On Thursday, August 6, 2015 at 7:43:19 PM UTC+1, Bernard Burton wrote:

Yes, Stephen is correct. All objects above absolute zero are emitting
radiation. A thermometer in a medium at constant temperature will only read
a constant value if the amount of radiation it is emitting is exactly
balanced by that it is receiving from its surroundings, e.g. it is in
radiative equilibrium. The amount of radiation emitted by the surroundings
will depend on their temperature. If a portion of the surroundings at a
given temperature is replaced by one at a lower temperature, the amount of
radiation received by the thermometer will fall, and the indicated
temperature of the thermometer will fall until the radiation emitted by the
thermometer matches the new value coming from its surroundings, and it
regains radiative equilibrium.


Bernard,

That is just what I am saying! If you put an object in a cold store its temperature will fall to that of its environment. That is because the temperature at which the radiation is emitted from the walls is colder than the object you have just introduced. Or if you put a baby in an incubator with cold walls the same thing happens.

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