Sentence:  This and other fears of the solar 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 <WSD>terrestrial</WSD> and celestial motions . 
Meaning of the word marked with <WSD> tags:  of or relating to or inhabiting the land as opposed to the sea or air