Context for question: My girlfriend who is studying to be a nurse asked me to explain the difference between radiation and convection in context of the above question.
My answer: Radiation is the emission of heat by all bodies as long as their temperature is above 0K. Which means that convection would be how the baby would be affected and not by radiation.
The problem: It seems there are several nursing books (such as this one ) and even a physics book that seems to agree that apparently there is "cold" radiation as well.
I don't get it, can you radiate "cold"? If someone can explain how a cold wall/cold bottle/ cold anything would affect the baby by radiation (and not by convection).
Answer
There is no such thing as cold radiation.
In the examples you link above, the issue is that the walls of the incubator are colder than the air or the baby. What actually happens in this situation is this: all objects radiate with a certain intensity which is based on their temperature (among other things). A baby in an incubator is constantly radiating energy away into the surrounding air and parts of the incubator; what keeps the baby warm is the fact that this same air and incubator radiate the same amount of heat back to the baby as the baby is losing. As long as this balance is maintained the baby can maintain its body temperature.
In the case of the cold incubator wall, the situation is not that the incubator wall radiates cold to the baby but that the baby continues to radiate energy away (which it would be doing no matter where in the incubator it was at) but because the wall of the incubator is cold (in some relative sense) the amount of energy being radiated by the incubator wall back on to the baby is lower than would be if the wall was warm. Because of this, the baby radiates away more energy than it is receiving from its surroundings (because the wall isn't radiating as much because of its lower temperature). Thus the baby cools down.
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