5 Shuttle Trammel of Archimedes

Rotating counterweighted globe sealed within a clear liquid filled acrylic sphere. The rotation is powered by light that shines through the semi-transparent Jupiter globe on to solar cells within the globe which drive a motor. But what does the motor push against to maintain the rotation? Believe it or not it uses magnets to push against the Earth's magnetic field like a compass needle. Wonderful physics of all kinds in the design of this clever device