( ( ( ( ( Based ( on ( visible matter ) ) ) , ) and ) ( ( what ( we ( know ( of ( ( the amount ) ( of ( dark matter ) ) ) ) ) ) ) ( , ( ( ( the density ) ( of ( the universe ) ) ) ( is ( ( ( ( at least ) 25 ) % ) ( of ( ( ( ( ( ( ( the ( critical density ) ) , ) and ) possibly ) ( much more ) ) , ) ( maybe ( even ( 100 % ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (VP (VBN Based) (PP (IN on) (NP (JJ visible) (NN matter))))) (, ,) (CC and) (S (SBAR (WHNP (WP what)) (S (NP (PRP we)) (VP (VBP know) (PP (IN of) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (JJ dark) (NN matter)))))))) (, ,) (NP (NP (DT the) (NN density)) (PP (IN of) (NP (DT the) (NN universe)))) (VP (VBZ is) (NP (NP (QP (IN at) (JJS least) (CD 25)) (NN %)) (PP (IN of) (NP (NP (DT the) (JJ critical) (NN density)) (, ,) (CC and) (RB possibly) (NP (RB much) (JJR more)) (, ,) (ADVP (RB maybe) (NP (RB even) (CD 100) (NN %)))))))) (. .)))
Based on visible matter, and what we know of the amount of dark matter, the density of the universe is at least 25% of the critical density, and possibly much more, maybe even 100%.
(ROOT (S (NP (NNP Density)) (VP (VBZ describes) (SBAR (WHADJP (WRB how) (JJ much)) (S (NP (NN matter)) (VP (VBZ is) (PP (IN in) (NP (NP (DT a) (JJ certain) (NN amount)) (PP (IN of) (NP (NN space))))))))) (. .)))