( ( ( ( ( Theory ( requires ( that ( ( this rotation ) ( should ( amount ( to ( ( 43 seconds ) ( of ( arc ( per ( century ( for ( the ( planet Mercury ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) , ) but ) ( ( for ( ( the ( other Planets ) ) ( of ( our ( solar system ) ) ) ) ) ( ( its magnitude ) ( should ( ( be ( so small ) ) ( that ( it ( ( would necessarily ) ( escape detection ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNP Theory)) (VP (VBZ requires) (SBAR (IN that) (S (NP (DT this) (NN rotation)) (VP (MD should) (VP (VB amount) (PP (TO to) (NP (NP (CD 43) (NNS seconds)) (PP (IN of) (NP (NP (NN arc)) (PP (IN per) (NP (NP (NN century)) (PP (IN for) (NP (DT the) (NN planet) (NNP Mercury))))))))))))))) (, ,) (CC but) (S (PP (IN for) (NP (NP (DT the) (JJ other) (NNS Planets)) (PP (IN of) (NP (PRP$ our) (JJ solar) (NN system))))) (NP (PRP$ its) (NN magnitude)) (VP (MD should) (VP (VB be) (ADJP (RB so) (JJ small)) (SBAR (IN that) (S (NP (PRP it)) (VP (MD would) (ADVP (RB necessarily)) (VP (VB escape) (NP (NN detection))))))))) (. .)))
Theory requires that this rotation should amount to 43 seconds of arc per century for the planet Mercury, but for the other Planets of our solar system its magnitude should be so small that it would necessarily escape detection.
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (NP (NP (DT the) (JJS smallest) (NN planet)) (PP (IN in) (NP (PRP$ our) (JJ solar) (NN system))))) (. .)))