Question

Alright, so we have all seen the movies where someone gets blasted out of the airlock on their starship, or their suit decompresses while on a space walk. The poor schmoe usually either decompresses so violently that blood is oozing out of every orifice in their body, or they freeze instantly.

From this I have two questions:

1. Would the decompression really be that violent?
   1. Clearly the drastic difference in pressure from a normal "earth" like environment to space would be bad, but would it be that devastating.
   2. I vaguely remember that standard atmospheric pressure was something like 15 psi, which doesn't seem like enough to mess you up that bad.
2. Would you actually freeze instantly in space?
   1. Heat, or lack thereof is a measure of internal energy, but in a vacuum there wouldn't be anything to have internal energy, so does space even have a temperature?
   2. Wouldn't some form of matter have to be present in order to cool off? If there were no matter besides yourself and a few stray particles here and there, it seems like it would take a very long time to cool off.

Answer 1

Most of what is shown in sci-fi on this is believed to be false. You do not freeze to death and your blood does not boil.

Provided you do not try to hold your breath there are not likely to any ill effects for at least 30 seconds or so. If you do try to hold your breath as the de-pressurisation takes place you can suffer a "burst lung" i.e. an embolism, just as a diver would if he holds his breath during an ascent from depth.

After some time in space the lack of oxygen will be the most damaging. A few minutes will lead to death.

I found this answer at http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html where you can find a lot more details.