Long before telescopes, Greek scientists such as Aristotle (384–322 B.C.) and Ptolemy (A.D. 100–165) argued that the Sun traveled around Earth.
This seemed so obvious to most people that few questioned it. Then, in 1543, Polish astronomer Nicolaus Copernicus proposed the theory that Earth actually traveled around the Sun. This set off a decades-long effort to find out if Copernicus was right or wrong. The telescope became key to finding the answer. Telescopes have since become more sophisticated, expanding our knowledge beyond Copernicus’s dreams.
