Wikipedia:Reference desk/Archives/Science/2015 January 11

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January 11

Can a goat really eat and digest a tin can?

Question as topic. I've found comments from goat owners online who say that they've never seen it happen for real. I know that goats, with their famously resilient stomachs, can and do eat things like newspaper, cardboard boxes, clothing and shoes without an apparent problem. I've even seen videos of them eating lit cigarettes without seeming to give the slightest damn. Anyone have a definitive answer? --Kurt Shaped Box (talk) 01:43, 11 January 2015 (UTC)

I doubt they could digest it. The greater question is whether they could pass it. Even humans can (and do) eat lots of undigestible stuff. If it is small enough, it will just show up in the stool later. --Jayron32 01:57, 11 January 2015 (UTC)

I suspect they were just eating the labels off the tin cans, which might involve putting cans in their mouths as they work the labels loose with their tongues. StuRat (talk) 02:00, 11 January 2015 (UTC)

That's what they used to teach us, decades ago - that they are, if anything, eating the label and the tasty glue. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:16, 11 January 2015 (UTC)

(EC) No,goats do not eat tin cans. It seems implausible that a typical tin can (actually tin coated steel) such as one I am looking at`which is about 3 inches in diameter by 4 3/8 inches high would pass through the esophagus of a goat, without killing the goat. It also seems implausible that it would pass through that esophagus if it were flattened. It also seems implausible that a goat's teeth could tear it into fragment small enough to swallow. A goat will certainly chew on a tin can, either to get the food residue on the inside or to eat the paper label on the outside, or to eat the glue..I recall an old published psych experiment, probably from the 1960s wherein goats were the subjects being conditioned, and the reward was the opportunity to chew on a length of chain, so they definitely are not averse to chewing on iron. Edison (talk) 02:10, 11 January 2015 (UTC)

Interesting question. A quick web search turns up some sources like Modern Farmer magazine that weigh against it ( [1] ). There's not really any general theory of biology that can honestly tell you a goat can't eat a tin can with any confidence; on all things goaty I'd trust a farmer's experience over a biologist's prediction any day.

The mention of goats chewing on a chain makes me wonder if there could be some "germ of truth" based on a sort of pica for them to obtain trace metals. I don't know if modern pet goats get too many vitamins/minerals or too good a diet to show some of that behavior. One thing that's clear, though, is that calling on YouTube for goat tin can gets lots of items that reflect the presence of the meme... yet no video of goats actually eating cans, or even chewing on them a bit. There's a curious example of one eating a page out of a book [2] which might reflect on the label eating behavior suggested above, but the video stops before we see whether it swallows or not. Wnt (talk) 00:40, 12 January 2015 (UTC)

Goats use their mouths to examine things in the same way that we use our hands, so people often think they are eating something when they are just investigating it. For example, they will pull clothes off a washing line to see what they are and check if they are worth eating, but then drop them and move on. What is surprising is that they will eat thorny bushes, brambles etc. without any problem, so they must have very tough mouths and guts. Richerman (talk) 07:31, 12 January 2015 (UTC)

Yep. Just makes more sense for them. Hooves and horns are useful, but are about the clunkiest and least sensitive things any mammal has. With those crazy lips, they can eat the leaves from around the thorns so nimbly, you'd swear they were crazy. Just magicians, though. InedibleHulk (talk) 08:27, 12 January 2015 (UTC)

They have very nimble lips and can eat round thorns but I've also known then to eat brambles with no problem. According to this it's all down to their hard palate - and presumably a very leathery tongue. I suppose they chew them up well before swallowing. Richerman (talk) 10:02, 12 January 2015 (UTC)

Helps to have a rumen, too. InedibleHulk (talk) 00:35, 13 January 2015 (UTC)

Climate change vs. Global Warming

Is it true that the term, "global warming" was changed to, "climate change" as a euphemism to respond to arguments presented by conservative pundits who denied global warming existed simply because sometimes it got really cold outside? ScienceApe (talk) 02:09, 11 January 2015 (UTC)

Yes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:14, 11 January 2015 (UTC)

Well, "global warming" isn't such a good term anyway, because the globe is only warming on average, with parts warming a lot, and other parts not at all, or even cooling a bit. Also, climate change includes things like changes in humidity, rain, and drought patterns, along with more numerous and more intense storms (hurricanes, tornadoes, cyclones, etc.). StuRat (talk) 02:41, 11 January 2015 (UTC)

