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1.2. Geocentrism and heliocentrism

Geocentrism and heliocentrism

Just as we have seen some of the possible origins of the universe according to different beliefs, there have also been differences in the concept of the universe.
The oldest civilizations believed that the universe consisted of a flat and immobile Earth, and a sky located above, in which the stars would be.
The Greeks were the first to observe and deduce that the Earth is a spherical body that floats in space with the other stars. From then on, other more scientific theories emerged such as geocentrism and heliocentrism.

Geocentrism

The geocentric  is the theory that the Earth  is at the center of the universe, and the sun and all celestial bodies revolving around it .

This theory was accepted by various ancient civilizations. In the second century, Ptolemy collected the dominant ideas of the time and introduced epicycles, a theory that was in force until it was replaced in the sixteenth century by heliocentrism.

According to Ptolemy, the Earth was in the center, and around it the Sun , the Moon and all the celestial stars would rotate in increasingly larger spheres (epicycles).

The stars are fixed in a vault that, like the rest of the stars, would also rotate around the Earth.

The epicycles are a geometric model devised three centuries before Ptolemy that allowed the ancient Greeks to explain the variations in the speed and direction of the apparent movement of the Moon , the Sun , and the planets.

Discovering words: geocentrism

Geocentrism is a word of Greek origin formed by geo (Earth) and centrism (grouped or center).

Heliocentrism is a word of Greek origin formed by helios (Sun) and centrism (grouped or center).

Heliocentrism

Until about 500 years ago, almost everyone believed in the geocentric model. Although in 200 BC, Aristarchus of Samos already thought that the Earth was not the center of the Universe, it took until 1543 for Copernicus to propose his heliocentric model.

The Copernicus model was not really taken seriously until, almost a hundred years after his death, Galileo collected observations in favor of heliocentrism. This caused the Inquisition to judge Galileo as a heretic by defending that the Sun was the center of the Universe and that the other stars revolved around it, and the Moon, around the Earth. 

The heliocentric is an astronomical according to which the model Earth and the planets move around the sun , which is still in the center of the universe.

According to heliocentrism, the Earth rotates on itself, and the Moon around it.

The stars are fixed in a vault that remains immobile.

Of course, there is currently no doubt that the Earth revolves around the sun. The heliocentric model is no longer in force, since although it is known that the Sun is the center of the Solar System, it is neither the center of the galaxy (Milky Way) nor of the Universe.

Newton and Kepler explained what the orbits of the planets looked like with precise mathematical calculations and showed that stars do not remain fixed.