Parallax Heliocentric Theory

parallax heliocentric theory Model of the Solar System in which the Sun is at the centre and the planets revolve around it. A heliocentric theory was proposed by the Greek astronomer aristarchus in the 3rd century bc, but it seemed counter-intuitive at the time and was not widely adopted. geocentric theory, championed by Aristotle and Ptolemy and by later scholars and theologians, was to remain supreme for nearly 1500 years.

It was Nicholas Copernicus who re-invigorated heliocentric theory with his copernican system, published the year of his death. Opposed by both Roman Catholic and Protestant ecclesiastics, its influence spread only very slowly. However, the great improvements in observational accuracy introduced by Tycho brahe showed up the inadequacy of geocentric theory. Brahe himself favoured a hybrid, now referred to as the tychonic system, in which the Earth remained at rest and was orbited by the Sun, but the other planets orbited the Sun. His observations showed that the stars were much more distant than the planets and he also realized that comets moved in orbits that would have taken them through the 'crystalline spheres' of Aristotle's geocentric theory. Thus the spheres could not be real.

The telescopic discoveries by galileo - that a body other than the Earth, namely Jupiter, had moons in orbit around it, that the planet Venus exhibited phases like the Earth's Moon and that the Sun was covered in spots which made it less than 'perfect' - was evidence enough to put an end to the geocentric theory. Galileo's open advocacy of the Copernican position placed him in conflict with elements within the Catholic Church. His main publication in support of heliocentrism, the dialogues of 1632, led to his trial before the Inquisition. When Johannes Kepler, using data accumulated by Brahe, discovered his three laws (see kepler'slaws), the need for the complicated epicyclic motions was swept aside by the simplicity of elliptical orbits.

In the decades following Kepler's and Galileo's discoveries, heliocentric theory gained wide acceptance. Isaac Newton, with the publication of his principia in 1686-87, showed that the assumption of an inverse-square law of gravitational attraction would account for Kepler's laws. Following his work, the heliocentric theory of the Solar System could no longer be questioned.