The pundits and politicians who denied (and who continue deny) global warming based on the fact that "it sometimes still gets cold outside" aren't going to be satisfied anyway; a change in terminology isn't going to satisfy someone who makes a living from conflating "anecdote" and "data". One could argue that the terminology change is more useful (and perhaps more effective) in communicating the important or significant effects to the general public, however. "Climate change" – more extreme weather events like hurricanes, droughts, floods, etc. – is something that has a more conspicuous, tangible, visceral, and even economic impact than "global warming"—so what if it's a couple of degrees warmer? TenOfAllTrades(talk) 03:18, 11 January 2015 (UTC)

They don't mean the same thing. Global warming is an increase in the global average temperature, and climate change is a change of weather patterns. The former is one possible cause of the latter.

Google Ngram Viewer doesn't appear to support the claim that "climate change" has replaced "global warming" in more recent years. If that graph is to be believed, there was never a time when "global warming" was used much more than "climate change". Interestingly, the American English and British English trends are quite different from one another. -- BenRG (talk) 03:25, 11 January 2015 (UTC)

(edit conflict) Through the mid-2000s, "climate change" was essentially the European term for "global warming" as used in the U.S. Usage goes back and forth so that now "climate change" is seen a little more commonly in the U.S. than it was before. This happened in no really systematic way and there was never a conscious decision to replace "global warming" with "climate change." After all, the IPCC -- the Intergovernmental Panel on Climate Change -- was constituted way back in 1988. Short Brigade Harvester Boris (talk) 03:31, 11 January 2015 (UTC)

No. In the 1970's the term was "inadvertant climate modification" because they didn't know if it was warming or cooling. "Global warming" was coined in the 1970's in a paper that advocated that the climate change would be one of warming. In 1979 the Charney report was released and Charney adopted Broecker's usage. When referring to surface temperature change, Charney used "global warming." When discussing the many other changes that would be induced by increasing carbon dioxide, Charney used "climate change." Scientists maintain the distinction while clueless journalists (and Wikipedia articles) do not.[3]. --DHeyward (talk) 05:00, 11 January 2015 (UTC)

Until the late 1980s, the common term was actually "climatic change" comparitive Ngrams, used for both changes in the geological past and those taking place recently. Mikenorton (talk) 08:34, 11 January 2015 (UTC)

See Frank Luntz about him advising republicans to say climate change instead of global warming as a survey found it less worrying. So basically the opposite to the implication in the question. Both terms seem okay to me, people kow what they mean. Dmcq (talk) 10:43, 11 January 2015 (UTC)

"Climate change" is preferred by many climate scientists and atmospheric scientists, in part because many local regions could get cooler, or have more rain, or have less rain, or get warmer, etc. The local effects of CC are hard to predict, but several impacts will be more notable to people than simply "warmth." See also global weirding, and Effects_of_global_warming#Projected_impacts. Many of the most negative impacts of CC are not directly due to warmth, but warming is still indirectly responsible, e.g. speculation of the shutdown of some ocean conveyors would make the UK very cold, even though warming could be the cause. Same goes for more frequent storms and more frequent droughts, etc. SemanticMantis (talk) 16:12, 12 January 2015 (UTC)

What is the reason that the saturation (oxygen) rises after smoking?

Today someone showed me by the oxymeter that BEFORE he smoked he had 94% saturation, but AFTER he smoked it raised to 98%. What is the explanation for that? 213.57.31.194 (talk) 02:56, 11 January 2015 (UTC)

I don't know if it applies to smoking, but in general, carbon monoxide attached to hemoglobin can deceive oxygen saturation sensors. Jc3s5h (talk) 03:00, 11 January 2015 (UTC)

Indeed; see this paper: "... Pulse oximetry is unreliable in estimating O2Hb saturation in CO-exposed patients and should be interpreted with caution when used to estimate oxygen saturation in smokers." TenOfAllTrades(talk) 03:08, 11 January 2015 (UTC)

There are other factors as well including vascular and circulation changes from nicotine or changes in temperature (i.e. smoking outside). The pulse oxymeter is really not very useful except to correlate other clinical signs (i.e. congestion, labored breathing and low readings in a controlled setting like a hospital). 94% is relatively low number for awake and healthy patients but really a blood gas analysis and lung function test would be needed to show that it is abnormal. I've seen emergency pediatric doctors require the sleeping SpO2 to be above 90% before discharging asthmatic children but also at the same time, tell parents to throw their own pulse oxymeter away because the real signs are in behavior and type of breathing. They say the oxymeter should not be used to decide whether intervention is necessary and the number doesn't add any value. YMMV. --DHeyward (talk) 06:36, 11 January 2015 (UTC)

