Obviously, the Earth revolves around the Sun. This is obvious now in part because we—maybe not me or you, but someone—can go to space, and see it happening. The trouble is that is was not at all obvious in 1543. Nicolaus Copernicus died in 1543: he lived just long enough to see the publication of his magnum opus, On the Revolutions of the Heavenly Spheres. It is said that he held a copy of it on his death bed.