Wikipedia:Reference desk/Archives/Science/2013 April 18

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April 18

How to destroy a planet in star completely

From i have learned the way scientist predicts inner planets to get swallowed up is to telltrace the chemicals, for example lithium and sodium. But if we get a hypothetical planet in the star how would I destroy it? I learned when a hypothetical rocky planet gets in the sun, they will not instantly get destroyed, they won't completely get destroyed until it gets to the sun's core. So when earth gets in the sun, will earth wait until it gets to hotter layers of the sun to get destroyed completely (only the crust to core) all at once, or it will first eat away the crust and erode the planet progressively (through the mantles to earth's core) as earth gets deeper in the sun. For scientist to predict the inner planets to get swallowed up to they try to find the missing planets and compare their solar system planets to our solar system's planets, or they always find the chemicals inside the star like sodium, lithium rocks which got evaporated into gas. Is this possible other sun-like solar systems might have planets closer to sun like Mercury or much closer to sun than Mercury, like 0.05 AUs away from their sun.--69.226.42.134 (talk) 00:39, 18 April 2013 (UTC)

As a rocky planet approaches the star, the solar wind, and radiational heating, will erode the atmosphere of the planet. Once the planet is close enough to the star, those same processes will start to significantly melt and evaporate the planet progresively. This will continue as the planet enters the star. Since heat transmission is not instantateous, the planet may sink well into the star, where temperature is tens of thousands of degrees. The greater temperature only affects the rate at which the planet evaporates completely. A planet may exist close a star, but not indefinitely, as it experiences errosive processes as described above. It is even possible for a planet to orbit within a star, if it has sufficient orbital velocity. Plasmic Physics (talk) 04:07, 18 April 2013 (UTC)

Also note that in the red giant phase a star expands out to some of it's planets, making the density of the star extremely low (the mass is the same, but the volume is far greater). So, while still quite hot (although not as hot as the original star), the density is so low that it takes a long time to heat up those planets. On the other hand, if something caused the planet to fall into a normal-sized star, the much greater density would make short work of the planet.

Something else to note is that the heavier elements in a planet would cause it to eventually sink into the core of the star, whether it was solid or vapor when it got there. StuRat (talk) 04:58, 18 April 2013 (UTC)

Thermal convection currents will slow down the net movement of heavy elements towards the core consideably, and may even prevent it. I believe that most stars would be hot enough at the centre to cause a planet to simply smear out and dissolve before reaching the actual core. Now that I think about it, what kind of turbulance would it cause if a solid object the size of several thousand kilometres colides with the core of a star which is itself a dense object? Somekind of star quake? Plasmic Physics (talk) 05:17, 18 April 2013 (UTC)

I can see them being delayed, but heavier elements must eventually sink to the center, I would think. I wonder if these elements would have an effect of reducing nuclear fusion, and thus reducing the star's output. StuRat (talk) 07:28, 18 April 2013 (UTC)

One other consideration is how hot the planet is to begin with. The Earth has a molten core/mantle, so only the crust would need to be melted. StuRat (talk) 04:58, 18 April 2013 (UTC)

The mantle is not really molten as it is, that is a common misconception. The mantle is infact a type of hot solid, called a rheid. Plasmic Physics (talk) 05:17, 18 April 2013 (UTC)

I was using "molten" to describe it's temperature. That is, it would be liquid, were the pressure not so high. Thus, once the outer layers melt away, the core will be liquid. It won't need to heat up. StuRat (talk) 06:27, 18 April 2013 (UTC)

Yeah, that's right. I should have thought it through. Can the mantle temporarily cool down as the planet is eroded away? Plasmic Physics (talk) 08:26, 18 April 2013 (UTC)

No — something as nearly incompressible as solid/liquid rock will not do any appreciable P-V work on its surroundings as it expands, and so its temperature will not drop significantly. (In particular, not enough to counteract the external heating!) --Tardis (talk) 01:45, 19 April 2013 (UTC)

The thing to remember is that the solid lithosphere of the earth is only 20 to 60 miles thick...much thinner in some places. As a mental image of this, think of the earth shrunk to the size of an apple...the skin of an apple is about as thick as the solid part of the earth on that scale. The remaining 4,000 miles down to the center (the white flesh of the analogous apple) is hot enough to be molten if the pressure were any lower. So only the top 20 miles of rock has to be melted/vaporized to get to the mantle - that reduces the pressure on the mantle - so some of that turns to a true liquid...and when that's boiled away, the pressure further in is reduced still more. Ultimately, the rest is only held together by gravity - and as it's eroded, the gravity (and therefore the pressure keeping it solid) would be shredded/dispersed more and more quickly as it boils away.