Attached with nails

Why do nails work? Is it solely friction? Push a pin into a pincushion, and you can pull it right out, but hammer a nail into a block of wood, and there's no way to pull it out without using the hammer or some other tool. Does the hammering process disrupt bits of wood that block the nail from being pulled? I understand why screws work (they bore thread-shaped holes in the wood, and the space between the threads provides significant resistance), but just as a stripped screw can easily be pulled, a nail "should" be easy to pull, but it's not. Nyttend (talk) 05:55, 11 January 2015 (UTC)

The nail compresses the wood around it, the compressed wood presses back against the nail, and there's your source of friction. --65.94.50.4 (talk) 06:06, 11 January 2015 (UTC)

Framing nails also have a coating of glue that melts from friction of driving it and then binds it to the wood. I believe it also protects the nail from rust so they don't have to be galvinized. --DHeyward (talk) 06:39, 11 January 2015 (UTC)

For wood, Young's modulus and the bulk modulus are sufficiently high that when the wood is compressed by action of the intruding nail it applies a large compressive stress to the nail. The friction force that must be overcome if the nail is to be extracted is numerically equal to the coefficient of friction applicable to a wood/steel interface, multiplied by the normal force at work between the nail and the wood. The normal force is very large, thanks to the large compressive stress that exists between the wood and the nail. The coefficient of friction between wood and steel is also high. Consequently, to extract the nail a large force must be applied to overcome the force of friction that resists movement of the nail.
For a pin cushion, Young's modulus and the bulk modulus are many orders of magnitude smaller than they are for wood. Consequently, compressive sress in the pin cushion's filling is almost zero and normal force is almost zero. I suspect the coefficient of friction between the cotton filling and steel is also less than for wood and steel.
If the nail is driven into a pre-drilled hole, the wood surrounding the hole does not need to be compressed as much as when the nail is driven without the aid of a hole. Consequently the wood is not compressed as much, the normal force is less, and the friction force is less, allowing the nail to be extracted with less force. Dolphin (t) 10:23, 11 January 2015 (UTC)

Another point here is that in most structures where nails are used, the forces applied to the structure are generally at right angles to the long axis of the nail. Imagine, for example, hammering a nail into a wall and hanging a picture on it. So the forces applied to the nail aren't pulling it out of the hole so much as deforming the nail - or forcing it to break through the wood along it's entire length. When overloaded, what generally happens is that the nail bends - and then pulls out relatively easily because some of the force is now directed along the length of the nail rather than at right angles to it. When nails are required to resist a pull at 90 degrees to the surface of the wood, they are generally hammered in at an angle for precisely that reason. SteveBaker (talk) 16:23, 11 January 2015 (UTC)

Decent large nails usually have little ridges near the top to help with the friction aspect - see this image. Alansplodge (talk) 22:44, 11 January 2015 (UTC)

Agree with the above, that it's more about the material than the fastener here. Try pushing a nail into a pincushion, and you will be able to easily pull it out (but it will likely leave a large hole behind). If you could manage to drive a pin into wood, it would also be quite difficult to extract. The thinness of the pin would make it nearly impossible to drive it into wood without it bending, though. Perhaps a high speed, like from a tornado, would make this possible. StuRat (talk) 04:18, 12 January 2015 (UTC)

With any slender body, including a pin, that is to be driven into a solid material such as wood, the failure mechanism is going to be failure as a column - see Column#Equilibrium, instability, and loads. See also Buckling#Columns. If an attempt is made to drive a pin into timber with a single blow, or a small number of blows, the pin will inevitably fail as a column before it is fully inserted. Even at high speed from a gun or a tornado the pin would buckle as a column before it was inserted very far. That is why nails are usually hammered into place with a number of blows rather than one giant blow, and the nail is supported laterally until it is firmly established in the timber. Dolphin (t) 05:06, 12 January 2015 (UTC)

I seem to recall a piece of straw stuck into a tree by a tornado. At those speeds materials behave differently, as there isn't time for the buckling to occur. Similarly, if you watch a bullet shot through a rubber sheet using high speed photography, the rubber doesn't stretch, but fractures as if it was glass. StuRat (talk) 05:20, 12 January 2015 (UTC)

