Stuck in a Sphere @ the Center of the Earth

Are you hung over? *glare*xaos

Only a little. I popped a couple aspirin and downed half a pot of coffee. Is it just me, or are the lights really bright in here?

[QUOTE="xaos"]Are you hung over? *glare*Oleg_Huzwog

Only a little. I popped a couple aspirin and downed half a pot of coffee. Is it just me, or are the lights really bright in here?

Dunno; you *could* be having a stroke :(xaos

My backstroke is pretty strong. I'm also decent at the breaststroke. Never could get the hang of the butterfly.

[QUOTE="xaos"]Dunno; you *could* be having a stroke :(Oleg_Huzwog

My backstroke is pretty strong. I'm also decent at the breaststroke. Never could get the hang of the butterfly.

See how I fail to make a single prurient joke, despite the abundant potential?xaos

So if this was a game of volleyball, you'd ignore the perfect set. C'mon - get yourself up and swat those balls when they come to you!

[QUOTE="xaos"]See how I fail to make a single prurient joke, despite the abundant potential?Oleg_Huzwog

So if this was a game of volleyball, you'd ignore the perfect set. C'mon - get yourself up and swat those balls when they come to you!

Bah, with a setup like that, I think softball is a better analogy. *waits patiently*xaos

Well, if we're going to play softball, I'll need a glove.

[QUOTE="xaos"]Bah, with a setup like that, I think softball is a better analogy. *waits patiently*Oleg_Huzwog

Well, if we're going to play softball, I'll need a glove.

Sure, it's always important to have the right equipment when you playxaos

thinking... thinking... thinking...

Nope, I can't come up with anything further. What was this thread for, again? Something about gravity?

maybe we are in a sphere at the center of the (hollow) earth. romocop33

Force of gravity between any 2 masses in the universe:

F=G(Mo)(Me)/r^2

Where F= The force of gravity

G= Gravitational constant (which is 6.67x10^-11)

Mo= Mass of object (you)

Me= Mass of Earth (in our case it is the earth)

r= Distance between them.

Thus the closer to earth you get the stronger gravity is.

Also some people have been saying you would burst? I think you're getting confused with atmospheric pressure, if it isn't present you would explode as there would be no force to push back on your body. That is why in a vacuum (space) you would burst.

Force of gravity between any 2 masses in the universe:

F=G(Mo)(Me)/r^2

Where F= The force of gravity

G= Gravitational constant (which is 6.67x10^-11)

Mo= Mass of object (you)

Me= Mass of Earth (in our case it is the earth)

r= Distance between them.

Thus the closer to earth you get the stronger gravity is.

Also some people have been saying you would burst? I think you're getting confused with atmospheric pressure, if it isn't present you would explode as there would be no force to push back on your body. That is why in a vacuum (space) you would burst.

Nkemjo

[QUOTE="MrGeezer"]

Question...If fighter pilots pass out after experiencing certain G forces, that implies that they could not tolerate being on any body which would cause such G forces.

The fact that you think it's irrelevant indicates that you don't even know what I'm asking.

SpaceMoose

Gravity does not even cause those G forces, except for 1 G. It's caused by the acceleration of the plane against your body. If a plane could fly in space, it could even do it there. And again, this is a different situation because the plane is pushing on part of your body, not every particle in it equally (which, as I said, is generally only possible with gravity), so like I said, it's irrelevant. If you had some kind of magical plane, where all of the force from its acceleration was distributed evenly among all of the mass in your body, including your blood and oxygen, then you wouldn't feel it.

Yes I've done problems before, but I don't recall doing any problems relating to a planet say, 10 times as massive as Jupiter.

MrGeezer

What difference does it make? The planet still has a large volume. You would still not be pulled in different directions by it, which is the whole point here. We're not talking about whether higher gravity would crush you. It's like your just changing the whole thing to a different subject altogeter. If Earth had 3 times its current mass, or 10 times its current mass, but the same volume, it would not change this problem at all. Okay, the surface gravity would be higher, but in the center, you would still have a net zero pull on you. What is your point? The planet's mass is entirely irrelevant.

