Earlier quoted context omitted.
Hot take of the day: Computer scientists are in denial about it, but CS is a branch of theoretical physics, not mathematics. You can point to this or that model of computation, such as lambda calculus or mu-recursive functions and try to claim its abstracted well beyond the particular laws of physics for some specific universe, but they all have some kind of rate limit built into them... and where does the motivation…
A thought provoking leading question I have is (1) a space heater throws power into a coil and generates heat and nothing more in the world (2) an LLM into a GPU throws power into the GPU and generates heat and organized information. Is (2) generating less heat so that the laws of thermodynamics account for the increased amount of "useful stuff" generated (the organized information)? Switch (2) for a bitcoin miner if…
Yes:
https://en.wikipedia.org/wiki/Landauer%27s_principle
But modern computers are nowhere near this theoretical limit, nor any of the other limits I mentioned above. Nevertheless, most of heat generated from modern CPUs does come from bits turning on and off. Each transistor is a tiny capacitor, that holds a charge when its ON. When it switches OFF, it dumps that charge down the drain, creating waste heat. This is a limitation of our technolgy, not a fundamental limit of physics.
Could be worse, though; early chips would disipate heat even when they weren't doing anything. CMOS improved this enormously by pairing up "complementary" transistors so current only flows when something changes.
Still, from the universe's point of view, what we consider a super advanced computer is a lot closer to a space heater than anything that pushes up against its computational limits. Consider, for example, that quarks operate on time scales of 10^23 Hz, and the universe is happy to run three of those in every proton in every star in the universe. In fact, it runs 10^24 of them for one CPU, and that same CPU can't even simulate the quarks of one proton in real time.
Let's face it: we're like kids in Minecraft who think it's cool watch a calculation of 2+2 trickle through a redstone computer in a minute, while the GPU is rendering a billion triangles every second to give them that view.