Thread: Gravity in The Core of The Planet

So, with no gravity, there would be no pressure, right? If you fell down the elevator shaft would you fall all the way to the center? Or would you slow down until you started floating? Would you fall back up to the halfway point? Like bungee jumping? I always assumed that it was the center of the mass that was the center of gravity. But of course there couldn't be any gravity because there is no more 'down' to fall. Just like at the north pole you can't go in any other direction except south. At the center of the Earth all directions are up.

Interesting. It's weird to think such high pressures could exist at the centre of the Earth where there's no gravity. I suppose this is because the atmosphere above and below you is acting like a heavy cork, keeping the local atmosphere around you squashed in.

Originally Posted by Dannon Oneironaut

So, with no gravity, there would be no pressure, right? If you fell down the elevator shaft would you fall all the way to the center? Or would you slow down until you started floating? Would you fall back up to the halfway point? Like bungee jumping? I always assumed that it was the center of the mass that was the center of gravity. But of course there couldn't be any gravity because there is no more 'down' to fall. Just like at the north pole you can't go in any other direction except south. At the center of the Earth all directions are up.

Yes, that's a good way to think about it ('by symmetry').

If there were no air in the tunnel, you would accelerate towards the centre (to a very large speed), then keep going whilst decelerating, until you came back outside the other side to ground level, and then you would fall back again.

If there were air, air resistance would mean you would only overshoot the centre a tiny bit, and then pretty quickly come to rest at the centre.