( ( full ( A ( lunar eclipse ) ) ) ( ( occurs ( when ( ( ( ( ( ( ( the Sun ) , ) Earth ) , ) and ) Moon ) ( are ( ( lined up ) ( so ( ( ( Earth 's ) shadow ) ( falls ( on ( the Moon ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ full) (DT A) (NN lunar) (NN eclipse)) (VP (VBZ occurs) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (NNP Sun)) (, ,) (NP (NNP Earth)) (, ,) (CC and) (NP (NNP Moon))) (VP (VBP are) (VP (VBN lined) (PRT (RP up)) (SBAR (IN so) (S (NP (NP (NNP Earth) (POS 's)) (NN shadow)) (VP (VBZ falls) (PP (IN on) (NP (DT the) (NNP Moon))))))))))) (. .)))
full A lunar eclipse occurs when the Sun, Earth, and Moon are lined up so Earth's shadow falls on the Moon.
(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.