Ptolemaic system

“ By means of his cumbersome system of epicycles he could roughly compute the positions of the planets at any time, could foretell the time of rising and setting of the moon, and predict eclipses. But, while the Ptolemaic system is false, while it does not agree with what we now know to be the true system of the heavens, yet it is mathematically possible. ”

“ WHEN we recall that the Ptolemaic system of the universe was once taught side by side with the Copernican at Harvard and at Yale, we are impressed, not so much with the age of our universities, as with the youth of modern astronomy and with the extraordinary vitality of old ideas. ”

“ The later Greeks, the Arabians, and the earliest modern astronomers, must have conceived the hypotheses of the Ptolemaic system with tolerable completeness. And yet, we may assert, that during the stationary period, men did not possess the notions, even of space and number, in that vivid and vigorous manner which enables them to discover new truths. If they had perceived distinctly that the astronomical theorist had merely to do with relative motions, they must have been led to see the possibility, at least, of the Copernican system ”

“ Ptolemaic System, the highly complex system of astronomy ascribed to Claudius Ptolemy, which assumed that the earth was the centre of a sphere which carried the heavenly bodies along in its daily revolution, accounted for the revolutions of the sun and moon by supposing they moved in eccentric circles round the earth, and regarded the planets as moving in epicycles round a point which itself revolved in an eccentric circle round the earth like the sun and moon. ”

“ If they are once accepted, they may go on bidding defiance to truth for fifty or even a hundred years and more, as stable as an iron pier in the midst of the waves. The Ptolemaic system was still held a century after Copernicus had promulgated his theory. ”

“ Although complex and unwieldy, it explained all phenomena satisfactorily enough as they appeared to the senses; and it brought phenomena into a system. (The Ptolemaic system has been fully described in vol. i, pp. 322 ff.) To recapitulate it: the world-all was conceived as a hollow sphere with the earth as the centre and the fixed stars in the periphery, while the planets were supposed to move in epicycles. The universe was divided into the heavenly and terrestrial realms, which were occupied by various spirits. God resided outside this hollow sphere and held it, as it were, in his lap. ”

“ According to the Ptolemaic system the earth is a motionless sphere fixed at the center of the universe. It can have no motion, for there must be some fixed point in the universe to which all the motions of the heavenly bodies may be referred; if the earth had motion, it was argued, this would be proportionate to the great mass of the earth and would cause objects and animals to fly off into the air and be left behind. ”

“ The Ptolemaic system demanded large epicycles, depending [Pg 27] on the motion of the earth, these are what Copernicus overthrew; but to express the minuter details of the motion smaller epicycles remained, and grew more and more complex as observations increased in accuracy, until a greater man than either Copernicus or Ptolemy, viz. Kepler, replaced them all by a simple ellipse. ”

“ In her fair cheekes two pits do lie,
To burn those slain by her eye.—Carew.
P. 27. There are many allusions, in these poems, to the science of astronomy, but they are all drawn from the systems of the ancient philosophers, particularly that of Ptolemy; which, like the doctrines of Aristotle in logic and metaphysics, kept possession of the schools for near 2000 years. In the Ptolemaic system, there were supposed to be twelve distinct heavens, one above another. ”

“ In this revised form of "anthropo-centrism" we see how the general movement of thought has instinctively adapted itself to the astronomical revolution. On the Ptolemaic system it was not incongruous or absurd that man, lord of the central domain in the universe, should regard himself as the most important cosmic creature. ”

“ The Ptolemaic system of astronomy, numberless other systems and theories of scientific and philosophical explanation are discarded, known to be false and worthless. Ethical precedents and principles cannot be applied to the needs of the modern world. ”

“ In all the systems derived from Ptolemy, the order of the planets remained the same, and Mercury and Venus were placed nearer to the earth than the sun is. According to many authors, however, Plato made a variation in this [Pg 193] respect, by putting them outside the sun, on the ground that they never were seen to pass across its surface. He had obviously never heard of the "Transit of Venus." This arrangement was adopted by Theon, in his commentary on the Almagesta of Ptolemy, and afterwards by Geber, who alone among the Arabians departed from the strict Ptolemaic system. ”

