Astronomy and its limits: from the myth to heliocentrism

ASTRONOMY AND ITS LIMITS: FROM THE MYTH TO HELIOCENTRISM

The first hypothesis about the structure and the origin of the universe are to be found in mythology: in fact the relationship between astronomy and religion, that will last for ages, is justified by the mystery that the universe represented for the primitive men. The sky was considered the reign of the supernatural and  divine because it was not accessible. So, the first civilizations tried to establish links among the heavenly phenomena and the human ones in order to explain some of the mysterious events that surrounded them.

The first astronomers were the Sumerian and Babylonian priests that 5000 years ago observed the movements of the Sun, the Moon and the planets and their differences with the stars. They found out that the eclipses repeat periodically but they could not make their own cosmological model. Also the Egyptians were interested in astronomy and they formulated a solar calendar, dividing the day in 24 hours and the hours in 60 minutes, but they  produced only myths without real basis.

The Greeks have been great astronomers because they improved both the instruments to observe the Universe and their mathematical knowledge. They elaborated few hypotheses about the origin and the structure of the Universe but since the VIIth century B.C. they created and believed in a perfect and ordinate system in which the Earth was the centre and the dominant part. At that time, the Greeks still thought that the Earth was a plate disk and that the Sun had the dimension of the Peloponnesus.  Pythagoras and his school in the Vth century B.C. found out that the Earth is spherical but they also believed that the Universe was formed by ten (perfect number) celestial bodies: the Earth, the Moon, the Sun, the five planets already known ( Mercury, Venus, Jupiter, Mars and Saturn) , the fixed stars and they added an invisible planet called Anti-Earth to obtain 10 as a result. However, a real model was created and theorised only a few centuries after, in the IInd century A.D. by Claudius Ptolemy; it was described in his work "Almagesto". This was the geocentric model.