( ( ( ( ( ( ( The force ) ( that ( governs ( ( the motions ) ( of ( within ( the ( solar system ) ) ) ) ) ) ) ) ( , ( ( keeps ( ( the planets ) ( in orbit ) ) ) ( around ( the sun ) ) ) ) ) , ) and ) ( ( ( the moon ) ( in ( orbit ( around ( the earth ) ) ) ) ) ( is gravity ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (NN force)) (SBAR (WHNP (WDT that)) (S (VP (VBZ governs) (NP (NP (DT the) (NNS motions)) (PP (IN of) (PP (IN within) (NP (DT the) (JJ solar) (NN system))))))))) (, ,) (VP (VBZ keeps) (NP (NP (DT the) (NNS planets)) (PP (IN in) (NP (NN orbit)))) (PP (IN around) (NP (DT the) (NN sun))))) (, ,) (CC and) (S (NP (NP (DT the) (NN moon)) (PP (IN in) (NP (NP (NN orbit)) (PP (IN around) (NP (DT the) (NN earth)))))) (VP (VBZ is) (NP (NN gravity)))) (. .)))
The force that governs the motions of within the solar system, keeps the planets in orbit around the sun, and the moon in orbit around the earth is gravity.
(ROOT (S (NP (NNS Planets)) (VP (VBP are) (VP (VBN held) (PP (IN by) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NN gravity))))) (PP (IN in) (NP (NP (JJ elliptical) (NNS orbits)) (PP (IN around) (NP (NN sun))))))) (. .)))