Comment by tbrownaw
What does volume have to do with energy balance?
What does volume have to do with energy balance?
Heat isn't produced by the volume. Heat may be produced by something within the volume, but it's not the volume's existence that causes heat to be produced. There is no fundamental reason a bigger terrarium should produce more heat, nonetheless that heat production should be directly proportional to volume.
Yes, obviously it'd be the stuff in the terrarium rather than the space it occupies that produces heat, but the amount of stuff you can fit in it is determined by the occupiable space. And if that stuff is producing heat, such as by decay, there's going to be more heat with more stuff. Though even if it cooks itself for a while, it should eventually settle on a temperature determined mostly by orbital parameters and material properties rather than size, since the stuff can't be net exothermic forever. But greater atmospheric depth probably still increases equilibrium temperature by reducing heat transfer through that side of the terrarium.
> but the amount of stuff you can fit in it is determined by the occupiable space.
You can fit more into a larger terrarium, but that doesn't require a larger terrarium to contain more. Regardless of what is contained within the terrarium, it's heat production is limited by what it receives from the environment.
> But greater atmospheric depth probably still increases equilibrium temperature by reducing heat transfer through that side of the terrarium.
Greater atmospheric depth affects heat transfer by changing the density of the atmosphere, which is relevant for an atmosphere held to a body by gravity, but not for one contained in a pressurized vessel like a terrarium. A terrarium with a 1 atm internal pressure has an atmosphere depth equal to earth's atmosphere regardless of size (at least up until the point where the terrarium's gravity is comparable to a planet).
Heat is transferred through the surface area and produced by the volume (assuming there's something going on in the system that's exothermic).