Wednesday, October 9, 2013

The Conservatism of Copernicus

The work of Nicholas Copernicus is perhaps more interesting for what it omits than for what it actually says. Copernicus has been portrayed as a great scientific reformer against the dogmas of the Church. The Bible seemed to suggest that the Earth was at the center of the universe. Aristotle provided a sophisticated way of conceptualizing how this might appear from a God's-eye-view of things. Copernicus is thought to have inaugurated the modern scientific enterprise with his attack on geocentric accounts of celestial motion. While he lived, Europeans still believed that the moon, sun, planets, and stars all revolved around the earth; but a century and a half after his death, most educated Europeans accepted that the sun was the center of the solar system, the planets orbited the sun.

Copernicus cuts an ambiguous figure against this historical backdrop. He did not do his work like we would expect most scientists do their work. In the ample spare time a gentleman of means had at his disposal, Copernicus collected observational data about the position of objects in night sky. But his contributions, in this regard, were paltry at best. The truly creative work Copernicus did was to rethink old tables of information. In an Aristotelian cosmos, the celestial bodies like moon, sun, and the wanders, or planets, were thought to travel in perfectly circular orbits. Anyone watching the sky night after night would, of course, happen upon the observable reality that planetary orbits are anything but circular, most obviously with the phenomenon of retrograde motion. For Aristotle's successors, including the great Ptolemy, the ultimate purpose of astronomical observation was to develop a theoretical account that 'saved the appearances' in such a way the assumption of perfectly circular orbits held good. With the data available to him, Copernicus realized that there was a simpler way to save the appearances, which didn't involve jumping as many hurdles as Ptolemy had to jump. Put the sun in the center and have the planets and earth revolve around the sun in perfectly circular orbits.

Nor is the transition from a geocentric to a heliocentric description of the solar system, for which Copernicus is responsible, the most important impetus towards a modern scientific methodology. Far more important was the work of Galileo Galilee and Isaac Newton, who reworked how the nature of motion of understood--this irrespective of whether we are talking about the perfectly circular motion of the sun or moon or the imperfect linear motion of an arrow shot from a bow or an apple that falls from a tree (onto Newton's head). In an Aristotelian universe, an object fell to the ground when dropped because that was the direction of the center of the earth--indeed, of the universe--towards which all heavy things tended.But ff the earth is no longer at the center of the universe, the central tenet of Aristotelian physics loses its justification: that all terrestrial objects tend towards their natural place of rest (heavy objects downward towards the center of the universe, airy objects upwards away from the center of the universe).