A lot of Corner readers may already know these things, but Stephen Barr’s review of Owen Gingerich’s God’s Planet contained a lot I had not known.

The idea then current was that astronomy is a branch of mathematics devoted to calculating where and when things appear in the sky, whereas it was the job of “philosophy” (as science was then called) to explain the nature and causes of things. It is telling that the great astronomers Tycho Brahe and Johannes Kepler held the title of “Imperial Mathematician” in Prague, whereas Galileo, when accepting a position at the Medici court, insisted his title be “Mathematician and Philosopher to the Grand Duke.” Boundaries between the disciplines were differently drawn and highly permeable. So too with science and theology. Astronomers on all sides made scriptural and theological arguments to support their ideas. Kepler saw Trinitarian symbolism in the relation of the sun and planets. And Newton invoked divine intervention—in a scientific treatise—to explain the stability of the solar system.
Copernicus was led to his new system partly by aesthetics. He regarded a feature of the Ptolemaic system called “the equant” as ugly and artificial. And the way that system explained certain aspects of planetary motion was ad hoc. Moreover, some beautiful patterns emerged if one assumed the sun was at the center: For example, the speeds of the various planets became correlated in a simple way with their distance from the sun. As late as 1674, the English scientist Robert Hooke noted that the strongest and “better reasoned grounds” for embracing the Copernican system were its “proportion and harmony.” . . .