ABSTRACT
An explanation of spin-orbit coupling given to a 14-year-oldgirl [Marianne Mayer] on New Year's morning at about 5:00 am, at the end of a long, long party: 'Last night you danced a waltz. Now, the traffic of the ballroom goes around and around the room, and that is the orbit. In addition, each couple rotates about its own axis, and that is the spin. Everybody who has ever danced a fast Viennese waltz knows that it is much easier to spin the same way around as the orbit than the opposite way around. That is spin-orbit coupling.'
