From clipping fingernails to making sandwiches, the simple tasks we take for granted on Earth become trickier in the weightless conditions of space.

But Canadian astronaut Chris Hadfield on the International Space Station is demystifying some of these zero-gravity chores with home videos, pictures and social media updates showing what life is like in orbit.

In one of his latest YouTube videos, Hadfield answers a crucial question: How do astronauts brush their teeth in space without making a mess?

"We don't have running water. You can't have a tap; you can't have a sink 'cause water would flow everywhere," Hadfield explains in the video. "So what do you do to wet your toothbrush and where do you spit afterwards?" [Quiz: The Reality of Life in Space]

Hadfield then demonstrates how the astronauts do it. He squeezes a small amount water out of a bag, catches the floating droplet with a toothbrush, and lets the bristles absorb the water. After applying some toothpaste from the astronauts' shared tube directly on the brush, Hadfield gets to work.

"Get 'em all — especially the ones in the back," the ever didactic space man says while brushing. "You should brush your teeth for about as long as you can sing 'Happy Birthday' — that should be long enough."

Hadfield explains what happens next. "I got a mouthful of toothpaste stuff. I got a dirty toothbrush. So what I do," he says with a slight grimace and a gulp, "is just swallow the toothpaste. It's edible. Won't kill you. And what else am I gonna do? Put it in a rag and have a dirty rag? Doesn't make any sense."

"In space, you'd all swallow your toothpaste," Hadfield adds, before rinsing the brush with a little water in his mouth.

In past videos, the Canadian astronaut provided a step-by-step guide on how to make a space peanut butter and honey sandwich and how to wash your hands in space, as well as how to safely trim your nails and how to make a bag of dehydrated spinach look like something you would eat on Earth.

Hadfield is one of six astronauts currently living on the International Space Station as part of its Expedition 35 crew. He is Canada's first commander of the space station, with two American astronauts and three Russian cosmonauts rounding out the crew.

The International Space Station has been permanently staffed with rotating crews since 2000, when the first three-person team took up residence. Construction of the $100 billion orbiting laboratory began in 1998, with five different space agencies and 15 countries participating in its assembly.

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