( Indeed ( , ( ( ( the force ) ( of gravity ) ) ( ( ( keeps ( ( the Moon ) ( in ( ( ( orbit ( around ( the Earth ) ) ) and ) ( ( the planets ) ( in orbit ) ) ) ) ) ) ( around ( the Sun ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Indeed)) (, ,) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NN gravity)))) (VP (VBZ keeps) (NP (NP (DT the) (NN Moon)) (PP (IN in) (NP (NP (NP (NN orbit)) (PP (IN around) (NP (DT the) (NN Earth)))) (CC and) (NP (NP (DT the) (NNS planets)) (PP (IN in) (NP (NN orbit))))))) (PP (IN around) (NP (DT the) (NNP Sun)))) (. .)))
Indeed, the force of gravity keeps the Moon in orbit around the Earth and the planets in orbit around the Sun.
(ROOT (S (NP (NNP Gravity)) (VP (VBZ is) (ADJP (JJ responsible) (PP (IN for) (NP (NP (DT the) (NNS orbits)) (PP (IN of) (NP (NP (DT the) (NNS planets)) (PP (IN around) (NP (DT the) (NN sun))))))))) (. .)))
Gravity is responsible for the orbits of the planets around the sun.