Describe the model of the universe held by the ancient Greeks.?

Question

Does Their view of the cosmos seem reasonable, considering their ability to observe at the time?

Answer 1

The ancient Greeks held both geocentric and heliocentric theories about the universe.

The heliocentric model did not originate with Copernicus but with Aristarchus, of Samos (310 BC - ca. 230 BC).

http://en.wikipedia.org/wiki/Aristarchus...

His view had some flaws but was consistent with their ability to observe at the time.

Here's a great reference for further study.

http://physics.gmu.edu/~jevans/astr103/C...

Answer 2

The Greek believed that the Earth was at the center of the universe, and everything rotated around the Earth.

Answer 3

Just about every Greek philosopher had his own view of the cosmos.  

Some views were more popular than others and some views survived and got into the so-called western civilization (like the view that Earth was the centre of the universe: it fitted so well with the Biblical view).

There were some who thought (and taught) that the Sun was the centre and that Earth was in orbit around the Sun, just like the other planets.  They even thought that this was a natural process.

Others, of course, knew that the planets (including the Sun and the Moon) were pushed around by gods (and later, by angels) for the purpose of writing messages for us in the sky (thus was born astrology).

Another version had a central fire so strong, that we had to be shielded from it.  We lived on one face of a cylinder, the face away from the central fire.   The Sun was a reflecting body, acting like a mirror to give us light and heat from this central fire.

There were also the sperical heavens:  the sky was an opaque sphere, with holes in it (stars) allowing us to see the fires beyond.

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Many of them already knew that Earth was round (not necessarily a sphere) as the meridian passage altitude of stars changed as one traveled to a different latitude.  They also understood that from the shape of Earth's shadow on the Moon during lunar eclipses.

Those who believed in a sun-centred system also understood the cosmos to be large.  Otherwise, constellations would get bigger and smaller in the course of the year, as we orbit in their direction, then away from them.

Some had calculated the value of the precession cycle to an acceptable accuracy (comparable to that attained by the Mayans and the Chinese astronomers).