is 25 kg, which goes for 8000 US dollars.  That's probably a typical scenario if you want to buy it in non-consumer form. Looie496 (talk) 14:58, 10 August 2015 (UTC)

Scientific notation for inverse units (like per unit area or per second)
When I was in high school (England, UK, 2003), I was told that the old notation of m/s (metres per second) and kPa/m2 (kilopascals per square metre) were going away and the correct notation would be m.s-1 and kPa.m-2. Is this correct? Who decided this? Was it just the UK department of education or something bigger? --129.215.47.59 (talk) 13:47, 10 August 2015 (UTC)


 * You know what, I asked this same question last decade: . Sagittarian Milky Way (talk) 14:02, 10 August 2015 (UTC)


 * In my experience, which was a long time ago, but was in the US, both forms were accepted. I think that they still are.  There are times that the use of the negative exponents is clearer, but anyone who can use scientific notation can transform the notation.  In the case of meters per second, I think that the division form is clearer, because it really is meters in a second.  In the case of energy, I think that the negative exponent is clearer.  Robert McClenon (talk) 14:48, 10 August 2015 (UTC)


 * It seems like it doesn't matter - and for simple things like kilometers-per-hour, it probably doesn't - but there are units for things like molar entropy (m2.kg.s-2.K-1.mol-1) that would be impossibly horrible if expressed with slashes and words like 'per'. Acceleration (meters per second per second) trots off the tongue easily enough - but electric field strength (meter kilogram per second per second per second per amp) does not!  So, while it's not unreasonable to continue to use the slash notation for simple informal stuff like m/s, the approach that uses negative superscripts is more practical for complicated cases.


 * I was unable to find who started using it or when - or whether some standards organization started mandating it - or some educational department head started demanding that it be taught. Those are all good questions!  SteveBaker (talk) 16:03, 10 August 2015 (UTC)


 * I believe many style guidelines still allow the use of the solidus, but require that you only use one without brackets, and use brackets to avoid ambiquity where needed in any case. Some may suggest it's simpler or better to use negative exponents in complicated cases (without any specific definition of what's mean by this). I think some also allow a horizontal line instead of a solidus, but this often doesn't work well when typesetting.
 * See for example BIPM, US NIST, IAU.
 * Simpler student guidelines may recommend the negative exponents throughout to avoid mistakes and so they get in to the habit of understanding what they mean.
 * Nil Einne (talk) 18:46, 10 August 2015 (UTC)

Dogs
Why are dogs so interested in (and will sometimes eat) human faeces and other human body fluids?--86.176.8.152 (talk) 16:09, 10 August 2015 (UTC)


 * Read this or this or this. Also, for future questions you may have on any topic: Instead of coming here and waiting for answers, just type your question (whatever it is) into the search bar at the website http://www.google.com  It will give you lots of answers for your question, and you can do it on your own, without anyone else's help, and faster than it would take to wait for someone else to do.  Everyone here will do that as a first step when answering your questions, and you can get them answered faster if you just do it yourself.  Not every question can be answered like that, but this one clearly could, as the links I gave you above are the first three answers when I typed "Why do dogs eat poop?" into Google.  -- Jayron 32 16:37, 10 August 2015 (UTC)


 * It's not just human poop they like, any poop will do. The real Q is why evolution hasn't given them the instinct to avoid poop, since it's an obvious source of disease, which would seem likely to prevent them from passing on their poop-eating genes.  Cats, for example, quite sensibly bury theirs.  So, any evolutionary benefit to eating feces would have to outweigh this rather substantial negative.  (Another negative is that humans may not want to adopt dogs that have poo-breath, leave steaming piles in the house, leave a turd as a present on the master's pillow, etc.)  StuRat (talk) 18:30, 10 August 2015 (UTC)
 * Humans "adopting" dogs is an extremely recent phenomenon. Just a couple of hundred years ago dogs were kept almost exclusively for work, hunting, droving or guarding, how proficient a dog was at those things would have outweighed how sweet their breath was. Having a dog purely as a companion was almost unheard of. Vespine (talk) 22:54, 10 August 2015 (UTC)


