Every Falling Thing

The Moon is falling. It has been falling for four billion years and never lands, because it is also moving sideways fast enough to keep missing. That single idea, that the Moon and an apple obey the same rule, is the moment physics became one subject.

Before it, the heavens ran on one set of laws and the ground on another. After it, a thrown stone, a comet, a tide and a planet nobody had seen yet were all the same problem, and the problem could be solved with a pen.

Thirty-five chapters. No equations to work through. The full story, from balls on a ramp to the arithmetic that steers a spacecraft.

• Why things were once thought to fall toward the center of the universe


• Balls rolled down ramps, and what they proved about speed and time


• The tower, the feather and the vacuum


• Why a stone thrown sideways traces the same curve as one dropped


• The ship's cabin: why you cannot feel steady motion


• The man with the brass nose who measured the sky for twenty years


• The war on Mars, and the eight minutes that broke the circle


• Three laws of planets, found in someone else's data


• The quiet years at Woolsthorpe, and the question a comet-hunter asked


• Three laws for everything that moves, stated so they stay stated


• The Moon falls too, and the calculation that proved it


• What survives a collision, and why spinning things are stubborn


• The coincidence at the heart of gravity that took two centuries to explain


• Why the ocean breathes twice a day


• The turning floor, and the slow wobble of the axis


• Two bodies solved exactly, three bodies and the birth of chaos


• Energy as the other bookkeeping, and nature's cheapest path


• The comet that came back on schedule, and the planet found with a pen


• The hunt for a planet that did not exist


• Weighing the Earth with a mountain, then with a shed


• The tyranny of the rocket equation, and stealing speed from a planet

Ending at the edge of the clockwork. Where the laws stop being exact, why they are still good enough to fly a spacecraft, and what replaced them at the margins.

This is the story of how one rule turned the sky into a machine, told through the people who found it and the objects they used.

Scroll up and start reading.