Science desk
< February 28	<< Feb \| March \| Apr >>	March 2 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 1

Caterpillars

Does a catterpillar have bones — Preceding unsigned comment added by 117.206.155.229 (talk) 02:30, 1 March 2014 (UTC)[reply]

Bones are unique to fish and higher vertebrates, although Echinoderms, which are related to Chordates, do have calcified plates. Caterpillars are softbodied larva of certain types of insects, which have chitin to harden or support their exoskeletons. They aren't even closely related to us. What makes you ask the question? μηδείς (talk) 02:43, 1 March 2014 (UTC)[reply]

Caterpillars certainly don't have bones ... yet, it's interesting to consider the blurry edge of the concept. Bones are a sort of calcified cartilage found in bony fishes and their descendents, but not sharks. Yet sharks are certainly capable of impressive swimming! So how essential is the calcification to the idea we might really have in mind when we talk about a bone? Now... when we speak simply of cartilage in invertebrates, we find things like molluscs and horseshoe crabs have it. [1] For insects, it's not so clear ... but put it this way: fruit flies need a protein called osteonectin or SPARC which binds calcium and has a role in membranes that can define bones [2] to assemble their ventral nerve cords with collagen [3], which are the equivalent of vertebrate dorsal nerve cords i.e. spinal columns, which also need it for this purpose. [4] Now this doesn't mean that caterpillars have a spine, but it gives us a hint that the differences aren't really as big as we might imagine when we just look at their outer structure.

Fundamentally, insects have a hydrostatic skeleton that rapidly hardens between molts to form a true exoskeleton. Humans don't use hydrostatic skeletons for much - what comes to mind is the eye, which forms a hard ball under fluid pressure, and the penis, which in most other species is organized around a baculum bone. (Despite the human use of a purely hydrostatic skeletion there is such a thing as a penile fracture, interestingly enough) Wnt (talk) 05:19, 1 March 2014 (UTC)[reply]
- I nearly threw up just now. That is one of the most painful images I can recall ever seeing. Thanks for that.--Onorem (talk) 13:01, 1 March 2014 (UTC)[reply]
  - Wnt's post, with its failure to explain the collapse of the Twin Towers, has got to be one of the most painful I have seen too. μηδείς (talk) 16:23, 1 March 2014 (UTC)[reply]

Predation question

What bird species (if any) are natural predators of the swallowtail butterfly? 24.5.122.13 (talk) 09:19, 1 March 2014 (UTC)[reply]

Our article on swallowtail butterfly gives an example, the red-winged blackbird. — Preceding unsigned comment added by BbBrock (talk • contribs) 10:27, 1 March 2014 (UTC)[reply]

And presumably any other insectivorous birds in the locality that are large enough to catch one. Richerman (talk) 12:53, 1 March 2014 (UTC)[reply]

Doesn't it taste awful, like the monarch butterfly? 24.5.122.13 (talk) 19:54, 1 March 2014 (UTC)[reply]

No, they pretend to taste awful, like the viceroy. --jpgordon^{::==( o )} 22:18, 3 March 2014 (UTC)[reply]

Bending moments

Why do physicists talk about pivots when referring to bending moments, while engineers never seem to mention pivots? Using this pivot theory, would the pivots on , for example, a beam with 3 simple supports evenly spaced and a uniformly distributed load applied, just be where the bending moment is 0? It wouldn't be where the simple supports are because the bending moment is maximum at the middle support. Clover345 (talk) 12:58, 1 March 2014 (UTC)[reply]
Also in this case, why is the shear force from the central support double the shear force from the end supports according to the shear force diagram? Clover345 (talk) 13:14, 1 March 2014 (UTC)[reply]

(1) Please define pivot, because I'm not familiar with pivot theory. (2) Each of the end columns takes half the load from the half of the beam that it supports -- in other words, a quarter of the total load -- but the central column takes the other half of the load from BOTH halves of the beam, which is twice the load on either of the end columns. 24.5.122.13 (talk) 20:00, 1 March 2014 (UTC)[reply]

