# Thread: Would it feel cold to be in outer space?

1. If I were to hitch hike my way to the darkness of interstellar space, which have a temperature of -270 degrees Celsius, and just hang there, my naked skin exposed to the vacuum, would i freeze? Normally we freeze when we touch something cold, but vacuum isn't really a thing you can touch, so I guess heat transfer will occur through radiation only. That means, it would take quite some time, before I started freezing.

It just sounds wrong that my surroundings is at -270 degrees Celsius without me feeling the cold. Am I right, or how am I wrong?

2.

3. Yes. Assuming you are in an un-insulated spacesuit, and far from any warm radiating body, you would freeze to death. You would be losing heat by radiation, i.e. your warm body will be radiating heat into space.

4. Good question. The near-vacuum of space would prevent heat loss by conduction, but you will still (a) radiate heat (b) loose heat by evaporation.

I wonder how close to the Sun you would need to be, before your freeze. The Solar System is permeated by the Solar Wind. At Earth's orbit, it receives about 1200W per square metre. Plus the Solar Wind ions are at a temperature of about a million degrees, but their density is very very small, so that effective temperature of space is around 4K.

5. incidently,you would freeze almost instantly,due to the vast temperature difference your body heat would literally be torn from you.so it would be about as painless as death gets.

6. Originally Posted by brane wave
incidently,you would freeze almost instantly,due to the vast temperature difference your body heat would literally be torn from you.so it would be about as painless as death gets.
I'm not sure about that. How is the temperature lost? It can be only by radiation (and evaporation of liquids), which would be quite slow, so I reckon several minutes. You would freeze quickly in liquid nitrogen by conduction.

7. Suggestion (I assume this is possible but no idea where to find it) : Look up for the internal heating data and "energybill" for the internal heating system in spaceships and or spacesuits. Besides that I expect an increase for the difference between sunnyside and shadowside. The data won,t show that difference.

8. Thanks for the replies. iantresman and Ghrasp; my question is about being for away from anything (interstellar or even intergalatic space). There should be no light except the background radiation.

You all agree that I would freeze to death within minutes, at most. Would I radiate heat faster in space than I do here on Earth? I can't believe that I radiate heat away that violently right now... Haven't thought of evaporation, but again, I see no reason as to why it should happen so very quickly

9. Originally Posted by jmd_dk
You all agree that I would freeze to death within minutes, at most. Would I radiate heat faster in space than I do here on Earth? I can't believe that I radiate heat away that violently right now... Haven't thought of evaporation, but again, I see no reason as to why it should happen so very quickly
You would radiate more quickly in space, because the temperature difference is greater. See "Kirchhoff's law of thermal radiation".

But heat loss from conduction would be zero in space, as there is nothing to conduct to. I would guess that dipping your arm into liquid nitrogen at -196-deg C, would more quickly freeze your arm than having your arm in space at -276-deg C.

10. Before trying I would first take a long term corse here : Home - Wim Hof, The Iceman - Inner Fire

11. Deep space doesn't really have a temperature in the way that we normally think of it. So you wouldn't feel particularly cold floating around naked in a vacuum. Evaporation of moisture from the skin surface may cool you a little though. The idea that you'd freeze solid within seconds to minutes is something you tend to see in the movies.

12. You couldn't really float around naked (if you were alive), because you would have to be depressurized and would suffocate. Or if only part of your body were exposed to the vacuum, that body part would blow up like a balloon and burst. But, if you were in an uninsulated suit, you would radiate the heat away (or heat up from the sun) at a rate depending on your emissivity. That's why space suits are made of shiny material.
Thermal radiation - Wikipedia, the free encyclopedia

13. It's a thought experiment Harold. For those 10-30 seconds that you were alive and conscious you would not feel cold. The amount of heat radiating from the body would not be quick enough to feel anything. Why would the rate of EM emission from the body increase in a vacuum? Don't we use vaucum in a flask for precisely this reason? It's the temperature differential from the body to environment that counts in regards to the OP's question, which specifically asks about naked skin. Since the sort of deep space the OP is talking about is nowhere near a star and has no real temperature we could for all intents and purposes treat it like an insulator, therefore the vacuum of deep space does not feel cold.

14. Contrary to what some have said, the biggest source of heat loss, by far, would be through evaporation. At zero atmospheric pressure the fluids in your skin would instantly boil away taking heat with them. The only other major heat loss mechanism is infrared radiation.

I can't recall what the movie was called but it involved a rescue mission to the surface of Mars, where at 'face' mountain, aliens are found and they leave taking the guy from CSI-New York with them. Near the beginning Tim Robbins sacrifices himself to save his wife by taking off his helmet in space. His face is shown to wither away instantly to a dry, leathery look as all the moisture and oils evaporate instantly. I believe that was an accurate account of what happens.

15. The film was mission to mars.

16. Originally Posted by Zwirko
Why would the rate of EM emission from the body increase in a vacuum?
It's not the vacuum but the ambient temperature, which is somewhere close to -270C in outer space. If you plug that into this applet
Radiation: Cooling Mechanisms for Human Body
the rate of heat loss from a human body goes from about 120 watts at normal room temperature to 966 watts. So, I think you would feel pretty cold.

