( ( That is ) ( , ( ( ( ( ( ( an increase ) ( in ( the ( separation distance ) ) ) ) ( causes ( ( a decrease ) ( in ( ( the force ) ( of gravity ) ) ) ) ) ) and ) ( ( ( a decrease ) ( in ( the ( separation distance ) ) ) ) ( causes ( ( an increase ) ( in ( ( the force ) ( of gravity ) ) ) ) ) ) ) . ) ) )
(ROOT (S (INTJ (DT That) (VBZ is)) (, ,) (S (S (NP (NP (DT an) (NN increase)) (PP (IN in) (NP (DT the) (NN separation) (NN distance)))) (VP (VBZ causes) (NP (NP (DT a) (NN decrease)) (PP (IN in) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NN gravity)))))))) (CC and) (S (NP (NP (DT a) (NN decrease)) (PP (IN in) (NP (DT the) (NN separation) (NN distance)))) (VP (VBZ causes) (NP (NP (DT an) (NN increase)) (PP (IN in) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NN gravity))))))))) (. .)))
That is, an   increase in the separation distance causes a decrease in the force of gravity   and a decrease in the separation distance causes an increase in the force of   gravity.
(ROOT (S (NP (NNP Gravity)) (VP (VBZ causes) (S (NP (NNS rocks)) (VP (TO to) (VP (VB roll) (ADVP (RB downhill)))))) (. .)))