History

Classical astronomy

Classical astronomy

The Greeks related the movements of the stars to each other and devised a spherical cosmos, whose center occupied an igneous body and around it the Earth, the Moon, the Sun and the five known planets revolved; the sphere ended in the sky of the fixed spheres: To complete the number of ten, which they considered sacred, they imagined a tenth body, the Anti-Earth.

The bodies described, according to them, circular orbits, which had definite proportions in their distances. Each movement produced a particular sound and together they originated the music of the spheres.

They also discovered that the Earth, in addition to the rotation movement, has a translation movement around the Sun, however, this idea failed to thrive in the ancient world, tenaciously clinging to the idea that the Earth was the center of the Universe.

Eudoxio and his disciple Calipo proposed the theory of the homocentric spheres, able to explain the kinematics of the solar system. The theory was based on the fact that the planets revolved in perfect spheres, with the poles located in another sphere that in turn had their poles in another sphere. Each sphere rotated regularly, but the combination of the velocities and the inclination of a sphere in relation to the next one resulted in an irregular planet movement, as observed. To explain the movements I needed 24 spheres.

Calipo improved his calculations with 34 spheres. Aristotle presented a model with 54 spheres, but considered them with their own real existence, not as calculation elements as their predecessors. Hipparchus reduced the number of spheres to seven, one for each planet, and proposed the geocentric theory, according to which the Earth was in the center, while the planets, the Sun and the Moon revolved around it.

Claudio Tolomeo adopted and developed the Hipparchus system. The number of periodic movements known at that time was already enormous: it took about eighty circles to explain the apparent movements of the heavens. Ptolemy himself concluded that such a system could not have physical reality, considering it a mathematical convenience. However, it was the one that was adopted until the Renaissance.

In this chapter:

Astronomy in ancient Greece: In Greece, what we now know as Western astronomy began to develop ... Read pageAstronomy in Alexandria: In the second century A.D. the Greeks combined their celestial theories with observations transferred to planes ... Read pageAstronomy in Rome: The Roman Empire, both in its pagan and Christian times, gave little or no impetus to the study of science ... Read pageAstronomy in the Visigoth court: A Despite being one of the darkest stages in history, in the Visigothic court there was a ... Read pageArab Astronomy: The Arabs were the ones who, after the decline of Greek studies and the entry of Europe into a phase of ... Read pageAstronomy in the Middle Ages: In the Middle Ages astronomy flourished in Arab culture and in the kingdoms of Europe that… Read page