Planets in the Copernican system
Teaching Guidance for 14-16
Copernicus did not only offer an alternative model that looked simpler than the heliocentric model. He also extracted new information from his heliocentric scheme: the order and relative sizes of the planetary orbits.
But he did not know the real values of planets' orbit radii. For that he needed an accurate measurement of one of the distances. All he had was a Greek measurement of the distance of the Earth from the Sun.
Estimating the size of the planets themselves would have to wait until telescopes had been invented. A rough model of the solar system known to Copernicus would then be:
- Sun - beach ball
- Mercury - a grain of sand, 16m from the Sun
- Venus - a pea, 29m from the Sun
- Earth - a pea, 40m from the Sun
- Mars - an apple pip, 61m from the Sun
- Jupiter - a ping pong ball, 210m from the Sun
- Saturn - a ping pong ball, 380m from the Sun