It takes the International Space Station one and a half hours to fly around the planet, making for 16 complete laps a day.
It takes the space station one and a half hours to fly around the planet, making for 16 complete laps a day. For those on board, the visual effect is spectacular. Open the covers over the windows and the light can be so blinding that astronauts reach for their sunglasses. But after 45 minutes of daylight, a dark line appears on the planet, dividing Earth into night and day. For a couple of seconds, the space station is bathed in a coppery light and then complete darkness. Another 45 minutes later, and just as abruptly, the sun rises to fill the station with brilliant light again.
The onslaught of apparent days and nights would play havoc with astronauts' body clocks, so a shutters-down and bedtime schedule is imposed by mission controllers. Each of the crew has a closet-like cabin where they can hook a sleeping bag to the wall and settle down for the night. Some strap pillows to their heads to make it feel more like lying down. The lights don't go out completely, though. People dozing in orbit see streaks and bursts of bright color caused by high-energy cosmic rays painlessly slamming into their retinas. Fans and air filters add to the distractions, so some astronauts wear earplugs to block out the constant hum.
Unsurprisingly, falling asleep can take some getting used to. Just as you are nodding off, you can feel as though you've fallen off a 10-story building. People who look half asleep will suddenly throw their heads back with a start and fling out their arms. It gets easier with time. One Russian crew member is renowned for doing without a sleeping bag and falling asleep wherever he ends the day. Anyone still awake after bedtime would see his snoozing form drift by, slowly bouncing off the walls, his course set by the air currents that gently pushed and pulled him.
Newcomers are always in awe of the views. It is the sight of our planet that takes the breath away. Onboard, the best vantage point is from the gun-turret-like cupola whose six windows look down on a panoramic view of Earth. But for the really exceptional vistas, you need to step outside.