How is heat dissipated? When radiant heat warms an object does it just radiate back off with no light behind it? How does it move through space?
It radiates as electromagnetic waves, often infrared. So it is light, just not visible light most of the time.
The other way I can think of is if there are volitiles, then heat can be carried off as kinetic energy of molecules, if they move fast enough to escape local gravity.
That would be electromagnetic radiation … and the energy is “contained” in the photons that are emitted. So yes, it does radiate back out in the form of light, where light has it’s broadest definition.
Are the photons behaving as if they had mass in this example?
No, the photons are just behaving as photons. Why would they need mass?
And just to touch on a common misconception, by the way, there’s absolutely nothing special about infrared in this regard. Any light that hits something and gets absorbed will heat it up, and any object above absolute zero will emit light. The frequency of light emitted will vary, but the peak of it will be proportional to the temperature of the emitting object. It happens that most of the things we think of as “warm” or “hot” have a temperature corresponding to infrared, but the Sun, for instance, is hot enough that its peak emission is in the visible range, and something hotter than the Sun (a welding torch, for instance) will have a peak in the ultraviolet.
I can’t tell you much about the specific thermodynamic laws of heat in space (or areas of no atmosphere), but what I cant tell you is that if one were to ever take ones suit of in space, the following events would unfold in quite rapid succession.
Considering the fact that our bodies are constantly generating a certain amount of heat constantly, this heat normally dissipates into the air around us, making it no big deal. But when one removes said atmosphere (in which the heat has a chance of escaping), the heat remains in the body, and long story short, you fry yourself from the inside.
If you're wondering whether or not you would explode, no that wouldn't happen, because of the human skins amazing capability of stretching. And even before you could suffocate (or die of any other reason), your own body would kill itself by heating itself to the point of no return.
An accident once happened aboard one of the multitudes of space shuttles that have been sent out, in which a man that was outside taking a space walk, encountered a leak in his suit. He was quickly brought back to the ship, but he says that the last thing he remembered before he blacked out, was bubbles in his mouth. This was due to the fact that in the short period of time in which he had been in an atmosphere lacking environment, his mouth had gotten to the temperature in which the saliva inside was begging to boil. Interesting story no?The fact that his body fluids began to boil indicates lower pressure, not increased temperature.
That’s right. The boiling saliva would probably make your mouth feel cooler - assuming you had the time to register that sensation, alongside all the other discomforts of zero external pressure.
When did this happen? I don’t see it in this list of EVA accidents. I think an EVA accident severe enough to cause the astronaut to black out would be widely known.
This is what brought my question up. I was wondering how our bodies would react in a leaky space suit.
To elaborate - this video demonstrates an analogous situation by placing an egg in a vacuum chamber (first with the shell, then just the membrane, then cracked in a glass)
The fluids boil at the lower pressure, but get colder, and eventually freeze because the evaporation lowers the temperature.
So no. A human would not die of overheating. A human would suffocate, then boil away and possibly partially freeze.
Then at some point in the process (after we’re dead), we’d start sublimating away? What a way to go …
It wasn’t an EVA, it was a ground test of a spacesuit.
Overheating can be a problem in space, but it’s not a problem that’s fixed just by wearing a suit. There’s not much practical difference between heat being trapped in your skin and heat being trapped in your suit. To fix it, you need to either have a large thermal mass in the suit (so it heats up slowly), or a coolant that you can eject to shed heat, or a hose connecting to your spacecraft to carry away heat. The first two solutions will put a limit on how long a spacewalk can be, and the third will force you to stay close to your main craft.
Nifty scientific stuff aside, heat dissipates pretty crappy in space, being not much matter to dissipate it to.
So cooling something in space is actually a bit of a problem.
It can only transfer via radiation, not conduction or convection.
Or via evaporation/boiling.
Any fluids that are in your body and can get out will carry away a certain amount of heat. This would not normally include blood, unless you haemorrhage around the orifices (but I don’t know of any cases where this has occured).
Welding torch hotter than the sun?
What others (aside from NickerBot) have said is true, but there’s another consideration in this situation: the thermal conductivity of air is almost constant down to quite a low pressure (<10% of an atmosphere), and doesn’t drop by even half until you get down to ~1% of an atmosphere.
So if there’s even a tiny amount of air left in your suit, overheating would not ever be a concern. There’s no pressure at which you would overheat before suffocating.
There seems to be a significant fundamental conception that “heat” is a thing by itself. Heat is the measurement of the latent thermal energy in a system, generally in terms of its potential for to perform work or difference that can be transferred between two systems, or between a system and from/to a high/low temperature reservoir. A “hot” object or system is one in which the particles within it (whether it is a crystalline solid, amorphous solid, liquid, gas, or plasma) are in a certain amount of average randomized motion, which can be extracted by allowing the state of the object to change (transfer thermal energy by some mechanism). A hot object can transfer energy directly (by conduction to another system), indirectly (by convection through a fluid), or by emission (the issuance of photons to carry the heat away in the form of electromagnetic radiation of a specified distribution depending on the temperature and emissivity of the surface), but “heat” isn’t just taken from one system and put into another as if it is a bag of marbles. The efficiency of the transfer depends on the emissivity and absorbtivity processes of the giving and receiving systems respectively.
In the vacuum of space and in absence of any evaporation or other mechanism to carry away thermal energy, a body will radiate energy to the 2.7 Kelvin microwave background in proportion to the outward facing aspect and emissivity of the surface (crudely, the fraction of energy radiating in comparison to an ideal black body). This radiaction rate can be quite high for an object with very large temperature compared to terrestrial temperatures (like a star), but it is quite slow in comparison to the temperature most solid materials or people can tolerate. Therefore, the thermal energy that a spacecraft or astronaut builds up can only be rejected at a very limited rate, which in turn places limits on how much work can be done without running into a thermal overload condition, especially if the spacecraft or astronaut is exposed to intense sunlight for a significant aspect. Space suits therefore have very complex thermal control systems to ensure that they keep the occupant within habitable temperature ranges, and spacecraft often have large areas of surface dedicated to radiators that face away from the Sun and radiate away excess thermal energy (again, to the cosmic microwave background).
Stranger
Hotter than the surface, at least. The core of the Sun is millions of degrees, but the surface is only a few thousand. Lots of things that humans make get hotter than that.