( ( A ( lunar eclipse ) ) ( ( is ( caused ( by ( ( the moon ) ( passing ( through ( ( the ( earth 's ) ) shadow ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN lunar) (NN eclipse)) (VP (VBZ is) (VP (VBN caused) (PP (IN by) (NP (NP (DT the) (NN moon)) (VP (VBG passing) (PP (IN through) (NP (NP (DT the) (NN earth) (POS 's)) (NN shadow)))))))) (. .)))
A lunar eclipse is caused by the moon passing 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.