[AskMaxim]

Those who studied the 2nd law of thermodynamics know that a heat engine works on a difference of temperatures. What about live creatures?
How can humans move in a 40C / 104F heat? I know an answer. What about you?

[Subjectivist]

Humans are not heat engines in the same way that steam engines are. We function not by exploiting the difference between heat potentials from one temperature to another, we function by harnessing the electrical potential between chemical bonds.

[AskMaxim]

Yes, we run on batteries. Thumbs up, Subjectivist!

By the way, the universe is not all about thermodynamics either.

[hvacman]

I beg to differ. Metabolic energy is inputted (food or fat), work is done, waste heat is rejected. There are irreversible losses with a net entropy increase. It is a thermochemical energy process as opposed to a more commonly-envisioned Carnot type compression/expansion heat engine process. The body is more like a fuel cell than a steam engine, but it is subject to the same 1st/2nd thermodynamic laws that govern all all energy transfer machines. Irreversible entropy increase - that is what the 2nd law is about.