VII. FROM COPERNICUS TO KEPLER

We have left astronomy to the last, for its heroes come toward the end of this period and constitute its pièces de résistance.

The same Church that was to silence Galileo led the way in a major achievement of modern astronomy—the reform of the calendar. The revision that Sosigenes had made for Caesar about 46 B.C. had overestimated the year by eleven minutes and fourteen seconds; consequently, by 1577 the Julian calendar lagged behind the progress of the seasons by some twelve days, and ecclesiastical feasts had fallen out of the season for which they had been intended. Several attempts at calendar reform had been made—under Clement VI, Sixtus IV, and Leo X—but difficulties had been found in securing general agreement and requisite astronomical knowledge. In 1576 a revised calendar drawn up by Luigi Giglio was presented to Gregory XIII. The Pope submitted it to a commission of theologians, lawyers, and scientists, including the Bavarian Jesuit Christopher Clavius, famous in mathematics and astronomy; the final draft was apparently his work. Long negotiations were carried on with princes and prelates to secure their co-operation; many objections were made, and the effort to win the consent of the Eastern churches failed. On February 24, 1582, Gregory XIII signed the bull that established the Gregorian calendar in Roman-Catholic lands. To equate the old calendar with astronomic realities, tendays were to be omitted in October 1582, the fifth was to be accounted the fifteenth, and complicated allowances were to be made for the reckoning of interest and other commercial relations. To offset the error in the Julian calendar, only such century years as are divisible by 400 were to have a twenty-ninth day in February. Protestant nations resisted the change; in Frankfurt am Main and Bristol the populace rioted in the belief that the Pope wished to rob it of ten days; even Montaigne, avid of time, complained, “The eclipsing or abridging of ten days, which the Pope hath lately caused, hath taken me so low that I can hardly recover myself.”65 But slowly the new calendar—which would need no further correction for 3,333 years—won acceptance: by the German states in 1700, England in 1752, Sweden in 1753, Russia in 1918.III

A similar lag occurred in the acceptance of the Copernican astronomy. In Italy it might be studied and taught if presented as hypothesis rather than demonstrated fact;66 Giordano Bruno defended it, and Campanella already wondered whether the inhabitants of other planets thought themselves, as earthlings do, the center and purpose of all things.67 Generally, Protestant theologians vied with Catholic in denouncing the new system. Bacon and Bodin alike repudiated it.68 More surprising was its rejection by the greatest astronomer of the half century that followed Copernicus’ death (1543).

Tycho Brahe was born in 1546 in the then Danish province of Scania, now the southern extremity of Sweden. His father was a member of the Danish Council of State; his mother was mistress of the robes of the Queen. His rich Uncle Jorgen, disconsolately childless, abducted him, wheedled the parents into consent, and gave the boy every advantage of education. At thirteen Tycho entered the University of Copenhagen. According to Gassendi, he was drawn to astronomy when he heard a teacher discuss a forthcoming eclipse of the sun. He watched the eclipse come as predicted, and marveled at the science that had reached such prophetic power. He bought a copy of Ptolemy’s Almagest, pored over it to the neglect of other studies, and never abandoned the geocentric view there presented in the second century of our era.

At sixteen he was transferred to the University of Leipzig, where he studied law by day and the stars by night. He was warned that this regimen would lead to physical and nervous breakdown. Tycho persisted, and he spent his allowance on astronomical instruments. In 1565 his uncle died, leaving him a large fortune. After settling his business affairs, Tycho hurried to Wittenberg for more mathematics and astronomy; thence, driven by plague, to Rostock. There he fought a duel and had part of his nose cut off; he ordered a bright new nose of silver and gold and wore it the rest of his life. He dabbled in astrology and predicted the coming death of Suleiman the Magnificent, only to find that the Sultan had already died.69 After much travel in Germany he returned to Denmark, busied himself with chemistry, and was brought back to astronomy by discovering a new star in the constellation Cassiopeia (1572). His carefree observations of this transitory star and his account of it in his first publication, De nova Stella, gave him a European reputation, but shocked some great Danes, who considered authorship a form of exhibitionism incompatible with blue blood. Tycho confounded them by marrying a peasant girl. He seems to have felt that a simple housewife was the best mate for an absorbed astronomer and was the best match open to a man with a golden nose.

Dissatisfied with astronomical facilities in Copenhagen, he set out for Cassel, where Landgrave William IV had built (1561) the first observatory with a revolving roof, and Joost Bürgi had developed a pendulum clock which made possible an unprecedented accuracy in timing the observation and movements of stars. Fired with new zeal, Tycho went back to Copenhagen and interested Frederick II in projects for an observatory. The King gave him the island of Hveen (Venus) in the Sound, and a good pension. With this and his own means Tycho built there a castle and gardens which he called Uraniburg (Heavenly City), with living quarters, library, laboratory, several observatories, and a workshop to make his own instruments. He had no telescope; twenty-eight years were to pass before its invention; yet it was his observations that guided Kepler to epochal discoveries.

In twenty-one years at Hveen Tycho and his pupils gathered a body of data exceeding in extent and accuracy anything hitherto known. He took records of the sun’s apparent motion every day for many years. He was one of the first astronomers to allow for the refraction of light and the fallibility of observers and instruments; so he repeated the same observation time and again. He discovered and reduced to law the variations in the motion of the moon. His meticulous tracing of a comet in 1577 led him to the now universally accepted belief that comets, instead of being generated in the earth’s atmosphere, are true celestial bodies moving in fixed and regular courses. When Tycho published his catalogue of 777 stars, and marked them with loving care on the great celestial globe in his library, he had justified his life.

In 1588 Frederick II died. The new King was a boy of eleven; the regents who ruled him were not as patient with the pride, temper, and extravagance of Brahe as Frederick had been; soon the governmental grants ran low, and in 1597 they ceased. Tycho left Denmark and settled in Benatek Castle, near Prague, as the guest of Emperor Rudolf II, who looked to him for astrological predictions. Brahe imported his instruments and records from Hveen, and advertised for an assistant. Johann Kepler came (1600), and worked fitfully but devotedly for his difficult master. Just as Brahe was hoping to develop his massive accumulation of data into a reasoned theory of the heavens, he was struck down at table by a burst bladder. He lingered in pain for eleven days, and died (1601) mourning that he had not completed his work. The funeral orator said that he had “coveted nothing but time.”70

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