Schlieren!

Forgive me while I post a Wikipedia article that I thought was cool...

Schlieren (from German; singular "schliere") are optical inhomogeneities in transparent material not visible to the human eye. Schlieren physics developed out of the need to produce high-quality lenses void of these inhomogeneities. These inhomogeneities are localized differences in optical path length that cause light deviation. This light deviation is converted to shadow in a schlieren system.

Why yes, my birthday is coming up!

http://www.treehugger.com/files/2008/08/born-in-september-charity.php

Wow. Just wow.

I wish I found this link two days ago.

Turns out some AA batteries are filled with smaller, more useful (in some situations) button batteries