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Heliocentric Model

The heliocentric theory was proposed by many astronomers throughout history, withvarying degrees of success and recognition. This theory is about how the earth and

universe orbits around the sun.

The idea was rst proposed by a Greek astronomer and mathematician names

ristarchus of !amos in the "rd century #$. His idea placed the Earth and other

planets in motion around the central !un. However, his theory was re%ected by

everyone in favour of ristotle&s Geocentric theory that the earth was central.

$laudius ptolemy '()*+) - was a philosopher from le/andria. He theorised thatthe earth was motionless, because constant wind gales would sweep across the

earth if it were moving, and that all the planets and stars moved around it instead.

0tolemy devised a comple/ system of 1epicycles1 to account for the apparent

forwards and backwards motion of the planets. 2n 0tolemy&s epicycle system,

everything revolved around the earth in a large circle while spinning in smaller

circles. This theory was widely accepted by people at that time because of their

strong religion and belief that everything was centred around God.

2t was not until the +th century that the rst scientic treatise provided detailed

support for heliocentrism. 0olish mathematician, astronomer, and catholic cleric,3icolaus $opernicus, put forth the theory that the sun is at rest near the centre of

the universe, and that the earth spins on its a/is once daily and revolves annually

around the sun. He published -e revolutionibus orbium coelestium 'English4 5n the

6evolutions of the Heavenly !pheres in +)7".

The deconstruction of the Heliocentric model was achieved in steps. Giordano #runo

strongly advocated how the sun infact wasn8t the center of the universe, rather one

of a few billion stars. Throughout the +( thand +9thcenturies, the !un8s status as the

only one in the universe was slowly being replaced by the !un being merely one

star among many. The Heliocentric model was totally replaced in the :; thcentury bythe model we have today.

Even if the discussion is limited to the solar system, the !un is not at the geometric

center of any planet&s orbit, but rather appro/imately at one focus of the elliptical

orbit.

7/23/2019 Heliocentric Model

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Edwina and Eric

slightly away from the center of the !un.=9)> 'The masses of the planets, mostly

?upiter, amount to ;.+7@ of that of the !un. Therefore, a hypothetical astronomer

on an e/trasolar planet would observe a small 1wobble1 in the !un&s motion.