Sentence:  Geocentrism has been displaced by <WSD>heliocentrism</WSD>. Heliocentrism, in turn, the claim of the sun, surrounded by its satellites, to a sovereign place in the heavens, has become ridiculous in the face of the wilderness of suns that people the abysses beyond us. 
Meaning of the word marked with <WSD> tags:  The theory that the sun is the center of the universe.