US astronomer Neil deGrasse Tyson, director of New York's Hayden Planetarium, currently hosts the television series Cosmos — an update of Carl Sagan's 1980 show — broadcast in 181 countries and 45 languages. As it winds down, Tyson talks about the rich mix of science and pop culture, the 'neurosynaptic snapshot' of public responses to his tweets, and his momentous meeting with Sagan.