Heliocentrism

Heliocentrism (also known as the heliocentric model) is a superseded astronomical model that placed the Sun at the center of the universe, with the Earth and the planets in its orbit. It superseded geocentrism, which placed the Earth at the center of the universe. In modern astronomy, heliocentrism has been superseded by models based on relativity, in which the universe does not have an absolute center or preferred frames of reference. Historically, heliocentrism was opposed to geocentrism, which placed Earth at the center. The notion that Earth revolves around the Sun had been proposed as early as the 3rd century BC by Aristarchus of Samos, who had been influenced by a concept presented by Philolaus who in the 5th century BC had the thought that Earth was spherical and revolving around a "mystical" central fire, and that this fire regulated the universe. In medieval Europe, however, Aristarchus' heliocentrism attracted little attention—possibly because of the loss of scientific works of the Hellenistic period. It was not until the 16th century that a mathematical model of a heliocentric system was presented by the Renaissance mathematician, astronomer, and Catholic cleric, Nicolaus Copernicus, leading to the Copernican Revolution. In the following century, Johannes Kepler introduced elliptical orbits for all planets discovered up to his time (genuinely heliocentric), and Galileo Galilei presented observations of the Solar System made using his telescope. With the observations of William Herschel, Friedrich Bessel, and other astronomers, it was realized that the Sun, while near the barycenter of the Solar System, was not central in the universe. Modern astronomy does not distinguish any universal center. After these discoveries, informal language still holds to the remaining truth value of the term, narrowed to the scope of our planetary system.