The History of Astronomy: A Very Short Introduction by Michael Hoskin

Author:Michael Hoskin [Hoskin, Michael]
Language: eng
Format: epub
ISBN: 0192803069
Publisher: Oxford University Press
Published: 2003-01-15T07:00:00+00:00

Chapter 5

Astronomy in the age of Newton

The outlook of the later Middle Ages had been dominated by Aristotle, and that of the Renaissance by Plato. But in the period following, the ‘mechanical philosophy’, alternatively known as the ‘corpuscular philosophy’, became increasingly attractive. It had originated with the Greek atomists, who explained the different qualities we perceive in the bodies around us as being the ways our senses interpret the movements of unchanging particles; and this appealed to an age that found a refreshing clarity about explanations that used concepts like speeds and shapes, concepts that were mathematical at least in principle. Machinery was becoming ever more ingenious – witness the great clock in the cathedral in Strasbourg. But in these machines, complex effects were being produced by simple (and intelligible) means: matter – cogs, weights, and so forth – in motion.

God was now the great clockmaker, His creation hugely complex in structure, but intelligible simply as matter in motion. Galileo was one of many attracted by this revival of ancient ideas, but it was his younger contemporary, René Descartes (1596–1650), who carried the mechanical philosophy to its extreme. At the school at La Flèche his Jesuit teachers introduced him to Galileo’s telescopic discoveries within months of their announcement; more importantly, they instilled in him a profound admiration for the certainty to be found in geometrical theorems. For Descartes, there was a vast gulf between the certainly true and what was only very probably true; and he decided that to bridge the gulf one must imitate the reasoning of the geometers. Furthermore, it was the geometers who had always had the correct understanding of space: the infinite, homogenous, undifferentiated space of Euclid was not the idealized abstraction it had been taken to be, but the space of the real world.

As a philosopher, Descartes was ruthless. Unlike Galileo, who could never mention Aristotle without getting involved in a squabble, Descartes dismissed Aristotle with contempt and set about creating his own philosophy. Until now, all discussion had referred back to Aristotle, favourably or otherwise; soon all discussion would be referred back to Descartes.

In the Cartesian universe there were no longer any privileged places, such as the centre of the Earth or the centre of the solar system, that were different from ordinary places because it was around them that motions took place. Analysing the fundamental concept of matter per se, Descartes rejected properties like colour or taste that belong to some matter but not to all, and ended by concluding that matter and space were in many respects identical. This being so, space without matter – a vacuum – was an impossibility: the world is a plenum. Furthermore, since space was uniform, so was matter. This meant that the differences we perceive between this material object and that are due entirely to how the (uniform) matter is moving in the two spaces involved: motions are everything when it comes to understanding the universe.

Because God lives in the eternal present, He conserves this particular

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