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We've all heard the phrase 'I'm washing my hair tonight' - mostly in rather uninventive sitcom scripts.
It's usually writer shorthand for; this character can't be bothered to go to the pub, or they're not actually interested in going on that date.
The reason it never caught on was most likely because washing one's hair is a simple task - it doesn't take too long and it's certainly not something that would result in an evening wasted.
In space however, it's a different story. Washing hair in zero gravity is a precarious business - but it needs to be done.
On a trip to the International Space Station in 2012, Expedition 36 astronaut Karen Nyberg demonstrated just how she and her colleagues keep their hair clean while floating around in orbit.
As you can see in this video from Nasa, it's not entirely dissimilar to how we wash hair on Earth, except we don't have to catch the water as it floats away from us.
They also have to use no rinse shampoo (we sincerely hope they are using the right shampoo) and a towel, rather than a hair-dryer, as they have limited supplies.
Although it looks like a real ordeal, it's cool to know that astronauts are keeping themselves and their hair clean in outer space.
If you weren't impressed already, Karen reveals that there is an even more fascinating aspect to cleaning hair on the ISS.
In an extended video, Karen states that as her hair dries, the evaporated water is condensed by the space station and eventually turned into drinking water.
How about that? We wonder if it tastes of shampoo?
According to Nasa, Karen, who was on her second space mission at the time time, also took along sewing and sketching materials on the six-month long trip.
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