Almost every planet in the solar system rotates in the same direction it orbits the Sun—except Venus. It spins backward, and no one knows exactly why. One theory is that a massive collision long ago flipped it over. Another idea suggests that atmospheric tides, caused by its thick clouds, gradually slowed and reversed its rotation. Whatever the cause, a Venusian day lasts longer than its year, and if you could stand on the surface (which you can’t, because it’s hellishly hot and crushing), you’d see the Sun rise in the west and set in the east.