A rigid beam resting on three or more supports is statically indeterminate - it cannot be analysed using nothing more than Newton's first law, Newton's third law and the principle of moments. In practice, a beam with three or more supports must be considered flexible and its deflection properties must be taken into account in order to obtain sufficient extra information to render the problem amenable to analysis. Dolphin (t) 04:23, 2 March 2014 (UTC)[reply]

I think Clover345 specifically stated that the load is uniformly distributed along the beam, which is an additional constraint on the system. Are you saying that it will still be statistically indeterminate even under this condition? 24.5.122.13 (talk) 05:18, 3 March 2014 (UTC)[reply]

Yes. Newton's laws of motion (the first and the third) and the principle of moments yield a maximum of two independent equations. These can be used to solve two unknowns, such as the reaction at two supports. If the beam sits on three or more supports, Newton's laws of motion and the principle of moments are not sufficient - extra information must be supplied and used. The extra information usually used in the case of a flexible beam resting on three or more supports, is information about the deflection characteristics of the beam. Information about the load on the beam (whether the beam carries a uniformly distributed load, or not) does not provide the sort of information necessary to obtain a third independent equation and so solve for the load at three supports. (Note that the expression is statically indeterminate, not statistically indeterminate. Dolphin (t) 11:38, 3 March 2014 (UTC)[reply]

@Clover345: I've never used the term "pivot" in a situation like this, but from a little googling, it appears to just be another term for simple support, i.e. a support that can rotate but not translate. So no, the pivots would not be at the points of zero bending moment, they would be at the supports. There is no reason to think that the bending moment must be zero at an interior pivot.

For your second question, Dolphin51 is correct; you can't know the reactions without more information about the deformation characteristics of the beam material. But if you assume Euler-Bernoulli beam theory (ignoring shear deformation), you can calculate shears and reactions. You need to be careful with your wording; "shear force from the central support" could be interpreted two ways. The shear in the beam at the end support is (3/8)wL, and the shear in the beam on each side of the interior support is (5/8)wL. But the reaction at the interior support is the sum of those shears, or (5/4)wL. So the central support carries 62.5% of the load, and each end support carries 18.75% of the load. One way to think about "why" this happens is that the beam at the interior support can resist rotation, while the end support can't. It's therefore stiffer, and attracts more of the load. --Floquenbeam (talk) 20:55, 3 March 2014 (UTC)[reply]

Digestive enzymes have anything to do with Obesity?

Anything it all in the etiological sense? thanks. Ben-Natan (talk) 13:32, 1 March 2014 (UTC)[reply]

Enzymes have everything to do with pretty much everything that happens in biological systems - without the appropriate enzymes, we'd be unable to digest food at all - and pretty soon, we wouldn't be obese anymore! So "in the etiological sense" (meaning a direct causative link), yes of course. But if you're asking whether some specific enzyme deficiency, excess or malformation could be the specific cause of obesity, then that's a very different question. There are many causes of obesity - and because close to half of the people in the USA and parts of Europe are obese, it's hard to argue that faulty enzymes are to blame. Check out Obesity#Causes for a list of the likely and known causes. SteveBaker (talk) 14:37, 1 March 2014 (UTC)[reply]

You should consider whose digestive enzymes are at issue. Gut microbiota have been implicated in obesity, and they have a very important role in digesting food. Not only do you depend on them for production of some vitamins -- there's actually a potentially deadly pathogen Bacteroides fragilis, which appears to be very important to prevent autism.^[5] Indeed, when I read that, it occurred to me that if bacteria have such a significant role on the human consciousness, it may not really even be truly accurate for us to say we are "human". We are, I suppose, colonial organisms, a community which includes human cells, but also the microbes that live within us. Wnt (talk) 19:56, 1 March 2014 (UTC)[reply]

Alloy with electrical resistivity sharply increasing over a certain temperature

Is there a metal alloy that undergoes a solid to solid phase change at some elevated temperature, say several hundred centigrade, whereupon electrical resistivity significantly or dramatically increases? 121.221.210.239 (talk) 15:09, 1 March 2014 (UTC)[reply]

