I am currently reading Paolo Rossi’s The Birth of Modern Science [available here]. The chapter on Copernicus discusses his De Revolutionibus Orbium Coelestium from 1543, which is today seen as the revolutionary work that established the heliocentric system and forever removed the earth from the center of the universe. Rossi however demonstrates how un-revolutionary Copernicus’ work in fact was, not only in terms of style and format – which were based entirely on Ptolemy’s Almagest from 1400 years earlier, but also in terms of argumentation. Virtually all of Copernicus’s arguments existed in one form or another before him, and some of them were in fact Ptolemy’s – most important of all being the argument on the uniform and regular circular motion of heavenly bodies. Fascinatingly, Copernicus argued that his work is important because it explains Ptolemean astronomy better than its author did – and the concept of circular motion across heavenly spheres was crucial for that. Apparently Johannes Kepler commented that Copernicus had interpreted Ptolemy rather than nature when he wrote his treatise (deducing from authority was a very Medieval approach to science, and the fact that the greatest scientific achievement of the Renaissance was achieved in that way is a damning comment on the notion of the Renaissance as a negation of scholasticism).
Copernicus never went as far as Giordano Bruno and suggest an infinite universe, populated by bodies in irregular motion. Rather, the revolutionary aspect of Copernicus’s work was in using the very same facts as everyone else, to propose a previously unsought direction disguised as an improvement on the dogma. It’s hard to get more unintentionally subversive than that. From the perspective of scientific advancement, the fascinating observation here is that a revolutionary jump was achieved thanks to a proposal asking many more questions than it could answer, rather than delivering a coherent theory to substitute the previous one. For example, Copernicus’s position on the earth’s rotation led directly to the need to explain gravity (now that the earth was not the center of a spherical universe), which in turn led to Newton.
This realization is interesting, because it questions, as so many other examples, the image of science as a monolithic coherent discipline engaged in an ever-forward progress. The move, if there is any move at all, is never forward, but more sideways-backwards-sideways until a new way to question the obvious emerges somewhere on the periphery.
Of course, it never hurts to ruffle a few feathers in the process – apparently Martin Luther fumed against ‘that fool astronomer who claims that the earth moves’.