pressure - What exactly happens to an exposed human body in space?

I know that space is a vacuum, has no air, and is very, very cold. From what I have seen in movies and TV shows when a space suit is exposed the oxygen will escape like a visible gas and the person would explode.

In the movie Event Horizon one of the characters is blown out of an airlock and one of his comrades tells him to expel all the air in his lungs and to curl up, as he does he seems to be bleeding a lot.

In the movie The Hitchhikers Guide to the Galaxy it says you can hold your breath for a little while before anything happens. Of course all these examples are science fiction so they may or may not be accurate.

I am wondering what would happen if a human body was exposed in space? Would it blow up like so many shows seems to hint? Would the person be frozen to death because of the temperature in space?

NOTE: I ask this as in a fan fiction I am writing, in one scene the main character's daughter is sucked out through a hull breach of the ship before her friend willingly jumps out and holds her as she teleports the two through space to the nearest planet. I want to explain how the adverse effects on an exposed human body are negated, but I can't do that if I don't know what I am negating.

Answer

Unlike most depictions that you see in movies or heard of maybe, the human body can actually maintain its stability for a short while. I am not sure of exactly how long it takes for a permanent injury to occur or swellings to start appearing, but what is known is that there's no immediate injury.

Meaning you do not explode, your blood doesn't boil, nor does it freeze, and you don't lose consciousness instantly. Why? there are two important factors in play:

• Containing effect of your skin and your circulatory system allow us to withstand the instantaneous drop of pressure for a while.


• You do not instantly freeze because, although the space environment is extremely cold (close to 0 Kelvin), heat does not transfer away from your body quickly. In fact space is mostly a vacuum and can hardly transfer heat, so you can imagine that the main temperature worry for space suits is how to get rid of naturally generated body heat, not keeping heat inside!

Finally, surprisingly one actually dies of asphyxiation. Air would immediately leave the lungs due to the enormous difference of pressure between your body and the vacuum around you. Then any oxygen dissolved in the blood would empty into the lungs to try to equalize the partial pressure difference, and your brain starts to die.

In a nutshell, our skin and lack of matter(no atoms/molecules: exchange kinetic energy with what? of course radiation still takes place) in space make the instantaneous effects impossible.

For further reading: Human body in a vacuum