Sentence:  This and other fears of the <WSD>solar</WSD> system have disappeared gradually , first , with the Ptolemaic system and its built-in concept of periodicity and then , more firmly , with the Newtonian innovation of an universal force that could account quantitatively for both terrestrial and celestial motions . 
Meaning of the word marked with <WSD> tags:  the sun with the celestial bodies that revolve around it in its gravitational field