Halley (1656-1742) later befriended Newton, and in fact paid the 1687 publishing costs of Newton's Principia Mathematica, where many of Newton's scientific discoveries and theories were first published.
Halley was also a scientist, and he used Newton's theories and a careful study of historical observations of comets to propose a test of Newton's Law of Gravitation (hypothesis).
Halley, using Newton's theory of gravitation, predicted the return of a particular comet in the year 1758. Although Halley died 16 years before the comet arrived, it's arrival completed one of the grandest hypothesis tests in the history of science.
Today, after careful study of the historical records, we now have 28 well-documented occurrences of Halley's Comet, which passes by about every 75 years and last appeared in 1986.
The comet's arrival also extended the realm of "Universality" beyond the planets to include all the Solar System.