Wikipedia:Reference desk/Archives/Science/2013 July 25

= July 25 =

Is this a horse fossil?
http://i.imgur.com/XbtT0ZJ.jpg Found in a wash in Arizona (we didn't dig it up). What is it? It was definitely fossilized. 24.255.30.187 (talk) 03:06, 25 July 2013 (UTC)


 * It does look like some type of equine, but hard to say exactly which. There should be a front set of teeth too.  You might want to uncover a bit more to see if they are there.  Here's a page of horse dentistry: .  I'd report it to a nearby university archaeology department.  At the very least it should make a nice practice dig for the students, at best you might have found some type of equine missing link and end up with it named after you. StuRat (talk) 07:08, 25 July 2013 (UTC)


 * I doubt that it's actually a fossil, though, given that it's embedded in loose dirt. An equine in Arizona would have to be either less than 500 years old or more than 10,000 years old, and I suspect that this is less than 500 years old. Looie496 (talk) 14:24, 25 July 2013 (UTC)
 * Thus the suggestion to ask an archaeologist, rather than a paleontologist makes sense. Roger (Dodger67) (talk) 19:01, 26 July 2013 (UTC)

Is a fat person more resistant to alcohol intoxication than a skinny person is?
Or is that just a myth? ScienceApe (talk) 16:14, 25 July 2013 (UTC)


 * Yes, very much so. According to Alcohol_tolerance body weight plays an important part...so not necessarily fat versus skinny - but tall versus short, men versus women too. SteveBaker (talk) 16:37, 25 July 2013 (UTC)


 * True. My wife is skinny (not quite anorexic but nearly so) an is extremely intolerant to alcohol. I only have to arrive home at night, having drunk just half a pint of mild cider and she makes me sleep in the dog kennel.--Aspro (talk) 19:13, 25 July 2013 (UTC)


 * We got a handy picture of this event. --Cookatoo.ergo.ZooM (talk) 21:28, 25 July 2013 (UTC)
 * Not one we can post to the Ref Desk, unfortunately. File:Internet dog.jpg if anyone wants to look at it. Tevildo (talk) 21:55, 25 July 2013 (UTC)


 * In the form that you put it, it's a myth. There are a lot of other factors that determine susceptibility to alcohol than mere physical size. For example, I'm a big boy (120 kg), but a single glass of wine is more than enough to get me under the table, and two would probably get me arrested. I'd be well under the legal limit, but completely unable of driving an automobile safely. On average, larger people may indeed tolerate larger amounts of alcohol, but the exceptions to the rule would be so frequent that the rule would not be very useful. People often assign unjustified magical significance to averages, and a lot of questions even on this noticeboard will be requests for averages. They don't realize that averages mean jack shit when you are talking about particular cases. Dominus Vobisdu (talk) 21:59, 25 July 2013 (UTC)
 * Anyway, back in empirical land, averages and statistics are very useful when talking about this. Dominus suggests that because he's an outlier everyone's an outlier and stats are meaningless. The technical term is variance and it turns out the variance on weight and alcohol's effects are quite manageable. Size and tolerance has a robust relationship. Shadowjams (talk) 05:03, 26 July 2013 (UTC)
 * Yes, I agree. We cannot proceed on the basis of single-person anecdotes.  The data is unambiguous.  Typically larger people have greater alcohol tolerance than smaller people.  If Dominus goes on a diet and loses a bunch of weight, his/her alcohol tolerance would almost certainly get even worse. SteveBaker (talk) 19:46, 26 July 2013 (UTC)

Precision engineering contest?
I remember reading some time ago about an incident in, I think, the late nineteenth or early twentieth century (possibly associated with the Paris Exposition or one of the early World's Fairs). To demonstrate their precision engineering skills, a firm (American?) sent out samples of a very finely-drawn wire. Their (German?) arch-nemeses sent it back with a hole drilled down the middle. Does anyone know any more details of this? Tevildo (talk) 22:06, 25 July 2013 (UTC)


 * http://www.snopes.com/business/genius/wire.asp
 * —Steve Summit (talk) 22:08, 25 July 2013 (UTC)
 * Thank you - I must now admit to feeling mildly embarassed. C. Plinius Secundus has a lot to answer for. :) Tevildo (talk) 22:30, 25 July 2013 (UTC)

G forces when two cars collide
When a 2,000-pound car runs head on into a 4,000-pound car, how much more g-force does someone in the smaller car experience, compared to the larger car? Bubba73 You talkin' to me? 23:33, 25 July 2013 (UTC)


