talkmagic.co.uk

pcwells wrote:spherical lump of bone and gelatinous goo.

Sounds like a British Railways pie.....

Don't forget to say hi to Doug McLure once you're down there.....

Ok, here's the list of assumptions:

Assuming the earth is perfectly spherical,
Assuming it is comprised entirely of the same material,
Assuming it has a regular density throughout,
Assuming you wouldn't die of heat/pressure/starvation/dinosaur attacks
Assuming you dug straight down into the exact centre of the earth

Once you hit the middle you'd be weightless, as the gravitational pull from all around you would balance out. Then, as you went past the middle, it would start to feel like you were digging upwards, as gravity would be pulling you back towards the centre, as this point is the centre of gravity of the earth.

Importantly, gravity doesn't propegate out from the centre of the planet like some big ol' magnet (of course, the earth's magnetic field DOES, but that's another matter entirely), gravity comes from every piece of matter in existence, and all these little gravitational pulls eventually add up to pull you towards the middle.