Hipparchus and Ptolemy - Ancient Greek astronomers

Hipparchus did not speculate but only developed ideas that were based on reliable data. He refused to develop new ideas unless he had data to support them.

Ptolemy was a mathematician. He developed the ideas that:

• The Earth does not move but is at the centre of the Universe.
• Everything else in the Universe revolves around the Earth.
• The Earth is small compared with the distances to the fixed stars
   
  

His ideas are called the geocentric model of the Universe.

Some time after the lives of Hipparchus and Ptolemy, Europe went into a long period of political instability that lasted about a thousand years. They were the European Dark Ages. People lacked the organisations that allowed them to develop new ideas.  Fortunately, further east, Islamic astronomy blossomed.

The fixed stars

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