17. Originally Posted by Harold14370
It's not the vacuum but the ambient temperature, which is somewhere close to -270C in outer space. If you plug that into this applet
Radiation: Cooling Mechanisms for Human Body
the rate of heat loss from a human body goes from about 120 watts at normal room temperature to 966 watts. So, I think you would feel pretty cold.
Sure, but what I'm thinking is that a vacuum has no temperature. Objects in space have thermal energy, not the space itself. Does that applet apply in this case? There are bound to be a few rogue ions or atoms around but surely the density is so low that we can not speak of ambient temperatures in the way we do here on Earth? There is no temperature differential between the skin and "nothing".

Our hapless test-subject would surely cool down over a long period of time to just a few degrees above absolute though. While he was still living I don't think that he would feel all that cold.

I could be hopelessly wrong though, and I nervously await correction.

18. I tend to agree with Zwirko.

There is simply not enough matter floating around for conduction to have any meaningful value. So apart from the evaporation, radiation would be the main avenue of losing heat.

AFAIK, you would also not blow up like a balloon.

Edit: A partial answer on the NASA Website.

19. Looks like I was wrong about blowing up like a balloon. I stand by my calculation on the heat loss. This is for radiational cooling, not conduction or convection. This is what takes place to cool down the earth on a starry night. The earth is radiating out into space which is at near absolute zero, with only a little bit of radiation coming in.

20. Originally Posted by Harold14370
I stand by my calculation on the heat loss. This is for radiational cooling, not conduction or convection.
I get pretty much exactly the same value (930W), assuming the human body acts as a black body. However, exposure to a vacuum will not make you feel cold initially, because the heat is not rapidly removed from your skin in the same way that it is when you jump into a cold swimming pool for instance. You will feel increasingly cold, though, as the difference between your core temperature and surface temperature increases.

With regards to freezing (someone mentioned it earlier), a [dead] human weighing 60kg would take more than 6 hours to freeze. In reality, your body is constantly producing heat through respiration; to completely counter the effects of the radiation your body emits, you would need to consume around 20,000 colories per day.

21. But how does ambient temperature affect the rate of heat loss through radiation?

Edit: I guess it is affected by the amount of ambient heat in terms of IR radiation hitting the body. If the body is in the shade of something, it would essentially not be hit by any IR radiation, or only the bit from the 2.725K temperature of space (evidentially this is what is meant by the temperature of space, i.e. the amount of IR radiation around). So, in contrast to being naked on earth, even in the coldest place on earth, the body would lose heat at a much faster rate than anywhere on earth. It would still take a while to cool all the way down to 2.725K, but I guess then, based on this, you would certainly feel cold. Not from space itself, but from the coldness of the outermost layer of skin. In direct sunlight though, the body would be in danger of cooking, as the radiation from the sun is 1,413 – 1,321W/m2.

In a thermos flask, the vacuum layer provides insulation from conduction and convection mostly, while the shiny coating lowers both the emissivity and absorption rate of the inner flask. Bodies with high emissivity absorb IR faster than bodies with low emissivity.

22. Basically, you emit radiation at the same rate (proportional to the fourth power of your absolute temperature) no matter what the ambient temperature is. However, when there is matter around you, radiating in proportion to the fourth power of its temperature, then the net loss of heat is less than just what you are emitting. In outer space, there is (almost) nothing radiating any heat toward you.

23. Yes, just the CMBR temperature of 2.725K (barring other objects in the vicinity).

Interesting this!

24. we would not feel cold when we are out in space. on earth we feel cold because the air is in contact with us. if our body is exposed to space(vacuum) our body will give out heat in the form of radiation(energy we cannot see). but the temperature of our body would not go down and we wont freeze to death.

25. Originally Posted by parag1973
if our body is exposed to space(vacuum) our body will give out heat in the form of radiation(energy we cannot see). but the temperature of our body would not go down and we wont freeze to death.
This violates the first law of thermodynamics (unless you are suggesting that we are capable of releasing; through metabolic functions; the nearly 1000 calories per hour needed to replace the lost energy, as briefly outlined in my previous post).

26. We could sharpen our pencil a bit and consider that some heat could be conserved by reducing skin temperature. The lowest we could go would be around 10 degrees C. Immersed in water at this temperature, you'd probably die within several hours. If we plug 10C as our skin temperature in the previously mentioned applet, 3K ambient, 0.97 emissivity, and 2 square meters of surface, we end up with about 707 watts of heat being radiated.
Then we look up the metabolism of an average adult male during heavy work, and that's only 430 watts, and a person could obviously not even maintain that indefinitely. So, you're gonna freeze.
Hypothermia Prevention: Survial in Cold Water | Minnesota Sea Grant
Radiation: Cooling Mechanisms for Human Body
Persons and Metabolic Heat Gain

27. Like stated above im nearly positive you would radiate heat. Untill I guess you either die orhit equilibrium(which ever came first. In this cause death would be first. I want to know how fast that, because that is an intresting question! I couldn't see it being "ripped out of you" that impractical. It could only be torn away over time that's the equivilent of saying you'd instantly blow up without the suit like someone mentioned above... You'd more than likely just suffocate.. I think a human skeleton, can hold itself solid enough to not explode or implode. The only force acting outward would be inhalation I doubt your skin pushes out against the atmosphere... Hence bone under skin in your skull to protect and ribs. I'm sure it would be an uncomfortable feeling... The tendency to want to expand in a vacuume. But probably no more so than the feeling of suffocation... I don't know that for sure but that's my opinion, it seems impractical...

