The heliocentric model is the theory which states that the Sun is the centre of the universe and the planets which orbit around it. The heliocentric model replaced geocentricism. Geocentrism is the belief that the Earth is the centre of the universe. The word ‘helios’ is Greek and means ‘Sun’. With heliocentric meaning that the Sun is at the centre, a heliocentric system is one which the planets revolve around a fixed Sun. Therefore Mercury, Venus, Earth, Mars, Jupiter and Saturn all revolve around the Sun. In this system, the Moon is the only celestial sphere which revolves round the Earth and together with the Earth, revolves around the Sun.
The geocentric model (otherwise known as the Ptolemaic system) was the dominant theory in Ancient Greece, throughout Europe and many other parts of the world for centuries. This theory was developed by philosophers and was named after Claudius Ptolemy who lived circa 90 to 168 A.D. It was developed to explain how planets, the Sun and stars, orbit around the Earth. But this theory is said to have existed long before Ptolemy voiced his opinion. Greek manuscripts, as early as the 4th century, show that Plato and Aristotle were writing about the geocentric model back then.
It was not until the 16th century that the heliocentric model began to become relatively popular. With the progress of technology more evidence was gained in its favour. But the concept of heliocentric had existed throughout the world for centuries. Historians state that Aristarchus of Samos developed a type of heliocentric model as far back as 200 B.C. It is also said that Muslim scholars built on Aristarchus’ work in the 11th century as well as European scholars in Medieval Europe. Astronomer Nicolaus Copernicus devised his own version of the heliocentric model in the 16th century. He also built on Aristarchus’ work. Historians state that he mentioned the Greek astronomer in his notes.
These days, when people speak of the heliocentric theory they are usually referring to Copernicus’ model. The Revolutions of the Heavenly Bodies, a book in which Copernicus published his theory, had Copernicus placing the Earth as the 3rd planet from the Sun. In his model the Moon is shown to orbit the Earth not the Sun. He went on to theorise that the stars do not orbit the Earth. His theory is that the Earth rotates and this makes the stars look as if they have wandered across the sky. Copernicus used geometry to take his heliocentric model one step further. No longer was it deemed a philosophical hypothesis. It was now seen as a the ideal tool to predict planets and celestial body movement.
But the heliocentric model was shunned by the Roman Catholic Church. This was an extremely influential church back in those times. They deemed the theory heretical and nothing more. Some scientists wondered if this attitude had anything to do with Copernicus waiting until he was on his deathbed to publish his theory. He certainly would not have welcomed death at the hand of the church. When Copernicus had died, the Roman Catholic Church pushed even harder to suppress his theory. Galileo was then arrested by the church was promoting what they called the heretical model and he was placed under house arrest for the last 8 years of his life. Approximately the same time Galileo made his telescope, Johannes Kepler (an astronomer) was attempting to prove the heliocentric model with various types of calculations.
Time passed and although it was a slow and often condemned process, the heliocentric model was finally accepted. It replaced the geocentric model. But success was questionable as new evidence came to light. Many began to question whether the Sun really was the centre of the universe. A plethora of schools teach children that heliocentrism is the correct principal of the universe. But astronomers use whichever view they find makes more sense to their own theories.
