I'm embarrassed to report that -- for just a moment -- I had a chilling thought. I thought I was about to learn that we are digital copies of ourselves living

I'm embarrassed to report that -- for just a moment -- I had a chilling thought. I thought I was about to learn that we are digital copies of ourselves living in a full-earth simulation carried out by some future facebook. Facebook! The horror... :( I checked my calendar--nope, not April 1... And kept reading.