Q: Hi Bill. Something strange happened to me last night. I had this feeling that I just really wanted to lay down and close my eyes. The more time that passed the harder it was to keep my eyes open... I finally closed them. Next thing I remember, I open my eyes to find that it was about 8 hours later. And I have no recollection  of those 8 hours passing... but I felt oddly refreshed. What happened?
A: i'm not sure