So...a question...ARE THERE ANY "NORMAL" BODIES WHICH HAVE A MASS WHICH WOULD PROVE LETHAL TO A HUMAN?

MrGeezer

Yes, but not from pulling you in different directions. Just from being crushed under your own weight, which is not merely from the gravity itself, but from the equal and opposite push of the planet's surface against your feet. (For you to not be acclerating relative to the planet, since F = ma, there must be a force which exactly cancels out the force due to gravity, which would be the surface pushing against you. Technically it would be the planet pushing against you that would kill you, since this is NOT evenly distributed among your entire body. The planet would only be pushing agains the surface of your feet, and then those particles would be pushing against the ones above them, and so on.)

Gravitational force exerted is EQUALLY as much a property of MASS as it is a property of space in which that mass is contained. You can't discount EITHER. For any given r^2, you can find an m1 or m2 which produces ANY given G. But you seem to be suggesting that a LETHAL G is ONLY possible when dealing with black holes. I'm not calling you wrong, since I've never done the calculations. But I have brought up the point that airplane science has PROVEN that humans cannot tolerate G forces FAR below that experienced near black holes. As far as whether or not any G forces that high can be experienceds on the "surface" of any "normal" objects such as planets is the question that I am asking.

MrGeezer

No, it's possible to be LETHAL with a large planet, but it's not from pulling you in different directions... It's lethal from being crushed under your own weight against the planet's surface, and it would never be lethal at the center (well, not from gravity anyway), since the net gravity on you there would always be essentially zero regardless of the mass. The point is that most of the mass is sufficiently far away from you that the difference between its pull on one part of your body and another is negligible (the radius squared would be effectively the same for the majority of the planet). If you had a very, VERY SMALL black hole next to you WITH A LOT OF MASS, (Let's say a black hole that is a foot across. It doesn't matter if that's possible or not; that isn't the point.) then NOW you would have a lot of mass exerting it's gravitational pull on you FROM UP CLOSE, and thus now the difference in the radius squared between one part of your body and another would actually be significant, resulting in a different graviational pull exerting on different parts of your body.

THat's a qualitative assertion. The question is HOW strong gravity has to be before a 6 foot difference in radius becomes significant. And you well may be correct that black holes are the only objects that can do this, but I don't see any kind of QUANTITATIVE analysis bearing this out. The fact is that inside ANY mass there WILL be a difference between the net force exerted on your head and the net force exerted on your feet. This is true of people standing on the surface of the earth. But just like you can't make a blanket statement that standing on the surface of any body is safe due to the fact that standing on the surface of earth is safe, you also can't make a blanket statement that being in the center of the sun is equivalent to being in the center of the earth. You cannot make such a blanket statement bewcause there IS a difference in the magnitude of the forces that we are dealing with. How big this difference is depends both on the size of the object AND its mass, and you simply cannot categorically state the resultant net force without a QUANTITATIVE analysis. The very same forces that rip you to pieces as you approach a single black hole are ALSO at play when standing on ANY body.

And the G forces experienced by acceleration are not fundamentally different than gravity itself. You can, in fact, accelerate an object so that it is indistinguishable (with respect to that object) whether or not it is actually under the influence of gravity or is merely being accelerated. A G-force of one in deep space IS equivalent to being on the surface of the earth. There is no difference. The only relevant thing is the magnitude of the force, and that's identical whether or not it's as a result of gravity or as a result of being flung around really fast.

Or let me put it this way...we commonly think of entire bodies as points when dealing with gravity. However, gravity is cumulative. In reality, the gravitational force that we feel is the result of the sum of the gravitational force that we experience due to EVERYTHING with mass.

If you're in the center of the earth, you can draw a line straight through you. This line being the midpoint at which the mass of the body that you're in is divided COMPLETELY in half.

