The Rise of Copernicanism

Aristotle had placed the Earth at the centre of the universe, not because it was the most important place, but because it was the coldest, most impure place in the cosmos and it would therefore fall as far as it could - to the centre. The celestial bodies were made out of a very pure and perfect element and travelled on the surface of spheres, the most perfect geometric shape.

The mediaeval Church adopted this system, and for Christians the Earth was central as being of the place of the cosmos’ salvation. Not surprisingly astronomical observation of the planets fitted only erratically with this Earth-centred (geocentric) scheme and complicated explanations were devised to overcome these anomalies. These were refinements on Ptolemy’s system (2nd Century CE). In the 1530s the Polish mathematician Nicolaus Copernicus began to challenge the Ptolemaic model and suggest a sun-centred (heliocentric) model; this was only published as Copernicus was dying (in his great book De Revolutionibus of 1543).

There followed a period of what T.S.Kuhn has called ‘paradigm shift,’ a crisis in the (newly developing) scientific community, in which two radically different models were in competition.Nor was it clear that Copernicus was right - his circular orbits gave no better fit than its best geocentric competitor - that of the Imperial mathematician Tycho Brahe. (See Tycho’s system.) This is because the planetary orbits are in fact ellipses, a model first proposed by Johannes Kepler (1571-1630), who was one of the very few thinkers other than Galileo to adopt Copernicanism before 1600.

A key element in the crisis between heliocentrism and geocentrism was the career of Galileo Galilei.

Email link | Feedback | Contributed by: Dr. Christopher Southgate
Source: God, Humanity and the Cosmos  (T&T Clark, 1999)