Heliocentric Model of the Solar System

Introduction

The Astronomical heliocentric model describes that the Earth and the other planets revolve around the Sun at the center of the Solar System. In ancient times, 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, but in the prehistoric world, Aristarchus's heliocentrism attracted very little attention, might be possibly because of the loss of proper scientific works.

Further at the end of 13th century, the great saint of western India, Saint Dnyaneshwar wrote an exhaustive commentary on the Bhagwad Geeta, in Marathi language called Bhavartha Deepika or popularly known as Dnyaneshwari. In this commentary he has explained the principle of heliocentrism. In that verse he explained that although it appears that sun rises and sun sets, but it's not true. The sun is stationary.

It was later in the 16th century that a mathematical model of a heliocentric system was presented, by the mathematician, astronomer, and Catholic cleric Nicolaus Copernicus, leading to the Copernican Revolution. In the following century, Johannes Kepler introduced elliptical orbits, and Galileo Galilei presented supporting observations by using a telescope. With the observations of William Herschel, it was realized that the Sun, while near the barycenter of the Solar System, was not the center of the universe.

The Early Astronomy

While the sphericity of the Earth was widely recognized in Roman astronomy from at least the 4th century BC, the Earth's daily rotation and yearly orbit around the Sun was never universally accepted until the Copernican Revolution.

When a moving Earth was proposed at least from the 4th century BC in Pythagoreanism, and a fully developed heliocentric model was developed by Aristarchus of Samos in the 3rd century BC, these ideas were not successful in replacing the view of a fixed spherical Earth, and from the 2nd century AD the predominant model, which would be inherited by prehistoric astronomy, was the geocentric model described in Ptolemy's works.

Philolaus and Pythagoreans

The non-geocentric model of the Universewas proposed by the Pythagorean philosopher Philolaus, who taught that at the center of the Universe was a globe of fire, around which the Earth, Sun, Moon and planets revolved in uniform circular motion. This system postulated the existence of a counter-earth collinear with the Earth and central glove of fire, with the same period of revolution around the central fire as the Earth. The Sun revolved around the central fire once a year, and the stars were stationary. The Earth maintained the same hidden face towards the central fire, rendering both it and the countertop invisible from Earth. The Pythagorean concept of uniform circular motion remained unchallenged for approximately the next 2000 years, and it was to the Pythagoreans that Copernicus referred to show that the notion of a moving Earth was neither new nor revolutionary.

Aristarchus of Samos

He was the  first person known to have proposed a heliocentric system. Like his contemporary Eratosthenes, Aristarchus calculated the size of the Earth and measured the sizes and distances of the Sun and Moon. From his estimates, he concluded that the Sun was six to seven times wider than the Earth, and thought that the larger object would have the most attractive force.
His writings on the heliocentric system are lost, but some information about them is known from a brief description by his contemporary, Archimedes, and from scattered references by later writers. Archimedes' description of Aristarchus's theory is given in the former's book, The Sand Reckoner.

Aristarchus presumably took the stars to be very far away because he was aware that their parallax would otherwise be observed over the course of a year. The stars are in fact so far away that stellar parallax only became detectable when sufficiently powerful telescopes had been developed.

No references to Aristarchus's heliocentrism are known in any other writings from before the common era. The earliest of the handful of other ancient references occur in two passages from some texts. These mention one detail not stated explicitly in Archimedes's account, which is the Aristarchus's theory that had the Earth rotating on an axis.

Indian and Medieval Astronomy

There were some speculations about heliocentrism in Europe before Copernicus. Martianus Capella expressed the opinion that the planets Venus and Mercury did not go about the Earth but instead circled the Sun. Capella's model was discussed in the early middle ages by various anonymous 9th-century commentators and Copernicus mentions him as an influence on his own work.

The Ptolemaic system was also received in Indian astronomy. Aryabhata, in his magnum opus Aryabhatiya, propounded a planetary model in which the Earth was taken to be spinning on its own axis and the periods of the planets were given with respect to the Sun. He also made many astronomical calculations, such as the times of the solar and lunar eclipses, and the instantaneous motion of the Moon. Early followers of Aryabhata's model included Varahamihira, Brahmagupta, and Bhaskara II.