However, since we are about 6 feet tall, we would extend 3 FEET in either direction of this line at which the forces are equal. If this body is massive enough, then at a distance of 3 feet from the center line, you would have a HUGE difference in the mass pulling on your feet and the mass pulling on your head. This mass might be small in comparison to the mass OF THE ENTIRE BODY, but it might not be small COMPARED TO YOU.

Even if we account for equal forces in different directions cancelling each other out, this only applies for something AT THE MIDPOINT of the body. Even 3 feet away from the midpoint, there WILL be differences, which will be magnified by the mass of the object that you're in.

For earth, this difference is insignificant.

Hell, for EVERY body in the universe, this difference may be insignificant.

But you CANNOT come to such an assertion without a QUANTITATIVE analysis of the body that we are talking about.

Just as you cannot make assumptions about the earth based on your experience with the gravity exerted by a CD case, you cannot make an assumption about a large star based on the experience with the gravity exerted by the earth.

Now, we can can state the being in the center of the earth would not kill you (due to gravity) because the net gravity exerted on any given part of you would have to be less than the net gravitational pull on the surface.

But the thing is, even in the center of the earth, the net pull on any given part of your body is NOT zero. This difference would be magnified in a more massive body, as any deviation from the midpoint of the body would result in a LARGER amount of mass pulling on you from another direction.

Now, once again, it very well may be that in any celestial body (aside from black holes), such a difference would be insignificant to us. But you CAN'T make such an assertion by considering what would happen if you were in the center of the earth.

e G forces experienced by acceleration are not fundamentally different than gravity itself. You can, in fact, accelerate an object so that it is indistinguishable (with respect to that object) whether or not it is actually under the influence of gravity or is merely being accelerated. A G-force of one in deep space IS equivalent to being on the surface of the earth. There is no difference. The only relevant thing is the magnitude of the force, and that's identical whether or not it's as a result of gravity or as a result of being flung around really fast.

MrGeezer

Really. Okay, tell me what plane I can get in where the plane's accelration will have a direct force on, say, the blood in my veins. How exactly does that work? The plane seat is pushing directly against the blood cells now? Because that is effectively what gravity does...

Look, supose I attach a rocket to, let's just say, a ball of really soft clay, and this rocket is designed to accelerate at the rate g, and I put this apparatus in a vaccuum. Does the clay deform? Yes, because the force is not evenly distributed, and there is no way you could ever make it so it is, at least not with any observable amount of clay.

I drop some clay in a vaccum on Earth, where it will accelerate at the rate g. Will the clay deform without hitting anything? No, because the force is distributed evenly among all the mass, not just some surface of it. Hence the difference. Gravity acts on the whole thing equally, not EXACTLY equally, but the difference is so small that it doesn't matter. Any other typical source of acceleration does not work like that.

THat's a qualitative assertion. The question is HOW strong gravity has to be before a 6 foot difference in radius becomes significant. And you well may be correct that black holes are the only objects that can do this, but I don't see any kind of QUANTITATIVE analysis bearing this out. The fact is that inside ANY mass there WILL be a difference between the net force exerted on your head and the net force exerted on your feet. This is true of people standing on the surface of the earth. But just like you can't make a blanket statement that standing on the surface of any body is safe due to the fact that standing on the surface of earth is safe, you also can't make a blanket statement that being in the center of the sun is equivalent to being in the center of the earth. You cannot make such a blanket statement bewcause there IS a difference in the magnitude of the forces that we are dealing with. How big this difference is depends both on the size of the object AND its mass, and you simply cannot categorically state the resultant net force without a QUANTITATIVE analysis. The very same forces that rip you to pieces as you approach a single black hole are ALSO at play when standing on ANY body.

MrGeezer

Another simple question:

Do you understand this?

