Even as a kid I heard about the Heat Death of the Universe, and I later learned more during my studies of physics up to A-Level.
The cap was put upon Heat Death by the general adoption of the Big Bang theory of the origins of the universe - not just in professional physics, but also as a Western cultural dogma.
But really, the idea is not derived from physics, as a consequence of our society's fundamental operating assumptions; our whole way of reasoning in public discourse.
The basic idea as I grasped it in childhood was that the end point of everything would be when every-thing that existed had cooled down to reach the same degree of (extreme) coldness. Or that there was a finite amount of hot material in an infinite empty-cold universe, and therefore that all the warmth would be diluted-out. Or that energy came from heat differences, and these differences would diminish until no more energy remained to keep anything moving.
Another way of thinking about Heat Death is that it is the inevitable outcome in reality as it is described by Science (ie: with a capital letter, the discourse and mode of thinking that is "science") - because Science regards "entropy" as the fundamental and ultimate source of all energy, heat, and life.
In other words, for Science everything is fuelled by "entropy" in a parasitic fashion. The universe began with a source of heat and energy; and ever since, that is being used-up.
Or; for Science there is just so-much "Life", and life necessarily feeds on life - so that at some point all life shall be consumed.
When I was a kid this all seemed compelling, but I was troubled by the thought that in a universe that was eternal going backwards, a universe that had always existed; then the Heat Death could not be true (or, at least, not inevitable), or else it would already have happened.
Nowadays, I regard the Heat Death idea as a reductio ad absurdum of the assumptions of Science; in other words, I think Heat Death is a correct inference from the basic and bottom-line way that Science as a mode of discourse was set-up in the 17th century.
To refute Heat Death entails revising the basic assumption of Science; which is that in Science God, and especially divine creation, are excluded from permissible explanations.
In other words; a valid refutation of the Heat Death idea entails assuming the reality of Divine Creation.
Divine Creation might be assumed explicitly, or implicitly; it might posit a personal God or posit an abstract deity - but one way or another a purpose and genuinely creative creation must be introduced; and that creation must also be assumed to constitute an inexhaustible, eternally-self-renewing source of "energy".
This, for example, is assumed by the last rival to the Big Bang theory, the Steady State theory (of Hoyle, Bondi, and Gold) - which posited an everlasting "creation" of the expanding-universe in the centre, that compensated for the everlasting "dilution" of that universe at the edges.
The Steady State theory was (whether probably consciously, as with Hoyle, or apparently unconsciously as with Gold and Bondi) "smuggling" deism back into Science, which was why it had a bad reputation among the mainstream scientists even when it was performing very well as a predictive model.
My conclusion is that if Science is regarded as a true and complete description of reality, then the Heat Death is indeed inevitable.
But in reality Heat Death is not inevitable; and the reason is that the basic assumptions of Science leave-out divine creation.
Since divine creation is real, then Heat Death need not happen.