I was trying to find the resistance of some metals at different temperatures a while back and couldn't ind anything very useful so good luck, I'd be interested too. Dmcq (talk) 18:50, 1 March 2014 (UTC)[reply]

Plutonium undergoes several phase changes, but IDK about whether this affects its electrical resistivity. 24.5.122.13 (talk) 20:02, 1 March 2014 (UTC)[reply]

Correction: I do know now that it does affect its resistivity at low temperatures. From the article: "The resistivity of plutonium at room temperature is very high for a metal, and it gets even higher with lower temperatures, which is unusual for metals.[10] This trend continues down to 100 K, below which resistivity rapidly decreases for fresh samples.[10] Resistivity then begins to increase with time at around 20 K due to radiation damage, with the rate dictated by the isotopic composition of the sample.[10]" So as the temperature decreases, the resistivity of plutonium first goes up, then down quickly, then back up again -- VERY unusual behavior indeed! 24.5.122.13 (talk) 20:08, 1 March 2014 (UTC)[reply]

Gee, thanks, but as I am not a terroist with military connections, I'm not likely to come across any plutonium. Is there any metal alloy that is not radioactive that undergoes an electrically significant solid-to-solid phase change at elevated temperatures? With regard to Dmcq, were you interested in the normal continuous change in resistance of metals as temperature is increased? For metals commonly used in engineering, this is well documented. Any particular metal you are interested in? 121.221.210.239 (talk) 00:26, 2 March 2014 (UTC)[reply]

One I found was GeSbTe by googling for [alloy "phase change" resistivity]. DMacks (talk) 04:15, 2 March 2014 (UTC)[reply]

Thanks. There are several alloys in this class. They show a decrease in resistivity with increase in temperature though. I'm looking for alloys that show an easilly reversible increase. 121.221.210.239 (talk) 07:54, 2 March 2014 (UTC)[reply]

Not a metal, but you might be interested in PTC thermistors, based on materials such as Barium titanate--Srleffler (talk) 07:57, 2 March 2014 (UTC)[reply]

Thanks. But, again, I'm interested in materials that show a significant or dramatic increase in resistivity within a small temperature change (at an elevated temperature), not the gradual continuous change over a wide temperature range such as displayed by thermistors. And it must be a metal or metal alloy - or at least something that is not brittle like a ceramic. All essentially pure metals do, of course, show a more or less linear relationship between resistivity and temperature, whilst no phase change occurs. And alloys are available that show a sensibly constant resistance over a limited temperature range, such as those used to make resistors for the electronics industry. 121.221.210.239 (talk) 09:12, 2 March 2014 (UTC)[reply]

Look at these chiselers holding onto a paper from 1929 about this. Anybody with access want to post a copy of some of this stuff to Commons "for Aaron"? [6] Wnt (talk) 14:24, 2 March 2014 (UTC)[reply]

Let's back up a step here...is there some actual application or higher-level goal you have in mind? DMacks (talk)

Yes. I'm trying to work out how certain types of current-regulating barretters might work. Note that the wikipedia article on barretters is crap, but it does mention the iron-hydrogen barretter. These comprise a pure iron wire in a low pressure hydrogen atmosphere. They work because at a temperature around 1500 K the hydrogen atoms migrate into between the iron atoms, dramatically increasing the electrical resistance. This increases the power dissipation, increasing the temperature, absorbing more hydrogen, causing increased resistance and more heating ..... Because of this positive feedback situation above 1500 K, iron-hydrogen barretters show a characteristic dip (a negative resistance region) in current as voltage is increased beyond that needed to get 1500 K, and a section of the iron wire that has gone into hydrogen absorption visibly glows. As voltage is further increased, more of the wire length begins to glow, until the entire length is saturated with hydrogen and is glowing, whereupon with further increase in voltage the current increases again. There is thus three distinct regions in iron-hydrogen barretter operation - 1) at low voltage (typically zero to about 5 volts, current increases with voltage, 2) at moderate voltages (typically 5 to 12 V) voltages current falls slightly with voltage, & 3) a region at high voltages (typically above 12 V) where curent again increases with voltage. I already know all about this type as it is well covered in the literature.

