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The heliocentric model is a theory that places the Sun as the center of the universe, and the planets orbiting around it. The heliocentric model replaced geocentrism, which is the belief that the Earth is the center of the universe. The geocentric model was the prevailing theory in Ancient Greece, throughout Europe, and other parts of the world for centuries. It was not until the 16th century that the heliocentric model began to gain popularity because technology progressed enough to gain more evidence in its favor. Although heliocentrism did not gain popularity until the 1500′s, the idea had existed for centuries throughout the world.
In fact, Aristarchus of Samos – Samos was an island near Turkey – developed a form of the heliocentric model as early as approximately 200 B.C. Other ancient civilizations held the same beliefs including various Muslim scholars in the 11th century who built on Aristarchus’ work and European scholars in Medieval Europe.
In the 16th century, the astronomer Nicolaus Copernicus devised his version of the heliocentric model. Like other before him, Copernicus built on Atistarchus’ work, mentioning the Greek astronomer in his notes. Copernicus’ theory became so well known that when most people discuss the heliocentric theory today, they are referring to Copernicus’ model. Copernicus published his theory in his book On the Revolutions of the Heavenly Bodies. Copernicus placed the Earth as the third planet from the Sun, and in his model, the Moon orbits the Earth not the Sun. Copernicus also hypothesized that the stars do not orbit the Earth; the Earth rotates, which makes the stars look like they have moved in the sky. Through the use of geometry, he was able to turn the heliocentric model from a philosophical hypothesis to a theory that did a very good job predicting the movement of the planets and other celestial bodies.
One problem facing the heliocentric model was that the Roman Catholic Church, a very powerful organization in Copernicus’ time, considered it heretical. This may have been one of the reasons why Copernicus did not publish his theory until he was on his deathbed. After Copernicus died, the Roman Catholic Church worked even harder to suppress the heliocentric view. The Church arrested Galileo for promoting the heretical heliocentric model and kept him in house arrest for the last eight years of his life. Around the same time that Galileo created his telescope, the astronomer Johannes Kepler was refining the heliocentric model and trying to prove it with calculations.
Although its progress was slow, the heliocentric model eventually replaced the geocentric model. As new evidence appeared though, some began to question whether the Sun was actually the center of the universe. The Sun is not the geometric center of the planets’ orbits, and the center of gravity of the Solar System is not quite at the center of the Sun. What this means is that although children are taught in schools that heliocentrism is the correct model of the universe, astronomers use either view of the universe depending on what they are studying, and what theory makes their calculations easier.
Astronomy Cast also has an episode about the center of the universe.