42
 

Douglas Adams knew what he was talking about when he said the answer was 42:

That is awesome. Douglas Adams was years ahead of his time!

He knew what he was talking about, but I'm pretty sure others knew that before he did.

For example, from wiki's info on "gravity train": "...In the 17th century, British scientist Robert Hooke presented the idea of an object accelerating inside a planet in a letter to Isaac Newton. A gravity train project was seriously presented to the Paris Academy of Sciences in the 19th century. The idea was rediscovered in the 1960s when physicist Paul Cooper published a paper in the American Journal of Physics suggesting that gravity trains be considered for a future transportation project..." Several of these concepts worked out the 42min time from the fact that the time only depends on the density of the earth and the gravitational constant. E.g.: http://www.math.purdue.edu/~eremenko/dvi/gravsol.pdf

Hmmm. Thanks for blowing my mind, sion.

I wonder what benny lava would say about this.

This concept and what would happen if a tunnel would be dug through the earth and elephant dropped in was one of the questions in a children's book of puzzles I got in first grade (book published in...'70-something I believe).

Any any case, I love that first guy that talks in the video. Whenever he's on the show (and he's been in many History channel shows dealing with space and physics), he's ALWAYS smiling. Now there's a person who loves what he does.

Hah. Nice, always great to see a 42 somewhere. It's all connected, man.
But I don't think intra earth travel could ever work. Imagine being in one of these "gravity trains" while an earthquake happens.

shame about conservation of energy and irreversabilities. it will theoretically never work.