This week marks the fortieth anniversary of the Nuclear Non-Proliferation Treaty, when nuclear powers agreed to eventually eliminate their nuclear weapons, and non-nuclear states agreed not to seek to develop nuclear weapons capabilities. Forty years later, there are 189 signatories to the treaty and nine nuclear armed states in the world. The United States and Russia still have the world’s largest stockpile of nuclear weapons. We speak with Joseph Cirincione, president of the Ploughshares Fund and author of Bomb Scare: The History and Future of Nuclear Weapons. [includes rush transcript]