( However ( , ( ( during ( a ( lunar eclipse ) ) ) ( , ( ( ( the ( earth 's ) ) shadow ) ( ( ( ( ( falls ( over ( the moon ) ) ) , ) eventually ) ( enveloping it ) ) . ) ) ) ) ) )
(ROOT (S (ADVP (RB However)) (, ,) (PP (IN during) (NP (DT a) (NN lunar) (NN eclipse))) (, ,) (NP (NP (DT the) (NN earth) (POS 's)) (NN shadow)) (VP (VBZ falls) (PP (IN over) (NP (DT the) (NN moon))) (, ,) (ADVP (RB eventually)) (S (VP (VBG enveloping) (NP (PRP it))))) (. .)))
However, during a lunar eclipse, the earth's shadow falls over the moon, eventually enveloping it.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (NN earth) (POS 's)) (NN shadow)) (VP (VBZ falls) (PP (IN on) (NP (DT the) (NN moon)))))) (, ,) (NP (DT the) (NN shadow)) (VP (VBZ causes) (NP (DT a) (NN lunar) (NN eclipse))) (. .)))
When earth’s shadow falls on the moon, the shadow causes a lunar eclipse.