The friction with the sun's atmosphere alone would be horrific - the sun rotates every 25 days, the earth orbits in 365 days. The surface of the sun right now is moving at about 7,000 kph - and conservation of angular momentum suggests that it would slow down dramatically as the diameter of the sun increases. The earth is moving around an orbit at 100,000 kph...so there would be a 93,000 kph "wind" of solar atmosphere blowing past the earth's surface. Quite aside from the heat - that wind alone would remove a liquified surface material at an impressive rate as soon as any significant amount of the sun's atmosphere reached our orbit.

The details of what will ultimately happen depends in great detail on things we're not 100% certain about. How fast will the sun expand? How much will the sun's upper atmosphere and radiation affect the earth before we're physically close enough to be "swallowed up"?

There are at least four possible scenarios:

• The earth is actually far enough from the sun that it doesn't get "swallowed up" at all - but continues to orbit - albeit with atmosphere stripped, oceans boiled and molten surface.
• That the earth is slowly eroded over centuries to millenia as the temperatures rise...before the sun gets large enough to swallow it up.
• That something disturbs the earths orbit enough to cause it to spiral into the sun - which would blast it to atoms relatively quickly...depending on the rate of descent.
• The earth isn't the only body being messed with as all of this happens - so other gravitational disturbances might even fling the planet away from the sun...with all manner of possible consequences.

Any of those things seems possible on the basis of the evidence we have - and the rapidity with which the events unfold make a huge difference to the outcome - so it's really tough to describe what will happen in any kind of detail.

SteveBaker (talk) 13:52, 18 April 2013 (UTC)

There are a huge number of archived threads about this stuff, for example [1]. Wnt (talk) 21:44, 18 April 2013 (UTC)

Lever frame, again

Is it possible in principle, using a mechanical lever frame, to "clear" the interlocking signals even though the points are set for the siding? Or do the signals themselves have to be cross-wired to achieve this? (Note that in France, a dark signal is a clear signal -- completely contrary to American practice -- so shooting them out would also be an option.) Thanks in advance! 24.23.196.85 (talk) 05:49, 18 April 2013 (UTC)

I'm not familiar with the details of French railroad signaling, but in British practice, there are (usually) two signals associated with points: the "protecting signal" which gives the train permission to traverse the points, and the (not always present) signal that indicates which way the points are set.

The protecting signal for a trailing movement (one from a branch of the "Y" intersection to the base) is interlocked so that it shows danger when the points are set incorrectly for the movement, and must be manually set to danger before the points can be moved; someone with a crowbar and knowledge of the switch mechanism can easily defeat the interlocking.

The protecting signal for a facing movement (one from the base of the "Y" to a branch) is interlocked so that it must be set to danger before the points can be moved, but doesn't have any interlocking for which way the points are set.

The direction signal, especially in older mechanical systems, is part of the mechanism that moves the points, and is controlled by the same lever. You'd need someone out there at the signal to get it to show the wrong direction, though if the French system is as you describe (no light for a "through" movement, light for a branch movement), simply disconnecting the signal from the mechanism is sufficient (a fail-safe design that puts the protecting signals to danger if a fault is detected is only likely in an electromechanical system, not a pure mechanical system). --Carnildo (talk) 02:50, 19 April 2013 (UTC)

So, I gather from what you said that there's some additional sabotage required to defeat the signal, but it's quite easily done. Thanks! And BTW, a crowbar would only add about a pound or so to the Maquis' load-out, so no problem there (especially since they only need one for the whole team). 24.23.196.85 (talk) 03:13, 20 April 2013 (UTC)

Oh, and BTW, even an electromechanical or fully electrical system is not entirely fail-safe... 24.23.196.85 (talk) 03:16, 20 April 2013 (UTC)

With a modern fully-electrical system, track circuits would detect a broken rail, the sabotaged bridge would show up on the dispatcher's board as occupied, and the relevant block signal would automatically be set to danger. --Carnildo (talk) 02:15, 21 April 2013 (UTC)

True, but if the saboteur loosens the rail-joint in such a way as to leave the bond wire in place, the track circuit won't detect the break (as indeed was the case in the Carlin wreck). 24.23.196.85 (talk) 02:41, 21 April 2013 (UTC)

