ELI5: What would happen if you took off your helmet in outer space?

Ever put a vaccum cleaner on your eyeball? (actually don't!) but it will be part of the experience of decompression in space.

The air will be sucked out of your lungs (or more like pressed out by your body's internal pressure.) Very uncomfortable.

You won't freeze immediately, but fast enough for it to be really painful. You'd might experience frostbite at your hands and feet, but will suffocate before freezing kills you.

Freezing is the sensation of heat leaving your body. It basically feels like touching a hot oven door, but in the other direction. Remember, your body is about 310 Kelvin hotter than space. The oven about 200 Kelvin hotter than you. So even without heat transfer by air, the radiated heat is still significant.

/r/explainlikeimfive Thread