If not, take calculus or whatever, and then we can argue about this some more, but hopefully at that point, there would be no argument... :roll:

Hmm...I wasn't aware that the earth was a spherical shell. Is this why miners suddenly become weightless once they go deep within the earth?

And BTW, Pilots pass out in airplanes because their blood can't circulate properly. Exactly as what would happen if you were to stand on a planet with an equivalent gravitational pull.

Hmm...I wasn't aware that the earth was a spherical shell. Is this why miners suddenly become weightless once they go deep within the earth?

MrGeezer

I'll take that as a "No."

And BTW, Pilots pass out in airplanes because their blood can't circulate properly. Exactly as what would happen if you were to stand on a planet with an equivalent gravitational pull.

MrGeezer

So what? What the hell does that have to do with being pulled in opposite directions at the center of the Earth? You've derailed this so far that I don't even know what the hell we're discussing anymore.

So what? What the hell does that have to do with being pulled in opposite directions at the center of the Earth. You've derailed this so far that I don't even know what the hell we're discussing anymore.

SpaceMoose

We were just discussing how you think that celestial bodies (planets/moons/suns) are infinitessimally thin spherical shells with a uniform density.

Hmm...I wasn't aware that the earth was a spherical shell. Is this why miners suddenly become weightless once they go deep within the earth?

And BTW, Pilots pass out in airplanes because their blood can't circulate properly. Exactly as what would happen if you were to stand on a planet with an equivalent gravitational pull.

MrGeezer

[QUOTE="SpaceMoose"]

So what? What the hell does that have to do with being pulled in opposite directions at the center of the Earth. You've derailed this so far that I don't even know what the hell we're discussing anymore.

MrGeezer

We were just discussing how you think that celestial bodies (planets/moons/suns) are infinitessimally thin spherical shells with a uniform density.

No, it was a question about whether you understood that level of calculus, to which the answer is apparently an evasive, "No." But don't let that stop you from arguing about things you don't really grasp. Hasn't so far, since you want to be a smart ass now.

[QUOTE="MrGeezer"][QUOTE="SpaceMoose"]

So what? What the hell does that have to do with being pulled in opposite directions at the center of the Earth. You've derailed this so far that I don't even know what the hell we're discussing anymore.

SpaceMoose

We were just discussing how you think that celestial bodies (planets/moons/suns) are infinitessimally thin spherical shells with a uniform density.

No, it was a question about whether you understood that level of calculus, to which the answer is apparently an evasive, "No." But don't let that stop you from arguing about things you don't really grasp. Hasn't so far, since you want to be a smart ass now.

So...you're saying that you DIDN'T just support your case by simplifying all celestial objects as having a uniform density?

Well, now that you've decided to start lying, and pretending like you didn't just say something which was put down in words for everyone to see, then I can stop wasting my time with you.

BTW, you got an attitude with me first, when I was just asking you for clarification, so don't DARE get upset at me "being a smartass". By "being a smartass", what you really mean is that YOU tried to be a smartass and then I told you why your "haha, you're so stupid" comment had no bearing on the discussion at hand. You don't know my educational background, you just made assumptions and then got upset when your whole attempt to humiliate didn't work.

So now that you've demonstrated that you have no interest in friendly debate, and that you've shown that you're willing to go so far as to retroactively pretend like you didn't just say **** that I just read, then you're not worth my time.

Goodbye.

Damn. Now I can't argue anymore about how turning airplanes will pull a person in two different directions.

...or something like that.

Well, this ended nicely.xaos

I can only stand the same fallacious arguments so many times after I've already explained what their fallacies are...

Plus threads involving him usually don't end well anyway. :P

No, you would experience 0 gravity at the center of the earth.yoshi-lnex

But a planet with high gravity would crush you if you were on the surface, and a pilot can only tolerate so many G's in an airplane. Therefore, you would be pulled apart if you were at the center of the Earth.

[QUOTE="MrGeezer"]

Hmm...I wasn't aware that the earth was a spherical shell. Is this why miners suddenly become weightless once they go deep within the earth?

