(This is Part 4 in a series on the history behind the story of Galileo’s persecution by the church. Here are the links for Part One, Part Two, and Part Three.You can download the whole article the series is based on here.)
So far in this series we’ve looked, generally, at some of the factors that led to Galileo’s famous clash with the church in 1616. In particular, we’ve seen that the issue was more complex than simply being a case of “Christianity” opposing “Science.” Today, we’ll continue with Kirsten Birkett’s article to see the system of thought that the scientific establishment held. It was this system of thought, this paradigm adhered to by the scholars of the day, that made the ideas put forward by Copernicus and Galileo so hard to accept:
There is a deep and important reason why Copernican theory was not convincing as a new scientific theory. It had no physics to back it up. It is all very well to hypothesize that the Earth moves around the sun—and certain astronomical observations might thereby be better accounted for—but what makes the Earth move? Copernicus had no answers. He had no laws of motion, and no theory of gravity (that was to come two centuries later, when Isaac Newton finally came up with his basic laws of physics). At the time, the only known physics was Aristotelian.
According to Aristotle, ‘earth’—regarded as an element in itself—does not fall ‘down’ but is attracted by nature to the centre of the universe. That is why the Earth is at the centre; it is the place where matter naturally congregates. The heavenly bodies—suns, planets, stars—are of an entirely different kind of matter, whose nature is to move in circles and is not attracted to the centre of the universe._ In such a physics there is no place for a moving Earth. The moving planets were, by definition, not Earth. Copernicus’ theory did not fit into Aristotelian physics, and he did not have a new physics in which to embed a new astronomy. This was a serious lack. It was as if today someone proposed that the moon literally gets bigger and smaller every month—it fits what we see in the sky, but it makes no sense according to what we know about matter and the laws of gravity.
The theory was not worthless, by any means. It had a mathematical elegance that Ptolemaic theory lacked—enough to impress Galileo, who was a very competent mathematician. Without proper physical laws, however, it could not hope to gain widespread acceptance amongst the academic community; in particular, amongst the physicists, or natural philosophers as they were known.
This clash with Aristotelian thought is something we must take seriously. It is hard to imagine now just how immense a challenge Copernican theory was. If it were true, the entire body of received knowledge about physics—laws of motion, theories of matter, the most fundamental ideas about what the universe is made of and why it behaves the way it does—would have to change. When Galileo began championing Copernican theory, he was not merely suggesting an interesting new technical piece of astronomy. He was, implicitly at first and later explicitly, challenging centuries of accepted knowledge.
Aristotle’s system of knowledge was remarkably satisfying and complete. He was regarded as having solved essentially all the problems of the physical universe._ Aristotle’s laws worked, they explained everything, and civilized humanity had recognized that for centuries. If there was to be any differing opinion, it could perhaps come from those who preferred Plato to Aristotle; but that an astronomer could come up with an entirely new theory was ridiculous, and that Galileo would actually defend such a theory and teach it to his students was very worrying. It was quite natural that his fellow academics opposed him. It was, after all, the duty of established scholars to protect the young from dangerous ideas.
It is often quoted as a laughable example of blind dogmatism that some Aristotelian scholars refused to look through Galileo’s telescope to see the moons of Jupiter. They insisted that even if they saw something, it must be a trick, and so refused even to look. Yet from a scientific point of view they had a point. They knew, from their knowledge of the established body of physics, that there could be no moons of Jupiter. What is more, Galileo was unable to explain satisfactorily how the telescope worked. Yet he expected the philosophers to overturn centuries of knowledge on the basis of this mysterious metal tube. There was some justification in their refusal to play his games. In their eyes it was Galileo who was ridiculous—even pitiable—for thinking he could teach anything to Aristotle.
This is fascinating and helpful. Quite simply, it was not any teaching from the Bible that made scientists (or the church, for that matter) oppose these new theories. It was the scientific theories of Aristotle. And it was the weight of evidence that the academic establishment had built up which seemed to uphold Aristotelian theory. What we’ll see, as we continue, is what a precarious position Christians put themselves in when they hold too tightly to a certain body of scientific knowledge, and even equate it with biblical teaching, and then the theories change.
Next time, however, we’ll get a glimpse at two other factors that led to Galileo’s trouble: politics and personal rivalries…