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Assume that a person is shielded by magic. The only thing this magic does is to keep air away from that person (ignore for now any consequences to said unfortunate individual). Aside from this, the magic can be ignored. This has the result that the person is encased in a sheath of empty space, about 2-1 inches thick. Nothing, including air pressure, is in this area.

What would happen if someone put their hand in this sheath of empty space? Based on what I know (and have seen in the movies), I believe some form of rupturing of the skin would take place, but I don't know how severe this would be. I also don't know if it would happen immediately, or if the hand could potentially be unharmed, at least for a time.

Along the same lines, what would happen if an entire person was exposed to such an environment?

P.S. While the tag 'atmosphere' may not exactly be appropriate, there was an extreme lack of appropriate tags, and I figured those following 'atmosphere' would be able to answer the question.

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  • $\begingroup$ When you say "briefly," what do you mean? Are we talking half a second, under 14 seconds (14 seconds is when you pass out in a vacuum), under 3 minutes, or under a few hours? $\endgroup$ – Cort Ammon - Reinstate Monica Aug 7 '15 at 17:08
  • $\begingroup$ Briefly - enough for the guy to stick his hand in, realize what is happening, and withdraw it. $\endgroup$ – Thomas Reinstate Monica Myron Aug 7 '15 at 17:47
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Obviously, this person will face nearly the same issues as someone in the vacuum of space.

There have been several experiments and incidents where portions of (or entire) humans (and even more animals) are exposed to a hard vacuum, which is what you're describing.

The Wikipedia page describes the symptoms for being in space like this:

The key concerns for a human without protective clothing beyond Earth’s atmosphere are the following, listed roughly in the descending order of mortal significance: ebullism, hypoxia, hypocapnia, decompression sickness, extreme temperature variations and cellular mutation and destruction from high energy photons and (sub-atomic) particles.

Your situation is only slightly different in the items of least mortal significance are not a factor. The symptoms of highest mortal significance are still factors.

Ebullism
The formation of gas bubbles inside the fluids of the body. Think about opening a bottle of carbonated beverage, in a less dramatic way, something similar will happen to any exposed fluids in and on your body.

Hypoxia
Also known as "I can't breathe!". You're no longer getting oxygen. This is an immediate problem. Everything in your body will be letting you know that you need to do something about this right now.

Hypocapnia
Less well known, but you can simulate it by hyperventilating. So may be known as "I breathed too much!". This is a reduction of carbon dioxide in your blood. This causes pins and needles, muscle cramps and tetany in the extremities, especially hands and feet.

Decompression Sickness
Ah, the bends. It sounds like an affliction of someone who frequently drops things. In this case you may drop an arterial gas embolism into your brain and you will have a stroke. Which is less a whimsical name for a clumsy person and more of a you need help with the toilet now, if you're lucky.

These symptoms could be worsened depending on the speed at which the pressure drops around the target (and vice versa). But in general it would be an effective way to kill someone in a few minutes. Incidentally your exposed subject will likely feel very warm, as vacuum is an excellent insulator. Additionally they will be flushing as their capillaries and blood vessels near the surface of the skin expand (some small ones may break, but no one is going to explode).

The most important part to remember about vacuum is that vacuum doesn't suck. When there is a low or zero pressure things blow into them. Humans don't explode in space because our bodies aren't an explosion being held in by air pressure. Did you ever wonder how the tires on the space shuttle don't explode in space? It's because moving them from Earth atmosphere to vacuum is equivalent to putting 14.7 psi more air pressure into them, an insignificant amount compared to the 340 psi they're already inflated with.

