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The basic elements of Ptolemaic astronomy, showing a planet on an epicycle with an eccentric deferent and an equant point.

Claudius Ptolemy

Claudius Ptolemy

Although the basic tenets of Greek geocentrism were established by the time of Aristotle, the details of his system did not become standard. This honor was reserved for the Ptolemaic system, espoused by the Hellenistic astronomer Claudius Ptolemaeus in the 2nd century AD. His main astronomical book, the Almagest, was the culmination of centuries of work by Hellenic, Hellenistic and Babylonian astronomers; it was accepted for over a millennium as the correct cosmological model by European and Islamic astronomers. Because of its influence, the Ptolemaic system is sometimes considered identical with the geocentric model.

Tomb of Galileo Galilei, Santa Croce

Galileo also worked in applied science and technology, improving compass design.

Galileo made original contributions to the science of motion through an innovative combination of experiment and mathematics

Galileo Galilei (15 February 1564[2] – 8 January 1642)[1][3] was an Italian physicist, mathematician, astronomer, and philosopher

On 7 January 1610 Galileo observed with his telescope what he described at the time as "three fixed stars, totally invisible

Aryabhata, 5th century, developed a computational planetary model which has been interpreted as heliocentric

To anyone who stands and looks at the sky, it seems clear that the Earth stays in one place while everything in the sky rises and sets or goes around once every day.

To anyone who stands and looks at the sky, it seems clear that the Earth stays in one place while everything in the sky rises and sets or goes around once every day.

Kak interprets this to mean that the Sun is stationary, hence the Earth is moving around it. A more common interpretation, however, is that the Sun "never actually sets or rises" because it was believed to have two sides: one light and one dark. Consequently, when the sun reaches the western horizon, it simply flips on itself and invisibly returns to its original place in a continuous cycle

. From his estimates, he concluded that the Sun was six to seven times wider than the Earth and thus hundreds of times more voluminous