The Principia (Mathematical Principles of Natural Philosophy)

The Principia, written by Isaac Newton, is a foundational work that explains how objects move and interact through gravity and motion. It introduces the laws of motion—describing how objects stay at rest or in motion unless acted upon—and formulates the law of universal gravitation, showing that every object attracts every other with a force proportional to their masses and distance. These principles unify celestial and earthly physics, laying the groundwork for classical mechanics. Essentially, the Principia mathematically reveals the natural laws governing everything from apples falling to planets orbiting the sun.