In England in 1665, Isaac Newton, having fled Cambridge University to escape the Great Plague, settled back in the town of his birth, the rural community of Woolsthorpe, Lincolnshire. Over the next several years, he developed calculus and revolutionary ideas about light. In 1687, he published his Law of Universal Gravitation, stating that every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. For the first time, scientists could calculate the force of attraction between objects in space. This was a giant step forward in scientists’ ability to understand the heavens. But the most important realization to emerge from Newton’s era was simply that the universe is governed by physical processes. Given the right tools, these processes can be understood by humans. No longer did the universe obey the whims of mystical and unfathomable powers: what was out there was just physics.