Freeze or explode

[Nibelung44 (OP)]

Hi,

Something that got my attention in Gravity (the movie). The casualties have their body frozen. I would have thought that in space, the total absence of pressure would first spill in a pulp any organic creature, and then freeze the remains. Perhaps it would look less pretty in a movie though.

Any idea what is right or wrong? Corollary question, at which atm pressure we blow out? Is 0.3 atm enough to not die instantly?

[ExChairman]

I read somewhere that our bodies can survive in space...
A very short time and with cold damage...
In theory you could jump between two openings, but I wouldnt recomend it Keep your eyes Shut and hold your breath!

[Black]

I read somewhere that you should not hold your breath.

[Garfunkel]

Gasses expand without pressure, so in a vacuum, you need to exhale quickly or the gasses in your lungs might rupture them. Of course, you'll still suffer damage as other gasses in your body will expand as well. SCUBA divers are taught to blow air out as they rise if they have to do an emergency lift to the surface. You wouldn't explode, it's not that rapid.

[Maltay]

Do not try to hold your breath.  Same problem as a SCUBA diver trying to ascend while holding their breath.  As the air expands because of the lower pressure it can cause an air embolism.  This basically means your lungs expand too far and you rupture a lung.

You would also start to suffer some of the issues a SCUBA diver suffers from surfacing too fast unrelated to lungs.  In general, this is called decompression sickness.  The short version is rapid depressurization causes formation of bubbles of inert gases in your tissues.  Nitrogen is a common culprit.  The problem is the bubbles can form or migrate almost anywhere.  Most common places are large joints (e.g., elbows, hips, knees, and shoulders) causing joint pain.  This is the bends.  Other places include the ears (e.g., vertigo, nausea, and vomiting), brain (e.g., amnesia and seizures), skin (e.g., itching and edema), etc.  So rapid depressurization can be a big issue.

Freezing would not be an issue.  Space is cold, but not cold enough for it to matter.  You are going to run out of sufficient oxygen in your blood to keep your brain alive before you freeze.  On which note, once you stop breathing and you're not holding your breath, it takes about 15 - 20 sec for your blood to run out of sufficient oxygen to keep you conscious.

You would also get a sunburn from unfiltered UV radiation.

In general, I imagine you could be naked in space for a good 30 sec and come out of it with nothing more major than the bends and a bad sunburn.  That is recoverable in about a week.

The idea of blood boiling needs some explaining.  At very low pressures liquids boil because the vapor pressure exceeds the ambient pressure.  Vapor pressure increases with temperature.  So, high temperatures also make liquids boil.  You can find the vapor pressure curve with the relationship between pressure and temperature using Google.  Anyway, the reason this does not matter is your blood is never exposed to vacuum.  Your circulatory system is pressurized and stays that way until you lose lots of blood.  Thus, explaining the danger of losing lots of blood to injuries.  Basically, your blood pressure drops too low to carry sufficient oxygen to your brain quickly enough.  The common trauma response is to correct the circulatory pressure issue using saline solution, blood transfusions, etc.  Granted, liquid exposed to vacuum would boil.  So, saliva as your nasal passage and eustachian tubes cannot be closed.  Maybe sweat?  Possibly the liquid coating your eyes?  So, keep your eyes squeezed shut or suffer the world's worst case of dry eye

There is no pressure that would cause us to explode.  You can put someone at 0.001 ATM and they will just suffer the decompression sickness symptoms faster and have a better chance of badly injuring their lungs.  There is also no dying instantly.  You will be conscious for about 15 - 30 sec depending on how fast you depressurized and stopped absorbing oxygen into your blood.  Even unconscious, you would be alive for a good min or two as your brain burned through your body's oxygen.

Gravity was reasonably accurate.  Dead from hypoxia.  Boiling of surface liquids like saliva.  Bad edema of the skin from acute decompression sickness.  Slightly frosty from the low temperature and a good 15 - 20 min of floating in space.

[Theodidactus]

I did a lot of research on this for a book I'm writing set in 2093.

The human body does not explosively decompress at any pressure. However, it does expand to truly nightmarish proportions. There have been 2 incidents involving "space exposure" where pilots or astronauts had parts of their suits hit zero pressure with yucky results. In the absence of air pressure, parts of the human body can expand to TWICE or even THREE TIMES its normal size as cells swell. the corpses should have been bloated and skin resembling the appearance of a gooey mushy bannana sprinkled with frost. Also, most science fiction books exaggerate the rate at which air rushes out of a space ship. If you poked a tiny hole in the side of a reasonably well built space ship you'd get a lot of noise but it wouldn't like, suck furniture or people toward the hole.A big 'ole km-long space station could actually last hours with a fist-sized hole punched into it, enough time to stage an orderly evacuation.

PARTS of the human body can actually just go "pop", at least we think so, no one has ever proven it, but we think that if all the air started rushing out of a room, and you took in a big gulp of air and then jumped through the hole, your lungs would just fail in a few seconds. your sinuses and capillaries around your teeth and inner ear are also very sensitive to pressure and would probably start bleeding. I've hiked high enough to bleed out of my nose and I've heard stories about people having bleeding earholes on high mountains.

As the pressure drops, embolisms erupt over your whole body and this kills you long before anything else.
The second-most-lethal effects are the weird behaviors of body fluids in low pressure, blood can evaporate and stuff
the third-most-lethal effect is the lack of oxygen, but this kills in minutes.
temperature is the least of your worries. You will radiate off your heat from the side of your body unexposed to the sun, but it would take like, 5-10 minutes minimum.  You actually freeze to death faster in the antarctic than in space because of the absence of convection.

