Halley's Comet

Happened to read this:

Halley's comet, which passed around the sun early in 1986, moves in a highly elliptical orbit with an eccentricity of 0.967 and a period of 76 years. This orbit takes the comet inside the path of Venus, almost to Mercury's orbit, and out past even the orbit of Neptune and sometimes even the moderately eccentric orbit of Pluto. Edmond Halley is generally given the credit for bringing Newton's work on gravitational and central forces to the attention of teh world. After observing the comet personally in 1682, Halley became interested. Partly as a result of a bet between Christopher Wren and Rober Hooke, Halley asked Newton in 1684 what paths the planets must follow if the Sun pulled them with a force inversely proportional to the square of their distances. To the astonishment of Halley, Newton replied, "Why, in ellipses, of course." Newton had worked it out 20 years previously but had not published the result. With painstaking effort, Halley was able in 1705 to predict the next occurence of the comet, now bearing his name in 1758.

To think Newton figured it out already, before even seeing the comet...