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Updated: May 8, 2025
I have compared their achievement with that of the West: we have one whole manvantara and a pralaya of theirs to judge by, as against two fragments of western manvantaras with the pralaya intervening. It is not much; and we should remember that there are cycles and epicycles; and that Japan, or old China herself, within our own lifetime, may give the lie to everything.
It should be recalled, however, that this supposition of tangible spheres for the various planetary and stellar orbits was a mediaeval interpretation of Ptolemy's theory rather than an interpretation of Ptolemy himself, there being nothing to show that the Alexandrian astronomer regarded his cycles and epicycles as other than theoretical.
But the cycles and epicycles which Ptolemy devised, and by means of which he explained, as well as he knew how, the movements of the heavenly bodies around us, these have passed away. The breath of doubt has blown upon them; and they have gone, like mists driven by the wind. But has doubt quenched the light of any star? Has doubt taken away from the glory of the universe?
Indeed, he seems to have retained as much of this as practicable, in deference to the prejudice of his time. Thus he records the planetary orbits as circular, and explains their eccentricities by resorting to the theory of epicycles, quite after the Ptolemaic method.
In other words, the theory of epicycles will account for all the facts of the observed motions of all the heavenly bodies, but in so doing it fills the universe with a most bewildering network of intersecting circles. Even in the time of Calippus fifty-five of these spheres were computed.
In accepting the text as it stands we simply obey the Baconian maxim hypotheses non fingimus, but it is strange, and must be surprising to a philosophic mind, to what an extent the more extreme representatives of the negative criticism have gone back to the most condemned parts of the scholastic method; inconvenient facts are explained away by hypotheses as imaginary and unverifiable as the 'cycles and epicycles' by which the schoolmen used to explain the motions of the heavenly bodies.
Copernicus could not sever himself from this obnoxious tradition. It is true that neither the Pythagorean nor the Egypto-Tychonic system required epicycles for explaining retrograde motion, as the Ptolemaic theory did. Furthermore, either system could use the excentric of Hipparchus to explain the irregular motion known as the equation of the centre.
The idea of such an explanation did not originate with Hipparchus. The germs of the thought were as old as the Pythagorean doctrine that the earth revolves about a centre that we cannot see. Eudoxus gave the conception greater tangibility, and may be considered as the father of this doctrine of wheels epicycles, as they came to be called.
He improved the lunar theory considerably, and discovered minor inequalities which could be allowed for by the addition of new epicycles. We may look upon these epicycles of Apollonius, and the excentric of Hipparchus, as the responses of these astronomers to the demand of Plato for uniform circular motions.
A familiar story records that Alfonso, pondering the complications of the Ptolemaic cycles and epicycles, was led to remark that, had he been consulted at the time of creation, he could have suggested a much better and simpler plan for the universe.
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