( ( ( ( Recall ( that ( ( ( Fermat 's ) Principle ) ( states ( that ( light ( follows ( ( a path ) ( that ( minimizes ( total ( travel time ) ) ) ) ) ) ) ) ) ) ) ) -- ) ( regardless ( of ( ( the speed ) ( of ( the ( light ray ) ) ) ) ) ) ) . )
(ROOT (S (VP (VB Recall) (SBAR (IN that) (S (NP (NP (NNP Fermat) (POS 's)) (NNP Principle)) (VP (VBZ states) (SBAR (IN that) (S (NP (NN light)) (VP (VBZ follows) (NP (NP (DT a) (NN path)) (SBAR (WHNP (WDT that)) (S (VP (VBZ minimizes) (NP (JJ total) (NN travel) (NN time)))))))))))) (: --) (ADVP (RB regardless) (PP (IN of) (NP (NP (DT the) (NN speed)) (PP (IN of) (NP (DT the) (JJ light) (NN ray))))))) (. .)))
Recall that Fermat's Principle states that light follows a path that minimizes total travel time---regardless of the speed of the light ray.
(ROOT (S (NP (NP (NNP Fermat) (POS 's)) (NN principle)) (VP (VBZ states) (SBAR (IN that) (S (NP (NN light)) (VP (MD will) (ADVP (RB always)) (VP (VB take) (NP (NP (DT the) (NN path)) (PP (IN of) (NP (NP (DT the) (JJS least) (NN amount)) (PP (IN of) (NP (NN time))))))))))) (. .)))