Interactive Civilian wrote:I'm not going to defend the "freeze instantly in space" types, but I can't help but wonder how much heat will be lost through evaporative cooling as any liquids on the surface of the skin immediately boil off. Maybe not enough to freeze a body solid, but perhaps enough to freeze-dry surface cells causing a bit of frostbite? just curious.
Correct--any wet areas will rapidly become dry, frozen areas, as most of the liquid boils off, and the remainder freezes. As heat is conducted from warmer areas of the body, the surface ice will sublimate, until it's gone. (or until the body is too cool--but a human isn't moist enough on the surface to make that happen. Maybe inside the lungs or something...) After the corpse is dry, any further cooling will be radiative, so the rate will only depend on reflectivity and other heat sources.
Interactive Civilian wrote:
Zhatt wrote:They're beside the flipping Sun for goodness sake!
But they are also in the shadow of their ship. With no medium to conduct heat from the direct sunlight areas to the shadow areas, does their proximity to the sun really matter? Again, I'm not defending the "freeze instantly in space" types, but in the shadow of their ship (which, IIRC was designed to reflect on the front side, so it wouldn't be absorbing much to re-radiate into its own shadow as blackbody radiation), would it really be any different regardless of proximity to the sun?
Not defending the bad science. Just curious about the real physics of such a situation.
Yep, in the ship's shadow, proximity to the Sun doesn't matter. If the ship's surface is reflective, then it will couple poorly (in a thermal sense) with the victim floating nearby. So the body can be treated almost as though neither sun nor ship were present.
I shouldn't just give you the fish--let me teach you to fish, so you can answer this kind of question for yourself:
One reasonably good way to consider radiative thermal transfer in these hypothetical situations is to put your point of view at the body in question (in this case, the corpse), and look around in all directions (a ray-tracing algorithm, for graphics geeks), then measure the temperature of everything you see. In this case you'll see stars, empty space, and a spaceship, but not the Sun. Most of the area is empty space, at < 4K, which is plenty cold. Stars have a temperature of millions of degrees, but they take up a very small fraction of the total area you can see. The spaceship takes up a significant area, but since it's reflective, we don't measure its temperature, we measure whatever we see reflected in it, which again is mostly empty space. (If its albedo is 0.9, then we average 10% of the ship's temperature, and 90% of the reflected space) The victim could see his own reflection in the spaceship, so depending on its apparent size, that section of space appears to be at the same temperature as the body. Since we only care about the average temperature, not the fluctuations on every point as it cools, we can just average all those temperatures we can see, weighted by how much of the sky they take up, and say the body cools just as fast as if that were the uniform temperature in all directions. And that just comes down to the straightforward math for blackbody radiation.