I know the physics majors will cringe at the way I phrased this question—you don’t generate cold, you shed heat—but is such a thing possible in theory?
Can a biological animal, such as something which lives in a constantly hot environment, shed large enough amounts of heat that we might think of it as “generating cold?” I know, of course, that many animals on Earth have ways of taking advantage of things in the enrivonment (water, mud, dust, wind) to cool their natural high body temperatures during hot weather. I want to know if it’s possible not to simply prevent overheating but to actually biologically cool oneself to below ambient temperature.
I’m no biologist, but my gut reaction is to think that such a biological system would be inefficient and use much more energy than would be worthwhile. What do the know-it-alls say?
There are plenty of endothermic chemical reactions out there, so I’d imagine that an organism could, in theory, use endothermic reactions to convert thermal energy into chemical potential-energy, thus becoming colder than its surroundings.
You do it yourself. When it gets hot, your sweat glands generate sweat, which evaporates, and in doing so slightly decreases the temperature of your body. Many animals use some variant of evaporative cooling when outside temperatures get too hot for them.
Is that really “generating cold” like the OP was asking? I don’t think that if I stood by one of those (not necessarily touching it), I would feel cold the same way I would if I were close to a block of ice say.
The reason you won’t feel cold if standing next to a sweating animal is because the animal doesn’t get cool enough to notice. The reason for that is because there is an energy cost involved in cooling but there is absolutely no advantage to the critter in cooling itself below 98o or whatever its normal core temp is. Of course 98o won’t feel cool if you stand beside it because it is so close to your own core temp that you register it as lukewarm rather than cool. So it will never feel cool.
But the fact remains that AndrewL is 100% correct. Humans routinely cool themselves to well below ambient temperatures.
It’s also possible to shed heat by infrared radiation and maintain a temperature lower than ambient, if by ambient we mean (as we typically do) the temperature of the air around us. That is true because animals shed heat through the infrared to the sky above which is typically quite cold in the infrared, as distinct from the ambient air immediately around us.
This may not exactly count, but in heat transfer you’d consider the volumetric heat capacity times the time derivative of temperature as a heat source or sink. This is the “cooling” mechanism that makes you quite comfortable for a few minutes in a hot bath that would be lethal long-term. For humans this is an important mechanism over the course of minutes. Firemen working hard in heavy gear in a hot environment are surviving by using this mechanism.
Finally, you also may not buy this one, but in a literal sense it’s true: humans do what the OP asked every time we use air conditioning. Our use of tools in general is arguably just part of our biological functioning; I can’t think of a distinction to the opposite effect that isn’t a little contrived.
So are Sweating/Large surface areas for heat to dissipate from the only way animals cool themselves? Or are there animals that are cool becasue they have some endothermic reaction occuring somewhere in their body.
Thank you, AndrewL, you are technically correct, but that’s not what I’m asking for. I did say I knew that animals on Earth took advantage of things like water and wind to keep themselves from overheating. The evaporation of sweat is just such a thing—but so would bathing in a pool and allowing oneself to dry.
I was more interested in the possibility of some kind of interior biological process that could accomplish the same thing. I know of no animal that presently does this. Endothermic chemical reactions seem to be more along the lines I was thinking, or possibly an animal with an interior heat pump or something. Is such a thing possible in theory?
Perhaps if the creature had some really exotic biochemistry—like if it were Silicon based—there might be some advantage to making itself colder than it’s environment.
(If, if, if; maybe, maybe, maybe.)
