105. The book on the comet of 1577 is of special interest, as containing an account of Tycho’s system of the world, which was a compromise between those of Ptolemy and of Coppernicus. Tycho was too good an astronomer not to realise many of the simplifications which the Coppernican system introduced, but was unable to answer two of the serious objections; he regarded any motion of “the sluggish and heavy earth” as contrary to “physical principles,” and he objected to the great distance of the stars which the Coppernican system required, because a vast empty space would be left between them and the planets, a space which he regarded as wasteful.[63] Biblical difficulties[64] also had some weight with him. He accordingly devised (1583) a new system according to which the five planets revolved round the sun (C, in fig. 52), while the sun revolved annually round the earth (A), and the whole celestial sphere performed also a daily revolution round the earth. The system was never worked out in detail, and, like many compromises, met with little support; Tycho nevertheless was extremely proud of it, and one of the most violent and prolonged quarrels of his life (lasting a dozen years) was with _Reymers Bär_ or _Ursus_ (?-1600), who had communicated to the Landgrave in 1586 and published two years later a system of the world very like Tycho’s. Reymers had been at Hveen for a short time in 1584, and Tycho had no hesitation in accusing him of having stolen the idea from some manuscript seen there. Reymers naturally retaliated with a counter-charge of theft against Tycho. There is, however, no good reason why the idea should not have occurred independently to each astronomer; and Reymers made in some respects a great improvement on Tycho’s scheme by accepting the daily rotation of the earth, and so doing away with the daily rotation of the celestial sphere, which was certainly one of the weakest parts of the Ptolemaic scheme. [Illustration: TYCHO BRAHE.]