 * It is not possible to determine force, or acceleration, unless you know the duration of the collision. If you estimate the duration, you can estimate the average impact force, using the formula for impulse or non-instantaneous momentum-transfer.  Real-world collisions are partially elastic, partially inelastic - so you'd need elaborate measurements of the time-history of the deformation of each car to determine the actual maximum g-load each passenger experiences.  Nimur (talk) 23:55, 25 July 2013 (UTC)
 * The principle of conservation of momentum suggests the lighter car will suffer a greater change of velocity than the heavier one. If the ability of the two cars to crumple under the impact is the same, this suggests the lighter car will suffer a greater acceleration than the heavier one. The acceleration experienced by occupants of the two cars will be strongly dependent on whether they are wearing safety belts and the characteristics of those belts. If the belts are not flexible the acceleration will be higher than if the belts are flexible. If the lighter of the two cars provides superior crashworthiness and occupant restraint than the heavier of the two, it is feasible that the acceleration of occupants of the lighter car will be similar to, or not much more than, the acceleration of occupants of the heavier car. Dolphin  ( t ) 23:59, 25 July 2013 (UTC)
 * If I did the calculations right, if it were an elastic collision (which it isn't) the less massive one would experience twice the acceleration. Bubba73 You talkin' to me? 02:21, 26 July 2013 (UTC)
 * I think the above answers apart from bubba's are missing the point. All those "seat belt, crumple zone, etc" have nothing to do with it. Take this like a classic textbook question, which OF COURSE assumes "all other things being equal". If a car of mass A collides with a car of mass 2A: that's all you need to answer the question. Momentum is p=mv and force equals f=ma, you can work it out from that Vespine (talk) 04:59, 26 July 2013 (UTC)
 * If we are to treat it as a classic textbook question, it looks like homework. Wikipedia doesn't do students' homework for them. On the other hand, it may be an enquiry of a general nature in which case it isn't reasonable to assume all other things are equal; considerations such as the relative crashworthiness of the cars, and performance of seat belts, are highly relevant. Dolphin  ( t ) 05:20, 26 July 2013 (UTC)
 * With all due respect I completely disagree. If it is a homework question, we can point towards how they can go about working out the answer for them selves. If it is an enquiry of a general nature, then of course it is reasonable to assume all other things being equal. If car of mass A collides with car of mass 2A is a perfectly reasonable and solvable question, completely irrelavant of seatbelt performance. Did you see my link for an example? Vespine (talk) 05:32, 26 July 2013 (UTC)
 * When we consider vehicles of mass A and 2A respectively, we are treating them as rigid bodies and determining the acceleration of their centers of mass. A motor vehicle in a collision is not a rigid body, and the occupants are most certainly not rigid parts of their vehicle. The IP's question relates to the g-force someone in the smaller car experiences so the IP is not asking about relative acceleration of the vehicles, but relative acceleration of the occupants. Yes, I have seen the example given in your link. It is referring to the relative accelerations of the truck and the car, not the relative accelerations of the occupants. Crashworthiness is relevant. Dolphin  ( t ) 11:04, 26 July 2013 (UTC)

The data exists, sort of. If you plot casualty rates vs vehicle mass for IIHS data you find that the heavier variant of a given car is safer than the lighter variant /even if the heavier is a convertible/. This surprised them and me both. The wishful thinking of the lighter cars are better crowd is precisely that. Any crumple zone type feature works for both cars, the crash pulse seen by the occupants will be in inverse proportion to the mass of the cars. Yes, secondary safety will definitely be a factor, but for a given level of technology the heavy car is safer. Greglocock (talk) 05:36, 26 July 2013 (UTC)


 * The deciding factor is, while the light car will, at any given moment, experience twice the g force compared to the heavy car (Newton's 1st axiom), these g forces do not affect all components equally. At the moment of contact, the bumpers will experience an extreme deceleration, but the drivers will only begin to move forward (WRT the center of mass of the respective cars) and hardly experience any g forces because the belts are still hanging quite slack at that point. - ¡Ouch! (hurt me / more pain) 07:42, 26 July 2013 (UTC)

It isn't a homework problem. I was trying to explain to my wife how those crash tests among cars of the same class don't apply when comparing two cars of different classes. Bubba73 You talkin' to me? 15:54, 26 July 2013 (UTC)