Copernicus included the statement, The distance from the Earth to the Sun is imperceptible compared with the distance to the stars, because
a) the outer planets appear quite faint sometimes, and much brighter at other times, but stars do not.
b) otherwise the stars would make little circular motions in the sky as the Earth moves around the Sun.
c) stars are obviously so much dimmer than the Sun.
d) he believed the stars were attached to an actual crystal sphere, which had to be far away so that it was not visible.
e) he believed the stars actually moved through space, but they appear to be fixed because of their great distance.