Gravity Express Train

The answer is: 42!

Ok, this is really trippy. A 17th century thought experiment from Sir Isaac Newton and British scientist Robert Hooke:

High speed bullet train from New York to Tokyo.
Travel time: 42 minutes (if you don't melt first)

Imagine you could tunnel through the earth from one point to another, straight through the center of the earth. In theory, if you rode a train into the hole at one end, it would free-fall at incredible speed until it passed the center point, at which time gravity would pull in reverse and gradually slow the train to a stop right at the destination point - not accounting for friction, of course. Crazy.

But here's the really intriguing part: no matter how long the tunnel is, or where the tunnel goes, whether it's right though the center, or just cutting a chord through part of the earth, the trip time will always be exactly the same - 42 minutes, 12 seconds. How come?

See here: http://www.damninteresting.com/?p=696#more-696

Sound like b.s.? See here as well: http://en.wikipedia.org/wiki/Gravity_train