And BTW, Pilots pass out in airplanes because their blood can't circulate properly. Exactly as what would happen if you were to stand on a planet with an equivalent gravitational pull.

xaos

I was being sarcastic. THere is no special distance you have to go before it works. The reason it doesn't work with miners is because the earth doesn't act as a hollow sphere. If you go one thousand feet into the earth, you're still OUTSIDE of a bunch of other'spheres" beneath you.

Hence the fallacy of trying to prove a point by presenting a scenario which is fundamentally different than the scenario in which is originally up for discussion. Another good example of this is the commonly brought up refutation of evolution, which states that "a design must have a designer".

Hence the fallacy of trying to prove a point by presenting a scenario which is fundamentally different than the scenario in which is originally up for discussion.

MrGeezer

Ironic quote of the week.

[QUOTE="yoshi-lnex"]No, you would experience 0 gravity at the center of the earth.SpaceMoose

But a planet with high gravity would crush you if you were on the surface, and a pilot can only tolerate so many G's in an airplane. Therefore, you would be pulled apart if you were at the center of the Earth.

And my sister doesn't look like a monkey, therefore evolution is a lie.

Intentionally misrepresenting an opposing argument for the purpose of refuting is absolutely the LOWEST form of intellectual dishonesty (actually, I'd rank it just slightly less abominable than outright plagiarism), and it's no more respectable when it comes from someone who isn't a bible-thumping christian fundamentalist.

http://www.newton.dep.anl.gov/askasci/env99/env002.htm

There, I'm sure they are all wrong too, for completely tangential reasons which are only related by having to do with gravity or force in some way and have barely anything to do with the original scenario...

1) More than one person answered.

2) Not all of those answers are consistent with each other.

3) None of the answers were mathematical proofs.

Funny I didn't find this before since I already posted a differnet link from here:

http://hyperphysics.phy-astr.gsu.edu/Hbase/mechanics/earthole.html

Note that the force equation in this problem would give zero at the center of Earth and approximately zero anywhere near the center of the Earth.

It's also funny because the problem mentions the supposedly irrelevant shell problem I mentioned earlier. Now isn't that just precious?

Once again, does not account for changes in density.

Once again, does not account for changes in density.

MrGeezer

Whatever. You can argue with every physicist on Earth for all I care. Make them pull their hair out instead of me for a while. I've posted all there is to post about this problem.

[QUOTE="yoshi-lnex"]No, you would experience 0 gravity at the center of the earth.SpaceMoose

But a planet with high gravity would crush you if you were on the surface, and a pilot can only tolerate so many G's in an airplane. Therefore, you would be pulled apart if you were at the center of the Earth.

Those calculations you listed were likely for non-organic "points" in space, comprising no tangible volume. Humans are lop-sided creatures with uneven density; as such the forces would hardly be as ideal as what was used in the calculations (our heads weigh more than our feet, our heart is on our left side, ect. all subtleties skewing results). His point was that there likely exists a system whose mass and size would be great enough that the miniscule distance from arm to arm would be great enough to pull a person apart. In a highly exaggerated example like that, its not completely outrageous to think its plausible.

Then again, if the net force is zero for any particle in the hypothetical hollow sphere, i guess if you summed the total forces for all the particles in your body, the net force would still be zero...

hmm, well at least this gave me something to think about. Good link, btw.

No, you've posted all you're willing to post. I have no doubt that you're ABLE to post something that takes into account "real world situations". Most likely you just don't care enough to dig up any such information. I don't particularly care either, which is why I'm not gonna do any relevant calculations for myself.

Regardless, I've had enough of this discussion for at least tonight. I've got it bookmarked, so I can check back on it later if I regain interest in it. In the unlikely event that we find ourselves discussing this later, hopefully we can BOTH remain civil without trying to make the other guy look stupid. :|

In any case, I think both of us have sort of been asses here, so I think it's in our best interest that we give this **** a rest right now.

