Cool Do At Home Stuff

This is just cool.

Y'all remember some years ago, folks developed thermochromic pigments - chemicals that change color with temperature? The first commercial product marketed with this stuff was the Hypercolor™ line of clothing. This stuff faded off into pop obscurity.

However, some guy has figured out how to incorporate this stuff into Silly Putty, and, as it turns out, you can use this stuff and your household microwave to estimate the speed of light. No kidding.