( ( in ( a ( Lunar eclipse ) ) ) ( , ( ( the Moon ) ( ( passes ( through ( ( the ( Earth 's ) ) shadow ) ) ) . ) ) ) )
(ROOT (S (PP (IN in) (NP (DT a) (NNP Lunar) (NN eclipse))) (, ,) (NP (DT the) (NNP Moon)) (VP (VBZ passes) (PP (IN through) (NP (NP (DT the) (NN Earth) (POS 's)) (NN shadow)))) (. .)))
in a Lunar eclipse, the Moon passes through the Earth's shadow.
(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.