English mathematician and natural philosopher (otherwise called a physicist) Isaac Newton (1642–1727) was one of the greatest scientists who ever lived. Overall, he contributed to physics (such as the discovery of his three famous laws of motion); fluid dynamics (fluid motion); the union of terrestrial and celestial mechanics using the principle of gravitation—thus explaining Kepler’s laws of planetary motion; and he even explained the principle of universal gravitation.

By 1665 Newton had not only begun his work on differential calculus, but he also had published one of his greatest scientific works—Philosophiae naturalis principia mathematica (The Mathematical Principles of Natural Philosophy), often shortened to The Principia or just Principia. In it he presents his theories of motion, gravity, and mechanics, thus explaining the bizarre orbits of comets, tides and tidal variations, the movement of the Earth’s axis (called precession), and motion of the Moon. And although he used calculus to find many of his scientific results, Newton also explained them using older geometric methods in the book. After all, calculus was very new. Perhaps he was the first scientist-writer to make sure everyone understood what he was proposing.