time the concept of inertia had its modern meaning as the tendency of objects to remain in uniform motion and he viewed the Sun as just another heavenly body. Borelli developed the idea of mechanical equilibrium, a balance between inertia and gravity. Newton cited Borelli's influence on his theory.

In 1657, Robert Hooke published his Micrographia, in which he hypothesized that the Moon must have its own gravity. In a communication to the Royal Society in 1666