The Greek astronomer Claudius Ptolomy, lived
in Alexandra in Egypt, in the meeting point of the ancient Arabic and European cultures. He
summerized all astronomical knowledge of the Greek civilization in his book "The
Almagest". He catalogued 1028 stars and described all known variances of the
constellations and legends of them. He gave the starformations the traditional names of the
Greek and Roman cultures, which are still used.
The solar system according to Ptolomy
In his book Ptolomy also made a description of
the solar system, mainly based upon the results of the ancient Greeks, in particular of Hipparchus.
According to Ptolomy the Universe was an
enclosed sphere with the Earth fixed in the center. The stars were fixed on the inner side of
the peel of the sphere, that was constantly rotating around the Earth and in between the
Sun, Moon, and planets and other Universal appearances were in rotary motion.
In the Ptolemaen system a planet describes an
circular orbit (the epicykle), of which the center rotates in an other circle, around a point
that deviates from the centre of the Earth. By varying the speed of the planets and diameter of
the various circles this gave an acceptable description of the planetary movements.
Ptolomy was the last of the great ancient
astronomers, his ideas and descriptions of the planetary system lasted more than 1000 years.
Besides astronomer and astrologist, Ptolomy is
also famous as cartographer. His book 'Geographia' contained detailed
maps of the world, that served travellers for
hundreds of years. Even Columbus used his maps in 1492, when he discoverd America.