How does "outer space" affect the human body? Some movies show it as the body exploding, imploding or even freezing solid.

I know space is essentially a vacuum with 0 pressure and the dispersion of energy makes it very cold. So are the predictions above accurate?


There have actually been cases of (accidental!) exposure to near-vacuum conditions. Real life does not conform to what you see in the movies. (Well, it depends on the movie; Dave Bowman's exposure to vacuum in 2001 was pretty accurate.)

Long-term exposure, of course, is deadly, but you could recover from an exposure of, say, 15-30 seconds. You don't explode, and your blood doesn't immediately boil, because the pressure is held in by your skin.

In one case involving a leaking space suit in a vacuum chamber in 1965:

He remained conscious for about 14 seconds, which is about the time it takes for O2 deprived blood to go from the lungs to the brain. The suit probably did not reach a hard vacuum, and we began repressurizing the chamber within 15 seconds. The subject regained consciousness at around 15,000 feet equivalent altitude. The subject later reported that he could feel and hear the air leaking out, and his last conscious memory was of the water on his tongue beginning to boil

(emphasis added)

UPDATE: Here's a YouTube video regarding the incident. It includes video of the actual event, and the test subject's own description of bubbling saliva.

Another incident:

The experiment of exposing an unpressurized hand to near vacuum for a significant time while the pilot went about his business occurred in real life on Aug. 16, 1960. Joe Kittinger, during his ascent to 102,800 ft (19.5 miles) in an open gondola, lost pressurization of his right hand. He decided to continue the mission, and the hand became painful and useless as you would expect. However, once back to lower altitudes following his record-breaking parachute jump, the hand returned to normal.

If you attempt to hold your breath, you could damage your lungs. If you're exposed to sunlight you could get a nasty sunburn, because the solar UV isn't blocked by the atmosphere (assuming the exposure happens in space near a star). You could probably remain conscious for about 15 seconds, and survive for perhaps a minute or two.

The considerations are about the same in interstellar or interplanetary space, or even in low Earth orbit (or a NASA vacuum chamber). The major difference is the effect of sunlight. As far as temperature is concerned -- well, a vacuum has no temperature. There would be thermal effects as your body cools by radiating heat, but over the short time span that you'd be able to survive, even intergalactic space isn't much different from being in shadow in low Earth orbit.

Reference: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html

  • 2
    $\begingroup$ Thanks for the great answer and references. I tagged it intergalactic-space because it was the most accurate tag I could find. And my reputation doesn't allow tag creation. $\endgroup$ – n0pe Dec 8 '11 at 21:23
  • 3
    $\begingroup$ I'd just like to add the reason for the boiling saliva: It's not because his saliva somehow got really hot all of a sudden, it's because the boiling point of a substance becomes lower in a low-pressure/vacuum environment. I.e. Your saliva may boil, but it wouldn't burn you. $\endgroup$ – Cam Jackson Dec 9 '11 at 2:30
  • 2
    $\begingroup$ Quick clarification: The boiling points lowers as pressure lowers. At zero pressure (a perfect vacuum), water would basically boil at any temperature, even the near-0K of space. $\endgroup$ – Cam Jackson Dec 9 '11 at 2:37
  • 1
    $\begingroup$ @CamJackson: In a vacuum, water can either boil or freeze, depending on the temperature. It can't be in the liquid state at pressures below about 6 millibars (atmospheric pressure is 1000 millibars). The phase diagram of water shows the gory details. $\endgroup$ – Keith Thompson Dec 9 '11 at 23:04
  • 3
    $\begingroup$ @CraigFeinstein: Nope. Your skin itself provides enough pressure to hold you together. $\endgroup$ – Keith Thompson Sep 16 '12 at 20:15

You're right that there is almost zero pressure in space. Which means the pressure difference between the inside and outside of a spacesuit or spacecraft is only one atmosphere. The body can cope with much greater pressure changes. You need only think of diving. You will not explode in space. Space is very cold, but again being a vacuum there is nothing to conduct away your body heat other than self-radiation.

  • $\begingroup$ The body can cope with much greater pressure changes, but it doesn't cope well with outgassing in body tissues (a.k.a., "the bends"). Probably not an issue in case of space-suit failure though because the suit pressure would be very low to begin with, and the breathing mixture would contain no nitrogen. I read that NASA astronauts breathe pure oxygen at only 3 PSI during EVAs. $\endgroup$ – Solomon Slow Jun 2 '15 at 17:57

Not the answer you're looking for? Browse other questions tagged or ask your own question.