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As proposed by the Heliocentric Theory, the Sun is the center of the Solar System.
The first person to promote the idea of the Heliocentric theory was Philolaus, a Pythagorean philosopher. The first "scientist" was Nicolaus Copernicus. He used his teacher's, Tycho Brahe precise measurements to help formulate how the stars moved in the sky and found that the sun moved much faster relative to everything else. He then explained away the movement by applying the Sun as the center of our solar system.
Geocentric Model, Earth centered ) developed by the Ancient Egyptians, e.g. Ptolemy. This model put the earth at the center of the cosmos and the earth is the origin point from which all other objects are referenced by angles. This model is still used in the Right Acension (RA) system.
The idea that the Sun is at the centre of the planetary system is called the heliocentric concept. Nicholas Copernicus came up with a complete heliocentric theory of circles and epicycles published in 1543 that modelled the positions of the known planets quite accurately and at least as accurately as the previous geocentric model of Ptolemy. Later, measurements made by Tycho Brahe with unprecedented accuracy showed up some discrepancies in the previous models. Kepler used the results to form the modern model of the planetary orbits. It used the heliocentric idea, but the rest of Copernicus's theory was abandoned as Kepler introduced the new idea of elliptical orbits, with each orbit lying in its own plane, slightly inclined to the ecliptic by a different amount for each planet. So, the idea that the Earth revolves round the Sun is called the heliocentric theory but it is hardly a theory at all, it is better described as an idea or a concept. The next stage, carried out by Newton and others, described how the force of gravity held the planets in their orbits and it was able to determine the mass of each planet and the Sun.
A refracting telescope is a type of optical telescope. It was used in astronomical telescopes and spy glasses. Objective lens are used to produce the image.
The astronomical telescope.
Galileo
200 billion years ago
Galileo's discoveries showed faults with the old Ptolemaic theory, which had the Sun at the centre. So he was right to publicise these but not to proclaim that the heliocentric theory of Copernicus was correct. Tycho produced a geocentric theory that explained the phenomena discovered by Galileo, which were (mainly) the full range of phases dislplayed by Venus. Eventually Johannes Kepler brought out a new heliocentric theory with novel elliptical orbits for the planets. It was later backed up by Newton's theoretical discoveries and by later measurements, and it is the model used and accepted today.
Galileo Galilei . He only helped support the theory through his observations , he didn't invent the model, Copernicus did.
It was Galileo.
Galileo
As proposed by the Heliocentric Theory, the Sun is the center of the Solar System.
Galileo did not prove that Earth was not flat (It had already been agreed that it was round). Galileo invented the telescope and used it to prove that there were objects which did not orbit the Earth, supporting Copernicus' Heliocentric model for the universe. The Earth was known to be round by the ancient Greeks, but I do not who it found out initially (sorry).
He didn't know it, he just brought out a new theory that showed that with the Sun at the centre the planets' paths could be explained more simply. That was in 1543 and Kepler produced another heliocentric theory in 1609 which had the planets moving in elliptical orbits round the Sun. The only thing in favour of Kepler's theory at the time was that it explained the planets' positions more accurately than previous theories. But 80-90 years later Newton's discoveries in gravity and the laws of motion were used to prove by theory that the planets must move in elliptical orbits.
Kepler used Tycho Brahe's data to establish the heliocentric theory of the solar system.
Atomic theory