From nothing

In A Universe from Nothing Krauss states that soething can come from nothing. Is this pure speculation or is this accepted by the scientific community as possible. Pass a Method talk 05:52, 18 April 2013 (UTC)

See Conservation of mass-energy to see why this is utter bullshit. 24.23.196.85 (talk) 05:56, 18 April 2013 (UTC)

The answer lies in the closing statements of the final section of the article you linked to. Plasmic Physics (talk) 05:57, 18 April 2013 (UTC)

To be a little less terse, A Universe from Nothing refers to the quantum vacuum, which "is not truly empty but instead contains fleeting ... particles that pop into and out of existence" (due to the uncertainty principle) for really, really short periods of time (say on the order of Lindsay Lohan's attention span). It's also discussed in more gruesome detail in Virtual particle#Vacuums and Quantum fluctuation. So yes, this is a well-accepted idea in quantum physics. Clarityfiend (talk) 07:27, 18 April 2013 (UTC)

(ec) Based solely on the Wikipedia article, I think Krauss is talking about a vacuum fluctuation triggering cosmic inflation, which is both pure speculation and generally considered plausible given what we know about physics. Energy conservation is not an obstacle to this idea, at least not obviously. However, the vacuum in which this fluctuation happens isn't "nothing", so this really doesn't explain where all of existence came from. At best it could explain where the flat expanding space we see around us came from in a larger universe that was there already.

There have been various ideas about how all of existence could "come from" the philosopher's nothing. Aside from the fact that it seems hopelessly beyond the reach of experiments, this is also considered a reasonable line of speculation, maybe because the alternative doesn't seem to make any more sense. -- BenRG 07:33, 18 April 2013 (UTC)

I find it impossible to consider that the PN can give rise to anything - to consider that it can, is to consider that the PN has properties that allows it to yield something, and to give properties to the PN, is consider the PN as something. As soon as you define the PN, you create a paradox. Thus, a thing can only be yielded by a thing. Plasmic Physics (talk) 07:39, 18 April 2013 (UTC)

As a logical consequence, there is no such thing as the PN. Plasmic Physics (talk) 07:40, 18 April 2013 (UTC)

Futhermore, it is total non-sense to state: "The universe arose from the PN", however, the following is a reasonable statement, whether true or not: "The universe arose from the SN". Plasmic Physics (talk) 07:45, 18 April 2013 (UTC)

It appears i'm getting contradicting answers here. Pass a Method talk 08:05, 18 April 2013 (UTC)

Let me summarise what's been said: "...Something can come from nothing." is a generally true statement, as long as 'something' and 'nothing' is properly defined. However, the specific definitions of those terms as used by Krauss, makes that statement false. Plasmic Physics (talk) 08:14, 18 April 2013 (UTC)

At the very least, that statement is contestable. Plasmic Physics (talk) 08:15, 18 April 2013 (UTC)

No, the specific terms used by Krauss make the statement undeniably true. The quantum vacuum has fluctuations that can lead to the creation of virtual particles, which don't violate mass-energy conservation because they don't exist for long enough to have a well-defined energy. (Just as there's an uncertainty principle for position and momentum, there's also an analogous principle for energy and time.) The fundamental forces can be described as the exchange of virtual particles--for example, the electromagnetic force is due to the exchange of virtual photons. The Casimir effect is caused either by the zero-point energy of vacuum or the creation of virtual particles from the vacuum, depending on your preferred interpretation. Finally, it's possible for virtual particles to appear "real" in an accelerated reference frame. The most famous example is Hawking radiation, where virtual particle-antiparticle pairs are created near the event horizon: one falls in, the other escapes and is perceived in our reference frame (accelerated relative to the black hole) as a real particle. --140.180.254.78 (talk) 08:37, 18 April 2013 (UTC)

That is one of the terms defined, however, you're missing his definition of 'something'. Both terms need to be correctly defined to make the statement true. Plasmic Physics (talk) 08:48, 18 April 2013 (UTC)

Do you think a proton emitted as Hawking radiation counts as "something"? How about the Casimir force that tries to pull two parallel plates together? How about the photons in a black body, which can "come from nothing" just by increasing the temperature? --140.180.254.78 (talk) 10:53, 18 April 2013 (UTC)

