Question: why can't humans breathe in space

Karen answered on 12 Nov 2018:

The air that we breathe on Earth is just a thin layer around our planet, and it gets thinner the higher you go up! This means there is less and less oxygen. Even on top of Everest, the world’s highest mountain, people need to bring oxygen to survive. There’s just not enough oxygen for us in space, it’s also really cold and the pressure is different, meaning it would be difficult for our lungs to work!