The stuff you learn on the History Channel! I was amazed to learn that Copernicus was, in fact, not the first serious astronomer to propose that the Earth revolved around the Sun (and not vice-versa). A Greek philosopher named Aristarchus first brought forward the theory, but was shouted down by his contemporaries as his theories ran against the prevailing thoughts of, among others, Aristotle.
A brief web search brings up several pages [1, 2, 3] which reveal that Copernicus himself initially credited Aristarchus in his seminal work but removed the reference just before its printing.
Aristarchus also made many other amazing measurements including rough guesses (within a factor of two in most cases) of the sizes of the Moon, the Sun, and their relative distances to the Earth all in multiples of the Earth's own radius which was unknown at the time. (That the Earth was a sphere was well understood thanks to the first great mathmetician Pythagorus who discovered this fact some three centuries earlier, although the actual radius of the Earth was not known until a hundred years later, measured by the clever Eratosthenes using a well). I can't believe I've never heard of Aristarchus before today; it just goes to show you how bad the dark ages really were for knowledge. We basically had to relearn everything since the Renaissance. Lord knows what other things the ancients knew that we still don't.