(S (S (S (VP (VBG Approaching) (NP (BASENP (DT the) (NN speed)) (PP (IN of) (BASENP (NN light)))))) (VP (MD would) (VP (PRN (COMMA ,) (ADVP (RB however)) (COMMA ,)) (VP (VB require) (NP (BASENP (DT a) (JJ long) (NN period)) (PP (IN of) (BASENP (JJ constant) (NN acceleration)))))))) (PERIOD .))