heat

[Cannon]

So, astronauts wouldn't freeze immediately in space without spacesuit because there is no air to take their body temperature.

But why does a planet without atmosphere cool at night, there is no air, what makes him cold?

I know atmosphere is supposed to keep the warmth but, anyway, look at the astronaut example, there must be something to cool it

[CaptainKipard]

Is the answer infra red radiation?

[KerikBalm]

http://en.wikipedia.org/wiki/Black-body_radiation

"Although planets and stars are neither in thermal equilibrium with their surroundings nor perfect black bodies, black-body radiation is used as a first approximation for the energy they emit."

[RogueMason]

Yep, radiative heat and cooling. How did you think the Sun warms us up?

It's a lot more complicated, though. You have to consider latitude, ocean/land, albedo, atmospheric conditions, etc. At the most basic level, solar radiation (insolation, shortwave) is absorbed by the surface of some non-atmospheric world, say... Mercury. The heat that Mercury has gained will be emitted again as longwave (black body, IR) radiation. Of course, if a planet has interior heat such as that of our own Earth, then there will be some emission of radiation from that source, too, but this is relatively slow acting in comparison to the former process. And then there's the atmosphere to contend with on Earth as well, which will act like a greenhouse at varying degrees depending on the current chemical composition. In our atmosphere, we also have clouds, which like to absorb and reflect incoming radiation and emit it again.

This is a little more than the basics, and I've just been doing it in one of my university modules, so I will say right now; yes, it goes on and on. Fortunately for you, I won't go on and on. You're safe

[Cannon]

Yep, radiative heat and cooling. How did you think the Sun warms us up?

It's a lot more complicated, though. You have to consider latitude, ocean/land, albedo, atmospheric conditions, etc. At the most basic level, solar radiation (insolation, shortwave) is absorbed by the surface of some non-atmospheric world, say... Mercury. The heat that Mercury has gained will be emitted again as longwave (black body, IR) radiation. Of course, if a planet has interior heat such as that of our own Earth, then there will be some emission of radiation from that source, too, but this is relatively slow acting in comparison to the former process. And then there's the atmosphere to contend with on Earth as well, which will act like a greenhouse at varying degrees depending on the current chemical composition. In our atmosphere, we also have clouds, which like to absorb and reflect incoming radiation and emit it again.

This is a little more than the basics, and I've just been doing it in one of my university modules, so I will say right now; yes, it goes on and on. Fortunately for you, I won't go on and on. You're safe

K, thanks for detailed answer, really appreciate that, one more question, in stefan-boltzmann equation, there is "e", emissivity and it says dark objects are good absorbers and good emitters and shiny objects are opposite.

Well, sun is bright and shiny as hell, and emits a lot of energy, is this theory correct then?

I need to answer this for school though

[Kryten]

The sun can't really be approximated as a blackbody, given it's constantly producing more energy through nuclear fusion.

[RogueMason]

K, thanks for detailed answer, really appreciate that, one more question, in stefan-boltzmann equation, there is "e", emissivity and it says dark objects are good absorbers and good emitters and shiny objects are opposite.

Well, sun is bright and shiny as hell, and emits a lot of energy, is this theory correct then?

I need to answer this for school though

The Sun is bright as hell for it is essentially a giant globe of incandescent plasma undergoing nuclear fusion, and thus it emits one hell of a lot of solar radiation. The Stefan-Boltzmann equation doesn't apply to it in the sense that you're suggesting because it has no albedo i.e. it doesn't reflect anything, therefore emissivity in this respect can be ignored; it's neither dark nor shiny, just giving off light.

The equation can be used for some Sun-related stuff, however, but I really don't think that you'll be needing any of that, which is just as well, because I haven't covered that sort of stuff, and being an undergrad geologist, I'm not entirely certain that I want to (which would probably explain things if I've got anything mixed up here)