Ya, go ahead and leave as soon as I show up...

Jerks. >_>

Those calculations you listed were likely for non-organic "points" in space, comprising no tangible volume. Humans are lop-sided creatures with uneven density; as such the forces would hardly be as ideal as what was used in the calculations (our heads weigh more than our feet, our heart is on our left side, ect. all subtleties skewing results). His point was that there likely exists a system whose mass and size would be great enough that the miniscule distance from arm to arm would be great enough to pull a person apart. In a highly exaggerated example like that, its not completely outrageous to think its plausible.

Then again, if the net force is zero for any particle in the hypothetical hollow sphere, i guess if you summed the total forces for all the particles in your body, the net force would still be zero...

hmm, well at least this gave me something to think about. Good link, btw.

mikeg0788

I'm not quite sure I understand what you are getting at, but regarding the "heads weigh more than feet" thing:

The universal gravity equation is this:

F = G * m1 * m2 / r ^ 2

m1 (any particular part of the Earth) will be constant...well, not EXACTLY since stuff moves on the Earth, but you can't account for every single stupid thing like that anyway.

So let's mutitply G * m1 and call that constant K. Now our new equation then for this example is:

F = K * m2 / r^2

So, if one mass is twice another mass (say your head is twice as much as your foot, just for simplicity), then the force acting on it will be twice as much.

But then one of the most fundamental equations in physics is F = ma. If the force increases proportionately to the mass (and it does in the above example), then the acceleration is always the same at the same radius (which is why all objects would fall at the same rate if you took out wind resistance).

Now it's already kind of a mistake of perception to look at gravity as acting on your "head" or something as a whole object, since really it's just the grivitational pull of every particle on every other particle, but it gets rather difficult to describe things if you keep breaking them down to that level.

The parts of the Earth that are very close to you would have a significantly different gravitational pull on different parts of your body, but the total gravitational pull of those parts will be too small to have any real notable effect anyway, so while the difference may be large, that component of the total force on you is so small anyway that it doesn't even really matter. The overwhelming majority of the Earth is sufficiently far away from you that the difference between r1^2 (say, your head to whatever portion of the Earth is in question) and r2^2 (your feet to that portion of the Earth) is effectively zero.

[QUOTE="SpaceMoose"]

[QUOTE="yoshi-lnex"]No, you would experience 0 gravity at the center of the earth.mikeg0788

But a planet with high gravity would crush you if you were on the surface, and a pilot can only tolerate so many G's in an airplane. Therefore, you would be pulled apart if you were at the center of the Earth.

Those calculations you listed were likely for non-organic "points" in space, comprising no tangible volume. Humans are lop-sided creatures with uneven density; as such the forces would hardly be as ideal as what was used in the calculations (our heads weigh more than our feet, our heart is on our left side, ect. all subtleties skewing results). His point was that there likely exists a system whose mass and size would be great enough that the miniscule distance from arm to arm would be great enough to pull a person apart. In a highly exaggerated example like that, its not completely outrageous to think its plausible.

Then again, if the net force is zero for any particle in the hypothetical hollow sphere, i guess if you summed the total forces for all the particles in your body, the net force would still be zero...

hmm, well at least this gave me something to think about. Good link, btw.

One of my biggest issues is that the calculations ALL assumed uniform density. The calculations simply don't work if the density is not spread evenly amongst the "shells".

Granted, on earth, such differences in density would be small enough to be negligible. However, the earth is VERY small. There is still the question of what would happen on a very large body, in which a vary small deviation in density results in an unequal distribution of mass MANY times the total mass of the earth.

Would that still produce a net force identical to that experienced inside the center of the earth? I don't know.

And the thing that annoys me is that no one has EVER addressed this question. No one has provided a single shred of documentation showing that the very question is irrelevant, yet all I have gotten were insults for bringing the question up, by people who had absolutely nothing to say about it.

That gets on my nerves.

