Why was Ptolemy s Earth-centered system of epicycles taught throughout Europe for over a thousand years?
1 Answer
The prior fundamental assumptions that Earth was as the center of the Universe and that planetary orbits must be perfect circles had that strong of a cultural inertia.
Explanation:
As far back (at least) as Aristotle, two fundamental assumptions about planetary orbits were that (1) Earth was clearly at the center of the Universe with all other bodies rotating around it and (2) all orbital paths were perfect circles. A great deal of cultural inertia kept these fundamental assumptions in place for centuries, along with strong discouragement by the Church (which especially insisted on an Earth-at-the-center model) against any contradictions.
Many experimented with other structural models (e.g., Brahe's model of the Sun revolving around Earth and all other planets around the Sun) that led to simplifications of the orbital geometries.
But it wasn't until Kepler explicitly demonstrated that all existing models produced complex and weird planetary-path behaviors that he started experimenting with models using other conic-section shapes than just circles. He eventually found that many of the complexities and issues of the epicycles model simply disappeared if one assumed that planetary motion was in the shape of an ellipse with the center-point (such as the Sun) at one of the foci.
Some pretty good discussion of this progression (in much more detail than this) can be found here.
As odd as it seems in retrospect, that no one thought to try something other than circles (on circles on circles) for hundreds of years, it could be seen as a classic example of the sort of inertia that a given scientific model, however arguably cumbersome, can acquire over time, making it something of a box that becomes very difficult to notice is there, much less think outside of.
One could say that today's perturbation theory approach to quantum mechanics mathematics (which can grow extremely complex) suffers from a very similar problem to the old epicycle models, and it may be years or decades (or more) before someone finally discovers its mathematical equivalent of the ellipse.
