Are there warm places in space?

[Pbartender]

Will his body temperature drop? Will his heat radiate off of him into space (thus lowering his temperature).

Yes, his body temperature will drop. Yes some small portion of his body heat will radiate off into space.

However, most of his heat loss is not due to radiating it. Most of the heat will be lost by evaporation...

Under extremely low pressures and vacuum, the moisture in the layers of skin close to the surface will spontaneously "boil" off into space. As evaporation is an excellent way to remove excess heat (hence why we sweat when we're hot), your naked space walker will essentially be slowly cooled by dehydration from the outside in.

 

[Janx]

what about the toaster? it doesn't sweat.

 

[Mustrum_Ridcully]

what about the toaster? it doesn't sweat.

It will radiate the heat out, slowly. I am sure there is some formula that one could use to determine how long it would take.

A minor nitpick: There is no dark side of the moon. Every part of the moon gets exposed to the sunlight over time. But we can only see one side of the moon. I believe the term is "tidally locked" or something like that. Basically, the moon turns around his axis with the same speed as he travels around earth, so we see only one side of it.

 

[freyar]

It will radiate the heat out, slowly. I am sure there is some formula that one could use to determine how long it would take.

Absolutely there is a formula to tell you how fast a hot object radiates. With a real toaster, though, I think the big complication is figuring out how fast the heat conducts from the hot heating wires into the body of the toaster. The larger toaster body would radiate faster because it has a larger area, but spreading the heat through the whole toaster cools the whole thing down, slowing the radiation process. In any case, I'm not motivated enough to work the whole thing out.

 

[Mustrum_Ridcully]

Absolutely there is a formula to tell you how fast a hot object radiates. With a real toaster, though, I think the big complication is figuring out how fast the heat conducts from the hot heating wires into the body of the toaster. The larger toaster body would radiate faster because it has a larger area, but spreading the heat through the whole toaster cools the whole thing down, slowing the radiation process. In any case, I'm not motivated enough to work the whole thing out.

How about treating it as an idealized black body with a temperature?

"Take a frictionless environment"...
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[Umbran]

How about treating it as an idealized black body with a temperature?

That is pretty much exactly what it is. The approximation there is that the body is "black".

Note - this is how the Sun heats the Earth. Sunlight is just a *really* hot body radiating energy away in a vacuum.

 

[Umbran]

On the solar sail thing, the question is, does it really work? Have we launched one to prove it? The radiometer, as somebody mentioned is demonstrating a different effect because of the gas, and is not a solar sail effect.

That light exerts pressure was experimentally verified by Lebedev in 1900. So, yes, it will work in theory. The practice is a matter of engineering.

As for white or black sails, I'm not sure absorbtion into the material (per black) would make sense.

A black sail (that absorbs the light) will work. A white sail will work better. A mirrored sail works even better - thus pretty much everyone trying this works with nice, light, shiny mylar sails.