Some of you physicists out there can help me sharpen my understanding of some basic thermodynamics principles. To that end, here are a couple of questions I’m going to build up towards, or embed into some larger speculations for you to give me some clarity on.
I’ve been thinking about the internal energy of gases (a function of temperature), and how the particles in a gas are perfectly elastic in their collisions with each other or any container walls. Which makes sense, because a gas can’t just “lose heat” without losing it … to … somewhere. And heat is already the “lowest ocean” so-to-speak into which all energy drains. So an isolated system, so long as it is non-expanding (volume=constant), will forever stay at whatever temperature it happens to be at, right? And there is no “almost perfectly elasticity” - it has to be absolutely 100.000…% perfect elasticity, otherwise the 1st law is violated as heat energy would be lost to … nowhere. Am I correct so far?
But this brings me to a ‘heat-death’ question. The other way a gas can lose energy is from adiabatic expansion. That is, the gas does work, pushing outward, to expand its volume, causing its temperature (and internal energy) to fall by that corresponding energy of work done. But this is normally demonstrated as being against the walls of some container - though said container could be something so vague as surrounding atmospheric air masses being pushed aside. But on a cosmic scale, is it correct to think of our cooling universe as being largely due to its expansion; i.e. - cooling in an adiabatic sense? If it is space itself that is expanding, then are those somehow container “walls” being pushed outward? Or is it more in a straightforward sense of gas expanding out into pre-existing void already there (and itself expanding in advance of the gas)? I know that’s still a fairly Newtonian and therefore probably misguided sense of what is happening at such limits, but I don’t have any better sensibilities to go on here at the moment.
I’ve heard the cosmos described as a closed (even isolated?) system in the sense that even radiation doesn’t leave it, which if true, would preclude radiative heat loss. So all I’m imagining here is that heat loss would be due to unlimited expansion. If so, then everything asymptotically approaches absolute zero after vast eons of time, right? More like cold death than heat-death, I’m thinking, though I realize that concept has nothing to do with what we humans now characterize as pleasantly warm or hot.
That should be enough for some of you who really know something about this to bring me some needed education here.