Stuck in a Sphere @ the Center of the Earth

Saw this on discovery - you will bounce up and down for a bit and then be stuck there in the middle.

Maybe Ill ask my physics teacher about that...hmmmcarrot-cake

Saw this on discovery - you will bounce up and down for a bit and then be stuck there in the middle.

Sajedene

[QUOTE="Sajedene"]

Saw this on discovery - you will bounce up and down for a bit and then be stuck there in the middle.

West-Coast-G

I dunno ... oh and it was about falling through earth not being in the middle... found a link:

EDIT: lame it wont let me post the link because it edits out the word C L A S S I C!

http://www.straightdope.com/cla ssics/a1_165.html

Actually I think you would collapse into yourself, the center of earth is where everything is pulled together, so I think there is a tremendous inward force, I would not try it, that and the heat down there. :)harrisi17

[QUOTE="West-Coast-G"][QUOTE="Sajedene"]

Saw this on discovery - you will bounce up and down for a bit and then be stuck there in the middle.

Sajedene

I dunno ... oh and it was about falling through earth not being in the middle... found a link:

link

I dont remember lol. It was a while ago thats for sure.

That link is broken because gamespot keeps editing it as a bad word when its not.

[QUOTE="West-Coast-G"][QUOTE="Sajedene"]

Saw this on discovery - you will bounce up and down for a bit and then be stuck there in the middle.

Sajedene

I dunno ... oh and it was about falling through earth not being in the middle... found a link:

EDIT: lame it wont let me post the link because it edits out the word C L A S S I C!

http://www.straightdope.com/cla ssics/a1_165.html

No, there would be a net zero gravitational pull on you (well, not exactly of course since the Earth isn't a perfect sphere, but for all practical purposes), and I'm sorry to say that your physics teacher is rather clueless for someone who is supposed to understand basic physics.

And it wouldn't even really matter where you were. The gravitational force is going to be approximately the same and in approximately the same direction on your entire body in any sort of realistic scenario (like pretty much any that doesn't involve multiple black holes very close to you), just as it is on the surface.

No, there would be a net zero gravitational pull on you (well, not exactly of course since the Earth isn't a perfect sphere, but for all practical purposes), and I'm sorrty to say that your physics teacher is rather clueless for someone who is supposed to understand basic physics.

And it wouldn't even really matter where you were. The gravitational force is going to be approximately the same and in approximately the same direction on your entire body in any sort of realistic scenario (like pretty much any that doesn't involve multiple black holes very close to you), just as it is on the surface.

SpaceMoose

As a side note, interestingly enough, if you could take all earth's mass and compress it into a hollow spherical shell, then any point within the empty space inside the shell would have a net zero gravity, and anywhere outside of the shell, gravity would be just the same as it normally is on or above Earth's surface. This sort of thing is proven using the universal law of gravitation in combination with calculus. It's pretty cool stuff.SpaceMoose

As a side note, interestingly enough, if you could take all earth's mass and compress it into a hollow spherical shell, then any point within the empty space inside the shell would have a net zero gravity, and anywhere outside of the shell, gravity would be just the same as it normally is on or above Earth's surface. This sort of thing is proven using the universal law of gravitation in combination with calculus. It's pretty cool stuff.SpaceMoose

Can you explain that a little more? Im not following. West-Coast-G

Well, just ignore the black hole thing since that's just kind of going off on tangents.

Just sticking with the center of the Earth thing for now, the parts of the Earth that are "above" your head would pull not just your head, but also the rest of your body in that direction. But then the parts "below" your feet would pull your entire body in that direction, not just part of it. Now the same goes for every direction since there is also mass in the opposite direction. Hence the net force ends up being roughly zero.

No, there would be a net zero gravitational pull on you (well, not exactly of course since the Earth isn't a perfect sphere, but for all practical purposes), and I'm sorry to say that your physics teacher is rather clueless for someone who is supposed to understand basic physics.

SpaceMoose

That's what I imagined. If you were at the centre of the Earth's gravity rather than the centre of mass then net force of gravity would surely be exactly zero.

[QUOTE="SpaceMoose"]As a side note, interestingly enough, if you could take all earth's mass and compress it into a hollow spherical shell, then any point within the empty space inside the shell would have a net zero gravity, and anywhere outside of the shell, gravity would be just the same as it normally is on or above Earth's surface. This sort of thing is proven using the universal law of gravitation in combination with calculus. It's pretty cool stuff.West-Coast-G

OMFG that was hilarious!

