Direct exposure to the vacuum of space

I was watching a few sci-fi movies and was wondering the real science explaining what would happen if you were to be subject to the conditions of outerspace.

I read the wikipedia article on space exposure, but was still confused. If a person was about the same distance from the sun as earth is, would they still freeze to death? (as shown in the movie Sunshine)

I'm reading from all sorts of sites with conflicting information about what would actually happen when a person is exposed to the vacuum of space...

• You would definitely freeze, but it might take a day or so for your whole body to freeze solid, depending on all the variables. – endolith Nov 26 '12 at 22:48
• Possible duplicates: physics.stackexchange.com/q/3076/2451 and links therein. – Qmechanic Jan 27 '13 at 14:44

4 Answers

You'd freeze to death faster in the Atlantic ocean.

Space has essentially no thermal conductivity. All the heat you lose will be radiated away. According to the Stefan-Boltzman law, $W = \sigma T^4$, you would lose at most 500 watts per square meter of body surface area. By contrast, the convective heat transfer coefficient in water is about 12,500 watts/square meter / degree Kelvin temperature difference. So, I think freezing would be the least of your concerns.

• But what about evaporative cooling from the liquid boiling off the surface of your skin/inside of mouth/lungs, etc? – endolith Nov 26 '12 at 22:33

They would freeze.
They wouldn't freeze to death - since they would die of something else (lack of oxygen) first

Although a small part of you is facing a hot sun at 6000K most of your surface is facing cold dark space at 3K. You can work out what temperature you will reach - it depends only on how reflective you are.

Assuming you have the same reflectivity as the earth (35%) and you aren't close enough to the earth to receive any significant heat from it then you would end up at about the same temperature the Earth would have without the greenhouse effect of it's atmosphere = which is about -20C.

If you were made of much darker material like the moon - you would get much colder. Parts of the moon not facing the sun or earth get down to around -150C

Just want to add that freezing is 'not an issue'.

The problem is that water boiling temperature gets lower at lower pressure.

In vacuum blood boils even at 36.6, so all your blood circulation is stopped immediately due to bubbles of blood (water) vapor. So you loose consciousness in few seconds, and die in minutes due to lack of oxygen in brain.

If you would rotate around yourself at ~60RPM and not wearing white, you should nor freeze nor fry in short term (minutes). If you would freeze - then earth would also freeze. As earth is at equilibrium at 20C, you should be near it too if you are not wearing white.

• The argument that the earth's equilibrium temperature would be identical to a body's ignores a great deal of important detail. Just for starters, (a) the earth generates heat at its core, (b) the "green house" effect, (c) neither are black bodies, etc. – Carl Brannen Jun 24 '11 at 4:00
• and wearing white or green or black wouldn't change your equilibrium temperature, it would simply change the speed with which you approached equilibrium. It changes your albedo. – mwengler Aug 18 '12 at 3:27
• This says the blood will not boil. The reason you lose consciousness after 10 seconds is because that's how long the body takes to use up all the oxygen in your blood. – endolith Nov 26 '12 at 22:42

Remember the pressure in your body is 14.7 lb at sea level.So first, whatever air you have is now at that pressure in your lungs. An inexperienced diver experiences this when he dives 10 m taking a lung full of air and surfaces without exhaling.He will be lucky if he doesn't die from it. So you exhale... now if something does not burst in your body because of internal pressure or nitrogen gassing in your blood, well then you can die from lack of oxygen. Dissipation of heat is one of the biggest problems to a body in space. If the body is not rotating one side will cook and the other will freeze. If its rotating just right it will become a new moon<-- he he.

• Does Nitrogen gas out at 0 atm from what is dissolved in the blood at 1 atm? Was the person even breathing a nitrogen mix at the time he was spaced? – KalleMP Feb 19 '18 at 11:43