Air resistance would slow you down so much that you wouldn't get anywhere near China on your first pass, you'd probably just go slightly past (assuming you hadn't already been vaporized by heat, but that's another matter), then "bounced" back and forth, slowing down due to air resistance and friction from bumping into the walls of the tunnel, and eventually ended up stationary in the middle.

rusted - your speed doesn't diminish if gravity gets weaker as you fall, it'd still keep increasing (at a gradually slower RATE, proportional to the gravity pull) *if* there were no air resistance or other obstacles (like the friction from the walls).

Interesting point, though - could you call it a zero gravity zone? I thought at first you'd feel like being ripped apart, since you experience quite powerful gravity from all sides at once, but then again.. that's fallacious thinking, I believe. Each atom in your body is subject to the same pull from all sides, it wouldn't be like your left side were pulled left and vica versa. You'd probably not feel much different from being in space (regarding only the gravity, heh). Except that there wouldn't be a perfect balance of gravity pull to all sides from any point inside the earth, I think. So you might feel more pull/pressure up-down or right-left, depending on which way you were facing.

This is a very good question, and it is one that I have often pondered. I don't really have a thorough handle on physics, but it would seem logical that if gravity attracts smaller object to larger ones that the center of a large sperical objects such as a planet would likely be hollow. The reason I say this is that atoms found at the core would be drawn equally in all directions. As the atoms in the ceter were drawn outward the heaviest elements would be drawn away the strongest and the lighter elements would be left behind. Eventually, the heavier elements would compress to form a sort of hardend crust and the lighter elements would settle to form a sort of inner atmosphere where the lightest of all elements would tend to reside in the very center.

Another interesting aspect of this model is that as the elements are pulled away and the shell of the planet hardens, the outward pressure against the crust may eventually exceed the inward pressure causing the outer crust to crack allowing for the ongoing expansion of the planet.

I know that it goes against conventional thinking, but I suspect that the Earth, like all planets, may in fact be hollow at its core and it may be growing as well. My guess is that there is some naturally occuring process, which we are yet to understand, whereby matter is being produced within the vaccum found at the core of the planet.

I also suspect that there is a natural life cycle to the development and growth of these planets as well. Someday we will have a better understanding of all of this, until then, we can just assume that God made it with his bare hands... :)

Interesting question.
Ignoring the burning molten earth inside parts for a moment: The greater the mass of an object, the stronger the gravity. Wouldn't gravity get weaker toward the center of a mass?

If so, then your falling speed slows down as the center is approached. Therefore the answer to your question appears to be yes, you would stop in the middle because of gravity. Specifically because there is no gravitational force to pull you out.

Is the center of an object a zero gravity place?

This is an interesting question. First of all, let's assume you could bore a hole through the centre. Gravity would draw air into the hole. As the depth increased, the pressure would increase. As you get closer to the magma core, the temperature would increase, causing the air to expand and rise, just as the globs in a plasma lamp do.

To add to this, the pressure of the magma would escape into the hole, creating a volcano.

Jumping into a volcano will cause you to vaporise, and be expelled into the atmosphere.

So, in answer to your question, no, you wont get that far.

Actually, I think you'd be burned to a crisp by the Earth's molten core.

Supposing you could still exist in such an experience, I expect that you'd fall through and come coasting up to China, come to a stop momentarily, and start the return journey, going to and fro for some time until "air resistance" slowed you to reside in the middle of the Earth. Of course, the proposition is highly hypothetical!

i think you'de burn in the middle.

would be fun to find out for sure, we may find water down there instead of lava, compass spinning uncontrollably etc. please let me know when there's an expedition.

actually, i think you'd be burned to a crisp by the earth's MAGMA core

Last I checked the Earths core was made of magma. So I'm guessing you'd get burned.

I think you'd probably burn up in the core, or suffocate from the gases if you made it to the middle.