( This ( ( is ( how ( ( the sun ) ( heats ( the earth ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (SBAR (WHADVP (WRB how)) (S (NP (DT the) (NN sun)) (VP (VBZ heats) (NP (DT the) (NN earth)))))) (. .)))
This is how the sun heats the earth.
(ROOT (S (NP (NNP Heat)) (VP (VBZ travels) (PP (IN from) (NP (DT the) (NN sun))) (PP (TO to) (NP (NP (DT the) (NN earth) (JJ thermal) (NN radiation)) (PP (IN from) (NP (DT the) (NN sun)))))) (. .)))