( ( ( ( ( When ( ( ( the ( Earth 's ) ) shadow ) ( falls ( upon ( the moon ) ) ) ) ) ( , ( ( a ( lunar eclipse ) ) occurs ) ) ) ; ) ( conversely ( , ( ( when ( ( ( the ( moon 's ) ) shadow ) ( falls ( upon ( the Earth ) ) ) ) ) ( , ( ( a ( solar eclipse ) ) occurs ) ) ) ) ) ) . )
(ROOT (S (S (SBAR (WHADVP (WRB When)) (S (NP (NP (DT the) (NN Earth) (POS 's)) (NN shadow)) (VP (VBZ falls) (PP (IN upon) (NP (DT the) (NN moon)))))) (, ,) (NP (DT a) (NN lunar) (NN eclipse)) (VP (VBZ occurs))) (: ;) (S (ADVP (RB conversely)) (, ,) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (NN moon) (POS 's)) (NN shadow)) (VP (VBZ falls) (PP (IN upon) (NP (DT the) (NN Earth)))))) (, ,) (NP (DT a) (JJ solar) (NN eclipse)) (VP (VBZ occurs))) (. .)))
When the Earth's shadow falls upon the moon, a lunar eclipse occurs; conversely, when the moon's shadow falls upon the Earth, a solar eclipse occurs.
(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.