There is another type of current regulating barretter that is a high vacuum type - no hydrogen. This type has no distinct operating regions and shows no current dip as voltage increases - current merely assymtotes toward a certain value, until voltage is high enough to blow the wire. Good current regulation occurs above about 12 V. It's manufacture seems to have been a trade secret. This type operates at a much lower temperature and does not glow. How might it work? Some folk think it works due to the positive temperature coefficient of resistance with temperature (as occurs in any pure or nearly pure metal), but it is easy to show both by laboratory measurement and simple theory that this cannot account for the very good current regulation - vastly better than any metal filament lamp - that such barretters provide. 138.217.246.250 (talk) 02:12, 3 March 2014 (UTC)[reply]

I don't get it. Why wouldn't the laboratories do a basic elemental analysis to find out what kinds of atoms are available to play with? It would certainly provide some useful search terms. Wnt (talk) 13:25, 3 March 2014 (UTC)[reply]

In mentioning laboratory measurement, I meant electrical behaviour measurements done by laboratories equipped as electrical/electronic laboratories, not chemistry laboratories. 138.217.246.250 (talk) 14:48, 3 March 2014 (UTC)[reply]

Wnt is right. If you're trying to bust the identity of a "secret" material, especially if there is real (especially commercial, or lots of especially motivated for itellectual) value to be had in knowing, a key thing to do is do every analysis of every aspect of the device you can. That means also studying each piece of the device itself rather than just the device as a whole in the manner intended to be used. Companies will do elemental analysis for a small fee for virtually any given element, and the actual "cost" is negligible and process fairly easy if you have the instruments in-house. DMacks (talk) 16:54, 3 March 2014 (UTC)[reply]

DMacks, if you don't know the answer to the question, then don't keep posting. You are not helping, you are just wasting your own time. Leave it for someone who can answer it. The cost is not neglible, and necessitates destruction of the museum quality device. I just want to know how they work, there is no commercial gain in busting the secrets of something that was rendered obsolete 50 years ago. 138.217.246.250 (talk) 00:53, 4 March 2014 (UTC)[reply]

We're all here to learn. If you leave out key details (causing us to waste time finding answers off-topic for your situation) or demonstrate that you are not understanding what someone else is saying, I will feel free to explain. When you figure out more details, and to help everyone understand what you are talking about, please update our Iron-hydrogen resistor article. I googled patent literature and found mention of using nickel in series with iron, specifically mentioning that they have essentially consecutive useful temperature/current ranges. Having two different materials seems like a clever way to have a change-over, inflection, or non-overall-linear effect. DMacks (talk) 15:11, 4 March 2014 (UTC)[reply]

Did you read the question? I think not. Here it is again: Is there a metal alloy that undergoes a solid to solid phase change at some elevated temperature, say several hundred centigrade, whereupon electrical resistivity significantly or dramatically increases? All the details are there. Your decision to go off topic is exactly that - yours.

Ah. I didn't realize that it was a rare exemplar that would rule out destructive testing. That explains it. But there are forms of non-destructive elemental analysis, ranging from "completely nondestructive" neutron beam activation analysis to methods that require "just a scrape" of a surface. I don't know if you can get at the surface, or whether other budgetary limitations apply, but maybe someone can come up with a working idea still. Wnt (talk) 16:09, 4 March 2014 (UTC)[reply]

Of course I can't get at the surface. Look at the question I wrote at the top. It's about a metal device in a high vacuum. What do you think provides a vacuum? A sealed container of course. In fact a glass container, with gettering - same as with radio vacuum tubes. By neutron beam activation analysis, I assume you mean Neutron Activation Analysis (NAA). To use it, the glass container must be removed, as it block beta radiation and other problems. Depending on the sample under test, it may be necessary to perform chemical reduction first. So it's not non-destructive, though in other circumstances it can be. There is one company (ANSTO) in this country that does NAA and they ain't cheap. 120.145.178.113 (talk) 00:13, 5 March 2014 (UTC)[reply]