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  • $\begingroup$ Two questions: What would be the visible manifestations of Ebullism (would they explode?), and would all of these occur more or less immediately? Obviously Hypoxia would take some time, but what about the other ones? $\endgroup$ – Thomas Reinstate Monica Myron Aug 7 '15 at 16:21
  • $\begingroup$ They would not explode. There would be no visual manifestations unless you could see the fluid on their skin boiling. Hypoxia is a rather quick way to die actually. Depending on the person they may black out in about a minute. The other effects take just as long or longer than hypoxia. $\endgroup$ – Samuel Aug 7 '15 at 16:26
  • $\begingroup$ So if a hand were exposed to this vacuum just long enough for the person to realize what is going on and withdraw it... what would happen to the hand? Wikipedia mentions someone's hand expanding, but does not mention how fast it occurs. $\endgroup$ – Thomas Reinstate Monica Myron Aug 7 '15 at 16:30
  • $\begingroup$ @TommyMyron No permanent damage. Probably just some superficial bruising. The expansion would be from minor swelling, it would happen probably in the span of minutes. $\endgroup$ – Samuel Aug 7 '15 at 16:33
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    $\begingroup$ On the visual effects of decompression, it's worth remembering the Soyuz 11 crew - the capsule depressurised just before reentry and they spent several minutes in hard vacuum. The recovery teams believed they had been suffocated by fumes and attempted CPR... $\endgroup$ – Andrew Aug 15 '15 at 9:09
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Surprisingly not that much. Most of the really "nasty" things about vacuums take time. For example, it takes 14 seconds to lose consciousness in a vacuum, and several minutes to start seeing freezing effects. None of the exotic effects are going to occur until much longer.

His hand would most likely turn a little purple from the blood flowing into it. Maybe a few broken capillaries.

However, I'd like to point out that the rules of physics probably still apply. His hand is in vacuum, and his body is not. This means he is going to get pulled into the vacuum for the same reason your hand gets sucks onto the vacuum cleaner when you put your hand over the opening.

A hard vacuum is roughly 14psi. The cross sectional area of a human wrist is roughly 5ish square inches, so he would feel like he has a 70 pound weight dragging his arm into the vacuum!

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Most of the effects have been well described by Samuel, so I won't reiterate them. The really important thing to look for is how quickly the person is exposed to a vacuum and if they have a chance to be prepared. Perhaps strangely, a person suddenly flung into a vacuum with no warning might do a bit better, since they would probably have their mouth open in surprise and the air would quickly evacuate their lungs at about the same rate the air pressure is dropping around them. A person who thinks they are prepared and tries to hold their breaths had a good possibility of suffering severe damage to their lungs due to the pressure differential between the air in the lungs and the vacuum outside. (Stanley Kubrick, who was usually quite meticulous about detail, did miss this in the scene in "2001, A Space Odyssey", where David Bowman voluntarily ejects from the work pod into the emergency airlock without his helmet. Although it would be quite possible to survive being ejected into the airlock, the actor is visibly taking a deep breath before triggering the hatch, when he should hyperventilate to flood his body with oxygen, then empty his lungs before hitting the switch).

An unprepared person would rapidly black out (even if they did evacuate their lungs in surprise), while a well schooled and trained astronaut might be able to extend his survival time by hyperventilation prior to exposure to the vacuum (we are talking from several more seconds to perhaps a minute tops. Your astronaut hero isn't going to take a leisurely EVA across the spaceship without a helmet). Since your example is magic rather than physics, similar rules would apply (including the damage to your lungs attempting to hold in your breath), but unlike the situation with HAL, there is no airlock in easy reach for your hero.

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As Cort Ammon said you would probably get sucked into the vacuum and that would do the most damage. If the vacuum has low enough pressure the blood in your hand (and body) would start to boil. You can guess that would be a bad thing but other than your blood in a gas form, torn ligament (from folding like a deck chair when you get sucked into the vacuum), exploded lungs, hundreds of broken capillaries and certain death, you'd be fine!

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  • $\begingroup$ Your blood wouldn't boil. Body tissue itself would provide sufficient pressure to prevent it. $\endgroup$ – Keith Morrison Oct 19 '17 at 6:39

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