[TeMPOraL]

> Think on it in a different way, most of the very revolutionary theories, those that changed how we see the world, were relatively more simple, they were generally simple enough that one fringe could develop them to a point where they shined so brightly as to be next to irrefutable. Things like how the earth might be round, and circle the sun.

Intresting trivia: heliocentrism didn't show "shining brightly as to be next to irrefutable" - it was a fringe idea that could not be confirmed through observation at the time, required some pretty wild (for the time) assumptions - such as stars being very, very far away, to explain why there's no visible parallax from Earth's movements - and went against existing understanding of physics in general (such as, Earth is very big and heavy and bulky, so it's not obvious how could it be moving in circles very fast). Also, IIRC, the predictions made by heliocentric model were less accurate than geocentric ones.

It took astronomical observations with early telescopes to provide data points favoring a mixed geo/heliocentric model, and then further observations, work of Kepler and Newton's theory of gravity for heliocentric model to finally start making sense.

This does serve as an example backing TFA's thesis: some accepted theories, like (then) geocentric model, may be just local maxima - theoretical dead ends. A potential better theory will initially look bad in comparison, it needs work to develop past the accepted one.

[KineticLensman]

> Also, IIRC, the predictions made by heliocentric model were less accurate than geocentric ones

> work of Kepler

Yes. One problem of the early Copernican heliocentric model was that it stated that the orbits of planets around the sun were perfect circles. It wasn't until Kepler showed that a) the orbits were actually elliptical and b) the planets speeded up when they approached the sun and slowed down as they moved away that the actual movements of the planets could be more accurately predicted. Until this time, the older earth-centric models with all of the epicycles were 'better', even though totally unrelated to reality.

[avereveard]

one important point is that ground observations include mars moving backward fairly often. it took a while to formulate a movement form that satisfied that constraint better than epicycles

[KineticLensman]

Yes. This is one example of the fact that the Earth 'laps' the outer planets because it has a faster orbit. So the outer planets sometimes appear to go backward with respect to a fixed point such as a star as the Earth undertakes them. They also can move up and down with respect to that fixed point because their orbits are tilted somewhat compared with the Earth's orbital plane around the sun. The overall effect is that the outer planets sometimes trace out a little spiral, and the further they are from the sun, the more these spirals dominate their overall motion (because we are lapping them more often).

Obviously it's different for Mercury and Venus, whose orbits are inside ours. They instead switch between being visible in the morning or the evening.

All very complicated for those ancient astronomers!

[Patient0]

right on thanks for making this point - "Also, IIRC, the predictions made by heliocentric model were less accurate than geocentric ones." - that was my recollection also: the epi-cycles had greater predictive power and accuracy.