( ( In ( a ( lunar eclipse ) ) ) ( , ( ( the moon ) ( ( moves ( through ( ( the ( Earth 's ) ) shadow ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (DT a) (NN lunar) (NN eclipse))) (, ,) (NP (DT the) (NN moon)) (VP (VBZ moves) (PP (IN through) (NP (NP (DT the) (NN Earth) (POS 's)) (NN shadow)))) (. .)))
In a lunar eclipse, the moon moves 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.