[QUOTE="West-Coast-G"][QUOTE="SpaceMoose"]

No, there would be a net zero gravitational pull on you (well, not exactly of course since the Earth isn't a perfect sphere, but for all practical purposes), and I'm sorrty to say that your physics teacher is rather clueless for someone who is supposed to understand basic physics.

And it wouldn't even really matter where you were. The gravitational force is going to be approximately the same and in approximately the same direction on your entire body in any sort of realistic scenario (like pretty much any that doesn't involve multiple black holes very close to you), just as it is on the surface.

SpaceMoose

Well, just ignore the black hole thing since that's just kind of going off on tangents.

Well, just sticking with the center of the Earth thing for now, the parts of the Earth that are "above" your head would pull not just your head, but also the rest of your body in that direction. But then the parts "below" your feet would pull your entire body in that direction, not just part of it. Now the same goes for every direction since there is also mass in the opposite direction. Hence the net force ends up being roughly zero.

[QUOTE="West-Coast-G"]

Can you explain that a little more? Im not following. SpaceMoose

Well, just ignore the black hole thing since that's just kind of going off on tangents.

Just sticking with the center of the Earth thing for now, the parts of the Earth that are "above" your head would pull not just your head, but also the rest of your body in that direction. But then the parts "below" your feet would pull your entire body in that direction, not just part of it. Now the same goes for every direction since there is also mass in the opposite direction. Hence the net force ends up being roughly zero.

Actually I think you would collapse into yourself, the center of earth is where everything is pulled together, so I think there is a tremendous inward force, I would not try it, that and the heat down there. :)harrisi17

No, mass is attracted to mass. Since the center of the earth is hollow (except for you, but I've never seen anyone implode due to the gravitational attraction that their own cells have for each other), there would be nothing pulling you towards the center of the earth.

Wait, hold on. What if your closer to one side of the shell than you are to the other? Wouldn't the shorter distance have a greater gravitational pull than the pull pulling you the opposite way?West-Coast-G

It would be greater, but also as you move in that direction, more of the mass in in the opposite direction. The mathematics of it so happen to turn out that the net is always zero. Again, it's proven using calculus, so unless you have a knowledge of integrals, it's hard to go into detail about the specific math of it.

That's kind of the difference between high school physics and college physics. In college physics, they do a better job of explaining where all of the equations come from...usually by making you work it out on your own. :P

Edit: But if you really want to see the mathematical proof of it, here it is.

[QUOTE="West-Coast-G"] Wait, hold on. What if your closer to one side of the shell than you are to the other? Wouldn't the shorter distance have a greater gravitational pull than the pull pulling you the opposite way?SpaceMoose

It would be greater, but also as you move in that direction, more of the mass in in the opposite direction. The mathematics of it so happen to turn out that the net is always zero. Again, it's proven using calculus, so unless you have a knowledge of integrals, it's hard to go into detail about the specific math of it.

That's kind of the difference between high school physics and college physics. In college physics, they do a better job of explaining where all of the equations come from...usually by making you work it out on your own. :P

[QUOTE="SpaceMoose"]

No, there would be a net zero gravitational pull on you (well, not exactly of course since the Earth isn't a perfect sphere, but for all practical purposes), and I'm sorry to say that your physics teacher is rather clueless for someone who is supposed to understand basic physics.

Buffalo_Soulja

That's what I imagined. If you were at the centre of the Earth's gravity rather than the centre of mass then net force of gravity would surely be exactly zero.

Net zero gravitational force does not equal zero gravitational force.

You STILL would have gravity pulling on you from every direction. If I hold out my arms and have one robot pull on my arms, and have another robot pull on my other arm, the NET directional pull is zero. But that doesn't stop me from having both my arms pulled off.

Or suppose you've got two black holes very close to each other. Now suppose you teleport between those black holes. They are pulling at you in opposite directions. The NET directional pull is zero, since the force pulling on you in one direction is EXACTLY equal to the force pulling on you in the opposite direction. Thst does NOT mean that there is NO FORCE acting on you.

