The \textit{Principia} and comets (Q5890301)

The author stresses that Newton's law of gravitation indicated that any conic section was a permissible orbit for any celestial body, comets included. The comet of 1680 was one of the keys to his discovery. Its orbit was found to be essentially parabolic and the Principia showed, for the first time, how its orbital parameters could be calculated. The Principia can be regarded in part as a textbook on comets. Newton discusses their luminosity variation, tail formation, periodicity, mass, supposed influence on Earth, and role as a fuel for stars. NEWLINENEWLINENEWLINENewton's approach to orbital calculation was used to find the path and perihelion passage time of Halley's comet at its first expected return in 1758/59. The success of this calculation had a considerable effect on the standing of Newton at that time.