The first Greek astronomers: Thales, Pythagoras and Aristotle

The ancient Greeks have a legend that Thales of Miletus (600 BC) was the first man to reason. We know very little about the original work of Thales in astronomy, but we know that he had been a merchant and therefore must have been in contact with the Babylonian and Egyptian thought in its business travel. He was interested in astronomy is indicated by an anecdote of his life: Plato says that he once fell in an open all well looking at the stars and that a Thracian slave girl had laughed, saying: "he was so absorbed in the heavens that lacked what was under his feet."

Plato assigns two propositions in geometry to Thales.

The angles at the base of an isosceles are equal.

A circle is cut in two by its diameter

While we know very little details of Thales work in astronomy, could come from the Greek belief that the Earth is spherical with him. In times of Pythagoras (540 BC ad he was firmly established that the moon shines by reflecting the light of the Sun and the curved shape of the line between the light parts and dark of the Moon was evidence that the Moon is spherical.) Research obsessed Johann Kepler (1610 a.d.) for mathematical harmony in the movement of planets arose from mystical-philosophical belief of Pythagoras digital reports expressed the harmony of the music (prescribed Pythagoras contemplation of digital reports and geometric shapes for spiritual liberation).

Aristotle, who was the tutor of Alexander the great describes the progression of the phases of the Moon and found they result from the fact that we see different parts of the light parts more than a month. We, therefore, see only half of the total surface of the Moon at any time, and the shape of the Moon that see us is determined by the portion of the sunny side of the Earth, we can observe.

Aristotle also deduced that the Sun was more remote from the Earth from the moon. He could say because sometimes the Moon passes between Earth and the Sun causing the temporary phenomenon of the Eclipse of the Sun. Aristotle also argues that the Earth is round. His first argument was based on the fact that during a Lunar Eclipse, we see the shape of the shadow of Earth on the moon as a round. If the Earth, for example, a disk, we must sometimes see Sun strike the disk edge and its shadow on the moon would therefore be a line.

Second argument of Aristotle, is that the people who travel to the South observe invisible stars in their previous to appear above the southern horizon location. The skies of the North elevation of the North Star decreases as the blows of traveller to the South indicates that the traveller should have moved over a curved surface.

Aristotle, with his contemporaries, has rejected the idea that the Earth was moving. They felt that if really acted on earth around the Sun, we should be observe stars from different positions along the Earth orbit and thus see the stars as appearing to go in different directions. This should apparent change in the direction of stars of a motion of the observer on mobile land is called parallax.

It took later astronomers to come to the understanding that we reason that we observe not parallax with respect to the stars is that they are so far below that associated with Parallax shift can be detected with the naked eye.