Blessed is the 23.5° tilt of Earth’s axis. Without it there would be no seasons. How fun would that be? All the solar system’s planets spin on tilted axes, but none so much as Uranus, which nods 98°, a smidge past sideways. Scientists have always wondered how Uranus got tilted so much that it spins on its side; new research on the planet’s early formation points to a major collision that literally knocked the planet over. Four billion years ago, scientists believe a young proto-planet of rock and ice collided with Uranus, causing its extreme tilt. Instead of rotating like a top spinning nearly upright, as Earth does, the planet “rolls” on its side as it circles the sun.