Copernican Revolution

For the 1957 book by Thomas Kuhn, see The Copernican Revolution (book). For metaphorical uses of the term, see Copernican Revolution (metaphor).

Motion of Sun, Earth, and Mars according to heliocentrism (left) and to geocentrism (right), before the Copernican-Galilean-Newtonian revolution. Note the retrograde motion of Mars on the right. Yellow dot, Sun; blue, Earth; red, Mars.
(In order to get a smooth animation, it is assumed that the period of revolution of Mars is exactly 2 years, instead of the actual value, 1.88 years). The orbits are assumed to be circular.

The Copernican Revolution refers to the paradigm shift away from the Ptolemaic model of the heavens, which postulated the Earth at the center of the galaxy, towards the heliocentric model with the Sun at the center of our Solar System. It was one of the starting points of the Scientific Revolution of the 16th century.

Historical overview

In 1543 Nicolaus Copernicus published his treatise De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres), which presented a heliocentric model view of the universe. It took about 200 years for a heliocentric model to replace the Ptolemaic model.

To describe the innovation initiated by Copernicus as the simple interchange of the position of the earth and sun is to make a molehill out of a promontory in the development of human thought. If Copernicus' proposal had had no consequences outside astronomy, it would have been neither so long delayed nor so strenuously resisted.^[1]

Nicolaus Copernicus

Nicolaus Copernicus, in his On the Revolutions of the Heavenly Spheres (1543), demonstrated that the motion of the heavens can be explained without the Earth being in the geometric center of the system. This led to the view that we can dispense with the assumption that we are observing the universe from a special position. Although Copernicus initiated the revolution, he certainly didn't complete it. He continued to believe in the celestial spheres and could provide little in the way of direct observational evidence that his theory was superior to Ptolemy's.

Tycho Brahe

The Danish astronomer Tycho Brahe, while remaining a geocentric, contributed to the revolution by showing that the heavenly spheres were at best mathematical devices rather than physical objects, since the great comet of 1577 passed through the spheres of several planets, and, moreover, the spheres of Mars and the Sun passed through each other. Brahe and his assistants also made the numerous and painstaking observations which allowed Johannes Kepler to derive his laws of planetary motion. Kepler's revised heliocentric system gave a far more accurate description of planetary motions than the Ptolemaic one.

Johannes Kepler

Johannes Kepler proposed an alternative model, essentially the modern one, in which the planetary orbits were ellipses, rather than circles modified by epicycles as Copernicus used.

Galileo Galilei

Starting with his first use of the telescope for astronomical observations in 1610, Galileo Galilei provided support for the Copernican system by observing the phases of Venus and the moons of Jupiter (which showed that the apparently anomalous orbit of the Moon in Copernicus' theory was not unique). Galileo also wrote a defense of the heliocentric system, Dialogue Concerning the Two Chief World Systems (1632), which led to his trial and house arrest by the Inquisition.

Giordano Bruno

In the same period, a number of writers inspired by Copernicus, such as Thomas Digges and Giordano Bruno, argued for an infinite or at least indefinitely extended universe, with other stars as distant suns. Although opposed by Copernicus and Kepler (with Galileo agnostic), by the middle of the 17th century this became widely accepted, partly due to the support of René Descartes.

Isaac Newton

The Copernican revolution was arguably completed by Isaac Newton whose Philosophiae Naturalis Principia Mathematica (1687) provided a consistent physical explanation which showed that the planets are kept in their orbits by the familiar force of gravity. Newton was able to derive Kepler's laws as good approximations and to get yet more accurate predictions by taking account of the gravitational interaction between the planets.

Metaphorical use

Main article: Copernican Revolution (metaphor)

The philosopher Immanuel Kant made an analogy to Copernicus when describing a problem from a different point of view, and some later philosophers have called it his "Copernican revolution".^[2] The conditions and qualities he ascribed to the subject of knowledge placed man at the centre of all conceptual and empirical experience, and overcame the rationalism-empiricism impasse, characteristic of the 17th and 18th centuries. See also Subject-object problem.

See also

• Copernican federalism
• Scientific Revolution
• Subject-object problem

Notes

1. ^ Kuhn 1957, p. 94
2. ^ [1]

References

1. Blumenberg, Hans; Robert M. Wallace (translator) (1987). The genesis of the Copernican world. Cambridge, Massachusetts: The MIT Press. pp. 1,772. ISBN 978-026252144X. 
2. Koestler, Arthur (1959). The Sleepwalkers: A History of Man's Changing Vision of the Universe. Hutchinson. 
3. Koyré, Alexandre (1957). From the Closed World to the Infinite Universe. Johns Hopkins University Press. 
4. Kuhn, Thomas S. (1957). The Copernican Revolution. Planetary Astronomy in the Development of Western Thought. Cambridge, Massachusetts: Harvard University Press. ISBN 978-0674171039. 
5. Kuhn, Thomas S.; Conant, James and Haugeland, John (2000). The road since structure : philosophical essays, 1970-1993, with an autobiographical interview. Chicago: University of Chicago Press. ISBN 978-0226457982.