 * So, Stu, do you have any references to back up the statements you are making here, or should we just accept what you say because you're better than everyone else, and we should just trust you? -- Jayron 32 19:30, 10 August 2015 (UTC)


 * Have a link then: evolution. StuRat (talk) 19:42, 10 August 2015 (UTC)


 * So, the answer is "no", then. -- Jayron 32 20:16, 10 August 2015 (UTC)


 * No, the answer is "If your really need a source to show that evolution occurs when there's evolutionary pressure for or against something, then read the damn article and stop trying to make trouble already". Or do you require a source to prove that cats bury their poop ?  You keep pretending to know absolutely nothing and I might just start believing you. StuRat (talk) 22:48, 10 August 2015 (UTC)


 * Actually, it's a really dumb idea to talk about evolution, in something which has been as messed up by artificial selection as dogs. Nil Einne (talk) 12:47, 11 August 2015 (UTC)


 * Are you arguing that dogs have been bred to eat feces ? If so, why ?  If not, then they evolved that way on their own, or inherited that trait from wolves, who evolved it or inherited it, etc. StuRat (talk) 22:31, 11 August 2015 (UTC)


 * We have a decent article on coprophagy. SemanticMantis (talk) 19:25, 10 August 2015 (UTC)


 * Is there a British version of the humane society or health and human services where a person feeding his dog human feces or leaving it and other excrementa about can be reported? μηδείς (talk) 20:44, 10 August 2015 (UTC)


 * RSPCA  D b f i r s   22:11, 10 August 2015 (UTC)
 * The police! DrChrissy (talk) 22:36, 11 August 2015 (UTC)

Effects of gravity vs. simulated gravity
On space missions we research the effects of gravity on cells, tissue, atomic matter. Since the space missions aren't really at a distance that would remove gravity, we use the method of "falling around the planet" that simulates gravity. Are there theories or research on the possible different results when investigating in one condition over the other? — Preceding unsigned comment added by 99.57.49.187 (talk) 22:35, 10 August 2015 (UTC)


 * An object in orbit experiences weightlessness. There is no difference between that weightlessness and the weightlessness of being far from any massive objects or even being  the only object in the universe.  Simulated gravity is different, though.  The type where you spin a spaceship can indeed cause side effects, like nausea.  StuRat (talk) 22:45, 10 August 2015 (UTC)


 * There is no difference between acceleration caused by a gravitational field and equivalent acceleration caused by anything else. This is the central insight behind general relativity. Orbital trajectories don't simulate gravity; rather, they cancel out its acceleration. When you're in a stable orbit, you're in freefall towards the body that you're orbiting, but you're on a trajectory such that you keep missing the body you're falling towards. Douglas Adams was actually deeply correct when he said that the knack to flying is to throw yourself at the ground and miss. I suggest and  for some more insight. You're right that space missions don't "go beyond" the reach of gravity; the Earth's gravitational force in low Earth orbit is only slightly less than that at its surface. So when laypeople say "there's no gravity in space", they're wrong. Just think: what keeps the Moon orbiting the Earth, or the Earth orbiting the Sun? Also, to expand on what StuRat said, the side effects of simulated gravity aren't because it's somehow "different" from "real" gravity. Remember what I just stated above: there is no difference. Rather, it's because rotating around an axis can cause motion sickness if the difference in velocity between parts of your body is significant, as would happen in a small spacecraft rotating fairly quickly. This is because your inner ear is involved in your sense of balance and tells your brain about the motion it's experiencing. But if this information conflicts with other information from your eyes and other parts of your body, your brain can freak out. This is the same mechanism behind car sickness, seasickness, etc. --108.38.204.15 (talk) 23:43, 10 August 2015 (UTC)


