Here are some scary questions: How worried should we all be that our increasingly isolated and erratic president will wake up one day and launch a nuclear war? Are there any systems in place to prevent Donald Trump from doing that? Does he need to get signoff from anyone? On this episode, we explore those questions with Garrett Graff, the author of the new book “Raven Rock: The Story of the U.S. Government’s Secret Plan to Save Itself — While the Rest of Us Die.” Graff has answers to all those questions about whether and how fast Trump can launch a nuclear weapon — and whether or not Trump needs signoff from anyone else. Warning: Graff’s answers to those questions may terrify you.