Furthermore, one of the weaknesses of the Greek civilization militated strongly against the acceptance of this hypothesis so contrary to the evidence of the senses. Experimentation and the development of applied science was practically an impossibility where the existence of slaves made manual labor degrading and shameful. Men might reason indefinitely; but few, if any, were willing to try to improve the instruments of observation or to test their observations by experiments.
At the same time another astronomical theory was developing which was an adequate explanation for the phenomena observed up to that time.[18] This theory of epicycles and eccentrics worked out by Apollonius of Perga (c. 225 B.C.) and by Hipparchus (c. 160 B.C.) and crystallized for posterity in Ptolemy's great treatise on astronomy, the Almagest, (c. 140 A.D.) became the fundamental principle of the science until within the last three hundred years. The theory of the eccentric was based on the idea that heavenly bodies Following circular orbits revolved around a center that did not coincide with that of the observer on the earth. That would explain why the sun appeared sometimes nearer the earth and sometimes farther away. The epicycle represented the heavenly body as moving along the circumference of one circle (called the epicycle) the center of which moves on another circle (the deferent). With better observations additional epicycles and eccentric were used to represent the newly observed phenomena till in the later Middle Ages the universe became a
|
"——Sphere With Centric and Eccentric scribbled o'er, Cycle and Epicycle, Orb in Orb"—[19] |
Yet the heliocentric theory was not forgotten. Vitruvius, a famous Roman architect of the Augustan Age, discussing the system of the universe, declared that Mercury and Venus, the planets nearest the sun, moved around it as their center, though the earth was the center of the universe.[20] This same notion recurs in Martianus Capella's book[21] in the fifth century A.D. and again, somewhat modified, in the 16th century in Tycho Brahe's conception of the universe.
Ptolemy devotes a column or two of his Almagest[22] (to use the familiar Arabic name for his Syntaxis Mathematica) to the refutation of the heliocentric theory, thereby preserving it for later ages to ponder on and for a Copernicus to develop. He admits at the outset that such a theory is only tenable for the stars and their phenomena, and he gives at least three reasons why it is ridiculous. If the earth were not at the center, the observed facts of the seasons and of day and night would be disturbed and even upset. If the earth moves, its vastly greater mass would gain in speed upon other bodies, and soon animals and other lighter bodies would be left behind unsupported in the air—a notion "ridiculous to the last degree," as he comments, "even to imagine it." Lastly, if it moves, it would have such tremendous velocity that stones or arrows shot straight up in the air must fall to the ground east of their starting point,—a "laughable supposition" indeed to Ptolemy.
This book became the great text of the Middle Ages; its author's name was given to the geocentric theory it maintained. Astronomy for a thousand years was valuable only to determine the time of Easter and other festivals of the Church, and to serve as a basis for astrology for the mystery-loving people of Europe.
To the Arabians in Syria and in Spain belongs the credit of preserving for Europe during this long period the astronomical works of the Greeks, to which they added their own valuable observations of the heavens—valuable because made with greater skill and better instruments,[23] and because with these observations later scientists could illustrate the permanence or the variability of important elements. They also discovered the so-called "trepidation" or apparent shifting of the fixed stars to explain which they added another sphere to Ptolemy's eight. Early in the sixth century Uranus translated Aristotle's works into Syrian, and this later was translated into Arabic.[24] Albategnius[25] (c. 850-829 A.D.), the Arabian prince who was the greatest of all their astronomers, made his observations from Aracte and Damascus, checking up and in some cases amending Ptolemy's results.[26]
Then the center of astronomical development shifted from Syria to Spain and mainly through this channel passed on into Western Europe. The scientific fame of Alphonse X of Castile (1252-1284 A.D.) called the Wise, rests chiefly upon his encouragement of astronomy. With his support the Alfonsine Tables were calculated. He is said[27] to have summoned fifty learned men from Toledo, Cordova and Paris to translate into Spanish the works of Ptolemy and other philosophers. Under his patronage the University of Salamanca developed rapidly to become within two hundred years one of the four great universities of Europe[28]—a center for students from all over Europe and the headquarters for new thought, where Columbus was sheltered,[29] and later the Copernican system was accepted and publicly taught at a time when Galileo's views were suppressed.[30]
Popular interest in astronomy was evidently aroused, for Sacrobosco (to give John Holywood[31] his better known Latin name) a Scotch professor at the Sorbonne in Paris in the 13th century, published a small treatise De Sphæri Mundo that was immensely popular for centuries,[32] though it was practically only an abstract of the Almagest. Whewell[33] tells of a French poem of the time of Edward I entitled Ymage du Monde, which gave the Ptolemaic view and was illustrated in the manuscript in the University of Cambridge with a picture of the spherical earth with men upright on it at every point, dropping balls down perforations in the earth to illustrate the tendency of all things toward the center. Of the same period (13th century) is an Arabian compilation in which there is a reference to another work, the book of Hammarmunah the Old, stating that "the earth turns upon itself in the form of a circle, and that some are on top, the others below ... and there are countries in which it is constantly day or in which at least the night continues only some instants."[34] Apparently, however, such advanced views were of no influence, and the Ptolemaic theory remained unshaken down to the close of the 15th century.
Aside from the adequacy of this explanation of the universe for the times, the attitude of the Church Fathers on the matter was to a large degree responsible for this acquiescence. Early in the first century A.D., Philo Judæus[35] emphasized the minor importance of visible objects compared with intellectual matters,—a foundation stone in the Church's theory of an homocentric universe. Clement of Alexandria (c. 150 A.D.) calls the heavens solid since what is solid is capable of being perceived by the senses.[36] Origen (c. 185-c. 254.) has recourse to the Holy Scriptures to support his notion that the sun, moon, and stars are living beings obeying God's commands.[37] Then Lactantius thunders against those who discuss the universe as comparable to people discussing "the character of a city they have never seen, and whose name only they know." "Such matters cannot be found out by inquiry."[38] The existence of the antipodes and the rotundity of the earth are "marvelous fictions," and philosophers are "defending one absurd opinion by another"[39] when in explanation why bodies would not fall off a spherical earth, they claim these are borne to the center.