The best answer to the question is that it serves as essentially a universal resource that can be used to provide a measuring stick.
It does this by being a resource that is limited, fungible, always is better to have more of than less of, and is additive across decisions:
You have a limited amount of joules of energy/negentropy, but you can spend it on essentially arbitrary goods for your utility, and is essentially a more physical and usable form of money in an economy.
Also, more energy is always a positive thing, so that means you never are worse off by having more energy, and energy is linear in the sense that if I’ve spent 10 joules on computation, and spent another 10 joules on computation 1 minute later, I’ve spent 20 joules in total.
Cf this post on the measuring stick of utility problem:
Agree that free energy in many ways seems like a good resource to use as a measuring stick. But matter is too available and takes too much energy to make, so you can’t spend it on matter in practice. So it’s non-obvious why we wouldn’t have a matter-thermodynamics as well as an energy-thermodynamics. I guess especially with oxygen, since it is so reactive.
I guess one limitation with considering a system where oxygen serves an analogous role to sunlight (beyond such systems being intrinsically rare) is that as the oxygen reacts, it takes up elements, and so you cannot have the “used-up” oxygen leave the system again without diminishing the system. Whereas you can have photons leave again. Maybe this is just the fungibility property again, which to some extent seems like the inverse of the “breaking a system down into smaller components primarily requires energy” property (though your statements of fungibility is more general because it also considers kinetic energy).
The best answer to the question is that it serves as essentially a universal resource that can be used to provide a measuring stick.
It does this by being a resource that is limited, fungible, always is better to have more of than less of, and is additive across decisions:
You have a limited amount of joules of energy/negentropy, but you can spend it on essentially arbitrary goods for your utility, and is essentially a more physical and usable form of money in an economy.
Also, more energy is always a positive thing, so that means you never are worse off by having more energy, and energy is linear in the sense that if I’ve spent 10 joules on computation, and spent another 10 joules on computation 1 minute later, I’ve spent 20 joules in total.
Cf this post on the measuring stick of utility problem:
https://www.lesswrong.com/posts/73pTioGZKNcfQmvGF/the-measuring-stick-of-utility-problem
Agree that free energy in many ways seems like a good resource to use as a measuring stick. But matter is too available and takes too much energy to make, so you can’t spend it on matter in practice. So it’s non-obvious why we wouldn’t have a matter-thermodynamics as well as an energy-thermodynamics. I guess especially with oxygen, since it is so reactive.
I guess one limitation with considering a system where oxygen serves an analogous role to sunlight (beyond such systems being intrinsically rare) is that as the oxygen reacts, it takes up elements, and so you cannot have the “used-up” oxygen leave the system again without diminishing the system. Whereas you can have photons leave again. Maybe this is just the fungibility property again, which to some extent seems like the inverse of the “breaking a system down into smaller components primarily requires energy” property (though your statements of fungibility is more general because it also considers kinetic energy).
Thinking further, a key part of it is that temperature has a tendency to mix stuff together, due to the associated microscopic kinetic energy.