This question has been bothering me for such a long time.. And there's probably an obvious answer for it.. But when does the crew sleep? And when they do, who takes their place? We could assume that Spock, Sulu, and Scotty could sit in the captain's chair just like every other time Kirk is away, but the problem is they are always working at the same time. So wouldn't they need to sleep around the same time, too? Is there some replacement crew that works the graveyard shift on NCC-1701??