( Only ( ( during ( a ( lunar ( eclipse will ) ) ) ) ( ( the moon ) ( ( intersect ( ( the earth ) ( s shadow ) ) ) . ) ) ) )
(ROOT (S (RB Only) (PP (IN during) (NP (DT a) (NN lunar) (NN eclipse) (NN will))) (NP (DT the) (NN moon)) (VP (VBP intersect) (SBAR (S (NP (DT the) (NN earth)) (VP (VBZ s) (NP (NN shadow)))))) (. .)))
Only during a lunar eclipse will the moon intersect 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.