Levitron

The Levitron is another in the long line of Sean's office toys. The one pictured above isn't actually the one I have, but given that I got it in 1997 that's not surprising.

Anyways, this guy is a lot of fun. Strong magnets are built into the base and the top; you can optimize the weight of the top by adding or removing little washer-type discs. Basically, the magnets repel each other and by spinning the top perfectly you can create a stable state in which the top floats, spinning, in mid air. With so little friction to slow it down, once you get it going the Levitron will spin along happily for quite awhile.

Getting it going, however, is quite a trick (or at least it was with mine, which unlike the new version didn't have a "spinner" to get it started). You had to give it enough oomph to keep it balanced, but also do it very steadily so you didn't introduce any wobble. The base had to be pretty close to perfectly level and the weight of the top was key.

People spent hours trying to get it working; after a lot of practice I generally could do it in a couple of tries. It's been a long time, though --- I may have lost my edge.