You're on an airplane. You whip out your laptop to catch up on some work, to watch a movie, or to try out some of that new inflight WiFi. Of course, the second you pull out your computer, you begin doing some math in your head...
"This is a five-hour flight. My laptop battery is at 85%. That means I have about two-and-a-half hours of juice. So if I start using it now, I'll be out of power somewhere over Omaha, at which point I'll be stuck watching the last third of The Time ...
