GEOCENTRIC AND HELIOCENTRIC MODELS OF COSMOS

GEOCENTRIC AND HELIOCENTRIC MODELS OF COSMOS

By : Muhammad Muhibbuddin

In the history of universe, there are two differential patterns of discourse regarded cosmos, namely geocentric versus heliocentric dicourse. Both ever became subjects of study of science and were debated hardly among people, especially among scientists and intellectuals in ancient and medieval age. Even the such difference of thinking of cosmos  caused victim of humanity. A majority group used their power to punish and torture a minority arguing or opposing what the majority believed.

In erlier times, especially in medieval age, geocentric system became an absolute truth. It became a truth believed by majority group in years ago. In medieval age, the model of discourse was established to be a sacred doctrine of church. Hence, the discourse became  mainstay of truth concerning with cosmos. The truth was believed in by majority people and  crystallized to be an absolute doctrine. Whoever argued or criticized the doctrine, he or she would be punished or tortured. 

One of persons getting punishment was Galileo. He was punished  for his criticism to geocentric system. But, some modern scientists after Galileo, such as Newton, Kepler, etc.  proved that  the true system was not geocentric, but heliocentric. The heliocentric system of cosmos, until nowdays, becomes a universal truth modern people believe in it. The heliocentric, in modern era, was invented by Copernicus and proved by Galileo with his telescope, and then supported and developed by the subsequent scientists, such as Newton and Kepler. What is geocentric and heliocentric  models of cosmos?

Geocentric Model

In astronomy and cosmology, geocentric model is an illustration of universe where  earth is a centre of celestial body. Shortly, earth in geocentric system is a centre of universe. Because of becoming a centre, earth was surrounded by heavenly bodies. This system appeared as a predominant discourse of cosmos  among people in ancient civilization, such as in Greek people reflected in Aristotle and Ptolemy philosophy. As such, they believed that the celestial bodies, such as sun, moon, stars, and naked eyes planets moved to circle the earth.

There were some observations backing geocentric system up. The sun, moon, stars, and other planets appeared to revolve around earth every day, making the earth as a centre of system of comos. The stars were understood to be on celestial sphere, with the earth as a centre of universe, rotating every time, using  a line through north to south pole as a axis. The other observation supporting geocentric model was  the earth did not seem to move based on  observer standing on earth. So, the earth itself was stable and immobile.

The ancient people in post-socratic believed in spherical earth and combined it with geocentricc system. Meanwhile, medieval age philosophers often combined geocentric system with falt earth, such as St. Lactantius and St.Augustinus. Both of them assumed that the spherical earth is ridiculous thing.

Heliocentric Model

By the end of medieval age, counter-discourse of geocentrice appeared. The discourse of cosmology opposing geocentric model is heliocentrism. Heliocentrism is a system of universe which affirms that the sun is a centre of universe, and other planets move to circle sun. It differs with geocentrism affirming the earth as a centre, heliocentrism explains that earth, stars, and planets orbit around the sun and the sun itself orbits around the centre of the vast collection of stars, namely our galaxy (Milky Way).

Historically, the heliocentric model was invented by Copnernicus (1473~1543 AD) famously as a Copernican Revolution. But, before Copernicus invented heliocentric system, the ancient phylosopher, Aristarchus of Samos (3th BC) had proposed  heliocentric idea. But, the Aristarchus’s idea, at the time, did not get positive respond from people and became gone with the wind.

In his book, On the Revolutions of the Heavenly Spheres, Copernicus said that the sun, as source of light and heat,  should be a centre of cosmos. The earth and the other planets should orbit around the sun, and the variation in the apparent positions of the such planets  principally were produced by the combination of their own motion. The earth itself, according to Copernikus is a planet that orbits the sun each day, so it is reasonable to assume that  it rotated once every 24 hours in enormouse sphere.

Besides that, Copernicus also affirmed that the orbits of planets were circular and uniform, and in fact he gave them rather relative differential distances. For explaining the irregularities in the planetary lines, he therefore must resort to system epicycles, as Ptolemy done. The heliocentric system of cosmos in the following is to expand until now.