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heliocentric model
The heliocentric view centers around the belief that the Sun is the center of the universe and that the planets and other celestial bodies revolve around it. We have expanded on that to realize that the Sun is near the barycenter of our galaxy, but the basic premise is still true. While this is not revolutionary today, it was believed to be both ridiculous and heresy at different times in the past. The possibility that the Earth revolved around the Sun was first introduced by Aristarchus in the 3rd century B.C.; however, it was not until the 16th century that a fully predictive heliocentric mathematical model was presented by Nicolaus Copernicus.
It is hard to understand the revolution that heliocentrism caused without knowing that the previous view, geocentrism, was proposed in the 2nd century B.C by Ptolemy, who was considered one of the greatest thinkers of his time. His view was accepted widely because anyone who looked into the sky could see that objects moved across the sky and; therefore, the Earth must be stationary while other objects moved around it. This notion was supported by the all powerful church in the Dark and Middle Ages. Anyone who opposed it could be tried and tortured for their belief.
Copernicus presented a discussion of a heliocentric model of the universe. He discussed the philosophical implications, elaborated his system in full geometrical detail, used astronomical observations to establish the parameters of his model, and wrote astronomical tables that allowed computation of the past and future positions of the stars and planets. This moved heliocentrism from a philosophical speculation to a predictive geometrical astronomy.
Kepler’s laws of planetary motion were used as arguments in favor of the heliocentrism. Another apparent proof of heliocentrism was when Friedrich Bessel proved that parallax of a star was greater than zero. The realization that the heliocentric view was not true in a strict sense was achieved in steps. That the Sun was not the center of the universe, but one of innumerable stars, was strongly advocated over the course of the 18th and 19th centuries and the status of the Sun as one star among many became obvious. If you limit yourself to our solar system. the sun is not at the geometric center of any planet’s orbit, but only one focus in an elliptical orbit, also a planet’s mass cannot be neglected in comparison to the Sun’s mass, so the center of gravity of the solar system is displaced slightly away from the center of the Sun. Lastly, since the entire universe is in constant motion, it is impossible to believe that any one position can be stationary and have other revolve around it.
We have written many articles about the Heliocentric view for Universe Today. Here’s an article about the Heliocentric Model, and here’s an article about the difference between Geocentric and Heliocentric Model.
If you’d like more info on the Solar System, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.
We’ve also recorded a series of episodes of Astronomy Cast about every planet in the Solar System. Start here, Episode 49: Mercury.
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