Sentence:  This and other fears of the solar system have disappeared gradually , first , with the <WSD>Ptolemaic</WSD> 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:  (astronomy) Ptolemy's model of the universe with the Earth at the center