Can’t sleep? Try dozing off in zero gravity! Think you have trouble getting enough sleep? Imagine that when you said goodnight, you could expect the sun to set—and then come up again—about five times during your eight-hour “night.” Now consider lying down when there’s no, well, down—due to zero gravity. That’s the daily reality for astronauts living and sleeping in space. But they still manage to get their shut-eye! Learn how… They Get Primed for Takeoff. Beginning three to seven days before takeoff, astronauts are exposed to bright light at certain times throughout the day in order to manipulate their biological clocks to be wide awake at the time of the launch. They Manufacture a 24-Hour Day….