Now, would gravity kill you if you were in a hollow sphere within the center of the earth? I sort of doubt it, but I can't just dismiss it because there's an equal force in the opposite direction.

Net zero gravitational force does not equal zero gravitational force.

You STILL would have gravity pulling on you from every direction. If I hold out my arms and have one robot pull on my arms, and have another robot pull on my other arm, the NET directional pull is zero. But that doesn't stop me from having both my arms pulled off.

MrGeezer

Therein lies the difference. The robots are pulling on part of your body, not every particle in your body with roughly equal force.

[QUOTE="Buffalo_Soulja"][QUOTE="SpaceMoose"]

No, there would be a net zero gravitational pull on you (well, not exactly of course since the Earth isn't a perfect sphere, but for all practical purposes), and I'm sorry to say that your physics teacher is rather clueless for someone who is supposed to understand basic physics.

MrGeezer

That's what I imagined. If you were at the centre of the Earth's gravity rather than the centre of mass then net force of gravity would surely be exactly zero.

Net zero gravitational force does not equal zero gravitational force.

You STILL would have gravity pulling on you from every direction. If I hold out my arms and have one robot pull on my arms, and have another robot pull on my other arm, the NET directional pull is zero. But that doesn't stop me from having both my arms pulled off.

Or suppose you've got two black holes very close to each other. Now suppose you teleport between those black holes. They are pulling at you in opposite directions. The NET directional pull is zero, since the force pulling on you in one direction is EXACTLY equal to the force pulling on you in the opposite direction. Thst does NOT mean that there is NO FORCE acting on you.

Now, would gravity kill you if you were in a hollow sphere within the center of the earth? I sort of doubt it, but I can't just dismiss it because there's an equal force in the opposite direction.

Did you quote the wrong person? I didn't mean that you wouldn't feel your limbs being pulled, only that you would have equal pull in all directions on your own centre of gravity.

Or suppose you've got two black holes very close to each other. Now suppose you teleport between those black holes. They are pulling at you in opposite directions. The NET directional pull is zero, since the force pulling on you in one direction is EXACTLY equal to the force pulling on you in the opposite direction. Thst does NOT mean that there is NO FORCE acting on you.

MrGeezer

Now that part is correct. That is in fact why I said that very close black holes would be an exception where you could actually have significantly different gravitational pulls on different parts of your body, but that was just making it more confusing I figured so I dropped the subject.

[QUOTE="Buffalo_Soulja"][QUOTE="SpaceMoose"]

No, there would be a net zero gravitational pull on you (well, not exactly of course since the Earth isn't a perfect sphere, but for all practical purposes), and I'm sorry to say that your physics teacher is rather clueless for someone who is supposed to understand basic physics.

MrGeezer

That's what I imagined. If you were at the centre of the Earth's gravity rather than the centre of mass then net force of gravity would surely be exactly zero.

Net zero gravitational force does not equal zero gravitational force.

You STILL would have gravity pulling on you from every direction. If I hold out my arms and have one robot pull on my arms, and have another robot pull on my other arm, the NET directional pull is zero. But that doesn't stop me from having both my arms pulled off.

Or suppose you've got two black holes very close to each other. Now suppose you teleport between those black holes. They are pulling at you in opposite directions. The NET directional pull is zero, since the force pulling on you in one direction is EXACTLY equal to the force pulling on you in the opposite direction. Thst does NOT mean that there is NO FORCE acting on you.

Now, would gravity kill you if you were in a hollow sphere within the center of the earth? I sort of doubt it, but I can't just dismiss it because there's an equal force in the opposite direction.

In fact, after thinking about it, I'm concluding definitively that the gravity wouldnot kill you. However, this has NOTHING to due with net zero gravity and everything to do with the human body's TOLERANCE for variations in gravity.

We know that humans can survive zero gravity, which is why people don't die when they go into space.

Likewise, we know that humans can survive normal earth gravity, since I live on the surface of the earth and I am not dead.

And that's the key point. If I can survive "1 G", then any gravitational force exerted on any part of you while you're in the center of the earth will be LESS than "1 G". The gravitational pull on me HAS to be less than the gravitaional pull at surface level (survivable) and MORE than the gravitational pull in space (also survivable). Since humans can tolerate both of those extremes, gravity wouldn't kill you. Not saying that you wouldn't die. But if you did, it would probably have more to do with pressure or something (like, getting a bad case of the bends). But gravity? If you live on the surface of the earth and gravity hasn't killed you yet, then gravity wouldn't kill you if you were at the center of the earth.

