We usually measure the time it takes for a planet in our solar system to orbit the sun in months and years. But given the compact scale of this desktop solar system, the anodised aluminium balls can instead be used to measure seconds, minutes and hours.
The balls appear to magically circle the central gold sphere without any apparent forces acting upon them. But like with our own solar system, it's what you don't see that's keeping everything running. Inside the $US33 clock's housing is a set of moving magnets that drag the balls around on the surface. However, also like with our own solar system, knowing the secret doesn't make it seem any less magical. [Red5 via Fancy]