MythBusters busted the straw-in-a-tree example: [4]. DMacks (talk) 05:24, 12 January 2015 (UTC)

But others have proposed explanations for seeing the same result, and possibly also have actual experimental evidence contradicting MB's tests: [5]. DMacks (talk) 05:32, 12 January 2015 (UTC)

Yea, I've never been impressed by MythBusters. They often conclude, incorrectly, that since they couldn't do X, then X can't be done. StuRat (talk) 05:36, 12 January 2015 (UTC)

Body weight and g-force tolerance

Is it possible to get any meaningful calculation of how many G's would you theoretically tolerate based on your weight? Specifically, considering persons whose body mass index is lower than normal, for instance 58 kg for a 179-cm tall man (for 10 G, for example, this yields 580 kg, which is similar to Manuel Uribe). Brandmeister^talk 09:23, 11 January 2015 (UTC)

Our article, High-G training, links to several sources, including a NASA tech note that suggests astronaut-grade test-pilots can withstand 9g for 60 seconds while performing complicated tasks. In my experience flying the Citabria, most mortals start getting queasy or puking around a peak acceleration of +2g for just a fraction of a second - say, during the recovery from a spin - so although they will live through higher accelerations, they probably won't "tolerate" it. Here's a few videos from inside the cockpit and an external view of a Super Dec doing the same. Here's a tutorial video in a 7GCBC with a visible accelerometer on the panel. Quantitatively, the g-load a NASA test pilot would endure is some 5x greater than the peak accelerations experienced during these maneuvers. Nimur (talk) 09:49, 11 January 2015 (UTC)

A g-suit helps. I don't see why BMI should be relevant.--Shantavira|^{feed me} 10:06, 11 January 2015 (UTC)

And if without the suit? Lower value, of course, but still... Brandmeister^talk 10:19, 11 January 2015 (UTC)

Usually, queasiness/nausea (and stall/spin) is negative G-force with the feeling of falling. But I think the question is variations regarding body type and/or medical factors. I don't have the paper anymore but at one time, the air force studied whether their flight standards were based on anything more than a recruiting poster (i.e. 6' foot, 180 lbs, lean and physically fit). I think what they found was that shorter, slightly overweight, high blood pressure and near-sighted performed better at high-G. 5'6", 180 lbs, high blood pressure with glasses outperformed their "ideal" in stress tests. Some of the best videos are when pilots lose consciousness in the simulator. If you didn't know any better, it looks like the sim is producing a stress that the pilot is fighting. Then they go limp and it's clear all the stress is induced by the pilot to stay conscious through G-LOC.[6] This one has more funky chicken spasms. They go limp at the same G they were straining against. --DHeyward (talk) 10:32, 11 January 2015 (UTC)

JAR Professional Pilot Studies by Phil Croucher (p.1-28) says; "Your ability to withstand G forces is reduced by: • obesity • low blood sugar and • hypoxia". It doesn't say why though. Alansplodge (talk) 17:28, 12 January 2015 (UTC)

The PHAK has a whole chapter on this: Chapter 16 - Aeromedical Factors. The AIM also has Chapter 8, Medical Facts for Pilots. Nimur (talk) 19:32, 12 January 2015 (UTC)

Here's one of the studies[7]. Reduction in G-LOC correlated to increase in age, weight (age and weight are correlated), reduced height and systolic BP. This isn't obese vs. non-obese but comparing BMI's within a normal range. Heavier performed better in these experiments. Also, this isn't typical G-Forces, it's high G forces that induce G-LOC. --DHeyward (talk) 20:41, 14 January 2015 (UTC)

Reserves and ressources

I know the difference between Reserves and Resources. Reserves are economically recoverable and resources not. But the resources are geologically probable. But what are recoverable ressources (like in File:Uranium known recoverable resources.svg)? I can't figure out, where these are in the McKelvey diagram. May you help me?--Kopiersperre (talk) 16:46, 11 January 2015 (UTC)

This sort of question earns big bucks for highly trained geologists and tax attorneys! I think the best we can do is point you to our article, which you've already found, and to the references section it contains. In particular, the United States frequently reclassifies the taxable status of speculative reserves of minerals and energy... so the answer will constantly be changing. Nimur (talk) 17:16, 11 January 2015 (UTC)