Newton's Principia appeared, setting the foundation of modern physics

In 1687, Isaac Newton’s Philosophiae Naturalis Principia Mathematica — the Principia — was published under the auspices of the Royal Society in London, a date often marked as July 5, 1687.

The book set out Newton’s three laws of motion and his law of universal gravitation, showing that the same force pulling an apple to the ground also holds the Moon in its orbit. With these few principles and his new mathematics, Newton could explain planetary motion, tides, and the paths of comets — the birth of classical mechanics.

One framework, Newton argued, governed both terrestrial and celestial motion.

It nearly never appeared. The Royal Society had drained its funds on a lavishly illustrated History of Fishes, so the astronomer Edmond Halley paid for the Principia largely out of his own pocket. The gamble paid off: the work reshaped science for the next two centuries.