In physical cosmology, the Copernican principle states that humans, on the Earth or in the Solar System, are not privileged observers of the universe, that observations from the Earth are representative of observations from the average position in the universe. Named for Copernican heliocentrism, it is a working assumption that arises from a modified cosmological extension of Copernicus' argument of a moving Earth.
Figure 'M' (for Latin Mundus) from Johannes Kepler's 1617–1621 Epitome Astronomiae Copernicanae, showing the Earth as belonging to just one of any number of similar stars
Copernican heliocentrism is the astronomical model developed by Nicolaus Copernicus and published in 1543. This model positioned the Sun at the center of the Universe, motionless, with Earth and the other planets orbiting around it in circular paths, modified by epicycles, and at uniform speeds. The Copernican model displaced the geocentric model of Ptolemy that had prevailed for centuries, which had placed Earth at the center of the Universe.
Heliocentric model from Nicolaus Copernicus' De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres)
Nicolai Copernicito Torinensis De Revolutionibus Orbium Coelestium, Libri VI (On the Revolutions of the Heavenly Spheres, in six books) (title page of 2nd edition, Basel, 1566)
Statue of Copernicus next to Cracow University's Collegium Novum
Andreas Cellarius's illustration of the Copernican system, from the Harmonia Macrocosmica (1660)