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2/n In effect, Leibniz had posited two independent but superimposed vortices for each planet, the vortex that causes gravity and the harmonic vortex, so that he could recover Kelper's harmonic law and the law of the areas.
3/n Huygens, in correspondence, (Huygens to Leibniz 11 July 1692) challenged him on this, arguing that the harmonic vortex was not necessary since Newton had shown that gravity was enough for Kepler’s laws to hold.
4/n Leibniz replied he could not abandon this “deferent matter” [the harmonic vortex] because it explains why “all the planets [as well as the satellites of Jupiter and of Saturn] move somewhat in the same direction”; a thing that Newton’s theory just takes for granted.
5/nLeibniz wrote to Newton on the 7th of March 1692/3. In this letter, he praised Newton for having made “the astonishing discovery that Kepler’s ellipses result simply from the conception of attraction or gravitation and passage in a planet” .
6/n Leibniz added, however, that he thought that Newton’s account is incomplete since it leaves out the causes of attraction, which Leibniz took it to be “the motion of a fluid medium”.
7/n But the real purpose of Leibniz’s letter was to solicit Newton’s opinion regarding Huygen’s vortex theory.
In his reply (16 October 1693) Newton objected to vortex theory on the grounds that the vortices would disturb the motions of the planets and the comets.
In his reply (16 October 1693) Newton objected to vortex theory on the grounds that the vortices would disturb the motions of the planets and the comets.
8/n Newton made the further point that the laws of gravity he discovered were enough to account for the motion of the heavenly bodies.
9/n Moreover, as Newton put it, “since nature is very simple, I have myself concluded that all other causes are to be rejected and that the heavens are to be stripped as far as may be of all matter, lest the motions of planets and comets be hindered or rendered irregular”
10/n Newton’s disciple David Gregory in his Astronomiae physicae et geometricae elementa (1702), showed that Kepler’s third law was inconsistent with the idea that planets are carried by harmonic vortices. Besides, Leibniz’s theory cannot account for the motion of the comets
11/n Newton himself took issue with Leibniz’s account arguing that Leibniz had the wrong measure of centrifugal force, which was for Newton equal and opposite to the force of attraction and that Leibniz’s mathematical reasoning was unsound
