In an earlier chapter, an account has been given of the maritime discoveries of the sixteenth century and their immediate results in broadening intellectual interests. In this chapter, some attention already has been devoted to the rise of humanism and likewise to the invention of printing. It remains, therefore, to say a few words about the changes in astronomy and in scientific method that characterized the beginning of modern times.
[Side Note: Astronomy]
In the year 1500 the average European knew something about the universe of sun, moon, planets, and stars, but it was scarcely more than the ancient Greeks had known, and its chief use was to foretell the future. This practical aspect of astronomy was a curious ancient misconception, which now passes under the name of astrology. It was popularly believed prior to the sixteenth century that every heavenly body exerted a direct and arbitrary influence upon human character and events, [Footnote: Disease was attributed to planetary influence. This connection between medicine and astrology survives in the sign of Jupiter 4, which still heads medicinal prescriptions.] and that by casting "horoscopes," showing just how the stars appeared at the birth of any person, the subsequent career of such an one might be foreseen. Many silly notions and superstitions grew up about astrology, yet the practice persisted. Charles V and Francis I, great rivals in war, vied with each other in securing the services of most eminent astrologers, and Catherine de' Medici never tired of reading horoscopes.
[Sidenote: "The Ptolemaic System">[
Throughout the middle ages the foremost scholars had continued to cherish the astronomical knowledge of the Greeks, which had been conveniently collected and systematized by a celebrated mathematician and scholar living in Egypt in the second century of the Christian era —Ptolemy by name. Among other theories and ideas, Ptolemy taught that the earth is the center of the universe, that revolving about it are the moon, Mercury, Venus, the sun, the other planets, and the fixed stars, and that the entire machine is turned with incredible velocity completely around every twenty-four hours. This so-called Ptolemaic system of astronomy fitted in very nicely with the language of the Bible and with the popular prejudice that the earth remains stationary while the heavenly bodies daily rise and set. It was natural that for many centuries the Christians should accept the views of Ptolemy as almost divinely inspired.
[Sidenote: "The Copernican System">[
However, a contradictory theory of the solar system was propounded and upheld in the sixteenth century, quite supplanting the Ptolemaic theory in the course of the seventeenth. The new system is called Copernican after its first modern exponent—and its general acceptance went far to annihilate astrology and to place astronomy upon a rational basis.
Copernicus [the Latin form of his real name, Koppernigk (1473-1543)] was a native of Poland, who divided his time between official work for the Catholic Church and private researches in astronomy. It was during a ten-year sojourn in Italy (1496-1505), studying canon law and medicine, and familiarizing himself, through humanistic teachers, with ancient Greek astronomers, that Copernicus was led seriously to question the Ptolemaic system and to cast about in search of a truthful substitute. Thenceforth for many years he studied and reflected, but it was not until the year of his death (1543) that his results were published to the world. His book—On the Revolutions of the Celestial Bodies, dedicated to Pope Paul III—offered the theory that the earth is not the center of the universe but simply one of a number of planets which revolve about the sun. The earth seemed much less important in the Copernican universe than in the Ptolemaic.
The Copernican thesis was supported and developed by two distinguished astronomers at the beginning of the next century—Kepler (1571-1630) and Galileo (1564-1642), one a German, the other an Italian. Kepler taught astronomy for a number of years at Gratz and subsequently made his home in Prague, where he acquired a remarkable collection of instruments [Footnote: From Tycho Brahe, whose assistant he was in 1600-1601.] that enabled him to conduct numerous interesting experiments. While he entertained many fantastic and mystical theories of the "harmony of the spheres" and was not above casting horoscopes for the emperor and for Wallenstein, that soldier of fortune, [Footnote: See below, pp. 223, 226.] he nevertheless established several of the fundamental laws of modern astronomy, such as those governing the form and magnitude of the planetary orbits. It was Kepler who made clear that the planets revolve about the sun in elliptical rather than in strictly circular paths.
Galileo popularized the Copernican theory. [Footnote: Another "popularizer" was Giordano Bruno (c. 1548-1600).] His charming lectures in the university of Padua, where he taught from 1592 to 1610, were so largely attended that a hall seating 2000 had to be provided. In 1609 he perfected a telescope, which, although hardly more powerful than a present-day opera glass, showed unmistakably that the sun was turning on its axis, that Jupiter was attended by revolving moons, and that the essential truth of the Copernican system was established. Unfortunately for Galileo, his enthusiastic desire to convert the pope immediately to his own ideas got him into trouble with the Roman Curia and brought upon him a prohibition from further writing. Galileo submitted like a loyal Catholic to the papal decree, but had he lived another hundred years, he would have rejoiced that almost all men of learning—popes included—had come to accept his own conclusions. Thus modern astronomy was suggested by Copernicus, developed by Kepler, and popularized by Galileo.