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Astronomy in history

Models of the Solar System

Models are useful for helping us to think, understand, remember and predict.

In the ancient Greeks' model of the whole Universe, the Earth was at the centre. In this model, the Earth is fixed and everything else orbits around it. Up until 400 years ago, most people thought this, the geocentric model, provided a true picture of the way the Universe worked. 

Then, astronomers such as Copernicus and Galileo publicised a new model, with the Sun at the centre of the orbits of all of the planets (including the Earth). The new ideas were called the heliocentric model.

The geocentric model was based on ancient writings. The heliocentric model was based on observations. This switch in belief was a BIG change and caused problems as the highly religious climate in which Copernicus and Galileo worked centred on the belief that God had created the Earth at the centre of the Universe.

New observations showed that:

  • The heliocentric model provided better predictions of the movements of the planets.
  • Everything in the Universe does not go around the Earth.

Read more on the Solar System here

Next: How sky literate are you?

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An orrery, a mechanical device that shows the positions of planets according to the heliocentric model.

Religion vs Scientific Observation: a difficult decision in difficult times

In the 17th century AD the astronomer Galileo Galilei opposed the Roman Catholic Church with his strong support in his books for the heliocentric model. This went against the, then current, religious belief that God had placed the Earth at the centre of the Universe. Galileo was put on trial for heresy in 1633, refused to recant and was imprisoned or under house arrest for the rest of his life. What would you have done in his place?