How confident are we that most matter in the universe has so far escaped detection? And if there is dark matter, might there be dark stars and even a dark big bang? Leading physicist Katherine Freese joins Brian Greene to explore these dark matters. Watch this full discussion: worldsciencefestival.com/programs/dark-matters-have-we-really-failed-to-identify-most-of-the-cosmos #darkmatter #briangreene #worldsciencefestival #cosmology #katherinefreese