Video narration
Have you watched another vehicle seem to slide backward as yours moves forward? Copernicus, born in Poland in 1473, had church and administrative duties, but kept studying the sky. The trouble was, astronomers' explanations didn't fit together. Each part seemed right, but the whole picture was a mess. Then Copernicus reread ancient Greek thinkers, some of whom had suggested that Earth moved. His observations encouraged him to test that idea. Then came the turn: Earth itself was moving. From that starting point, the planets' paths could fit one explanation. Instead of a still Earth at the universe's center, he proposed that Earth spins each day and travels around the Sun. That change in perspective became known as the Copernican revolution: a whole new way to see our place in the universe. So what was moving? Earth: spinning on itself and traveling around the Sun.