“ But this, of course, is in no sense a guide to the state of general opinion regarding the theory. We shall gain a true gauge as to this if we assume that the greater number of important thinkers had accepted the heliocentric doctrine before the middle of the seventeenth century, and that before the close of that century the old Ptolemaic idea had been quite abandoned. A wonderful revolution in man's estimate of the universe had thus been effected within about two centuries after the birth of Copernicus. ”

“ The Ptolemean system of the universe, invented and duly described by Claudius Ptolemy, the great Egyptian geographer, who had lived in the second century of our era, which had served the simple needs of the men of the Middle Ages, had long been discarded by the scientists of the Renaissance. ”

“ But mistakes like these are hurtful only when persisted in in the face of fuller truth, after truth has been discovered. Only a very foolish man would now uphold the Ptolemaic astronomy. But the Ptolemaic astronomy, when first invented, was based on real if incomplete observations, and formed a groundwork without which further progress in that science would have been probably impossible. The theories and ceremonials of the Catholic Church suited well with an age in which little was known and much was imagined: when superstition was active and science was not yet born. ”

“ Small wonder is it, in the absence of the present day mechanical devices for the exact measurement of time and space as aids to observation, that the Ptolemaic, or geocentric, theory of the universe endured through centuries as it did, upheld by the authority both of the Church and, in essence at least, by the great philosophers whose works constituted the teachings of the schools. ”

“ On the score of simplicity, therefore, a daily rotation of the earth, once admitted as possible, is obviously far more probable than a daily rotation of the whole universe about the earth. The precession of the equinoxes is brought in finally to show how much more complicated and improbable, are the motions necessary to reconcile the facts with the Ptolemaic theory. On the third day the revolution of the earth about the sun is considered, of course as a mere hypothesis. ”

“ In Physics they did little. In Art nothing. In Metaphysics less than nothing.
We will first examine, as the more pleasant spectacle of the two, that branch of thought in which some progress was really made, and in which the Ptolemaic schools helped forward the development of men who have become world-famous, and will remain so, I suppose, until the end of time.
Four names at once attract us: Euclid, Aristarchus, Eratosthenes, Hipparchus. ”

“ Most of all it would be of value to note that the false inductions which have everywhere hampered the progress of science have been, from the stand-point of the generation in which they originated, for the most part logical inductions. We have seen that the Ptolemaic scheme of the universe, false though it was in its very essentials, yet explained in what may be termed a thoroughly scientific fashion the observed phenomena. It is one way of expressing a fact to say that the sun moves across the heavens from the eastern to the western horizon ”

“ As is well known, such libraries had existed in Babylonia for thousands of years. The character which the Ptolemaic epoch took on was no doubt due to Babylonian influence, but quite as much to the personal experience of Ptolemy himself as an explorer in the Far East. The marvellous conquering journey of Alexander had enormously widened the horizon of the Greek geographer, and stimulated the imagination of all ranks of the people, It was but natural, then, that geography and its parent science astronomy should occupy the attention of the best minds in this succeeding epoch. ”

“ An obscure passage in one of Plato's dialogues (the Timaeus) has been interpreted by many ancient and modern commentators as implying a belief in the rotation of the earth, and Plutarch also tells us, partly on the authority of Theophrastus, that Plato in old age adopted the belief that the centre of the universe was not occupied by the earth but by some better body. ”

“ The first three Ptolemies were endowed with many sterling qualities, and were conspicuous for their talents; but the remaining monarchs of the dynasty were, for the most part, degenerate and debauched. They were, however, patrons of the arts and sciences, and indeed they did more for them than did almost any other royal house in the world. Ptolemaic Alexandria was to some extent the birthplace of the sciences of anatomy, geometry, conic sections, hydrostatics, geography, and astronomy, while its position in the artistic world was most important. ”

“ Among the thirty-three demotic ostraca, i.e. demotic inscriptions upon potsherds and limestone flakes, found among the Ptolemaic remains in the upper stratum of Site 14, and all of the Ptolemaic period, only one has a definite date.
It is of ‘the year 21 of the kings Ptolemaios son of Ptolemaios and of Ptolemaios, his son,’ i. e. of Ptolemaios II, Philadelphos, and his son Euergetes I (about 265-264 B.C.) . The texts contain tax receipts, contracts, accounts, and lists of workmen.
One ostracon is of a quite unusual type (Pl. XXXVII. 3) . ”