The primary definition, I'm refering to is cosmic inflation, as stated by Ben above. Plasmic Physics (talk) 11:23, 18 April 2013 (UTC)

Not an answer: I've read various pop-sci things about dark energy having negative pressure, causing energy (more dark energy?) to be released as the universe expands, so that it might have had zero energy at the beginning, but I don't pretend to understand them, not sure my sources understood them, not sure they meant anything to begin with. :) Maybe this is a good elaboration of the idea. (oh - that's the same guy the OP mentioned) Wnt (talk) 03:15, 19 April 2013 (UTC)

Mental toll of spying

What are the possible mental/emotional impacts of being deployed as a spy in enemy territory for a long time? I could think of a couple off the top of my head: gradual onset of paranoia from the strain of leading a double life and always being on your guard; fatigue and irritability from the same cause; possible PTSD from a near-capture or from seeing another operative captured... What other possible impacts can you think of? 24.23.196.85 (talk) 05:55, 18 April 2013 (UTC)

One can also think of positives that boost self esteem: Success at changing outcomes, success at a difficult mission; some people thrive on adrenaline. Not all spying has any real life threatening consequences. During the occupation of Germany at the end of World War 2, there was a network of people in the US and British zones reporting on trasnportation traffic back to the Soviet Union. The US and British knew about them but left them alone becasue it suited them to have the Soviets impressed. I doubt that the British spies such Burgess, McLean, etc, felt any stress over what they were doing. They themselves thought they were doing good, and it was alife-long thing for them. Wickwack 58.164.233.93 (talk) 06:13, 18 April 2013 (UTC)

They could end up with something akin to Stockholm syndrome - by watching their subject so much they begin to empathise with them. There's a lot of stories spies that become defectors/traitor by switching sides and I would rationalise that due to having to lead a pretty amoral life where orders are undertaken with limited regard for your own personal moral-compass that some spies could become mercenaries (see Mercenary) who work for the highest bidder. ny156uk (talk) 16:44, 19 April 2013 (UTC)

Thanks! I was thinking more about Allied spies in World War 2 -- those would probably have experienced profound satisfaction from fighting the good fight, but also a great deal of stress because they would likely face torture and death if their cover was ever blown. 24.23.196.85 (talk) 02:33, 21 April 2013 (UTC)

Do great apes dislike each other?

I read that chimpanzees and gorillas are never caged together, and I do not understand why. Do they hate each other for some reason? --66.190.69.246 (talk) 11:55, 18 April 2013 (UTC)

I can't say I'm surprised if it's not a good idea to mix them. A gorilla is a big strong heavy animal, about 230 to 270 kg (quarter ton), and his personality is that of a quiet peaceful chap. A chimp is a noisy active agressive chap, but only 50 to 70 kg - same as a small human. So, it's likely a gorilla would find a chimp very annoying, but one good blow and that's the end of the chimp. Much the same as why german shepherd dogs can't stand little yappy poodles, and why I can't stand noisy yelling/screaming children or yappy poodles. Wickwack 120.145.164.27 (talk) 12:42, 18 April 2013 (UTC)

Then fortunately there are things like Punt the Pooch. DMacks (talk) 14:47, 18 April 2013 (UTC)

This is just of the top of my head -so don't quote me. Chimpanzees and gorillas probably compete for the same food resources. Both are territorial. Therefore, they would by natural enemies. --Aspro (talk) 18:05, 18 April 2013 (UTC)

This google book (chapter 7) [2] supports the notion that chimps and gorillas are aggressive towards eachother in the wild. I can't figure out how to copy/paste, but it but it describes how, in some places, the can compete strongly for space and resources. SemanticMantis (talk) 19:31, 18 April 2013 (UTC)

On a related note, this article postulates that bonobos are less aggressive than chimpanzees because there were no gorillas on the side of the river where the bonobos lived, resulting in less competition for food.--Wikimedes (talk) 20:22, 18 April 2013 (UTC)

"Dislike" is a difficult word to use here. I definitely don't "dislike" tigers or grizzly bears - they are very cool animals and I like them both. But I would feel distinctly nervous if I had to share my apartment with one that had just been captured from the wild! SteveBaker (talk) 12:33, 19 April 2013 (UTC)

Bili ape. --Yoglti (talk) 06:05, 20 April 2013 (UTC)

I think gorillas fear chimps. See this video. --Yoglti (talk) 06:08, 20 April 2013 (UTC)

