Eighteen centuries before Copernicus, someone sets the Earth going around the Sun. In a book that survives, the Greek astronomer and mathematician Aristarchus of Samos works out that the Sun is far larger than the Earth. In other writings, he proposes that the Sun and the stars stand still, and that the Earth circles the Sun, spinning as it goes. If so, why don’t the stars seem to shift as we move? Aristarchus has an answer: they are so far away that the Earth’s whole orbit is like a point next to their distance.

Those writings are lost. We know of them from the mathematician Archimedes, who sums them up in a book of his own, and from later writers. Hardly anyone follows Aristarchus. The Stoic philosopher Cleanthes thinks he should be charged with impiety for moving the hearth of the universe.

Every day, the sky turns around us. The Sun, the Moon, and the stars rise and set as if the Earth stood still at the center of everything. The Greek astronomer and mathematician Claudius Ptolemy, working in Alexandria, writes the Almagest, which works out the motions of the Sun, the Moon, and the planets in more detail than anyone before.

His Earth sits motionless at the center. The Sun goes around it on a circle set a little off-center, and the Moon and the planets move on circles that ride on bigger circles. These smaller circles, called epicycles, explain a puzzling sight: every so often, a planet seems to stop, drift backward among the stars for weeks, and then move on. With them, Ptolemy can predict where each planet will be for years ahead. And to anyone who would set the Earth spinning, he points to the clouds and the birds.

What if the sky isn’t turning at all, but we are? The Polish astronomer Nicolaus Copernicus publishes On the Revolutions of the Heavenly Spheres. A friend later writes that Copernicus saw the finished book only on the day he died.

In his system, the Sun stands near the center, and the Earth is just another planet: it spins once a day and circles the Sun once a year. Things Ptolemy had to set by hand now follow on their own. Mercury and Venus never stray far from the Sun because their orbits lie inside ours. And Mars seems to loop backward whenever the faster Earth overtakes it.

But Copernicus still needs small circles on his circles, and his predictions are hardly better than Ptolemy’s. One question troubles his readers: if the Earth moves, why don’t the stars seem to shift over the year? They are too far away, Copernicus answers, for the shift to be seen.

The sharpest eyes of the age can’t find the Earth’s motion. The Danish astronomer Tycho Brahe measures the sky from his observatory on the island of Hven, with instruments more precise than any before, good to about a minute of arc, a 60th of a degree. If the Earth circled the Sun, the stars should seem to shift a little over the year, as we see them from different sides of our orbit. Tycho sees no such shift.

So he builds a system of his own and publishes it in 1588: the planets circle the Sun, but the Sun, carrying them along, circles a motionless Earth. It explains everything Copernicus’s system does, without moving the Earth. In a letter the next year to the German astronomer Christoph Rothmann, a follower of Copernicus, Tycho spells out why a moving Earth makes no sense to him.

A tiny mismatch changes astronomy. The German astronomer and mathematician Johannes Kepler, who worked with Tycho in Prague until Tycho’s death in 1601, inherits his measurements of Mars. For years he tries to fit them with circles, as every astronomer before him had. His best attempt still misses some of them by eight minutes of arc, about a quarter of the Moon’s width. Others might have blamed the measurements, but Tycho’s were too good for that.

These eight minutes alone, Kepler writes in his Astronomia nova, have shown the way to reform all of astronomy. Mars moves not on a circle but on an ellipse, a stretched circle, with the Sun off-center at one of the ellipse’s two foci, and it moves faster when it’s closer to the Sun.

Years later, Kepler’s tables, built on ellipses, foretell that Mercury will pass across the face of the Sun on November 7, 1631. In Paris, the French philosopher and astronomer Pierre Gassendi watches it happen.

A new instrument settles an old question. The Italian astronomer and physicist Galileo Galilei turns a telescope to the sky. In January, in Padua, Italy, he finds four moons circling Jupiter: the Earth isn’t the only center that things go around.

Then, watching Venus through the fall, he sees it change shape like the Moon. At first it’s small and nearly round, then it grows larger and half-lit, and he expects it to become a large, thin crescent, which it soon does. On December 11 he hides the discovery in a Latin anagram, to claim it without yet giving it away. Unscrambled, it reads: “The mother of loves imitates the shapes of Cynthia,” that is, Venus imitates the Moon.

In Ptolemy’s arrangement, Venus always stays between the Earth and the Sun, so we could only ever see it as a crescent. Tycho’s system passes the test, though: there, as in Copernicus’s, Venus circles the Sun.

If the Earth moves, why don’t we feel it? Galileo answers with a ship, in his Dialogue Concerning the Two Chief World Systems. Shut yourself below deck on a ship sailing smoothly, he writes, with butterflies, a bowl of fish, and water dripping from a bottle. They all behave just as they would in port: nothing shows that the ship is moving. A stone dropped from the top of the mast lands at its foot, not behind it, because it keeps the ship’s motion as it falls. Cannonballs on a moving Earth do the same, so they fly as far to the east as to the west.

Galileo reasons this out rather than trying it. Gassendi tries it in 1640, on a galley in the harbor of Marseille, and the stone lands at the foot of the mast. The book costs Galileo dearly: in 1633, the Roman Inquisition condemns him, and he spends the rest of his life under house arrest.

