Interesting Phenomenon

Thanks! I was totally unaware of that!

Richard Saunders had an interesting response to that sentiment

It is a well known fact that some gasses do not follow the normal thermodynamic rules of gasses. When you calculate the state of a gas, you would normally use an approximation known as the ideal gas where the standard equation holds --> pV=nRT

This usually holds for monatomic gasses at high temperatures and low pressure. When the molecular size and intermolecular attraction becomes important, you need a different set of state equations.

I never understood how the ideal gas law would explain how a gas cools when it expands. Now I see that it's the gas deviating from the ideal gas law that explains it. An ideal gas would neither cool nor warm on expansion.

Nature is constantly seeking equilibrium.Mountains erode,a liquid will form a perfect sphere in the absence of gravity or other outside forces.

Two reasons(but not necessarily all) that a gas could expand.1.Higher pressure inside the container than outside, caused by heat or adding gas to the confining space or a decrease in outside pressure.

Our universe is expanding and it could be that the BB is still happening,or the "Void" that surrounds our universe is at a lower "pressure" than our universe.

A bubble will increase in speed as it rises due to a decrease in external pressure and the corresponding increase in volume of the gas.

A balloon will expand due to an increase in the quantity of internal gas,at a constant temperature.

That kind of sounds like our universe expansion.Perhaps we live in a bubble that we cannot see because the "Void" is our dimensional boundary.

Since there was no molecular motion (heat) within the Big Bang,(or a black hole) the temperature should have been cold when it expanded?

The lowest natural temperature in the visible universe is a gas cloud resulting from an explosion (rapid expansion). The Boomerang Nebula 1 degree K.

https://interestingengineering.com/science/what-is-the-coldest-place-in-the-universe

Physics can be fickle…

just like Newtonian and non-Newtonian fluids…

and by fickle, I mean interesting…