No, he just wants to get away from all that horrible screaming - it's what chimps do. Unfortunately we don't see the start of the interaction. A gorrilla at over three times the weight of a chimp shouldn't be any more fightened than should a 10 year old human be afraid of the rants of a 4 year old, but they ARE annoying. Wickwack 120.145.41.239 (talk) 22:23, 22 April 2013 (UTC)

dredging data

Is there data available on how much sand is dredged from different areas of the ocean floor off the coast of the United States? --149.152.108.90 (talk) 16:13, 18 April 2013 (UTC)

The environmental protection agency might have data regarding it. OsmanRF34 (talk) 18:07, 18 April 2013 (UTC)

OsmanRF34, that URL is incorrect. The Environmental Protection Agency's website is located at http://www.epa.gov and it has an entire website, Dredged Material Management. They also link to the U.S. Army Corps of Engineers Environmental Laboratory, who also maintain a webpage on dredging operations. Nimur (talk) 22:31, 18 April 2013 (UTC)

how much force is required to form m8 thread on aluminium?

how much force is required to form m8 thread on aluminium? — Preceding unsigned comment added by 115.241.59.6 (talk) 18:26, 18 April 2013 (UTC)

That depends on whether you are cutting or rolling a thread, also lubricants, die sharpness and things. Or are you talking about tightening torque? What exactly does your homework question ask? --Aspro (talk) 18:51, 18 April 2013 (UTC)

Infinite well

A particle of mass m is in an infinite well of width L, between x = 0 and x = L. At time t = 0 assume that it is in the following equal superposition of the ground and first excited states: $|\Psi \rangle ={1 \over {\sqrt {2}}}(|E_{1}\rangle +|E_{2}\rangle )$

What is the wavefunction as a function of x and t ($\Psi (x,t)$)? — Preceding unsigned comment added by Bjology (talk • contribs) 19:10, 18 April 2013 (UTC)

If a student starts from point P with x pieces of homework and 0 clues, how soon will they arrive at an F-grade? AlexTiefling (talk) 19:13, 18 April 2013 (UTC)

Is it correct that the wavefunction at t=0 at least is just ${1 \over {\sqrt {L}}}\sin(\pi x/L)+{1 \over {\sqrt {L}}}\sin(2\pi x/L)$? But how do you put in the time dependence. Do you need something like a time-dependent phase adjustment ${1 \over {\sqrt {L}}}\sin(\pi x/L+\phi _{1})+{1 \over {\sqrt {L}}}\sin(2\pi x/L+\phi _{2}t)$ or something else? — Preceding unsigned comment added by Bjology (talk • contribs) 19:18, 18 April 2013 (UTC)

Use the linearity of Schrödinger's equation: solve the problem for the E₁ and E₂ states individually and then add the results. -- BenRG 00:47, 19 April 2013 (UTC)

You're doing fine for t=0. For t>0, you do indeed need a type of time-dependent phase adjustment, but you're not doing that correctly. Red Act (talk) 01:04, 19 April 2013 (UTC)

Orbiting rod

What would happen to the orientation of a rigid, 10-kilometre-long, 1-centimetre-wide rod orbiting high enough above the Earth to avoid significant orbital decay, if it starts out pointing radially away from the Earth? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:14, 18 April 2013 (UTC)

Conserve angular momentum and solve based on initial conditions. Nimur (talk) 19:21, 18 April 2013 (UTC)

Not a HW question. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:28, 18 April 2013 (UTC)

My response never insinuated that your question was homework. My point is, the answer is not merely well-defined, but is trivial to compute, if you specify initial conditions more precisely than you have given. If you write out those initial conditions, you will have your answer. If one of us writes them out for you, chances are good that it will take longer for you to read and cogit the description than it would take for you to independently derive them. If you don't yet have mastery of the required mathematical skills and techniques necessary to understand and describe orbits in terms of momentum and energy, chances are very good that any correct explanation would be lost on you. So, start by reading the articles I linked above; and you can proceed by reading about gravity and orbit; and you can write out the results for yourself. The equations are not difficult. Nimur (talk) 19:34, 18 April 2013 (UTC)

For a not-perfectly-rigid rod, see also Tidal locking. --Dr Dima (talk) 19:27, 18 April 2013 (UTC)

