( ( Relate ( ( these ( changing positions ) ) ( to ( Earth-Sun motions ) ) ) ) . )
(ROOT (S (VP (VB Relate) (NP (NP (DT these) (VBG changing) (NNS positions)) (PP (TO to) (NP (JJ Earth-Sun) (NNS motions))))) (. .)))
Relate these changing positions to Earth-Sun motions.
(ROOT (S (PP (IN In) (NP (NN science))) (, ,) (NP (NN motion)) (VP (VBZ is) (VP (VBN defined) (PP (IN as) (NP (NP (DT a) (NN change)) (PP (IN in) (NP (NN position))))))) (. .)))