THE PASSING OF THE MECHANICAL AGE
( NEWTON TO EINSTEIN)
The earliest attempts to discover the pattern of events were limited, naturally enough, to the visible movements of objects either on what we have called the man-sized scale or on the far grander scale of astronomy -- these were the only movements which could be studied without instrumental aid.
The movements of the astronomical bodies were treated only in their geometrical aspect. The 'fixed stars' hardly came under discussion at all, since they appeared to have no motion beyond their diurnal rotation round the pole. This was of course a consequence of their great distance from the earth, but it was explained by supposing them to be immovably attached to a sphere which rotated round the earth as centre.
There remained the sun, moon, and planets. A whole succession of astronomers -- from Aristarchus through Ptolemy to Copernicus and Kepler -- had investigated the paths in which these bodies moved, but had shown very little concern as to why they moved in these particular paths rather than in others. Aristotle's pronouncement that a circular motion was natural to all bodies, because the circle was the perfect geometrical figure, seems to have stifled curiosity fairly thoroughly for nearly two thousand years; it was uncritically accepted by Copernicus, and even at one time by Galileo.
It was different with terrestrial bodies; there had been many attempts to explain their movements in what we should now describe as dynamical terms. The earliest Greek thinkers had imagined that the motion of every object was controlled by a tendency, inherent in the object, to find its 'natural place' in the world. A stone sank in water because the natural place for stones was the bottom of a stream; flames ascended in air because their natural
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Publication information: Book title: Physics & philosophy. Contributors: James W. Jeans - Author. Publisher: Cambridge [Eng.] : The University Press ; the Macmillan company. Place of publication: Cambridge, England. Publication year: 1943. Page number: 105.
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