It is marked by the publication of the "Principia" of Newton, an incomparable, an immortal work.
On the principle that all bodies attract each other with forces directly as their masses, and inversely as the squares of their distances, Newton showed that all the movements of the celestial bodies may be accounted for, and that Kepler's laws might all have been predicted--the elliptic motions--the described areas the relation of the times and distances.

As we have seen, Newton's contemporaries had perceived how circular motions could be explained; that was a special case, but Newton furnished the solution of the general problem, containing all special cases of motion in circles, ellipses, parabolas, hyperbolas--that is, in all the conic sections.
The Alexandrian mathematicians had shown that the direction of movement of falling bodies is toward the centre of the earth.

Newton proved that this must necessarily be the case, the general effect of the attraction of all the particles of a sphere being the same as if they were all concentrated in its centre.

To this central force, thus determining the fall of bodies, the designation of gravity was given.

Up to this time, no one, except Kepler, had considered how far its influence reached.