According to this statement which he made only as a possible explanation of the phenomena and not as an absolute truth, while there was little to choose between the Tychonic and the Copernican conceptions, he inclined slightly toward the former. He conceived of the earth and the other planets as each borne along in its enveloping heaven like a ship by the tide, or like a man asleep on a ship that was sailing from Calais to Dover. The earth itself does not move, but it is transported so that its position is changed in relation to the other planets but not visibly so in relation to the fixed stars because of the vast intervening spaces. The laws of the universe affect even the most minute particle, and all alike are swept along in a series of vortices, or whirlpools, of greater or less size. Thus the whole planetary system sweeps around the sun in one great vortex, as the satellites sweep around their respective planets in lesser ones. In this way Descartes worked out a mechanical explanation of the universe of considerable importance because it was a rational one which anyone could understand. Its defects were many, to be sure, as for example, that it did not allow for the elliptical orbits of the planets;[352] and one critic has claimed that this theory of a motionless earth borne along by an enveloping heaven was comparable to a worm in a Dutch cheese sent from Amsterdam to Batavia,--the worm has travelled about 6000 leagues but without changing its place![353] But this theory fulfilled Descartes's aim: to show that the universe was governed by mechanical laws of which we can be absolutely certain and that Galileo's discoveries simply indicated this.[354] [Footnote 352: Haldane: 291.] [Footnote 353: Monchamp: 185, note.] [Footnote 354: Haldane: 292.] This exposition of the Copernican doctrine strongly appealed to the literary world of the 17th and 18th centuries in western Europe, especially in the Netherlands, in the Paris salons and in the universities.[355] M. Monchamp cites a number of contemporary comments upon its spread, in one of which it is claimed that in 1691, the university of Louvain had for the preceding forty years been practically composed of Cartesians.[356] For the time being, this theory was a more or less satisfactory explanation of the universe according to known laws; it answered to Galileo's observations; it was in harmony with the Scriptures, and its vortices paved the way for the popular acceptance of Newton's law of universal gravitation. [Footnote 355: Ibid: 193, 279.] [Footnote 356: Monchamp: 177-181.]