AC world: "Cold is the absence of heat"

Carlo Rovelli from On Being: "Every time there is something that distinguishes the past from the future, there is heat. […] So only when there is some heat around, the phenomena are different in one direction of time from the other. So the direction of time is deeply connected to the existence of heat. That doesn’t explain the direction of time but is a first step toward understanding it. The direction of time has to do with the presence of heat.

Natalie Batalha: "Heat is an inevitable consequence of harnessing energy to do work, no matter what the mechanism. Sustainability has to do with how that heat is dissipated"