Why Jesuits Disbelieved Copernicism

Much has been written about how not everyone in the 16th and 17th centuries did not immediately accept heliocentrism. Usually it is implied that only narrow-minded Bible readers or Pope followers would refuse the obvious truth.

A new article on Galileo between Jesuits: The Fault is in the Stars

In the middle of the seventeenth century, André Tacquet, S.J. briefly discussed a scientific argument regarding the structure of a Copernican universe, and commented on Galileo Galilei's discussion of that same argument -- Galileo's discussion in turn being a commentary on a version of the argument by Christoph Scheiner, S.J. The argument was based on observations of the sizes of stars. This exchange involving Galileo and two Jesuits illustrates how through much of the seventeenth century, science -- meaning observations measurements, and calculations -- supported a view of the Copernican universe in which stars were not other suns, but were dim bodies, far larger than the sun. Johannes Kepler emphasized this, especially in arguing against Giordano Bruno. Jesuit astronomers like Tacquet and Scheiner understood this. Those who might have listened to Jesuit astronomers would likewise have understood this -- Robert Bellarmine, for example, whose role in the debate over Copernicanism is well known. To many, such a universe was, in the words of Galileo's Dialogue character Sagredo, "beyond belief," and no modern view of a universe of many distant suns would be scientifically supportable until after Tacquet's death in 1660. The Copernican universe of the seventeenth century looked radically different from the universe as modern astronomers understand it, and recognizing this fact allows for interesting questions to be asked regarding the actions of those, such as Bellarmine, who were responding to the work of Copernicus.

The main point here is that astronomers of the day thought that they could measure the apparent size of stars, and found them to be 1/15 the apparent size of the Moon. With better telescopes they got better estimates, but they still got apparent sizes that were much too large. There was an optical effect that made stars seem larger than they were, and the effect was not understood until centuries later.

The Jesuits were skeptical of Copernicism because it required stars to be ridiculously far and large. These were legitimate scientific objections. We now know that the stars really are far away, but they are not nearly so large as the theory of the day required.

Other objections included the lax of observed stellar parallax and Coriolis force. These were only seen centuries later.

Galileo had other arguments for heliocentrism, such as the moons of Jupiter and the phases of Venus. But as this paper notes, Tycho's geocentric model explained those just fine. And Galileops biggest argument was based on the tides, and that was completely bogus.

Merry Christmas.

Update: Leftist-atheist-evolutionist Jerry Coyne disagrees with this essay that argues that the Church was siding with the scientific consensus.

The Pope was a better scientist than Galileo, for he realized that there were arguments against Galileo’s hypothesis, and he just wanted Galileo to do good science and not assert he had “proof” of heliocentrism. ...

In taking this position, the pope was standing in a long tradition in natural philosophy that maintained that the job of astronomers was not to determine what the world was physically like but only to provide useful models for predicting the motions of planets. Stated charitably, the pope was instructing Galileo not to go beyond his evidence.

I would not say that the Pope was a better scientist, but the Church was looking for proof of heliocentrism, and Galileo did not have arguments good enough to convince most of the leading astronomers of the day.

Coyne wrote a book on Faith Versus Fact, so he overdramatizes conflict between religion and science. He says that unscientific creationism is driven almost entirely by religion. That may be true, but as a comment points out, there are lots of other unscientific ideas presented as science, such as the simulation hypothesis, and they are not driven by religion.

Coyne's targets for creationism are Evangelical Prostentants and Moslems, not Catholic. His main gripe with Catholics is the trial of Galileo 400 years ago.