The most common feeling that the sight inspires is one of curiosity. The science of astronomy was born out of this curiosity.
Now imagine that the night sky is a gigantic sphere with ourselves at its centre, a sphere that rotates from east to west around a line joining our position to the Pole Star. If all the stars were stuck onto this sphere, they would appear to go round this line, from east to west. This is the picture the Greeks had constructed in describing stars.
The planets, however, did not fit into the scheme so well. Instead of being stuck to this celestial revolving sphere, they seemed to have additional motions of their own. This is what you will find if, for example, you look at the positions of the planets Venus and Mars in relation to other stars. This explains the name ‘planet’ which means ‘wanderer’ in Greek.
Why do planets wander? When confronted with this question human beings found out two very different answers: one based on science, the other on superstition. The superstitious believed that planets wander because they have some ‘extra power’ which is denied to stars: and out of this belief arose ‘astrology’. Astrology assumes that planets are ‘powerful’ and exert their influence on human destiny.
But those with a scientific bent of mind tried to understand why planets move in this way. This gave rise to ‘astronomy’. Hipparchus and Ptolemy demonstrated that there is a pattern in the movement of planets, however, it appeared complicated because the Greeks had a stubborn belief that the earth is fixed in space and everything goes around it. By 1687 with Newton’s laws of motion and gravitation the movements of planets were explained accurately and today an astronomer can predict where a certain planet will be found at any given time in future.