28. Originally Posted by iantresman
Originally Posted by jmd_dk
You all agree that I would freeze to death within minutes, at most. Would I radiate heat faster in space than I do here on Earth? I can't believe that I radiate heat away that violently right now... Haven't thought of evaporation, but again, I see no reason as to why it should happen so very quickly
You would radiate more quickly in space, because the temperature difference is greater. See "Kirchhoff's law of thermal radiation".

But heat loss from conduction would be zero in space, as there is nothing to conduct to. I would guess that dipping your arm into liquid nitrogen at -196-deg C, would more quickly freeze your arm than having your arm in space at -276-deg C.
Lol absolute zero is -273.15 C.

29. Originally Posted by Harold14370
Then we look up the metabolism of an average adult male during heavy work, and that's only 430 watts, and a person could obviously not even maintain that indefinitely.
Ah, but is thiat 430 watts of useful output, or total output? And I would speculate that the reason a person cannot maintain such a high rate of work is due to muscular strain, rather than the output capacity of the human metabolism.

That said, arctic explorers (who can essentially be considered to be 'pushing the boundaries') burn around 6000 calories per day, compared to around 15,000 needed in space (using a revised calculations to allow for a lower surface temperature).

Better pack the electric blanket...

30. Originally Posted by drowsy turtle
Originally Posted by Harold14370
Then we look up the metabolism of an average adult male during heavy work, and that's only 430 watts, and a person could obviously not even maintain that indefinitely.
Ah, but is thiat 430 watts of useful output, or total output? And I would speculate that the reason a person cannot maintain such a high rate of work is due to muscular strain, rather than the output capacity of the human metabolism.

That said, arctic explorers (who can essentially be considered to be 'pushing the boundaries') burn around 6000 calories per day, compared to around 15,000 needed in space (using a revised calculations to allow for a lower surface temperature).

Better pack the electric blanket...
It was from a table designed for calculating air conditioning loads, so I'd say it's the total output.
6000 (kilo)calories per day burned by the arctic explorers works out to around 294 watts of power average for the day. That seems consistent with what I found.

A space blanket would work pretty well too.
Space blanket - Wikipedia, the free encyclopedia

31. I think to answer the question we should ask ourselves the question "Will there be *temperature* in space"
How is the temperature of space calculated? Is it the average temperature of matter or what? I think first we will have to
clarify some points.

32. That question has already been asked and answered. The CMB gives deep space a temperature of ~2.7 Kelvin.

33. It's an interesting question (the OP). I was wondering about frostbite and This Slate article about the film Sunshine seems to address that - the answer being no, it wouldn't happen.

Can you survive in space without a spacesuit? - By Morgan Smith - Slate Magazine

34. Originally Posted by drowsy turtle
Originally Posted by Harold14370
Then we look up the metabolism of an average adult male during heavy work, and that's only 430 watts, and a person could obviously not even maintain that indefinitely.
Ah, but is thiat 430 watts of useful output, or total output? And I would speculate that the reason a person cannot maintain such a high rate of work is due to muscular strain, rather than the output capacity of the human metabolism.

That said, arctic explorers (who can essentially be considered to be 'pushing the boundaries') burn around 6000 calories per day, compared to around 15,000 needed in space (using a revised calculations to allow for a lower surface temperature).

Better pack the electric blanket...
How does a space suit keep you warm then? Does it supply the additional 625 calories/hour needed to keep you warm via a heater, or is it by reducing how rapidly you emit black body radiation? Or both?

35. Originally Posted by kojax
How does a space suit keep you warm then?
I've always assumed the suits were there, primarily, to manage the radiation risk... While you'd probably feel a little cooler, the unfiltered exposure to the radiant marvels of the universe would bake you at the genetic level....

The hermetic environment would prevent loss of oxygen and reduce the chance of contracting the dreaded space AIDS...

In all seriousness, the EVA suit is more of a mini-craft than a suit. (It comes fully equipped with all the amenities - propulsion, ablutions, power windows)

36. A space suit has layers of insulation and also operates at less than atmospheric pressure (.29 atmospheres), which reduces conduction and convection. Therefore the surface of the suit (in the shade) would be at a lower temperature than bare skin so the radiation to space is reduced.
It seems that cooling is the bigger problem in a space suit, as they are generally working in sunlight.
The space suit does provide some protection from UV and beta radiation, but that is not the main function.HowStuffWorks "Spacesuit Capabilities"

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