Copernicus came up with a new theory of the planets' movements among the stars in 1543. It had the Sun at the centre instead of the Earth, which was in the centre in the ancient Ptolemaic theory. Both theories used circles and epicycles to describe the planet's orbits, which they modelled quite accurately. Copernicus's theory was promoted by Galileo.
The modern theory retains Copernicus's idea of placing the Sun at the centre, but it uses elliptical orbits for the planets and was devised by Kepler (1609) working with the latest observations by Tycho Brahe.
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