For and against a moving Earth, the arguments have piled up for a century. The Italian Jesuit astronomer Giovanni Battista Riccioli gathers them in his New Almagest, a vast survey of astronomy: 126 in all, 49 for a moving Earth and 77 against. Weighing them, he concludes that the Earth stands still. But he doesn’t keep Tycho’s circles. Impressed by Kepler’s ellipses, he works them into a system much like Tycho’s: the Moon, the Sun, Jupiter, and Saturn roughly circle the Earth, and Mercury, Venus, and Mars go around the Sun on ellipses.

His book also brings a new map of the Moon, drawn by his fellow Jesuit, the physicist Francesco Maria Grimaldi, with names still used today. Riccioli gives craters to astronomers on both sides, Copernicus, Kepler, and Aristarchus among them, and gives Grimaldi and himself craters side by side.

Hunting for one shift of the stars, an astronomer finds a different one. The English astronomer James Bradley wants to find the shift that Tycho couldn’t, known as parallax: as the Earth moves from one side of its orbit to the other, a nearby star should seem to move against the stars behind it. He measures the star Gamma Draconis with a telescope pointed straight up.

The star does move back and forth over the year, by about 20 seconds of arc either way, but its extremes come three months off from where the Earth’s position would put them. They follow the direction the Earth is moving in instead. So it’s a different shift, known today as the aberration of starlight, caused not by where the Earth is but by which way it’s going: light takes time to reach us, and because the Earth moves, it seems to come in at a slight slant, as rain does when you run through it.

Bradley finds the same aberration in other stars, and works out that light takes 8 minutes 12 seconds to come from the Sun, close to today’s 8 minutes 19 seconds. Of parallax, he finds no sign: it must be smaller than a second of arc. So Tycho’s objection stands.

After nearly three centuries, parallax turns up. The German astronomer and mathematician Friedrich Wilhelm Bessel picks 61 Cygni, a faint star that creeps across the sky faster than almost any other, a hint that it’s near. With a heliometer, a telescope whose lens is cut in half so that the halves can slide past each other to measure small angles, he compares its position with two fainter stars nearby, for over a year.

61 Cygni shifts back and forth with the seasons by 0.31 seconds of arc either way, about the width of a coin seen from 13 kilometers away. So it’s about 660,000 times farther from us than the Sun, and its light takes about ten years to reach us; today’s figure is 11.4 years. The stars are even farther away than Tycho said they would have to be, and the empty gap he found absurd is real.

Soon after, the Scottish astronomer Thomas Henderson reports parallax for the star Alpha Centauri, and the German-born astronomer Friedrich Georg Wilhelm Struve had already reported a smaller, less certain one for the star Vega.

You can watch the Earth turn. The French physicist Léon Foucault hangs a heavy ball from a long wire and sets it swinging. Nothing pushes the swing sideways, and yet over the hours it turns, slowly and steadily clockwise: about 11 degrees an hour in Paris, all the way around in about 32 hours. Only at the poles would it take a day; the farther from them, the slower it turns. It isn’t the pendulum that turns but the floor beneath it, carried around by the spinning Earth.

Foucault reports it to the Academy of Sciences on February 3. In March, he hangs a 28-kilogram ball from a 67-meter wire under the dome of the Panthéon, and crowds come to watch the Earth turn beneath it. The motion that Ptolemy and Tycho thought absurd is now something anyone can see.

The Sun doesn’t stand still either. Since 1918, the American astronomer Harlow Shapley has argued that it lies far from the center of our galaxy, the Milky Way, a vast, flat disk of stars. In 1925, the Swedish astronomer Bertil Lindblad proposed that the whole disk turns. The Dutch astronomer Jan Oort tests it. If the galaxy turned like a solid wheel, the stars around us would keep their places. But if stars nearer the center go around faster, as planets nearer the Sun do, the stars ahead of us and behind us should drift in a telltale pattern. Analyzing the measured motions of hundreds of stars, Oort finds just that pattern. The Sun, carrying the Earth and the other planets along, circles the center of the Milky Way.

Today, the Sun is known to lie about 27,000 light-years from the center, moving at about 230 kilometers a second and going around once every 230 million years or so. The planets follow their ellipses around it, nudged by each other’s pull, and in small ways, as Mercury’s orbit showed, that general relativity accounts for better than Newton’s law. Strictly, they circle the solar system’s center of mass, which, mostly because of Jupiter, wanders from near the Sun’s center to beyond its surface. And the Milky Way is one galaxy among billions. The German philosopher Immanuel Kant guessed as much in 1755: some of the faint, cloudy patches in the sky, called nebulae, might be other Milky Ways, far away. In the 1920s, the American astronomer Edwin Hubble showed that the Andromeda nebula is, in fact, another galaxy, far beyond our own.

So neither the Earth nor the Sun is the center of everything, and in Einstein’s theories, nothing is absolutely at rest. But measured against the faraway stars and galaxies, where the laws of motion are simplest, it’s the Earth that turns and goes around the Sun, as Foucault’s pendulum, the aberration of starlight, and parallax all show.