Did you quote the wrong person? I didn't mean that you wouldn't feel your limbs being pulled, only that you would have equal pull in all directions on your own centre of gravity.

Buffalo_Soulja

You actually wouldn't feel them being pulled though. The thing is to stop consdering things as they happen at the macro level and consider how they work at the particle level. If every single part of your body is being "pulled" with the exact same force, something that pretty much only gravity can do, you don't feel it. You only "feel" gravity at all because the Earth is beneath your feet pushing in the opposite direction. If you were freefalling and could somehow never come to Earth's surface, you wouldn't "feel" gravity at all. Other than the wind, you wouldn't be able to sense any force being exerted on you.

This has been great guys, but I have to go to bed, I've got an appointment in the morning. Thanks again guys, for all your input. I appreciate it. West-Coast-G

Good night then.

[QUOTE="MrGeezer"]

Net zero gravitational force does not equal zero gravitational force.

You STILL would have gravity pulling on you from every direction. If I hold out my arms and have one robot pull on my arms, and have another robot pull on my other arm, the NET directional pull is zero. But that doesn't stop me from having both my arms pulled off.

SpaceMoose

Therein lies the difference. The robots are pulling on part of your body, not every particle in your body with roughly equal force.

Gravity ALSO does not pull on every part of your body with equal force. The left wall of the sphere pulls more strongly on your left arm. Likewise, the right wall pulls more strongly on your right arm.

This is why a black hole would rip you to pieces before you get sucked in. Because the force exerted on your feet would be a LOT greater than the force exerted on your head.

However, this would not apply with the earth, as I have noted in my previous post. If earth's gravity posed a threat to life on earth, then we wouldn't exist on earth. Earth isn't massive enough to exert that kind of force on us, which is why you don't fall apart simply because you exist.

Gravity ALSO does not pull on every part of your body with equal force. The left wall of the sphere pulls more strongly on your left arm. Likewise, the right wall pulls more strongly on your right arm.

MrGeezer

It is equal for all practical purposes. The difference would be negligible since most of the mass is at roughly the same distance from every part of your body. If all of the Earth's mass was concentrated right near the center, then you would feel it, but it isn't. (Edit: Actually, you wouldn't really then either because of the mathematical proof I linked to earlier. See, you got me thinking about too many things at once. :roll:) A difference of a few feet is entirely negligible when the majority of the mass acting on you is much further away than that.

[QUOTE="Buffalo_Soulja"]

Did you quote the wrong person? I didn't mean that you wouldn't feel your limbs being pulled, only that you would have equal pull in all directions on your own centre of gravity.

SpaceMoose

You actually wouldn't feel them being pulled though. The thing is to stop consdering things as they happen at the macro level and consider how they work at the particle level. If every single part of your body is being "pulled" with the exact same force, something that pretty much only gravity can do, you don't feel it. You only "feel" gravity at all because the Earth is beneath your feet pushing in the opposite direction. If you were freefalling and could somehow never come to Earth's surface, you wouldn't "feel" gravity at all. Other than the wind, you wouldn't be able to sense any force being exerted on you.

[QUOTE="MrGeezer"]

Gravity ALSO does not pull on every part of your body with equal force. The left wall of the sphere pulls more strongly on your left arm. Likewise, the right wall pulls more strongly on your right arm.

SpaceMoose

It is equal for all practical purposes. The difference would be negligible since most of the mass is at roughly the same distance from every part of your body. If all of the Earth's mass was concentrated right at the center, then you would feel it, but it isn't. A difference of a few feet is entirely negligible when the majority of the mass acting on you is much further away than that.

No, the distance is negligible since we are only talking about small masses.

You admit that being stuck between two black holes is different. But WHY is it different?

It's different ONLY because black holes are VERY ****ING MASSIVE while the earth is NOT.

Or to put it this way...would you get ripped apart if you passed between two file cabinets? No. How is passing between two file cabinets different than passing between two black holes? The fundamental difference is that black holes are a LOT more massive than file cabinets. If file cabinets were as massive as black holes, then passing between two file cabinets could be equally as deadly.

