The Greek philosopher, Anaxagoras, stated around 450 BC that "the sun is a red-hot mass of metal." Too bad he didn't know about gases, but otherwise very near the truth. We may not think this revolutionary, but for Athenians the sun was a god, Helios, and Anaxagoras' observation was the equivalent of atheism to them. He even wrote a book called The Sun-God Delusion and had his own blog.