Cosmetically speaking you would also sunburn and your skin would dry out You could pretty much instantly develop cataracts but your eyes would have other problems before this was an issue.

Gravity was reasonably accurate except in its portrayal of death from fast-moving space debris. Which I also researched.

A fast moving projectile does NOT punch a cartoony hole in your body, as much as we all think it would. I tried to figure out what would happen if a .25 g washer moving at 50,000 m/s hit an astronaut right between the eyes. THe answer, I think, is that it punches a keyhole-shaped hole in his faceplate, deforms into a squiggly blob of death, tears a ragged hole in his face,and creates massive cavitations on the inside of his head that turn his brain into jello before blowing out the entire back of his helmet.

I can post citations to these studies later. I'm on my folks' computer because I'm home for thanksgiving.

Gravity's other massive sins are the yet-undiscovered materials "magic space rope" and "sandra bullock's short shorts."

Sandra Bullock's short shorts are made of some superconducting substance that instantly orient a spacecraft with earth's magnetic field, stopping erratic tumbles and turning them into straight-line trajectories.

Magic Space Rope is used in future space parachutes apparently. Magic Space Rope, when gripped by 2 A-list celebrities, instantly accelerates both parties apart using a force proportional to the sexual tension between the two celebrities. It behaves like no rope in the rest of the movie including the "tether" which is so crucial in the beginning and which they clearly studied the actual physics of. So magic space rope's appearance is rather jarring.

Also in general they hugely underestimated how hard it is to plot long-ranged travel in low orbit. Particularly with a single burn from an object that should be tumbling (as with the soyuz from the ISS) or with a wildly bouncing sandra bullock strapped to your back.

but really I liked the movie a lot. the only reason it's so easy to find scientific mistakes in it is because it's so realistic that they stand out. That part at the beginning where Ryan is just spinning aimlessly around was both terrifying and I think completely real.

Also real: the secret technique russians use to smuggle vodka onto the soyuz. No one knows how they do that but they do it.

[Dvorhagen]

My understanding is that the main hazard of being exposed to space is suffocation.  While the external decompression damage would be unpleasant, it would be most closely analogous to a bad sunburn -- you have to remember that the difference between the pressure in space and the pressure at sea-level is only 1 atm.  As long as you kept your mouth and throat closed (don't try to "breath vacuum"), your lungs would be fine; your skin does a perfectly good job of maintaining your internal pressure. 

As for freezing: space can be either very cold or very hot.  There's no medium to transmit heat, so an object's temperature is entirely dependent on how much heat it can absorb from sources like the Sun, and how long it takes for its thermal energy to radiate away as infra-red light.  It's actually much trickier to cool the ISS than to heat it. . .

[hunter james]

there is quite alot of pressure on your body constantly at one atmosphere pressure without like previously stated your body will swell out because all the pressure from inside of your body will be pushing out and space will not push in unlike air at one atmosphere which means you will swell not because space is sucking your body out but because your body is used to pushing outwards to stop itself from being crushed at one atmosphere.

[Dvorhagen]

There would certainly be inflammation, swelling, and burst blood vessels, and you certainly wouldn't want to be exposed to space for very long.  I'm just saying it wouldn't be nearly as bad as movies, etc. , depict it.  More on the order of bleeding eardrums, bloodshot eyes, and reddened skin than of bursting eyeballs and instant embolisms. 

The point is just that anoxia would kill you long before either cold or vacuum would.

[Maltay]

Please keep in mind you really only need to worry about gas.  The human body is primarily based on water or liquids close to water.  Water at 1 ATM is about as uncompressed as water gets without a phase change.  This is why I can SCUBA dive to 99 feet at 4 ATM and only need to worry about gas equalization through my eustachian tubes.  Going from 1 to 0 ATM very quickly would probably cause more than just a lung embolism.  Any gas in cavities, like in your sinuses, would expand.  Some spots, like your sinuses, are not so bad as you can exhale quickly and hope for the best.  Other spots, like tiny cavities of air in your tissues and joints, are potentially a big issue.  In general, expect a slightly swollen appearance.  However, also expect embolisms scattered throughout your body where your tissue tore from escaping gas.  Think of these more like internal injuries than anything else.  In general, your skin can take more of a beating than the tissues separating one organ from another.  These injuries may not be evident if just looking at the body, but the person would probably have had internal hemorrhaging.

[Geoffroypi]

 





Conclusion :

Bad guys explode in pain .
Good guys freeze instantly .


If i remember well, nasa website provides a good and reliable source of  informations about that subject, in case Maltay (very good) explanation isn't enough .

[Theodidactus]

My understanding is that the main hazard of being exposed to space is suffocation. 

It depends on what you mean by "suffocation". You can't actually hold your breath out there, at least, I don't think so. As I understand it, Your blood will rapidly lose its oxygen even if you're tightly closing your throat.

The point is just that anoxia would kill you long before either cold or vacuum would.

I think so. Just very quickly, less than a minute.

if you're interested, I've posted a link to the pubmed citaiton of the primary article I used in my own research on this. I can post a .pdf of the study when I get back to my home computer.

[Bremen]

For what it's worth, the freezing from vacuum exposure isn't because space is cold (while technically it is cold, there's so little there it can't steal much heat) but because liquids like sweat/spit/blood/whatever the name is for liquid in your eyes and such flash boil causing rapid cooling. It would be a very bad thing, and probably cause all sorts of harm, but I can't imagine it would kill you before all the other more immediate problems did.

[Sloshmonger]

Never get off the boat!

[Triato]

http://www.youtube.com/watch?v=pm6df_SExVw There is also another explanation in the vsauce channel. They made a pair of mistakes that they latter corrected if I remember right.