It's been a year since wheelchair-bound genius physicist Stephen Hawking died. He left a parting gift in the form of a book, Brief Answers to the Big Questions. It's getting attention from people around the world. One question Hawking paid particular attention to is whether artificial intelligence will outsmart us. As he put it, "The advent of super-intelligent AI would be either the best or the worst thing ever to happen to humanity." We look back at Hawking's life to explore his thoughts about this and other big questions.