How Long Would It Take to Fall Through the Earth?

There is a new paper on estimating how long it would take to fall through the Earth that does better than the standard crude approximation. I think this is very cool, and I definitely suggest taking a look at the other side of the link.

And I am again reminded that I should have found a way to take the course "Order of Magnitude Physics" at Caltech when I had a chance. (But, thankfully, I often get to think that way for my research.) I just did some googling, and I found the material from the 1995 and 1997 versions of the class.

But I still have one question: How can I make sure that I take the correct turn at Albuquerque?

(Tip of the cap to Physics Today for their post on Facebook.)