It has nothing to do with the fact that there's an equal force being exerted in the opposite direction. If the earth were massive enough, that WOULD just cause you to get ripped apart in every direction. However, as noted, the earth is NOT that massive. Which is why gravity rarely if ever rips anyone in half.

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

Gravity ALSO does not pull on every part of your body with equal force. The left wall of the sphere pulls more strongly on your left arm. Likewise, the right wall pulls more strongly on your right arm.

MrGeezer

It is equal for all practical purposes. The difference would be negligible since most of the mass is at roughly the same distance from every part of your body. If all of the Earth's mass was concentrated right at the center, then you would feel it, but it isn't. A difference of a few feet is entirely negligible when the majority of the mass acting on you is much further away than that.

No, the distance is negligible since we are only talking about small masses.

You admit that being stuck between two black holes is different. But WHY is it different?

It's different ONLY because black holes are VERY ****ING MASSIVE while the earth is NOT.

Or to put it this way...would you get ripped apart if you passed between two file cabinets? No. How is passing between two file cabinets different than passing between two black holes? The fundamental difference is that black holes are a LOT more massive than file cabinets. If file cabinets were as massive as black holes, then passing between two file cabinets could be equally as deadly.

It has nothing to do with the fact that there's an equal force being exerted in the opposite direction. If the earth were massive enough, that WOULD just cause you to get ripped apart in every direction. However, as noted, the earth is NOT that massive. Which is why gravity rarely if ever rips anyone in half.

Because with black holes, you can have a lot of mass concentrated in a very small volume. Thus if you had one black hole by your right arm, and one by your left, as ridiculously impossible as that is to begin with, then there would be a significantly different gravitational pull on both arms.

Universal gravity equation: F = G * m1 * m2 / radius ^ 2

In normal situations (like on Earth), the net gravity is coming from a very huge volume relative to your own size. The gravitational force of every individual particle is rather small, and the vast majority of the particles are roughly equidistant to every part of your body, relative to the size of your body. On the other hand, with small enough hypothetical black holes with most of the mass being very close to you, that would not be the case.

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

Gravity ALSO does not pull on every part of your body with equal force. The left wall of the sphere pulls more strongly on your left arm. Likewise, the right wall pulls more strongly on your right arm.

SpaceMoose

It is equal for all practical purposes. The difference would be negligible since most of the mass is at roughly the same distance from every part of your body. If all of the Earth's mass was concentrated right at the center, then you would feel it, but it isn't. A difference of a few feet is entirely negligible when the majority of the mass acting on you is much further away than that.

No, the distance is negligible since we are only talking about small masses.

You admit that being stuck between two black holes is different. But WHY is it different?

It's different ONLY because black holes are VERY ****ING MASSIVE while the earth is NOT.

Or to put it this way...would you get ripped apart if you passed between two file cabinets? No. How is passing between two file cabinets different than passing between two black holes? The fundamental difference is that black holes are a LOT more massive than file cabinets. If file cabinets were as massive as black holes, then passing between two file cabinets could be equally as deadly.

It has nothing to do with the fact that there's an equal force being exerted in the opposite direction. If the earth were massive enough, that WOULD just cause you to get ripped apart in every direction. However, as noted, the earth is NOT that massive. Which is why gravity rarely if ever rips anyone in half.

Because with black holes, you can have a lot of mass concentrated in a very small volume. Thus if you had one black hole by your right arm, and one by your left, as ridiculously impossible as that is to begin with, then there would be a significantly different gravitational pull on both arms.

Universal gravity equation: F = G * m1 * m2 / radius ^ 2

In normal situations (like on Earth), the net gravity is coming from a very huge volume relative to your own size, but with small enough hypothetical black holes, it isn't.

So how many Gs does it take before fighter pilots black out?

Gravity DOES vary among "normal" objects. Which is why the moon has less gravity than the earth. And the general trend IS that larger planets have a stronger pull on you.

Enough to kill you? I don't know. But you're oversimplifying things. You're defining the earth as the benchmark for what is "normal" when there are lotsa of "normal" planets that exert much more of a gravitational pull than the earth doews. And it doesn't require them to be black holes.

So how many Gs does it take before fighter pilots black out?

