Four Lights by Jupiter Kept Rearranging Every Night — and Ended an Earth-Centered Universe
In the winter of 1610, Galileo spotted four tiny points of light next to Jupiter, and their arrangement kept shifting from one night to the next. It was the first evidence that something other than Earth could have objects orbiting it, and a few weeks of notes toppled a 2,000-year-old assumption about the shape of the universe. You can still see those same four points next to Jupiter through a pair of binoculars.