sentences:  Few of Copernicus' contemporaries were ready to concede that the Earth actually moved.Even forty-five years after the publication of "De Revolutionibus", the astronomer Tycho Brahe went so far as to construct a cosmology precisely equivalent to that of Copernicus, but with the Earth held fixed in the center of the celestial sphere instead of the Sun.It was another generation before a community of practicing astronomers appeared who accepted heliocentric cosmology.