Today’s download is based on a series of posts on the “hole through the middle of the Earth”, which by devious means has been tied in with the solution of differential equations, buckling of columns, and a story by Bill Baily about when not to offer to buy the first round.

Elegant solutions, Simple Harmonic Motion, and the hole through the middle of the Earth
Elegant solutions, Column buckling, and the hole through the middle of the Earth
More on buckling columns
The hole through the middle of the Earth – acceleration
The hole through the middle of the Earth – revised transit time 
The hole through the middle of the Earth – moved to the Equator
Three blokes go into a pub …
The hole through the middle of the Earth – filled with air

… and for anyone making it to the end and wondering where the next episode is, it hasn’t been written yet.

Here are the download files:

http://interactiveds.com.au/software/Earth%20Density.xls
http://interactiveds.com.au/software/ODESolver-Buckle.zip

And the “three blokes” joke:

Three blokes go into a bar