If such a rod starts off radial to earth's centre then it will still tend to point at that point in the cosmos that it started off at, as it orbits earth. Its orbit will be around its centre of mass, i.e., 5 km from each end. Disregarding solar winds, it will just stay pointing at the same point in the astral sky. Any atmospheric drag from (say) atomic oxygen, (which would have more effect on its low end) would eventually have it spinning around its centre of mass. How does WWPU keep coming up with these questions? Has he tried decaffeinated coffee ;-)”--Aspro (talk) 19:57, 18 April 2013 (UTC)

Won't the lower end of the rod tend to orbit faster than the upper end? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:44, 18 April 2013 (UTC)

It is the centre of mass of the object (this hypothetical rod) that orbits. The fact that the lower end is closer to to the earths centre (at the outset) does not mean that the lower end will orbit faster... it is physically attached to the the rod's centre of mass; just as the the mass higher up at the other end is physically linked. Until solar winds and other influences 'force' the rod to move it will stay pointing where it was left. Out article Space elevator might make this clearer. It is just physics.(ah. say's me, as though I know it all...Chuckle) --Aspro (talk) 23:22, 18 April 2013 (UTC)

If the rod was small enough that the tidal force on the rod could be ignored, then the problem would be as simple as some people above are making it out to be. The rod's center of mass would simply orbit in an ellipse, and the rod would simply maintain a constant angular momentum around its center of mass. However, the tidal force can't be ignored for a 10 km long rod, so the rod's angular momentum can't be cleanly decoupled from its orbit.

It's unclear to me what the intended initial conditions of the rod are, even if I try to fill in the gaps with what seems like the most likely intended assumptions, such as that the initial orbit is circular. In particular, I don't know whether the intended initial angular momentum of the rod around its center of mass is zero, or is the right amount such that the rod remains vertical.

If the rod's initial angular momentum around it's center of mass is such that it remains vertical, then its vertical orientation would be stable, i.e., the rod would be tidal locked. A slight deviation from vertical in either direction would result in the tidal force on the rod producing a torque on the rod that would act as a restoring force. The resulting change in angular velocity around the rod's center would not violate the conservation of angular momentum, because it's only the system's total angular momentum which is conserved, so a small change in angular momentum of the rod about its center of mass can be compensated for by a small change in the rod's altitude.

As always where there is a restoring force around an equilibrium that's proportional to the deviation from the equilibrium, a sufficiently small displacement from the equilibrium (a vertical orientation, in this case) will result in oscillations around the equilibrium. In most dynamical systems there are also dissipative forces that would then dampen those oscillations, but it's unclear to me as to if and how that would happen in this situation, given the specification that the rod is completely rigid.

Also, for some initial conditions for the rod's angular momentum, I presume some form of orbital resonance would occur. Red Act (talk) 04:00, 19 April 2013 (UTC)

• Two days have passed now, since the last post. Can the OP “Whoop whoop pull up” consider this {{resolved}} ?Aspro (talk) 01:05, 21 April 2013 (UTC)

Au contraire, we'll be hearing quite a lot of the Last Post later on this week. -- Jack of Oz ^[Talk] 05:24, 22 April 2013 (UTC)

Digestion

Do men have a larger digestive system than women? Asking because women have a uterus which most likely limits the size of their digestive organs. Pass a Method talk 19:49, 18 April 2013 (UTC)

Ok, so the uterus take up room but have you noticed they bulge out (sorry ladies curve out) in places you don't ? These differences is what helps to create the female figure. Try taking a woman to an expensive restaurant, then ask yourself if they have a digestive system to match yours. Perhaps that is the point you realize you're both equals... I'm feeling hungry just pondering it.--Aspro (talk) 20:12, 18 April 2013 (UTC)

To be more specific, women have larger pelvises to accommodate the extra room taken up by the uterus, which it should be noted doesn't exist in the same neighborhood as the stomach. Excepting when a large fetus is occupying it, the uterus itself is not that large, about the size of the bladder, and it does not extend farther up than the rectum does; which is to say it only occupies the part of the body that the extreme end of the digestive system does. It is not in the part of the body that contains the bulk of the digestive system, which excepting the rectum, exists entirely above the pelvis. You can confirm this with pictures at Uterus and really any good picture of the human internal anatomy. Pregnant women, especially those in their third trimester, do have impacts on their digestive system, but then again they are carrying around a fairly large object by that point. --Jayron32 22:04, 18 April 2013 (UTC)