I've never presented myself as an authority on mathematics, astronomy, or geology. I was asking a serious question. If you're gonna sit there and call me stupid for asking the question, the LEAST one can do is be able to answer it.

One of my biggest issues is that the calculations ALL assumed uniform density. The calculations simply don't work if the density is not spread evenly amongst the "shells".

Granted, on earth, such differences in density would be small enough to be negligible. However, the earth is VERY small. There is still the question of what would happen on a very large body, in which a vary small deviation in density results in an unequal distribution of mass MANY times the total mass of the earth.

Would that still produce a net force identical to that experienced inside the center of the earth? I don't know.

And the thing that annoys me is that no one has EVER addressed this question. No one has provided a single shred of documentation showing that the very question is irrelevant, yet all I have gotten were insults for bringing the question up, by people who had absolutely nothing to say about it.

That gets on my nerves.

I've never presented myself as an authority on mathematics, astronomy, or geology. I was asking a serious question. If you're gonna sit there and call me stupid for asking the question, the LEAST one can do is be able to answer it.

MrGeezer

Then you would be pulled towards whatever side is more dense, but your whole body would be, not just part of it. There is going to be some point in that planet though where the net gravity from the planet is zero, and really, if any place in a geometrically imperfect object would be called the "center," it should probably be that in the first place. Point being that there will be some exact point (an infinitely small point of course) where the exact net gravity is zero, and everything around it will be close to zero.

[QUOTE="MrGeezer"]

One of my biggest issues is that the calculations ALL assumed uniform density. The calculations simply don't work if the density is not spread evenly amongst the "shells".

Granted, on earth, such differences in density would be small enough to be negligible. However, the earth is VERY small. There is still the question of what would happen on a very large body, in which a vary small deviation in density results in an unequal distribution of mass MANY times the total mass of the earth.

Would that still produce a net force identical to that experienced inside the center of the earth? I don't know.

And the thing that annoys me is that no one has EVER addressed this question. No one has provided a single shred of documentation showing that the very question is irrelevant, yet all I have gotten were insults for bringing the question up, by people who had absolutely nothing to say about it.

That gets on my nerves.

I've never presented myself as an authority on mathematics, astronomy, or geology. I was asking a serious question. If you're gonna sit there and call me stupid for asking the question, the LEAST one can do is be able to answer it.

SpaceMoose

Then you would be pulled towards whatever side is more dense, but your whole body would be, not just part of it. There is going to be some point in that planet though where the net gravity is essentially zero, and really, if any place in a geometrically imperfect object would be called the "center," it should probably be that in the first place. Point being that there will be some exact point (an infinitely small point of course) where the exact net gravity is zero, and everything around it will be close to zero.

There would have to be material very close to you that is superdense in order for that small portion of the entire planet to even have a measurable gravitational pull by itself, but since that level of density would, as far as I know, create a black hole (yes, somehow this ended up back on black holes again...), there would not be a planet in that case anyway, and if you were inside that...well, classical physics don't apply in a black hole anyway, so that's just a whole other can of worms, and its own entire area of study.

The thing is this...since denser materials tend to sink, wouldn't the densest materials usually tend to be right at (or near) the core anyway?

Now, yes, any object must have a center of mass, but I was under the impression that were were talking about the spatial center of a body, which need not correspond exactly with the center of mass. Perhaps the TC could now revise his initial question, to clarify which he was talking about.

Furthermore, let me once again clarify that I'm not even talking about a net force strong enough to (for example) make you collapse under your own weight or rip you apart. The thing is, although gravity would be acting on your whole body certain parts of your body definitely could be more susceptible to the effects of gravity. As in your skeleton is a rigid structure, while your circulatory system is not. It requires a larger gravitational field to make your skeleton collapse than it does to make you pass out because your heart has to work harder to pump blood up to your brain. As you said, gravity acts on ALL parts of the body, and I can certainly envision a scenario in which certain parts of the body are better able to cope with extreme gravity than others.

