SARA STEWART writes: You have to wonder where Viggo Mortensen finds the time to act. In between gigs like the “Lord of the Rings” trilogy and David Cronenberg’s movies (most recently “Eastern Promises”), the 50-year-old star is also a photographer, poet, musician, painter, publisher, activist and avid traveler. He’s fluent in Spanish, Danish, French and possibly Elvish. When we caught up with him, though, he kindly stuck to English, and to the projects at hand: first, “Good,” opening Wednesday, about a German professor who, through his passivity, unwittingly ends up a high-ranking member of the Nazi party. Early next year comes “The Road,” the adaptation of Cormac McCarthy’s novel about a father and son traveling in post-apocalyptic America. Q&A with Viggo Mortensen