Graham Allison, director of Harvard Kennedy School's Belfer Center for Science and International Affairs, looks at parallels in history to explain the relationship between U.S. and China. He argues that war between the two superpowers can be avoided. Sibling actors Tim and Tyne Daly join us to discuss their roles in the world premiere of Theresa Rebeck’s “Downstairs” at the Dorset Theatre Festival. They star as brother and sister, Teddy and Eileen. Teddy has moved back home and is living in Eileen’s basement. As the reuinte, they must come to grips with their present and past. Theoretical physicist Brian Greene and his wife, Emmy-winning TV producer, Tracy Day, join us to discuss the 10th Anniversary of the World Science Festival, which they cofounded. This year’s events and exhibition include "Holoscenes," a performance-installation that connects everyday actions to climate change. Minnesota Sen. Al Franken shares his views on the issues facing Americans, and discusses his transition from comedy into politics.