Editor's note: This story was originally posted 19 Feb 2013, but it's now graduated and become part of Astronomy 101! Please be aware that any references to events that seem current may not actually reflect events happening right now.
As you may have noticed from today's beautiful Google Doodle, today is the 540th birthday of Polish astronomer Nicolaus Copernicus. I don't do a lot of history on this blog, but Copernicus is such a curious case in the history of science that I have to give him a mention. He's best known, of course, for his theory of heliocentrism, the idea that the Sun, not the Earth, is at the center of the Universe. But his was not the first heliocentric theory, and it took refinements from Johannas Kepler, observations from Galileo Galilei, and theory from Issac Newton before it began to be accepted. Tycho Brahe, history's greatest naked-eye astronomer, rejected it on both physical and theological grounds. So why do we remember Copernicus?
Despite his theory's flaws, Copernicus was the first modern person to fully articulate the features of such system. Although there is strong evidence that some among the ancient Greeks supported a heliocentric model, no works from antiquity have survived explaining the mechanism. Published from his deathbed, On the Revolutions of the Heavenly Spheres was the first written work to explain the idea and use it to solve problems in astronomy, such as the peculiar motion of Mars.
Acceptance of these notions was hindered by the lack of a physical explanation for how the planets could move in such a way. It would be over one hundred years before the law of gravity was discovered by Newton, who included heliocentrism as part of the foundation of modern physics.
Today, Copernicus is remembered as one of the catalysts for the scientific revolution, a movement to more precisely understand the natural world which reached its pinnacle with Newton's work to lay the foundation of physics and the scientific method. His basic tenant, that Earth was not at the center of the world, is now immortalized in the Copernican Principle, one of the fundamental axioms of modern science. The principle states that we should never assume humanity has a privileged position in nature: the Earth isn't the center of the solar system, which isn't the center of the galaxy, which is just one among billions in the Universe. So, does this mean that we live in only one of innumerable universes? We don't yet know - but I'd like to think that Copernicus would say yes.