The larger point Kuhn is getting at is that early adoptees of new theories rarely do so "because of any scientific merit", but rather because the new theory appeals to them on a personal or aesthetic level. Novel theories, like those of Copernicus and De Broglie, often do a worse job of explaining the evidence than their established rivals, and early adoptees are essentially making a leap of faith in defiance of the bulk of the evidence. Only through the work of these early, 'irrational' adoptees are the rational reasons for adopting the new theory uncovered.
Well, the sun being the only object in our solar system that emits light is evidence for it being at the center.
It seems likely that there's something special about whichever body is in the center of the solar system. A lot of astronomers thought the Earth was special for being made of rock & water, and that this was related to the Earth being at the center, but they just conjectured that Mars & Venus & the other planets were made of something else. Whereas Kepler had much more direct observations about the sun's unique luminosity.
Aristarchus had a heliocentric model of the solar system in Ancient Greece, apparently motivated in large part by the fact that the sun was the largest object in the solar system.
In hindsight, we know that both luminosity and size relative to neighbors are both highly correlated with being at the center of a solar system, with Aristarchus's size thing having a tighter causal relationship with centrality.
Interesting about Kepler, but it is surely not an example of the "metaphysical foundations" of Burrt's title. (I have not read his book.) "Motivation" would be a more accurate word. Kepler's laws stand on their own, independent of his sun-salutation. Newton later put a foundation under them, and Einstein a deeper foundation.
I didn't read enough of Burtt's book or even the chapter to judge the question, it's possible he treats motivation as foundation, possible this part wasn't a claim about a foundation. I do suspect he isn't using the word "foundation" the way you are. At least, maybe Kepler regarded his theology as of the same type as you're treating Einstein, i.e., foundation is a subjective belief? The things we'd know if we read the book. :P
This is crosspostd from a late-night whimsical Facebook post, maybe should be a shortform post.
Wait wut?
You mean to say that Johannes Kepler adopted the Copernican heliocentric model not because of any scientific merit but because he worshiped the sun like some Egyptian?
I note a lot of references for future potential use, but this is one I had to look up then and there.
Kuhn takes this from E. A. Burrt who applies the term "sun worship" somewhat creatively. Kepler was in fact a devout Christian, not a follower of Ra (too bad, would have been cool). He was deeply motivated by finding simple models that showed had the natural world was simple and united (and thereby mirrored the divine), and that was one motivation for adopting Coperniciasm; however, Burrt says the most potent (and perhaps sufficient) factor for Kepler adopting the theory was the exaltation and dignity it gave to the sun.
In support, Burtt cites a fragment of a disputation that a 22yo Kepler argued in at Tübingen in 1593:
Alright, Burrt, "sun worship" seems fair. Dude was really into the sun.
In addition to his solar-adulations, Kepler was also a very badass mathematician and empiricist, extremely data and precision obsessed. He treated the parabola as the limiting case of ellipse and hyperbola, showed that parallel lines can be regarded as meeting at infinity, applied infinitesimals to volume calculations preparing the way for Newton and Leibniz, and other stuff I don't understand.
He also said badass things like: "without proper experiments, I conclude nothing!" [exclamation added] which I think I might find myself quoting appropriately or not.
Good stuff, Kepler, I'll remember to appreciate the Sun more because of you, and update that people choosing paradigms for non-scientific reasons can still result in tremendously great work.
Sun-worship reacts only, please.
See Also
References
[1] Kuhn, Thomas S., The Structure of Scientific Revolutions (pp. 151-152). University of Chicago Press. Kindle Edition.
[2] Burtt, Edwin A., Metaphysical foundations of modern physical science (p. 59). Dover Publications