( ( When ( ( the axis ) ( is ( tilted ( towards Vega ) ) ) ) ) ( ( ( the positions ) ( of ( ( ( the ( Northern ( Hemisphere winter ) ) ) and ) ( summer solstices ) ) ) ) ( ( will ( ( ( coincide ( with ( the ( ( aphelion and ) perihelion ) ) ) ) , ) respectively ) ) . ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (DT the) (NNS axis)) (VP (VBZ is) (VP (VBN tilted) (PP (IN towards) (NP (NNP Vega))))))) (NP (NP (DT the) (NNS positions)) (PP (IN of) (NP (NP (DT the) (NNP Northern) (NNP Hemisphere) (NN winter)) (CC and) (NP (NN summer) (NNS solstices))))) (VP (MD will) (VP (VB coincide) (PP (IN with) (NP (DT the) (NN aphelion) (CC and) (NN perihelion))) (, ,) (ADVP (RB respectively)))) (. .)))
When the axis is tilted towards Vega the positions of the Northern Hemisphere winter and summer solstices will coincide with the aphelion and perihelion, respectively.
(ROOT (S (NP (NP (DT The) (NN tilt)) (PP (IN of) (NP (NP (NN earth)) (PP (IN on) (NP (PRP$ its) (NNS axis)))))) (VP (VBZ causes) (NP (NN summer)) (S (VP (TO to) (VP (VB be) (VP (VBN warmer) (PP (IN than) (NP (NP (NN winter)) (PP (IN in) (NP (DT the) (JJ northern) (NN hemisphere))))) (SBAR (IN because) (S (NP (NP (DT the) (NNS rays)) (PP (IN of) (NP (DT the) (NN sun)))) (VP (VBP strike) (NP (DT the) (JJ northern) (NN hemisphere)) (ADVP (ADVP (RBR more) (RB directly)) (PP (IN in) (NP (DT the) (NN summer)))))))))))) (. .)))