Why do we spend 1/3 of our lives in the strange doppelganger state of sleep? Can we die from a lack of sleep? How long is it possible to keep yourself awake (and why does the Guinness Book of World Records no longer track that)? Why are some people night owls and some morning larks? What does any of this have to do with lightless underground caves, or with the length of a day on Mars? Join this week's episode to learn everything you've ever wanted to know about sleep and what your brain is actually doing during this time. This is the first of a 3-parter: next week we'll dive into dreams, and the week after that into lucid dreams.