Copernicus Proposes the Heliocentric (Sun-Centered) Universe

Nicolaus Copernicus proposed the Sun-centered (heliocentric) Universe in his book “On the Revolutions of the Celestial Spheres”, published literally from his death bed in A.D. 1543.  Copernicus lived in a section of Prussia that spent most of its history as a part of Poland.  Only one of many great contributions Copernicus made in his amazing life, this huge advancement in astronomy isn’t really the simple story we tell ourselves today.  Like most scientific advances, the truth is much more complicated and interesting.

First, the heliocentric idea was put forward as early as 200 B.C. by Aristarchus of Samos, barely 50 years after Aristotle.  But his model, which even correctly ordered the distances to the planets, suggested the stars were extremely distant, and included the idea that the Sun is just the closest of the stars we see in the sky, was not accepted by his peers or those who followed.  Science remained settled – and wrong – for a thousand years.  It’s not enough to be right, it seems.

Second, though a brilliant piece of mathematical reasoning, Copernicus’ model didn’t predict the future positions of the planets as well as the Earth-centered (geocentric) models of his day, and, relying on spheres and epicycles as it did, did not explain why the planets in his model don’t seem to vary in distance from the Earth in a way that was consistent with observations.  Copernicus actually needed more epicycles in his model than in the best geocentric models of his day.

Third, although his editor added a preface saying Copernicus didn’t mean to say the Universe was REALLY centered on the Sun but only to show his mathematical formulation, it seems pretty clear Copernicus actually did believe heliocentrism was the true nature of the Universe, based on philosophical and religious grounds.  Copernicus, in addition to being a brilliant mathematician, economist and astronomer, was a “canon” in the Roman Catholic Church. 

Why does Copernicus get credit for heliocentrism when Aristarchus does not?  Though it took another 80 years (or more) to win the argument, and even then relied on major improvements to win people over, it gained immediate and VERY active support from Galileo as well as direct observational support from Galileo’s telescope.  The biggest problems with Copernicus’s thesis also got tremendous help from Kepler’s elliptical orbit proposal within years of its publication.  So Copernicus quickly found supporters, contributors and corroborating evidence.  That helped give him staying power until others could fill in more of the missing evidence, theory and solutions to remaining problems.