( ( Since ( our ( planet rotates ) ) ) ( , ( it ( ( ( appears ( to ( ( a ( stationary observer ) ) ( on Earth ) ) ) ) ( that ( ( ( a ( gyroscope 's ) ) axis ) ( is ( ( completing ( a ( full rotation ) ) ) ( once ( ( every 24 ) hours ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Since) (NP (PRP$ our) (NN planet) (NNS rotates))) (, ,) (NP (PRP it)) (VP (VBZ appears) (PP (TO to) (NP (NP (DT a) (JJ stationary) (NN observer)) (PP (IN on) (NP (NNP Earth))))) (SBAR (IN that) (S (NP (NP (DT a) (NN gyroscope) (POS 's)) (NNS axis)) (VP (VBZ is) (VP (VBG completing) (NP (DT a) (JJ full) (NN rotation)) (ADVP (RB once) (NP (QP (DT every) (CD 24)) (NNS hours)))))))) (. .)))
Since our planet rotates, it appears to a stationary observer on Earth that a gyroscope's axis is completing a full rotation once every 24 hours.
(ROOT (S (NP (PRP It)) (VP (VBZ takes) (NP (NP (CD 24) (NNS hours)) (PP (IN for) (NP (DT the) (NN earth) (S (VP (TO to) (VP (VB make) (NP (NP (DT a) (JJ complete) (NN rotation)) (PP (IN of) (NP (PRP$ its) (NNS axis))))))))))) (. .)))