one more question

First, I assume you know that we can't really dig a hole all the way through the earth! Also for our test we will have to stop the spinning of the earth so that our object doesn't hit the side of the tunnel! But if we could do that.... Let's suppose we stood over the hole and dropped a ball from shoulder height. The ball would fall faster and faster as it falls because gravity keeps pulling on it. When it gets to the center of the earth, it is falling very fast. There is nothing to stop it so it keeps falling, except now the pull of gravity is in the other direction. So it starts slowing down. If there were no air in our tunnel to slow the ball down, the ball would pass all the way through the earth and come out the other side. It would stop at about shoulder height, then start falling back down the tunnel. It could keep doing this forever. If this seems strange, think about the moon. It has been "falling" in orbit around the earth for billions of years!

You would fall down towards the centre of the earth.