For a long time, the concept that the Earth was the centre of the Universe held sway. It was believed that everything else, including the Sun revolved around it. Simple observation of the stars do seem to show that the Earth is stationary. Any movement appears to be from everything else out there.
After all, the cornerstone of the main religions were that God created the Earth, and the other planets were where the Angles lived. Unfortunately, this geocentric doctrine kept running into problems, such as why the other planets seem to reverse their orbit and go backwards for a while. This retrograde motion of the planets is known as a parallax effect.
The Ptolemaic theory answered these problems, back in the 2nd Century, but the answers were pretty elaborate. As science has taught us, the simpler the explanation, the bigger the chance of it being true. The Ptolemaic theory, while trying to keep the Earth the centre of the universe, and solve the parallax effect became too complicated.
The first mention of the heliocentric model is by Aristotle, who wrote in the 4th Century BC that the Pythagoreans believed that the Earth, stars and planets circled a great fire (the Sun). It has also been said that this heliocentric model of the universe had more of a philosophical basis than a scientific or observed one.
Further reading: What is Difference between Heliocentric and Geocentric
A heliocentric model of the universe did not really surface again from the divine geocentric model, until Copernicus, in 1543, printed a book laying down his ‘hypothesis’ of a heliocentric model. The book was coached in terms of hypothesis rather than fact because of the power of the church and its geocentric beliefs.
Galileo, through his studies of the sky using a telescope, backed Copernicus’s model with observable fact, published in his book ‘Dialogo’ in 1632. Unfortunately, the church backed view of the universe and the Earth’s central position overwhelmed any and all stalwarts of the heliocentric model of the universe.
Although the church doctrine fought against the heliocentric model, the solar theory slowly crept into standard scientific thought. Every proof that the Earth revolved around the Sun was scientifically studied, proven, and published. Even so, into the middle 1800s, the church tried to suppress the heliocentric model and reinstate the geocentric view.
Interestingly, it is now accepted that the universe is neither heliocentric, nor geocentric. The Sun is just one star among many others, in a universe, beside many other universes, among many galaxies. Galileo touched upon this concept of one star among many among others, all those years ago. It took until the 20th Century and a scientific system free from doctrine to observe the sky and find the truth of our position in the great expanse of space.
