( They ( ( are ( possible ( because ( ( ( ( the Sun ) and ) ( the Moon ) ) ( ( appear ( from Earth ) ) ( to ( be ( about ( ( the ( same size ) ) ( in ( the sky ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (ADJP (JJ possible) (SBAR (IN because) (S (NP (NP (DT the) (NNP Sun)) (CC and) (NP (DT the) (NN Moon))) (VP (VBP appear) (PP (IN from) (NP (NNP Earth))) (S (VP (TO to) (VP (VB be) (PP (IN about) (NP (NP (DT the) (JJ same) (NN size)) (PP (IN in) (NP (DT the) (NN sky))))))))))))) (. .)))
They are possible because the Sun and the Moon appear from Earth to be about the same size in the sky.
(ROOT (S (NP (NP (DT The) (NN sun)) (CC and) (NP (DT the) (NN moon))) (VP (VBP appear) (S (VP (TO to) (VP (VB be) (PP (IN about) (NP (NP (DT the) (JJ same) (NN size)) (PP (IN in) (NP (DT the) (NN sky))))) (SBAR (IN because) (S (NP (DT the) (NN moon)) (VP (VP (VBZ is) (ADJP (JJR smaller)) (PP (IN in) (NP (NN diameter)))) (CC and) (VP (VBZ is) (ADJP (ADJP (JJR closer)) (PP (TO to) (NP (NN earth)))) (PP (IN than) (NP (DT the) (NN sun))))))))))) (. .)))