Part 5 (1/2)

Johann Kepler[159] earned for himself the proud t.i.tle of ”lawmaker for the universe” in defiance of his handicaps of ill-health, family troubles, and straitened finances.[160] Born in Weil, Wurtemberg, (December 27, 1571) of n.o.ble but indigent parents, he was a sickly child unable for years to attend school regularly. He finally left the monastery school in Mulifontane in 1586 and entered the university at Tubingen to stay for four and a half years. There he studied philosophy, mathematics, and theology (he was a Lutheran) receiving the degree of Master of Arts in 1591. While at the university he studied under Maestlin, professor of mathematics and astronomy, and a believer in the Copernican theory. Because of Maestlin's teaching Kepler developed into a confirmed and enthusiastic adherent to the new doctrine.

[Footnote 159: The authoritative biography is the _Vita_ by Frisch in vol. VIII, pp. 668-1028 of _Op. Om. Kep._]

[Footnote 160: Frisch: VIII, 718. [Transcriber's Note: Missing footnote reference in original text has been added above in a logical place.]]

In 1594 he reluctantly abandoned his favorite study, philosophy, and accepted a professors.h.i.+p in mathematics at Graetz in Styria. Two years later he published his first work: _Prodromus Dissertationum continens mysterium cosmographic.u.m_ etc. (1596) in which he sought to prove that the Creator in arranging the universe had thought of the five regular bodies which can be inscribed in a sphere according to which He had regulated the order, the number and the proportions of the heavens and their movements.[161] The book is important not only because of its novelty, but because it gave the Copernican doctrine public explanation and defense.[162] Kepler himself valued it enough to reprint it with his _Harmonia Mundi_ twenty-five years later. And it won for him appreciative letters from various scientists, notably from Tycho Brahe and Galileo.[163]

[Footnote 161: Delambre: _Astr. Mod._ 314-315.]

[Footnote 162: Frisch: VIII, 999.]

[Footnote 163: Ibid: VIII, 696.]

As Kepler, a Lutheran, was having difficulties in Graetz, a Catholic city, he finally accepted Tycho's urgent invitation to come to Prague.[164] He came early in 1600, and after some adjustments had been made between the two,[165] he and his family settled with Tycho that autumn to remain till the latter's death the following November.

Kepler himself then held the office of imperial mathematician by appointment for many years thereafter.[166]

[Footnote 164: Ibid: VIII, 699-715.]

[Footnote 165: Dreyer: 290-309.]

[Footnote 166: Frisch: VIII, 715.]

With the researches of Tycho's lifetime placed at his disposal, Kepler worked out two of his three great planetary laws from Tycho's observations of the planet Mars. Yet, as M. Bertrand remarks,[167] it was well for Kepler that his material was not too accurate or its variations (due to the then unmeasured force of attraction) might have hindered him from proving his laws; and luckily for him the earth's...o...b..t is so nearly circular that in calculating the orbit of Mars to prove its elliptical form, he could base his work on the earth's...o...b..t as a circle without vitiating his results for Mars.[168] That a planet's...o...b..t is an ellipse and not the perfect circle was of course a triumph for the new science over the scholastics and Aristotelians.

But they had yet to learn what held the planets in their courses.

[Footnote 167: Bertrand: p. 870-1.]

[Footnote 168: The two laws first appeared in 1609 in his _Physica Coelestis tradita commentarius de motu stellae martis_. (Frisch: VIII, 964.) The third he enunciated in his _Harmonia Mundi_, 1619.

(Ibid: VIII, 1013-1017.)]

From Kepler's student days under Maestlin when as the subject of his disputation he upheld the Copernican theory, to his death in 1630, he was a staunch supporter of the new teaching.[169] In his _Epitome Astronomiae Copernicanae_ (1616) he answered objections to it at length.[170] He took infinite pains to convert his friends to the new system. It was in vain that Tycho on his deathbed had urged Kepler to carry on their work not on the Copernican but on the Tychonic scheme.[171]

[Footnote 169: ”Cor et animam meam”: Kepler's expression in regard to the Copernician theory. Ibid: VIII, 957.]

[Footnote 170: Ibid: VIII, 838.]

[Footnote 171: Ibid: VIII, 742.]

Kepler had reasoned out according to physics the laws by which the planets moved.[172] In Italy at this same time Galileo with his optic tube (invented 1609) was demonstrating that Venus had phases even as Copernicus had declared, that Jupiter had satellites, and that the moon was scarred and roughened--ocular proof that the old system with its heavenly perfection in number (7 planets) and in appearance must be cast aside. Within a year after Galileo's death Newton was born[173] (January 4, 1643). His demonstration of the universal application of the law of gravitation (1687) was perhaps the climax in the development of the Copernican system. Complete and final proof was adding in the succeeding years by Roemer's (1644-1710) discovery of the velocity of light, by Bradley's (1693-1762) study of its aberration,[174] by Bessel's discovery of stellar parallax in 1838,[175] and by Foucault's experimental demonstration of the earth's axial motion with a pendulum in 1851.[176]

[Footnote 172: Kepler: _Op. Om._, I, 106: _Praefatio ad Lectorem_.]

[Footnote 173: Berry: 210.]

[Footnote 174: Berry: 265.]

[Footnote 175: Ibid: 359.]