I Didn’t Know That... : Science File / An exploration of issues and trends affecting science, medicine and the environment.

Q: What would happen to a man who fell into a hole through the center of the Earth?

A: Assuming he was not burned to a crisp by the intense heat or crushed by the great pressure, and that there was no friction in the hole, he would oscillate back and forth through the center of the Earth like a pendulum with a period of 42 minutes. That is, 42 minutes after entering the hole, he would emerge on the opposite side of the Earth, and 42 minutes later, he would be back where he started. The time required--based on the fundamental laws of gravity--was first calculated by mathematician Lewis Carroll, author of “Alice in Wonderland,” according to Martin Gardner in “The Annotated Alice.” Carroll also calculated that exactly the same amount of time is required for a person to pass through a straight, frictionless hole connecting any two points on the surface of the Earth, such as Los Angeles and New York.