(This is Part 3 in a series on the history behind the story of Galileo’s persecution by the church. Click here for Part one and an overview of why we’re discussing this. Click here for Part two.) The historical background to Galileo and his findings is very illuminating. Kristen Birkett explains:
What first becomes obvious in looking at the Galileo events is that the battle was not ‘science’ against an outside foe, Christian or otherwise, so much as old science against new science. It is a battle which has been repeated again and again throughout history. Newtonian physics seemed definite until Einstein came up with a new theory. Heat was explained as an accumulation of phlogiston until thermodynamics was developed. In retrospect, it is easy to pick the winners, but at the time such debates are usually very confusing. There are always more bad guesses than good ones, so how do you tell if the new theory is actually better than the old? Should scientists merely extract the good bits from the new theory and incorporate them into the old? Should the old be overthrown entirely in favor of the new?
Such a competition was played out in the astronomy of the late sixteenth and early seventeenth centuries. The old theory was geocentrism, in which the Earth is at the centre of the universe with planets (including the sun and moon) and stars revolving around it. All physics, dynamics and matter theory back up the cosmology. The new theory was heliocentrism, with the sun at the centre of the universe and the Earth, one of the planets, revolving around it. We, of course, know which theory won. The heroes of the story for twentieth-century viewers have to be those who supported the heliocentric universe. At the beginning of the seventeenth century, however, the geocentric universe looked far more likely—and it was the scientists of the day who thought so.
In 1543, in the last year of his life, a modest Polish astronomer named Nicholas Copernicus published a speculative astronomical theory. It was in a work entitled De revolutionibus orbium coelestium—“The revolution of the heavenly spheres.” It was different from the old Ptolemaic theory, in placing the sun rather than the Earth at the centre of the universe. It was like the old theory in that all the planets moved in circles around the centre.
… Copernicus’ theory was ‘better’ from a scientific point of view, in the sense that it was slightly simpler and explained a few astronomical events more satisfactorily, but it was by no means overwhelmingly convincing.
Why review this technical information? Simply to put the whole debate in context. We speak of ‘The Copernican Revolution’ as a crucial moment in Western history, when Copernicus discovered after centuries of error that in fact the Earth moves around the sun. Yet it was not quite like that. Copernicus’ theory was, from a purely scientific point of view, only marginally better. Of course he was right, but how could people know that at the time? Besides, he was not completely ‘right’—his commitment to circular motion meant that his theory necessarily had problems.
This helps to explain the fairly luke-warm reaction to Copernican theory in the years following his publication. It was not due to church interference, or Christian dogma—the theory was a matter of technical astronomy, and only of real interest to fellow astronomers. On the whole, they were not much impressed. Of those who showed any interest, most merely made use of Copernicus’ improved calculating techniques but ignored or rejected the theory as a new way of understanding the universe. For instance, in England the first clear exposition of Copernican theory was not until 1576, in the only work that century which explicitly endorsed the theory. Even those astronomers who were mildly in favour of Copernicanism were inclined to regard it as an adaptation of the Ptolemaic system, and used a semi-Copernican theory in which the Earth rotated in the centre of the universe.
By 1600 only ten astronomers can be identified who thought Copernicus was right. In other words, Copernican theory was not the great overnight revolution. It was a relatively unsuccessful addition to astronomical knowledge, which the majority of professional astronomers failed to take up. The church decision to reject it in 1616, though in hindsight wrong and made for the wrong reasons, was not at the time so very irrational.
Galileo was not defending the forward march of scientific free thought against reactionary dogmatism; he defended a speculative theory with little corroborating evidence, in opposition to the majority of scholars of the day.
I don’t know about you, but, never having studied this before, I had no idea how controversial, scientifically, the idea of the sun sitting at the center of the solar-system, rather than the earth, was. The first sentence in this passage really sheds light on what was going on: “…the battle was not ‘science’ against an outside foe, Christian or otherwise, so much as old science against new science.” This, for me, has the effect of reminding me that our current scientific knowledge does not belong in the privileged category of “what we know” but in the more dynamic category of “what we think, for now, based on things we see and our best interpretations of them.” In other words, it helps to remember that the history of science is one of process and changing beliefs as new discoveries are made. In the next post we’ll look at the system of thought that made it so hard for people to accept the new evidence Galileo brought forward. Here’s a teaser: it had nothing to do with the bible.