( ( ( Ancient artifacts ) ( of ( ( wood or ) fabric ) ) ) ( ( are ( dated ( by ( ( ( ( ( ( measuring ( ( the amount ) ( of carbon-14 ) ) ) ( in them ) ) , ) ( ( a ( heavy isotope ) ) ( of ( carbon ( created ( by ( ( cosmic rays ) ( in ( the atmosphere ) ) ) ) ) ) ) ) ) and ) ( ( decaying radioactively ) ( with ( ( a lifetime ) ( of ( ( about 5730 ) years ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Ancient) (NNS artifacts)) (PP (IN of) (NP (NN wood) (CC or) (NN fabric)))) (VP (VBP are) (VP (VBN dated) (PP (IN by) (S (VP (VP (VBG measuring) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (CD carbon-14)))) (PP (IN in) (NP (PRP them))) (, ,) (NP (NP (DT a) (JJ heavy) (NN isotope)) (PP (IN of) (NP (NP (NN carbon)) (VP (VBN created) (PP (IN by) (NP (NP (JJ cosmic) (NNS rays)) (PP (IN in) (NP (DT the) (NN atmosphere)))))))))) (CC and) (VP (VBG decaying) (ADVP (RB radioactively)) (PP (IN with) (NP (NP (DT a) (NN lifetime)) (PP (IN of) (NP (QP (RB about) (CD 5730)) (NNS years))))))))))) (. .)))
Ancient artifacts of wood or fabric are dated by measuring the amount of carbon-14 in them, a heavy isotope of carbon created by cosmic rays in the atmosphere and decaying radioactively with a lifetime of about 5730 years.
(ROOT (S (NP (NP (NNP Carbon) (CD 14) (NN isotope)) (PP (IN of) (NP (NN carbon)))) (VP (VBZ is) (ADVP (RB typically)) (VP (VBN used) (PP (TO to) (NP (NN date) (JJ ancient) (NNS items))))) (. .)))