To most of us, time seems like a one-way street, moving from past to future. But physicists like Sean Carroll have a different way of thinking about it. Podcast produced by David Levin. NOVA is produced by WGBH in Boston. Funding for NOVA is provided by David H. Koch, the Howard Hughes Medical Institute, the Corporation for Public Broadcasting, and public television viewers.For more science stories, visit our website at pbs.org/nova