In my post, Johannes Kepler and Inverse-Square Laws, I wrote that Johannes Kepler (1571-1630) was the first to propose an inverse-square law, for the propagation of light, but that he missed this opportunity for gravity; this task would fall on the shoulders of Isaac Newton (1643-1727).
Thanks for your blog, as always! One question springs to mind: how did Newton calculate the mass of planets?
Good question. Will look into this.