Isaac Newton’s theory of gravity was published as Philosophiæ Naturalis Principia Mathematica in 1687.
Translated, it means “Mathematical Principles of Natural Philosophy”.
Interestingly, Newton wrote it at the persistent urging of well-known astronomer Edmund Halley, a colleague and good friend.
When Newton finished it, Halley had the piece published with his own money.
The Principia described Newton’s laws of motion, Newton’s law of universal gravitation, and a derivation of Kepler’s laws of planetary motion.
The three books are often regarded as one of the most important works in the history of science.