Atoms on a Ring: The Way Up
Atoms have been caught in a ring of light. This is not a metaphor: laser beams form a ring-shaped trap in which atoms move in circles. The light not only holds them but also couples the atom's rotation to its internal 'compass'—the spin. As a result, an atom running around the ring senses which way it's going, and this changes its internal state.
This coupling is not just elegant.