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I was brainstorming ideas for my sci-fi world building project and I wanted to make a planet that had more interesting organisms. I had the idea for an extremely hot planet with perhaps a day temperature of 50-60 C where organisms desperately need to cool down. I recently heard of the Peltier effect and imagined an organism capable of utilizing it. Cooling down its insides while being burning hot on the outside cooking its prey just from touching them. Or perhaps it has bladed arms with the sharp edge burning hot and the dull side cold.

Could such organisms be possible?

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  • $\begingroup$ Humans are organisms and we are capable of using the Peltier effect for cooling. It is actually very common with portable coolers and dehumidifiers. It is true that the way we evolved this capability was not straightforward, but we did evolve it. $\endgroup$
    – AlexP
    Dec 31, 2022 at 16:17
  • $\begingroup$ It's your world. Anything can be possible. $\endgroup$
    – Ian Kemp
    Dec 31, 2022 at 16:37
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    $\begingroup$ Where is the excess heat being ejected to? (And Peltier cooling is amazingly inefficient.) $\endgroup$
    – Jon Custer
    Dec 31, 2022 at 16:54
  • $\begingroup$ Sounds a bit contrived, tbh. There are organisms on Earth that not only survive but even thrive in temperatures that are above boiling point of water, without any need for cooling. They are unicellular, though, but if ambient temperature was constantly 50 - 60°C, more complex organisms would surely evolve sooner or later. ui.adsabs.harvard.edu/abs/2014IJAsB..13..141C/abstract $\endgroup$ Jan 1, 2023 at 1:52
  • $\begingroup$ the Peltier effect only moves heat from A to B, it does not 'cool' as such - the process also generates additional heat. So you need some part of the organism that can dissipate heat well (which gets easier if the temperature is higher, relative to the environment, which is how peltier'coolers' are used usually, concentrating heat in one place that gets very hot and can be efficiently cooled by other means) - but which also can withstand the increased temperature from getting the heat from all other parts of the organism plus the heat produced by the peltier mechanism... $\endgroup$
    – bukwyrm
    Feb 17, 2023 at 10:19

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An organism could evolve such a feature, but not for cooling. 50-60 C is not a problematic temperature for organisms, you have thriving organisms at much higher temperatures. On Earth there aren't all that many multicellular organisms at 50-60 C range, but not because the temperature is an issue, but because that temperature range is kinda rare. And is usually found in deserts, so the issue is not temperature but lack of water. If your planet had higher temperatures than Earth, so you had such temperature ranges in places with enough water, multicellular life could prosper. Without the need for cooling. Earth's multicellular life don't particularly like that temperature range because we evolved for cooler temperatures, so our biochemical processes are fine-tuned to different temperatures. If life evolved in greater heat, then those processes would be fine-tuned to those temperatures.

Now your thermoelectric effect could evolve, in hot or cool climate. But not as a mean for cooling, as that is extremely inefficient. An organism would spend way too much energy for it to run the effect full time (which would be needed if it was a cooling mechanism). More energy than it can get from food. BUT! Such an feature would be usable as a weapon/defence mechanism. An extremely hot blade/horn/something could be an effective means of killing your prey. Maybe the prey has protein-based contact toxin on his skin, so the heat (for denaturation of that toxin) was a way to go.

As for biochemistry of this feature: it should be possible. Maybe this organism has some conductive organometals that it uses to generate this effect. Such a thing could evolve in place of nerves; so instead of neuron based control over body this world evolved something that is similar to wires. A tube made out of cells that produce that organometallic and fill the tube, and this transmit electric signals trough the body.

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For this to work you'd need an organism that can

  1. Utilize electricity on a large scale, much more than what existing nerves can probably handle.
  2. Biologically use two dissimilar conductive metals on a wide scale.
  3. Be able to genetically instructed to or consciously assemble a network of said dissimilar conductive metals to form a thermoelectric array.

Instinctively, I'd say electric bacteria would be the closest from our world to achieving this.

This is very hard to do as a living being in general though.

If these are large animals and have lungs, I'd say that there could be a secondary "thermal" lung that would be arranged in a manner that allows it to use the Stirling cycle to draw heat away from inside. If biologically implemented in a well enough manner the heat moved could exceed the heat generated by performing the necessary actions for a Stirling cycle by a margin that could make it biologically practical.

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I highly doubt it, as basic self-replicating systems such as those pivotal to life needs to start in a basic medium. For terran life it is water. Without water, nutrients couldn't disperse, proteins couldn't fold, temperature couldn't be mediated, and chemical messenger signals could not be exchanged.

Without a medium that allows this, it is extremely improbable that any such life could exist. I do however see the possibility of an engineered or artificial life form (think horizon-zero dawn) might use heat as a weapon or energy source, but not biological life, at least as we know it.

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  • $\begingroup$ Possibly the star in the system is starting to become a red giant and the planet is getting hotter and hotter, and the life forms are evolving to survive in the greater heat. $\endgroup$ Dec 31, 2022 at 17:05
  • $\begingroup$ Possible, but not overly likely. If that were to happen, it would cook away the atmosphere and take most of the water with it. Radiation would then be a problem and probably sterilize the planet. (at least its surface) $\endgroup$ Dec 31, 2022 at 17:21
  • $\begingroup$ 50-60 C is not exactly problematic temperature thou. $\endgroup$
    – Negdo
    Feb 17, 2023 at 14:05
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[Spoiler Alert!]In Project Hail Mary by Andy Weir, there are aliens that move using hydraulic/gaseous pistons(For lack of a better word) as muscles. They also see with sound waves. It might be possible that these aliens evolved to be able to generate sound waves, and have a fine control over generating sound waves that they could slow the movement of particles inside of them to cool nitrogen gas into liquid nitrogen.

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  • $\begingroup$ With gaseous pistons, you could employ the stirling cycle to cool instead. $\endgroup$
    – Harry Mu
    Feb 17, 2023 at 5:13
  • $\begingroup$ Welcome to worldbuilding! We appreciate your answer. I have given this answer a down vote as it doesn't answer the question. The request is specifically about organisms that use the peltier effect. Your answer offers a different effect that os hardly explained. Could you focus on the peltier effect, or show why this version of cooling might be the answer sought by the OP or other people with the same question? $\endgroup$
    – Trioxidane
    Feb 17, 2023 at 14:51

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