Lastly, I wasn't speaking strictly of planets. I was also including stars, many of which (as you know) are several times more massive than any known planet.

Now, you're obviously a very smart dude/chick. Probably smarter than me. And despite what you may think, I understand EXACTLY what you've been saying. But call it a failure to communicate or something (I'll take blame for not getting my point across), but I don't know that we've even been clear with each other. I don't have any problem with anything you've posted, it's just that nothing you've posted has answered my questions (Again, I take blame for not being eloquent enough with my questions). We both agree that there would be differences in the gravity experienced by the subject, it's just that you say that the differences would be so small as to be negligible, while I remain unconvinced.

I agree with pretty much everything you've said, but I consider this a problem of magnitude. And nothing anyone says will convince be until they address the degree of variation in gravity's magnitude.

HOW uniform in density are celestisial objects? (keep in mind that I am now explicitly talking about variation in density within "shells". Obviously denser meterials sink).

Furthermore, when at the spatial center of a large celestial body how much can we expect the OVERALL deviation from uniform density to be?

Thirdly, what is the magnitude that such a variation in density would cause to someone at the center (spatial center, not center of mass) of the most massive (not including black holes) objects known to man?

That's all I;m doing, dude. I'm not trying to say that you're wrong, I agree mostly with pretty much everything you've said. All I'm asking is whether or not calculations show your conclusions to apply to ALL objects. And since small asteroids are too small to be gravitationally significant to someone standing on (or in) them, and since objects larger than the earth are all going to be more or less spherical with a (ROUGHLY) uniform density within each "shell", the question boils down to whether or not a VERY small percentage deviation from uniform density in all but the most massive objects in the universe could cause a detrimental effect for a human at the center.

Again, it's only a trivial question of magnitude, and I frankly feel stupid for having even got into an argument over something so trivial.

However, the point remains that I still will not be convinced without seeing a scenario in which such variations are explicitly addressed quantitatively.

Furthermore, let me once again clarify that I'm not even talking about a net force strong enough to (for example) make you collapse under your own weight or rip you apart. The thing is, although gravity would be acting on your whole body certain parts of your body definitely could be more susceptible to the effects of gravity. As in your skeleton is a rigid structure, while your circulatory system is not. It requires a larger gravitational field to make your skeleton collapse than it does to make you pass out because your heart has to work harder to pump blood up to your brain. As you said, gravity acts on ALL parts of the body, and I can certainly envision a scenario in which certain parts of the body are better able to cope with extreme gravity than others.

MrGeezer

Are you talking about at the center of the Earth?

[QUOTE="MrGeezer"]

Furthermore, let me once again clarify that I'm not even talking about a net force strong enough to (for example) make you collapse under your own weight or rip you apart. The thing is, although gravity would be acting on your whole body certain parts of your body definitely could be more susceptible to the effects of gravity. As in your skeleton is a rigid structure, while your circulatory system is not. It requires a larger gravitational field to make your skeleton collapse than it does to make you pass out because your heart has to work harder to pump blood up to your brain. As you said, gravity acts on ALL parts of the body, and I can certainly envision a scenario in which certain parts of the body are better able to cope with extreme gravity than others.

SpaceMoose

Are you talking about at the center of the Earth?

No. I think that my second post in this thread, I said that there would be no detrimental gravitational effects to being at the center of the earth.

From that point on, I have been solely discussing whether or not the same would apply on bodies far more massive than the earth.

I conceded long ago that being at the center of the earth would be almost entirely like being in a zero gravity environment. I think that you and I are in 100% agreement on that point. The disagreement apparently only arises when we are talking about bodies FAR more massive than Earth. And even then, it's not so much that I disagree with you, but that I haven't seen any answers to my questions. Like I said before, you probably ARE correct, but I can't be swayed without seeing a quantitative analysis.

In any case, it's late, so I'll have to continue this discussion later.