Well, it's not my field, but the article neutron activation analysis says that the analysis is conducted in quartz vials, and often what is measured is prompt gamma emission and delayed gamma emission that penetrates to any side of a well far from the sample. In biology, somewhat similar measurements (radioactivity on a gel or in a wipe) seem to be very forgiving, but I don't have a feel for what it's like when trying to distinguish between elements. Wnt (talk) 19:29, 5 March 2014 (UTC)[reply]

Try Nickel titanium. It phase changes and does what you asked but not sure what temperature range you want. It's mostly used to retain shape after cooling. --DHeyward (talk) 02:43, 4 March 2014 (UTC)[reply]

No, unfortunately. Nickel titanium alloys have only been commercialised in recent years according to the article due to great difficulty in working them. I'm talking about something that was made in the 1950's. The resistivity change is not large enough and is in the wrong direction anyway. The transition temperature needs to be well above ambient, but below what will glow. Probably about 700 to 900 K. 120.145.178.113 (talk) 03:37, 4 March 2014 (UTC)[reply]

900K will glow red. 24.5.122.13 (talk) 03:53, 4 March 2014 (UTC)[reply]

Yes, in a dark room, and/or if the metal is a good black body radiator like carbon steel. Whatever the metal is in this case, it certainly won't be carbon steel. For example, aluminium, as any metal worker or welder will know, will not glow regardless of the temperature 120.145.178.113 (talk) 04:44, 4 March 2014 (UTC)[reply]

Aluminum is not normally heated to 900K during forging or welding, since its melting point is 933K. And molten aluminum DOES glow red. 24.5.122.13 (talk) 03:45, 6 March 2014 (UTC)[reply]

Well, obviously the metal in a barreter can't be molten. But I've got news for you, buddy. I've welded and cast aluminium, lots of times, which clearly involves melting it, and I've never seen it glow. Welding is a process which by definition involves melting. The reason why Aluminium won't glow is simple: the power radiated by any object is given by the Stefan-Boltzman law: P = AesT⁴, where P is watts per m², A is the surface area, e is the emissivity - a dimensionless constant, s is the Stefan-Bolzman constant, 5.67 x 10^-8 w/m2.K, and T is the temperature in kelvins. Emissivity ranges from zero (perfect white or transparent materials) to unity (a perfect black body). Aluminium has an emissivity of only 0.04 - that means it does radiate but only very weakly. You may see it glow in a dark room, even if not melted. Melting has got little or nothing to do with it. But under practical situations, there is no glow visible. By contrast, steels have an emissivity around 0.9 at elevated temperatures - that's why they glow when heated. 60.230.218.248 (talk) 06:54, 6 March 2014 (UTC)[reply]

Does anyone believe that dinosaurs still existed at the time of Jesus?

Question as topic. Just something I vaguely half-remember hearing once. I'm not talking about the belief that dinosaurs could be found in the Garden Of Eden, or that there were dinosaurs on the Ark - I know that some people definitely believe those... --Kurt Shaped Box (talk) 22:44, 1 March 2014 (UTC)[reply]

Birds are descended from theropod branch of dinosaurs. So yes dinosaurs about now, so they were about at the time of Jesus. Dja1979 (talk) 23:45, 1 March 2014 (UTC)[reply]

We both know that's not what Kurt means. Yes, many scientists like the idea of using cladistic nomenclature and adopting the point of view that as long as descendants of the Dinosauria clade exist then "dinosaurs" still exist, but Kurt is obviously using the term "dinosaur" in the colloquial, non-avian sense to refer to all the giant reptiles that, scientifically speaking, went extinct about 65 million years ago. Dragons flight (talk) 00:04, 2 March 2014 (UTC)[reply]

Does anybody accept the claim of a flying dinosaur that it was the father of Jesus? Hcobb (talk) 00:08, 2 March 2014 (UTC)[reply]

There is in fact a legend that a small flying dinosaur was a witness to Jesus's crucification and sang to comfort him as he was dying. 24.5.122.13 (talk) 06:20, 2 March 2014 (UTC)[reply]

