As with the Moon around the Earth , the planets in our Solar System are held in motion aroud the Sun by gravity.

Thousands of years ago the Greeks thought that there were only five planets with the Earth at the centre of it all.

Then in 1543, Nicholaus Copernicus came up with the bright idea that it was in fact the Sun that was at the heart of the Solar System and that the planets revolve around it.

Another scientist Johannes Kepler (1571-1630), using observations made by Tycho Brache (1546-1601) spent his whole life working out how the planets move across the night's sky.

He concluded that the planets actaully follow a path that draws out a shape called an ellipse.

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