Comment: On Galileo
Galileo's earliest surviving drawing of the moon can be dated to 30 November 1609, almost exactly 400 years ago. In the months before he made his observations, he'd become aware of an extraordinary new instrument that brought the far away much nearer: the telescope. Immediately, he'd seen its potential for science. And now, having polished up the original designs, and improved on its power, he turned the new instrument to the starry heavens and the still lunar surface. On that night – armed with his watercolours, ink and brushes too – he was the first to capture that most extraordinary of celestial sights: the details of an alien world.
What he experienced can still be enjoyed today. For it is easy to capture the wonder of the moment by focusing a telescope or binoculars on our heavenly companion. As an undergraduate I studied physics, and for one project I had to measure the heights of lunar mountains – a task that Galileo himself undertook. I had to take photographs of the shadows that fell across the peaks, valleys and plains. My efforts were, of course, utterly trivial so far as science is concerned. However, the experience was invaluable. I rose at 3am on dark, frosty mornings to ensure that there'd be clear skies. It reminded me of the monks who say the office of matins at similar hours while the world sleeps. What awaited was the gift that comes with contemplating the lunar surface, if through bleary eyes. The moon is a high-contrast place of greys and whites. Pitted like pumice, it feels close even when viewed through a relatively low-powered instrument.
Galileo's exploration of the moon was aesthetic as well as cartographical. In the book he wrote about his observations, The Sidereal Messenger, he commended his readers to the “great and marvellous sights” he'd seen. He also included one image painted in 1609 that was adjusted to make it more beautiful. “Galileo is much more interested in the play of light and shadow than in accurate mapping,” explains Owen Gingerich of the Harvard-Smithsonian Centre for Astrophysics. “He is interested in the heights and depths that reveal an earthlike moon.”
And that, in fact, is the lasting legacy of Galileo's work. He imagined the moon as earthlike. That could not be more significant. According to Aristotelian cosmology, the objects that filled the heavens were perfect, nestling among crystalline spheres. Rendering the moon with apparent flaws, such as craters and peaks, shattered those assumptions. Galileo's drawings were another nail in the coffin of the old cosmology.
Only, Galileo was far from the first to think like this. In order to interpret what he saw, he drew on an Alexandrian philosopher, John Philoponus, who'd lived 1,000 years before him. John was a Christian thinker who wrote about physics and theology. He challenged Aristotelian cosmology too, by reasoning that the earth and the heavens must be alike, and his ideas were known to many. But they were resisted by the establishment, perhaps because John had been declared a heretic by the church – not for his scientific views but because of his speculations about God. So, it is fascinating to ponder whether Galileo felt John was a kind of soulmate, as the Italian too headed for trouble with the church. He certainly cites John frequently in his writings. When he sketched his first images of the moon, he must have been thinking of the older iconoclast.
What they surely had in common was this powerful wonder at the natural world. It was a sense of religious awe coupled to a critical attitude, which is why they both challenged the received wisdom. As Galileo himself put it: “I shall concede to you indeed that the way in which God knows the infinite propositions of which we know so few is exceedingly more excellent than ours.”
guardian.co.uk, Saturday 28 November 2009Back to the top