Ken Burns has been making documentary filmsfor more than 30 years. Since the Academy Award-nominated Brooklyn Bridge in 1981, he has gone on to direct and produce some of the most acclaimed historical documentaries ever made. Stephen Ambrose, the historian, has said of Burns' films, "More Americans get their history from Ken Burns than any other source." Tuesday evening, Sept. 30, at 7 p.m. in MPAC, Burns will address his approach to "history" and his perspective on the American experience.