I couldn’t think of anyone better, or more charismatic, to carry on Carl Sagan’s Cosmos series and legacy than astrophysicist Neil deGrasse Tyson, who matches wits, and wit, so well with  Bill Moyers on this show, they ought to think about starring in the talk-show equivalent of a buddy movie. Their conversation began last week – and went so well, it’s going into overtime with tonight’s installment. It seems only fitting: their cosmic conversation, likes the universe itself, is expanding.