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Let's say that a hot gas is trapped in a metal box. This metal box is magnetically suspended in another structure with a low temperature. The inner box does not touch anything. And there is a void in the structure. To me there seems to be no way for heat transfer to occur. Will the gas change its temperature with time?

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Conduction, Convection, _______? –  user2963 Jan 1 '12 at 13:40
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@pewfly is right. If you want an example of a system like that, just wait for sunrise. –  Mike Dunlavey Jan 1 '12 at 14:36

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I can't make this a comment since I don't have enough reputation.

The metal box itself can absorb some of the heat (by conduction) and then give out energy in the form of electromagnetic radiation. If you want to do some real physics with such a system, you could idealize the box as a black body and continue.

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As far as I can understand, this is interesting, so the energy is converted anyway in other forms, and even if there is no heat transfer the temperature goes down as the box converts heat to electromagnetic radiation. And a black body facilitates a faster transfer. –  Palax Jan 1 '12 at 17:31
    
@Palax: it's not really accurate to say "even if there is no heat transfer"; heat is being transferred from the box into the electromagnetic field. –  Harry Johnston Jan 2 '12 at 2:01
    
you're right because electromagnetic radiation can cause heating, it is like a medium of transfer by electromagnetic radiation. thanks for your careful reading –  Palax Jan 2 '12 at 13:23

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