According to self-described "space dork" Andy Weir, he was just sitting around at home one day imagining a manned Mars mission — not with any goal in mind, but just as a thought experiment. Soon, he realized this would be a pretty good premise for a story. And boy was he right. His novel "The Martian" started as a series of blog posts and has become a blockbuster motion picture. In this interview, he reads excerpts from the novel and discusses the balance between pure fantasty and scientific accuracy in science fiction.