In the new sci-fi film Sunshine, an astronaut named Mace must leave his spacecraft without a protective suit. He makes it through his exposure with only a case of frostbite. Could you really survive outer space without a suit?

Yes, for a very short time. The principle functions of a spacesuit are to create a pressurized, oxygenated atmosphere for astronauts, and to protect them from ultraviolet rays and extreme temperatures. Without it, a spacewalker would asphyxiate from the lack of breathable air and suffer from ebullism, in which a reduction in pressure causes the boiling point of bodily fluids to decrease below the body's normal temperature. Since it takes a bit of time for these things to kill you, it's possible to make it through a very quick stint in outer space.