There is an argument between Ptolemy and Copernicus. Ptolemy says that the earth is the center of the universe whereas Copernicus says that the sun is the center. All seven planets revolve around the center. This rule is based on Ptolemy, the greeks. It is very hard to say that the sun, enormous body revolves around the smaller body, earth and the gravitation of the sun does not pull out the sun from the center. Look at the Rambam how complicated this is.
