Bristlebots!

.

When Sean was a little boy, he and I took a cigar box, some powered wheels, a coat hanger and a superball and built a robot with one bit of processing power.  Not byte -- bit.  I was pretty proud of that, and figured that we'd just set a record that would last forever.

I was wrong.

A bristlebot is a robot with zero processing power.  It's made by taping the motor from a pager and a watch battery to the back of a severed toothbrush head.  Let it go and it skitters around randomly.  So far, pure motion, no robotic behavior.

When placed in a confined space, the bristlebots continue to move about randomly.  However, when they take up at least 8 percent of the space's area, swarming behavior emerges.

The above video explains it all.  But if you want to cut to the emergent behavior, skip ahead to 1:27.

*