( ( The earth ) ( itself ( ( ( is constantly ) ( ( ( ( ( moving , ) ( ( rotating ( around ( the sun ) ) ) ( once ( a year ) ) ) ) , ) and ) ( ( rotating ( on ( its ( own axis ) ) ) ) ( once ( a day ) ) ) ) ) . ) ) )
(ROOT (S (NP (DT The) (NN earth)) (ADVP (PRP itself)) (VP (VBZ is) (ADVP (RB constantly)) (VP (VP (VBG moving)) (, ,) (VP (VBG rotating) (PP (IN around) (NP (DT the) (NN sun))) (NP (RB once) (DT a) (NN year))) (, ,) (CC and) (VP (VBG rotating) (PP (IN on) (NP (PRP$ its) (JJ own) (NNS axis))) (NP (RB once) (DT a) (NN day))))) (. .)))
The earth itself is constantly moving, rotating around the sun once a year, and rotating on its own axis once a day.
(ROOT (S (NP (NNP Earth)) (VP (VBZ rotates) (PP (PP (IN on) (NP (PRP$ its) (NNS axis)) (ADVP (RB once))) (CC times) (PP (IN in) (NP (CD one) (NN day))))) (. .)))