The Copernican Revolution is the name given to the slow replacement, between the sixteenth and eighteenth centuries, of the ancient picture of a stationary Earth at the centre of the cosmos by a system in which the Earth is one of several planets circling the Sun. It takes its name from Nicolaus Copernicus, whose book of 1543 set the change in motion, but it was completed by later astronomers and physicists. The phrase is also used for the wider cultural shift that followed, and, since the philosopher Thomas Kuhn, as the classic example of a "paradigm shift" in science.
The old cosmos
For well over a thousand years European and Middle Eastern astronomers worked within the Earth-centred model set out by Ptolemy in the Almagest around AD 150, which fitted neatly with Aristotle's physics. A Sun-centred universe had been proposed in antiquity by Aristarchus of Samos in the third century BC, but the idea had been overshadowed. Criticism of Ptolemy's details nonetheless continued, from Averroes and from Persian astronomers associated with the Maragheh observatory, and it fed into fifteenth-century Latin scholarship.
Copernicus
Copernicus, a Catholic canon who had studied at Bologna in 1496–1501, published De revolutionibus orbium coelestium in 1543, the year of his death; it was printed in Nuremberg. His main aim was to rid astronomy of the equant, a device he saw as breaking the rule that heavenly motions should be uniform and circular. To do so he put a stationary Sun near the centre, made the Earth spin daily and orbit yearly, and explained the apparent backward loops of the planets as an effect of the Earth's own motion. Yet he kept circular orbits and epicycles, and several historians stress that the book itself was cautious and traditional; Kuhn called it "revolution-making" rather than revolutionary.
Slow acceptance
Most astronomers read the book with interest but did not accept a moving Earth. A few, such as Thomas Digges and Giordano Bruno, used it to argue for a far larger or even infinite universe. Protestant leaders, including Martin Luther and Philip Melanchthon, attacked the theory as contrary to Scripture, while the Catholic Church used Copernican calculations in its 1582 calendar reform and otherwise stayed silent until 1610. Tycho Brahe admired the model's mathematics but rejected a moving Earth.
Telescope and ellipses
Two developments transformed the debate in the early seventeenth century. Galileo Galilei turned a telescope on the sky and in 1610 reported a rough, uneven Moon, moons orbiting Jupiter and a full set of phases of Venus, which the Ptolemaic system could not explain. Meanwhile Johannes Kepler, working from Tycho's measurements, developed his laws of planetary motion between 1609 and 1619 and replaced circles with ellipses, which greatly improved predictions. The Church's response led to the Galileo affair: in 1616 Copernicus's book was suspended until corrected, and in 1633 Galileo was tried and placed under house arrest.
Newton and proof
In 1687 Isaac Newton published the Principia, which explained Kepler's laws through universal gravitation and laws of motion and gave the Sun-centred system a firm physical basis. Further evidence followed: James Bradley's discovery of stellar aberration in 1727 and Friedrich Bessel's measurement of a star's parallax in 1838. The Catholic Church dropped its general ban on heliocentric books in 1758.
Wider meaning
Beyond astronomy, the shift is often described as removing humanity from the centre of creation and weakening the medieval blend of Aristotelian physics and Christian theology. Immanuel Kant compared his own philosophical method to Copernicus's hypothesis in 1787, and the phrase later became a general metaphor for any deep intellectual upheaval.
On our maps
Our 1530 and 1600 maps show Europe as Copernicus's book appeared, including the Holy Roman Empire, where it was printed; the 1700 map shows the continent soon after Newton's Principia.