MrGeezer

That is not even remotely relevant to this discussion. I'm not sure why it is in your mind other than it is measured in multiples of Earth's gravity, but it truly is not relevant. I have absolutely no idea why you would even bring that up. We're talking about what force one feels. There is no dispute that accelerating in a plane going around a curve causes one to feel more force. Nobody is arguing the point...

Gravity DOES vary among "normal" objects. Which is why the moon has less gravity than the earth. And the general trend IS that larger planets have a stronger pull on you.

MrGeezer

Yeah, but again, I don't see the relevance...

Enough to kill you? I don't know. But you're oversimplifying things. You're defining the earth as the benchmark for what is "normal" when there are lotsa of "normal" planets that exert much more of a gravitational pull than the earth doews. And it doesn't require them to be black holes.

MrGeezer

No, that is not what I'm saying at all. I'm saying that normally gravitational force on your body from a source is approximately equal among your entire body. It doesn't matter how big that force is. The key point is what the DISTANCE is of the mass that is exerting that force on you. True, that the keyboard I'm typing on right now has a much larger gravitational force on my fingers than the rest of my body, but that small component of gravitational force is so small that it's basically irrelevant. Most of the Earth is going to be roughly the same distance from all of your body, regardless of where you are in relation to the Earth. When something is even as small as a mile away, a difference of 5 feet is going to have a pretty much negligible effect on how much gravitational pull it has on you, since the force decreases exponentially with distance, and clearly most of the Earth is much further away from you than that no matter where you are on it or within it.

I'm sorry, but I have to ask this: Have you ever even done any problems (like say, in a physics class) involving the Law of Universal Gravitation?

[QUOTE="MrGeezer"]

So how many Gs does it take before fighter pilots black out?

SpaceMoose

That is not even remotely relevant to this discussion. I'm not sure why it is in your mind other than it is measured in multiples of Earth's gravity, but it truly is not relevant. I have absolutely no idea why you would even bring that up. We're talking about what force one feels. There is no dispute that accelerating in a plane going around a curve causes one to feel more force. Nobody is arguing the point...

Gravity DOES vary among "normal" objects. Which is why the moon has less gravity than the earth. And the general trend IS that larger planets have a stronger pull on you.

MrGeezer

Yeah, but again, I don't see the relevance...

Enough to kill you? I don't know. But you're oversimplifying things. You're defining the earth as the benchmark for what is "normal" when there are lotsa of "normal" planets that exert much more of a gravitational pull than the earth doews. And it doesn't require them to be black holes.

MrGeezer

No, that is not what I'm saying at all. I'm saying that normally gravitational force on your body from a source is approximately equal among your entire body. It doesn't matter how big that force is. The key point is what the DISTANCE is of the mass that is exerting that force on you.

I'm sorry, but I have to ask this: Have you ever even done any problems (like say, in a physics class) involving the Law of Universal Gravitation?

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.

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.

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

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.

Actually I think you would collapse into yourself, the center of earth is where everything is pulled together, so I think there is a tremendous inward force, I would not try it, that and the heat down there. :)harrisi17

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.

MrGeezer

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.

your body would prolly implode due to all the force on it.MarioFanatic

*facepalm*

[QUOTE="MarioFanatic"]your body would prolly implode due to all the force on it.SpaceMoose

*facepalm*

[QUOTE="SpaceMoose"]

No, there would be a net zero gravitational pull on you (well, not exactly of course since the Earth isn't a perfect sphere, but for all practical purposes), and I'm sorrty to say that your physics teacher is rather clueless for someone who is supposed to understand basic physics.

And it wouldn't even really matter where you were. The gravitational force is going to be approximately the same and in approximately the same direction on your entire body in any sort of realistic scenario (like pretty much any that doesn't involve multiple black holes very close to you), just as it is on the surface.

West-Coast-G

Well, first off, no matter where you are on earth I would imagine that the pull would never get greater than 1G. Miners have dug for miles and miles straight down into the earth to no consquence, and while you have a good question its not the first time its been asked...I am sure someone with a gravity meter has gone to the deepest point on earth to measure the grvity and it read the same as it did on the surface. If surface gravity is 1.0, and lets say the persons g-meter at 5 miles underground read 1.00001, then your question might have merit.

Dammit, a Physics discussion and I arrived too late. :(

Dammit, a Physics discussion and I arrived too late. :(

Oleg_Huzwog