( ( If ( ( the earth ) ( gets ( close ( enough ( to ( that line ) ) ) ) ) ) ) ( , ( then ( ( ( it 's ) shadow ) ( ( will ( ( ( fall ( upon ( the moon ) ) ) , ) ( causing ( a ( lunar eclipse ) ) ) ) ) . ) ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (DT the) (NN earth)) (VP (VBZ gets) (ADJP (RB close) (JJ enough) (PP (TO to) (NP (DT that) (NN line))))))) (, ,) (ADVP (RB then)) (NP (NP (PRP it) (POS 's)) (NN shadow)) (VP (MD will) (VP (VB fall) (PP (IN upon) (NP (DT the) (NN moon))) (, ,) (S (VP (VBG causing) (NP (DT a) (NN lunar) (NN eclipse)))))) (. .)))
If the earth gets close enough to that line, then it's shadow will fall upon the moon, causing a lunar eclipse.
(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.