Certainly, given that some people believe that dinosaurs still exist today (and I'm not just talking about the origin of birds). See Young Earth creationism#Paleontology and dinosaurs and Living dinosaur#In cryptozoology. Red Act (talk) 00:11, 2 March 2014 (UTC)[reply]

Certainly, someone believes anything you can think of. I would imagine if you've conceived of it, there's someone crazy enough to earnestly think it is true. Sort of a G-rated version of Rule 34. --Jayron32 02:09, 2 March 2014 (UTC)[reply]

At some level, you have to wonder how sincerely anyone could believe something like Grendel being a Tyrannosaurus, but there are indeed people who make such claims - and apparently "J.R." Tolkein proved it. Matt Deres (talk) 02:28, 2 March 2014 (UTC)[reply]

A group of Homo floresiensis taking on a Moa (or with less taxonomic accuracy, a Megalania) would be the equal of any fable. Wnt (talk) 04:22, 2 March 2014 (UTC)[reply]

Most questions that begin, "Does anyone believe…" probably need a "yes" answer. I'd rephrase slightly: Can anyone be identified that seriously believes Jesus rode a dinosaur? Certainly there are illustrations (and t-shirts) depicting such scenes. And there are those who maintain that Jesus's pet dinosaur was named "Skippy". But every one of these I have seen has their (you should pardon the term) genesis in well-deserved mockery of Young Earth Creationism rather than belief in the reality of the event depicted. Jesus and his apatosaurus or brontosaurus, Beginner's Bible Coloring Book. Often these illustrations are attributed on the Internet to sources, such as AIG or the Creationism Museum that would make them seem as if they represented sincere beliefs, but I haven't seen a case where the attribution was actually true. - Nunh-huh 08:17, 2 March 2014 (UTC) (Also, for those seeking devotional images, see here.)[reply]

Thanks for the answers so far, guys. I had also seen depictions of Jesus riding/feeding/holding dinosaurs and wondered whether they were parody or not. Poe's law time, maybe? --Kurt Shaped Box (talk) 12:33, 2 March 2014 (UTC)[reply]

Thing is, if you really believe in God, then all bets are off. The historical record doesn't need to be consistent anymore, anything is possible. God could have created the entire universe two seconds ago including all your memories as false memories about a World that has never actually existed. Count Iblis (talk) 16:18, 2 March 2014 (UTC)[reply]

Well yes, Iblis, if you assume an evil, deceiving God, unable to have conceived of evolution, since he's no smarter than his televangelists and money changers. μηδείς (talk) 16:36, 2 March 2014 (UTC)[reply]

It depends on whether you believe in the Bible-based God and the literal interpretation of the creation of the universe. I have also seen depictions of Jesus riding dinosaurs, I hope this is just to parody Creationists, because if they believe that kind of thing, who knows what's next. The Rambling Man (talk) 16:41, 2 March 2014 (UTC)[reply]

Well, if God created the universe with some effort, it might stand to reason that there was more than one draft involved -- I mean, we're only talking God, not Jack Kerouac. Maybe after the first day's editing it was enough to see the sun and the moon rise over the ocean and flat Earth for "all time", but then everything got revised to another version with some more backstory about how things got started, before long wacky ideas like round planets and excretion came in, and at some point, just for fun, the crazy notion of organisms just spontaneously coming out the way they're supposed to look because that just "works best" was invented. And it's perfectly conceivable that an omnipotent being could rewrite all of history from Big Bang to final heat death to be even more outlandish and clever and beautiful on the next draft... and wonder what the odds are it'll include a character somewhat based on mine. Wnt (talk) 21:10, 2 March 2014 (UTC)[reply]

Perhaps in the next revision, some population self-limiting mechanism will be "invented" that does not ultimately rely on the Malthusian self-limiting, in which case the population might be small enough that the chances of any recognizable resemblance for any of us would be remote. However, I sort of like Jarred Diamond's depiction of societies competing and overwhelming each other of the the ages, not dissimilarly from bacterial colonies competing in a Petri dish. —Quondum 02:49, 3 March 2014 (UTC)[reply]

