is a radiometer that is powered by light striking the surface of the leaves
on the spindle inside. The light causes the black surfaces of the panels
to heat up to a higher temperature than the white surfaces. Air molecules
inside the partially evacuated sphere are heated more by the black panels
and "KICK" off the surface with a higher momentum than those molecules
striking the white surface. The difference in the force of the "Kick" causes
the spindle to rotate. It is NOT powered by the momentum of the light photons
as many people mistakenly believe.