Who knew there was such a big market for levitating globes? This one isn't nearly as cool though since it needs a top and bottom magnet.
A magnetic field sensor continually measures the height at which the globes are suspended. This sensor feeds that data into a micro computer in the base of the unit. This computer then calibrates the electronic magnets at the top of the frame based on the distance between the globes and the top magnet to keep the globes correctly positioned.
There's a 4" and 8" version which sell for $39.99 and $74.99 respectively. Or a 443,520" version which I'm selling for $1 million. It floats in space and circles the sun and doesn't even need a stupid magnet.
Product Page [Think Geek]