Well, this is why religion isn't science. An omnipotent Creator can do anything -- entirely change the laws of logic and mathematics, revise history so that the bad things never even happened, even find a way to keep the plot elements he or she likes intact throughout such massive revisions. Even within a Ten Commandments (the movie) view of Christianity, Jesus could say "Lazasaurus, come forth" and pose with him for the camera. :) Wnt (talk) 04:01, 3 March 2014 (UTC)[reply]

That's not "religion", it's textual fundamentalism, the texts being rather poorly limited unscientific cartoons. There are philosophically serious religions which don't accept such silly reliance on human texts as if they were experimental evidence. It's rather insulting to Stoics, Buddhists, most Rabbinical Jews, and Catholics, for example, to insist religion is the same as literal faith in a text and only a text. μηδείς (talk) 05:18, 3 March 2014 (UTC)[reply]

There are many who think it IS religion. HiLo48 (talk) 07:52, 3 March 2014 (UTC)[reply]

I didn't suggest that literal faith in a text was the definition of "religion"; only that religion encompasses a larger sphere of philosophical inquiry in which people can question whether reality is real. To the scientific mindset this seems absurd (and I've been there - I was a Dawkins 20 years ago) but the scientific mindset doesn't have answers for everything e.g. why people "really" feel things rather than merely responding, like robots, to what they sense without being "consciously aware" of doing so. Because our perspective is that of the difficult-to-define consciousness rather than that of one or more atoms with a defined and ongoing existence whether they pass into the body and brain or out of it, our "reality" need not follow the material trajectory of those atoms, and may not correspond to physical law. And (like a Holodeck) the universe we perceive may simply not accurately reflect in its internal history all of the changes that have been or could be made to it. Wnt (talk) 09:03, 3 March 2014 (UTC)[reply]

Tidally locked planet rotation?

Sorry if this has already been asked.

Wouldn't a tidally locked planet with significant amounts of water flip as the ice built up on one side, making the planet heavier on one side than the other? If it would rotate because of ice buildup at all, would it flip, or would it rotate gradually to continually melt the glacier "twilight" zone? B^e——C_ritical 22:47, 1 March 2014 (UTC)[reply]

No to both -- tidal locking is due to the gravitational distortion of the planet's lithosphere itself, compared to which the mass of the ice is insignificant. 24.5.122.13 (talk) 23:04, 1 March 2014 (UTC)[reply]

And that's because the planet is flattened into a disk instead of a sphere? So that flipping would turn it on edge first, and that would take a huge imbalance to accomplish? Why wouldn't the lithosphere deform over time even under minor amounts of pressure from ice? So you might have one rotation over millions of years? B^e——C_ritical 23:37, 1 March 2014 (UTC)[reply]

The planet is elongated, not flattened, by the tidal effects. And the ice forms part of the mass of the planet, so it would not be correct to describe it as "heavier on the one side". —Quondum 04:32, 2 March 2014 (UTC)[reply]

Okay got it thanks, I was thinking of it wrong but elongation explains it and why it wouldn't flip (: B^e——C_ritical 05:22, 2 March 2014 (UTC)[reply]

One could say that a tide-locked satellite is elongated and flattened: typically the diameter in the direction of the primary is longer than the diameter along the orbit, which in turn is longer than the axis of rotation (the diameter perpendicular to the orbital plane). —Tamfang (talk) 00:42, 3 March 2014 (UTC)[reply]

The planets are elongated not by tidal effects but the centrifugal forces. Tidal effects are created by another celestial body in "close" enough proximity, and they are not stationary but moving around the planet like the tides on the earth surface created by the moon and to less extent by the sun. --AboutFace 22 (talk) 16:46, 2 March 2014 (UTC)[reply]

AboutFace, you may wish to read Tidal force – your interpretation of "tidal effects" is far narrower than the sense in which we are using it here. —Quondum 20:48, 2 March 2014 (UTC)[reply]