The Senate Foreign Relations Committee could vote to send the New START treaty to the full Senate on Wednesday, August 4. President Barack Obama and Russian President Dmitry Medvedev signed the agreement to further reduce nuclear stockpiles in April. The treaty is a reminder of the grip that nuclear weapons still hold on the world, a subject explored in Lucy Walker's new documentary Countdown To Zero. The film argues for complete world-wide disarmament, with the U.S. leading the way. CNN asked Walker whether such a lofty goal was truly realistic.