The strange, weightless environment of space is a fun place: tricks and stunts that are impossible on Earth become ordinary when in a spacecraft that is zooming around Earth. While a lot of fun, there are lots of everyday tasks that need rethinking in space: drinking water, washing and uh... going to the toilet. But also something that we do for nearly half of our lives: sleeping.

How do astronauts sleep in space, then? IFLScience decided to ask a former astronaut, Dr Story Musgrave, who had the privilege of going to space six times aboard NASA's space shuttles. The duration of these trips varied between 5 and 17 days, so there was plenty of time to practice catching forty winks far above the planet's surface.

Standard procedure for a good night's sleep is much like sleeping on the edge of a cliff: lots of straps. "They provide you with sleeping bags, and it's a standard sleeping bag except that it has more straps to hold your arms and your head down," said Musgrave

But Musgrave decided that you don't get to go to space every day, so why sleep according to standard procedure?

The cramped sleeping quarters on the space shuttles have a definite floor and ceiling. "So my friend chose to sleep on the floor because it is comfortable, and it is compatible with the orientation and the way they perceive things," he said.

"Well you have to shake this up, so I put my bed on the ceiling. You don't work this hard to get into space just to sleep on the floor!"

Sleeping on the ceiling may sound topsy-turvy, but Musgrave just commented on how it alters your perspective on things. "The whole world turned around," he said. To him, he was comfortable on the floor, and his colleagues were all sleeping on the ceiling. It's all a matter of perspective.

Being strapped in is all well and good, but Musgrave still wanted to take his experiences in space one step further. "I think the real, ultimate way is to go free-floating." You might think that bumping into things would be a concern if you slept untethered in space, but Musgrave pointed out that if you're moving slowly enough then the impact is so tiny that it doesn't even wake you up. Any switches or levers were fitted with covers to prevent a dozy astronaut from accidentally flipping one. 

There are some interesting effects on body position when an astronaut sleeps in space. The limbs find a comfortable balance between stretched and flexed. This perfectly balanced point between the two is known as the "neutral point."

^{Example of the "neutral point." Pilot Gregory C. Johnson resting at the end of a day on the Space Shuttle Atlantis. NASA.}

"100% of every joint in your body, right from the [toes] all the way to the finger joints, they arrive at the neutral point," Musgrave said.

You can experience the neutral point yourself on Earth, or at least something like it, underwater. It's probably not safe to sleep underwater in a scuba suit, but next time you're in the deep end of the pool, just try letting your muscles reach a relaxed equilibrium to imagine sleeping in space. 

Another interesting sensation, one that can make some people anxious, is the loss of stimulation in all of your limbs. With no bed pressing against their bodies, astronauts can wake up from free floating sleep completely disoriented and convinced that they don't have arms or legs. (This doesn't happen if you're snuggly in your sleeping bag though).

Musgrave had his own solution to sleeping untethered: "Sometimes I wore a belt to keep my knees up on my chest; that's important for your back that is expanding in zero G." This way, astronauts can sleep a little more comfortably in a slight fetal position. 

There was one relief when Musgrave was snoozing up in space: the sleeping cabin was blissfully quiet. Except for the occasional whirring of machinery, not a creature was stirring, not even an astronaut. That is to say that no one snored in space. 

There is a gravitational factor to snoring: the pharynx falls toward the back of the windpipe and into the breathing airflow. The rushing air vibrates the structures and causes a sound. With no gravity forcing the structures in the mouth backward into the astronaut's breath, it is difficult to create a monstrous noise. There have been some accounts of astronauts snoring in space, but Musgrave reported that in all his time sleeping in space, not one of his comrades snored. 

Musgrave painted a wondrous picture of sleeping by the window while the stars watch over you. And some of the less wonderful consequences.

"It was nice to sleep by the window with the day view, you've got stars all night and the Sun's going to wake you up," he said, before adding: "Wait, that's not a good part of sleeping." 

Sunrise in space isn't a slow, lazy process like it is on Earth: in fact it's almost rude in its urgency. With no atmosphere to dilute the morning rays of light, it's a simple process of "lights off, lights on."

Musgrave noted that he prefers sleeping on Earth but confessed that this is purely biological. "You've evolved over four million years to sleep in a gravitational field and sleep in a bed, but it is a privilege to have the opportunity to not have the gravity there."

^{Central Image: Portrait of astronaut Story Musgrave. NASA.}

^{Central Image 2: Richard Truly (head near the ceiling) and Guion Bluford (head near the floor). NASA.}