Let's put the uterus aside for the moment (but let's not table it, as I have to eat there). Looking strictly at the relative sizes of men and women overall, it would seem reasonable to assume that men's digestive systems are proportionally larger, on average. That is, a 180 pound man ought to have a 50% larger digestive system than a 120 pound woman, more or less. I'm not sure if this means a man's digestive system is longer, or just wider, however (probably a bit of each). Then, for a more scientific approach, we could also compare the flatus volumes produced by each. (Sounds like a fun topic for a Master's thesis.) StuRat (talk) 02:48, 19 April 2013 (UTC)

Stu, your estimate that the male digestive system is "50% larger" is literally naive. First, Wolfram alpha gives data (and sources) for mean weight of males and females, 166 lbs and 144 lbs, respectively, so your male/female ratio is far off base. Secondly, your assumption of linear scaling ignores the important aspect of allometric scaling. By your logic, a 6' tall human would have a head that is roughly 2 feet tall and weighs ~50 lbs. That's just 3X the size of a 2' child, right? [3]. I'm no expert here, and I don't know the true answer. I think Jayron's answer makes a lot more sense. Your claims here and "evidence" are not convincing. SemanticMantis (talk) 03:19, 19 April 2013 (UTC)

Your comparison of children to adults is a red herring, as obviously size ratios vary there. And I never claimed that men are 50% larger than women. I just said that, if a man was 50% larger than a woman, I'd expect their digestive system to be roughly 50% larger, as well. If you claim that their digestive systems are the same sizes, then you need to explain why. What, does someone 50% larger have lungs twice the size, in order to take up the space which otherwise would be taken by a scaled-up the digestive system ?

Here's a source: Landois, Leonard, & William Stirling: Textbook of Human Physiology: "The human intestine is ten times longer than the length of the body,... It's minimum length is 507, its maximum length 1194 centimeters (17 to 35 feet);...": [4]. I'm also going to assume that the diameter increases proportionately, meaning the volume would, as well. StuRat (talk) 05:08, 19 April 2013 (UTC)

I looked for this but somehow missed it. I'd think there must be a standard reference pathology textbook/manual somewhere that gives the normal range for stomach weight on autopsy. Noting that obese individuals don't actually have stomachs much if at all larger than others, I don't know if a sex difference can be expected; like everything in biology you need an empirical result. Wnt (talk) 04:54, 19 April 2013 (UTC)

The relavant article here would be Human sexual dimorphism, I can't see any mention there of digestion, intestine, stomach. My guess is no, the uterus does not "limit" the size of the female digestige system... Vespine (talk) 04:56, 19 April 2013 (UTC)

BTW, the OP is clearly NOT talking about a man which is 50% larger then a woman. Forget your quibbling, it's completely missing the point, the same arguments could be made about a woman which is 50% larger then a man. Vespine (talk) 05:31, 19 April 2013 (UTC)

This is a horribly difficult question to answer - not because we can't find the answers - but because it's just too vaguely couched.

It seems like we need to tighten the wording of the question. If the question is "Does an average man have a larger digestive system than an average woman?" - then because men are (on average) around 15% larger than women - we'd expect the answer to be "Yes". But if the question is "Does a 30 year old, 5'8", 150lb man have a larger digestive system than a 30 year old, 5'8", 150lb woman?" - then it's a tougher call. Aside from any sexual dimorphism, a 150lb man would be a smaller-than-average man - and a 150lb woman would be larger-than-average. If the woman is overweight and the man isn't - then you get one answer - but if the woman has a naturally chunkier build then the answer might be different. The answer in this case is highly unclear...but from what people have already said here - I strongly suspect that the answer is "No"...or at least "Not by much"...or "typically not".

More complicated is what we mean by "a larger digestive system"? Does our OP mean to ask "Can a woman eat more than a man at one sitting?" - or do we mean the total length of the digestive tract - the total volume - the maximum rate of material flow through it? These are all liable to produce very different answers - and may or may not answer what the OP *really* wants to know.

Worse still - the digestive tract is not a rigid container - it's flexible...I bet that (as with several other organs), that flexibility varies between individuals and decreases with age. It's very possible (without evidence) that an older and a younger man with identical "relaxed" stomach sizes would differ in the amount they can eat because the older man's stomach is less flexible and can't stretch out as much. That's certainly true for bladder capacities.

So, I think the disputes here relate more to the vagueness of the question.

SteveBaker (talk) 12:28, 19 April 2013 (UTC)