 * The equivalence principle hypothesizes that there is no fundamental difference between actual and simulated gravity. I should note that "falling around the planet" does not simulate gravity - this is freefall, and this is why there appears to be no gravity within the space station or other space vessels. Despite this theoretical basis, there are practical differences between actual and simulated gravity. For instance, if one were in a spinning spaceship, the apparent acceleration of gravity would vary based on distance from the axis of rotation. This could result in a situation where you regularly experience rapid changes in gravitational acceleration as you move about the ship, something you would never experience walking around on Earth. If there are windows in the ship, or you can see beyond your immediate vicinity, you could become nauseous from disorientation. There are also subtle differences between freefall and actual weightlessness. For instance, imagine you are in a large cubical room in freefall around the earth. You and a friend are floating above the ground on opposite sides of the room. While the room orbits the earth, you and your friend actually experience slightly different gravitational acceleration vectors, and will ever so slowly move toward one another, though this may be too slight to be perceptible. Finally, there is all manner of weirdness when you are orbiting an object that is spinning - weirdness that is imperceptible to mere humans, but has been measured by Gravity Probe B. None of this is in conflict with the equivalence principle, just a consequence of spacetime curvature being not-quite-uniform. Someguy1221 (talk) 23:48, 10 August 2015 (UTC)

Tyre pressure
The recommended tyre pressure for my caravan (trailer if you're American) is given as 36 psi for a maximum speed of 100 kph and 33 psi for a maximum speed of 140 kph - why the difference? Surely if the maximum speed allowed is 140 kph you are going to be travelling at 100 kph for some of the time anyway. Also, the tyre pressures for the rear tyres of the car (VW Passat) should be about 4 psi more than the front with light loading, but with a full load you need to increase the rear pressures a little and the front tyres a lot so that they have a higher pressure than the rear tyres. As the extra load is likely to be at the back (especially when towing) why do you need to add so much more to the front tyres? BTW I'm sorry about the mix of imperial and metric units (psi/kph) but that's the way they're given in the manual. It shows our schizophrenic relationship with metric in UK :-) Richerman    (talk) 22:46, 10 August 2015 (UTC)


 * Softer tires might tend to absorb vibrations which could be a problem at high speeds. StuRat (talk) 23:02, 10 August 2015 (UTC)


 * I kind of get the feeling they had one of their engineers calculate the "optimal pressure" for various speeds and then just threw that in the manual, likely because they're required to give different pressures for different speeds by law or something like that. The reason you want a lower fill pressure when the tire is being driven at higher speeds, everything else being equal, is because the temperature of the tire increases as it is driven faster, which increases the pressure of the gas in the tire (per the ideal gas law). You always want the tire to be as close to the ideal pressure as possible when in service, to get the best balance between traction and fuel efficiency, and of course to prevent damaging or destroying the tire from too high a pressure, so it makes sense to deflate the tires a little if you expect to spend more time driving them at higher speeds. As for why you fill the front tires more than the back tires with a heavier load, my guess is it's to keep the trailer balanced. The load at the back is going to push the back of the trailer down, and the front up, which decreases the traction on the front wheels. Jackknifing is a real problem with loaded trailers, especially at higher speeds. --108.38.204.15 (talk) 23:19, 10 August 2015 (UTC)


 * To be clear, the higher pressures for the car tyres are given for a fully loaded car rather than specifically for towing. Does higher pressure in the tyre increase the traction? You would think that lower pressure would mean more of the tyre surface is in contact with the road. Richerman    (talk) 23:42, 10 August 2015 (UTC)


 * Setting tire pressures for cars is a rather adhoc process, there is a push to transfer the job to the tire companies, which will be interesting. Mainly the reason we specify higher pressures for high loads and speeds is to reduce sidewall flexure which causes the tire to heat up, and possibly deflate. The higher pressures are pretty safe at lower speeds and loads, but they give a horrible ride. There are other considerations for a car, but that's the main hitters. Greglocock (talk) 07:45, 11 August 2015 (UTC)
 * (speculation) The faster you go, the hotter the tyres become, which increases the pressure. The recommend tyre pressure is for cold tyres. LongHairedFop (talk) 20:03, 12 August 2015 (UTC)