Florian Cajori on Gravity

“Laplace made the assumption that the transmission of gravity is not instantaneous, and he found that in order to produce the known effects in the secular acceleration of the moon, gravity must travel seven million times faster than the speed of light. ...Laplace's calculation has been found to be incomplete, and his velocity of gravity illusory.”

“Newtonian action at a distance is spoken of as "immediate action." Newton, on the other hand, postulates an agent and gives it time to act. To be sure, in his calculations of gravitational attractions, he assumes, as a necessary approximation (having no experimental data on the speed of propagation of gravitational action), that the action is instantaneous, but not so in his talks on gravity. In a letter to Boyle he considers the cause of gravitation between two approaching bodies. They "make the ether between them begin to rarify"; and again, in his hypothesis on light, he says, "So may the gravitating attraction of the earth be caused by the continual condensation of some other such like ethereal spirit... in such a way... as to cause it [this spirit] from above to descend with great celerity for a supply; in which descent it may bear down with it the bodies it pervades, with force proportional to the superficies of all their parts it acts upon."”

“Cotes's Preface [to the 2nd edition of Principia] is of historical importance... It is interpreted as advocating the theory of "action at a distance", and the theory that gravity is an innate property of matter. Phrases in Newton's Principia appear to carry a similar implication. ...In these expressions, the "bodies" or the "corpuscles" are represented as active, as "attracting." They are not passive like a chip of wood carried about by a eddy in a pool, or like a planet passively swept through space by a Cartesian vortex. It was easy, therefore, to jump to an inference that in the Newtonian theory, gravity was an innate, inherent property of matter. ...such an interpretation was made by writers on the European continent, for example by Huygens, Lalande, [Jean Baptiste] Bordas-Demoulin, and others. Thus, after the publication of the Principia in 1687, Huygens... abandoned the explanation of the planetary motion by Descartes' theory of vortices, and published his adherence to Newton's celestial mechanics. But Huygens did not accept the view that gravitation was an innate property of matter, a view which he attributed to Newtonian philosophy. On this point Huygens rejected what interpreted to be the tenet of Newton, and continued his adhesion to the tenet of Descartes. While the reader of the first edition of Principia had some justification in attributing to Newton the view that gravity was an innate property of matter, they were nevertheless mistaken. In the first edition Newton had made no explicit declaration on this point. ...Newton was no more a believer in gravity as an innate property of bodies than was Descartes. But the readers of the first edition of Principia had no means of knowing this.”