Page:The Harvard Classics Vol. 51; Lectures.djvu/115

 II. ASTRONOMY

STRONOMY was destined to liberate the modern intellect from the bondage of the Middle Ages, and by teaching man that the earth is not the fixed center of the universe, but a satellite of one among many stars, to shake the confidence with which he had long regarded the universe as made for him, the earth for his abode, the heavens for his enjoyment. This is the great contribution of astronomy to thought; to civilization it has also contributed some of the most important advances, such as an accurate calendar, the standard of time, and the exact measure of time, sound methods of navigation and geography; and commencing earlier than all the other sciences, it has built up one of the most admirable structures of scientific knowledge.

Astronomy was long the leader among the sciences, and as such gave to the world trigonometry, in part logarithms, and Newton's dynamics. But though astronomical progress has by no means ceased, the accelerated growth of other sciences—first physics, then chemistry, and of late biology—has rendered it less conspicuous. The continued importance of astronomy is, however, well illustrated by the marvelous results of spectrum analysis, while to-day the study of nebulae and of the physics of the sun possesses the highest interest.

HIPPARCHUS AND THE PTOLEMAIC SYSTEM

The principal results of ancient astronomy go by the name of Ptolemy (the Ptolemaic system), but are mainly due to the labors of Hipparchus. Hipparchus knew the latitude and longitude of 150 fixed stars within a fraction of a degree, when, in the year 134 B. C., a new star of the first magnitude suddenly appeared. Encouraged by this extraordinary event, he applied himself diligently to astronomical measurements, establishing the position of more than 1,000 fixed