When I read about the sound barrier I got lost in the amount of things that can be learned.

One being that it isn't just a simple thing speed up an airplane to faster than we have before. They have different designs because the air acts differently as the speed changes and doesn't function the same. Seeing how the shape (overall but especially the nose) changes for each type is pretty cool.

A lot of the articles get linked off here if you have an interest: http://en.wikipedia.org/wiki/Hypersonic