Wednesday, 19 October 2011

And Yet It Moves! Part II

This is the second post dealing with Galileo and the shift from geo-centrism to helio-centrism. Click here for the first post.
Copernicus had completed most of his calculations and his work was nearly ready to be published. But Copernicus delayed. One might assume, looking backwards at history with our modern notions, that he was concerned about religious persecution by the Catholic authorities but in actual fact, the papacy were very interested in the document and the cardinals wrote to Copernicus urging him to publish. The main religious opposition came from the Protestant side, with both Luther and Melanchthon (Luther’s most notable pupil and a crucial figure in the history of Lutheranism) writing against helio-centrism. But Copernicus was well beyond the reach of any Protestant authorities. So why did he not publish?

            As usual, we can’t really be sure, but it would seem that Copernicus was unhappy with his own ideas. He didn’t have any decent proofs of his own work that would stand up to scientific scrutiny, and as he was not using any advanced scientific equipment, even by the standards of the day, he was unlikely to find any. If he published a work without proof he would have to defend it to the world and he may not have felt equal to the task. His pupil, Rheticus, took it upon himself to publish the book while Copernicus was on his deathbed and the great secret that everyone already knew, was out.

The Copernican Model
            Copernicus’ work provoked a great deal of debate in Europe, but did not produce a scientific revolution per se. Astronomers, scientists and theologians all agreed that it was an interesting concept but many disliked the idea and most withheld judgement about it. This was not because the intelligentsia of the time were necessarily bound to tradition but because Copernicus’ theory was just, well, a theory. It was a theory without proof, a model of how the heavens moved. The problem was that, while it simplified some of the equations and provided a decent model for celestial movements, it suffered from many of the same defects as the Ptolemaic model.

            Copernicus had represented the Sun as being in the centre of the Universe around which the planets moved in perfectly circular orbits. From this one could work out the positions in which the planets should appear in the night sky. After all, this was in an age when space exploration was undreamt of and the night sky was all that the astronomers had to go on. And the helio-centric theory was wrong. Interestingly, the word planet derives from the Greek word for “wanderer” due to their unusual tracks in the sky. The planetary positions did not fit at all and Copernicus had to introduce epicycles to try and make it work. But even with these, the orbit of Mars meandered aimlessly and until a theory could be found to reconcile these anomalies, the thinkers of Europe withheld judgement. Copernicus was now passed away and now the challenge had been laid down to either refine and prove the ideas of Ptolemy or Copernicus or come up with a third theory.

Tycho Brahe

            A Danish scientist called Tycho Brahe took up the challenge. He came up with a theory where the Earth was at the centre of the Universe and the Sun revolved around the Earth but where the planets revolved around the Sun, rather than the Earth in the Ptolemaic sense. This theory had problems as well but Tycho Brahe made an effort to solve them by setting up a small island full of machines and observation towers to map the sky with unparalleled clarity and prove his theory. There is a modern tendency to ignore Tycho Brahe’s work (we now know that he was incorrect) but it should be remembered that Tycho’s measurements were probably the finest measurements ever carried out without the aid of telescopes and large volumes of data were collected with the help of his
Tycho Brahe's Island
assistant, Johannes Kepler. But still the theory didn’t quite work. Tycho Brahe died hoping that his assistant would continue to work on perfecting the Tychonic theory but it was not to be. Kepler became obsessed with the mystical notion of perfect shapes (circles, triangles, etc.) that, if their radii and lengths of sides held a certain proportion, could give the right figures for the orbits of the planets in a Copernican system. This sounds like a pretty silly notion to us, and it is actually nonsense, but it was to have important consequences. 

Kepler's Initial Vision of the Universe
            The political situation of the time was changing. The rapid spread of Lutheranism had pretty much stopped and the second wave of Protestantism (Calvinism) had begun. The Catholic Church had reasserted doctrinal points in the Council of Trent and had begun to combat the spread of Protestantism effectively. The Inquisition in Italy and Spain and the newly founded order of the Jesuits were crucial in this retrenchment of Catholicism. The old haphazard tolerance of the Middle Ages and the Renaissance disappeared as the champions of Reformation and Counter-Reformation kept watch for any deviation from the doctrines of their particular church.

            There are certain passages in the Bible that seem to suggest that the Earth remains in place. When Copernicus’ work was first published no one in the Catholic Church objected to it, but after a few years minor clerics began to question whether Copernicus could be reconciled with Scripture. The Protestants, who had no central authority anyway, became more amenable to the doctrine but it wasn’t considered important enough to really merit discussion from the pulpit. The Catholic Church made no official decision regarding Copernicus and whether his text was heretical but the Inquisition was examining any belief that deviated from the norm and it was possible that helio-centrism might be a cover for heresy. This uneasy situation, where helio-centrism was tolerated but could attract suspicion, lasted for a number of years. 

Galileo Galilei
Meanwhile, an Italian scientist by the name of Galileo Galilei (finally, we get to Galileo) heard of a Dutch invention, which we now refer to as the telescope. Galileo is often credited with the invention of the telescope but in fact he merely refined it. However, he was probably the first person to use it to look at the sky. Galileo discovered the larger moons of Jupiter fairly quickly and became enamoured of the heliocentric theory. If the planets had moons then possibly the earth, which had a moon, was also a planet. At the time philosophers believed (from Aristotle) that the celestial bodies were perfect and almost of a different order of being from earthly objects. Galileo discovered the imperfections on the Moon’s surface and speculated that the heavenly objects were in fact of the same order as the earthly ones.

            These were important discoveries but still very far from proofs. Galileo had become a strident advocate of Copernican theory. Unfortunately this confidence in his ideas was to bring the Church authorities against Galileo and trigger possibly the most famous confrontation of science and faith in history. 

The third post on the subject can be found here.