Celestial observations

Part of Copernicus’s genius was to find the radical potential in the ancient authors
Image of Harry Eyres

I’ve been spending the past couple of weeks in the company not of my usual poets, composers and painters but of scientists, or natural philosophers as they were known until the 19th century.

In particular, I’ve been studying the work of some of the great astronomers who turned around our view of humankind’s position in the universe, in the space of about 70 years from 1540 to 1610. That is, from the time of the completion and publication of Copernicus’s treatise On the Revolutions of the Heavenly Spheres to Galileo’s Sidereal Messenger – in which the Tuscan set out his astronomical discoveries, made using the newly invented telescope, including the moons of Jupiter, some of the individual stars in the Milky Way and the nature of the mountains on the Moon.

Even as a non-scientist who failed dismally in the first physics exam I took, and as a pretty average stargazer, I find this one of the most inspiring chapters in human history. It would be taught to every 11- or 12-year-old if I acquired control of the education syllabus.

Part of the inspiration is the breadth and sheer brilliance of these pioneering thinkers. They were polymaths, not narrow specialists, because the institutional structures of narrow specialism had not yet taken hold in the world of knowledge. But even among polymaths, these characters were rather remarkable.

The mild-mannered Nicolaus Copernicus was at various times a Greek scholar, student of canon law, physician, currency reformer (he anticipated by nearly 40 years Gresham’s Law that bad money drives out good) and senior civil servant. His astronomical discoveries, leading to the theory that the Earth revolves around the Sun rather than vice versa, could be considered merely a sideline in his life’s work. Galileo, too, was less concerned with astronomy in the first 40 years of his life, when he laid the foundations of modern physics. (He also played the lute and wrote sonnets.)

But you could also say that the most important discoveries made by these men, and by others such as the eccentric Tycho Brahe (the Dane who kept a tame elk, and lost part of his nose in a duel) and Johannes Kepler, were done by stargazing. It was Copernicus’s observation of the lunar occultation of the bright star Aldebaran with his teacher Domenico Maria Novara in Bologna in March 1497 that eventually led to his rejection of Ptolemaic and Aristotelian geocentrism.

Galileo made profitable use of the newly discovered telescope, grinding his own lenses and making his own instruments. He demonstrated their effectiveness in a great PR coup when, in August 1609, he took the Doge of Venice Antonio Priuli to the top of the bell tower of St Mark’s and showed how, with the telescope, he could spot ships approaching the harbour two hours before they were visible to the naked eye.

Stargazing was nothing new, of course. In fact, we can plausibly assume that it is one of the oldest of human activities. Some of the noblest poetry of the Old Testament is inspired by the majesty of the heavens. Copernicus started by revisiting the astronomical observations and calculations made by Ptolemy of Alexandria. Copernicus began from a position of great respect towards the ancient authors whose positions he would end up subverting. He praised the “admirable understanding and exactitude” of Ptolemy, “who . . . with the help of more than four-hundred-years-old observations brought this science almost to its perfection, so that nothing seemed to remain that he had not touched upon”.

Yet, Copernicus wrote, “we see so many things that do not tally with what should have taken place according to his theory, and this is because certain other motions were discovered later that were unknown to him”.

Part of Copernicus’s genius was to find the radical potential in the ancient authors who had allowed their minds to wander so freely. He permitted himself to speculate that Aristotle and Ptolemy did not have the monopoly of wisdom when it came to ancient physics and astronomy, and that the Pythagorean philosopher Philolaus might have had it right when he speculated that the Earth, instead of standing still, might be “moved about the element of fire in an oblique circle”.

None of this theorising would have held had it not been backed up by the stargazing observations of Brahe and his pupil Kepler, who accepted Copernicus’s new theory and also discovered that the planets’ orbits were elliptical; and Galileo, who fell foul of the Inquisition.

Stargazing, like everything else these days, has become terrifically specialised. Most of us in cities with polluted skies hardly look at the constellations from one year to the next. But thinking about these pioneering figures made me reflect how something as simple and universal as looking up into the night sky can lead to momentous discovery. There seems to be a connection between stargazing and that most precious thing, the freedom of the mind.

harry.eyres@ft.com, @sloweyres

More columns at ft.com/eyres

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