Let’s say we’ve got a hole through the earth and it goes from pole to pole. There’s also no air – otherwise you’d reach terminal velocity quickly because of air resistance. Also, assuming the earth has the same density everywhere and is perfectly spherical, you jumped in right into the hole. So how long would would it take for you to reach the other side of the hole?

### THIS IS COOL. I WANT TO LEARN SOMETHING ELSE, TOO!

Video via – MinutePhysics
Further Readings And References @ Hyper Physics, Shell Theorem (Wikipedia)