The Tropic of Capricorn wears an outdated label. At the December solstice, the Sun appears against Sagittarius, not Capricornus, the constellation that gave the latitude its name. The mismatch is no mistake. It is a record of a slowly changing sky and a name that stayed put.The culprit is axial precession, a stately wobble in the orientation of Earth's rotation axis. As that axis shifts, the posit...More