The "secret" of how this works was featured at one of the Carnivals of Education last spring. You can read the post here, if you're interested in peeking behind the curtain to know how it works.

http://chriswondra.com/2007/02/2...ers-the-secret/
The Science Goddess | Homepage | 08.22.07 - 1:12 pm | #

i don't get it.
Anonymous | 08.31.07 - 3:23 pm | #