Stellar Distances

Abstract

Although the heliocentric viewpoint is of such overwhelming simplicity and beauty that from a purely descriptive standpoint its acceptance could hardly be challenged; the question arose whether or not additional evidence exists. If it is not the Sun which revolves around the Earth, but rather the Earth which revolves around the Sun, then the effect of the Earth’s orbital motion should be revealed in the stars — just as it is the case of the planets in our solar system — in the form of parallactic shift in direction in the course of a year. The distance to the Sun has been measured in a variety of ways and was found to be very close to 150 000 000 km, i.e. the orbit of the Earth around the Sun would have a diameter of 300 000 000 km. So huge a baseline would seem to hold some promise of revealing annual parallactic changes in the positions of the ‘fixed’ stars. These shifts were not observed for three centuries after Copernicus; and in the meantime the heliocentric viewpoint was not acceptable to many astronomers, Tucho Brahe (1546–1601), for instance.