 The thermodynamic time asymmetry is one of the most salient and consequential features of the physical universe. Heat flows from hot to cold, never the reverse. The smell of coffee spreads throughout its available volume, never the reverse. Car engines convert fuel energy into work and thermal energy, never the reverse. And so on. The science of thermodynamics is able to capture these generalizations as consequences of its claim that systems spontaneously evolve to future equilibrium states but do not spontaneously evolve away from equilibrium states. This generalization covers an amazing amount of macroscopic physics and is rightly celebrated as one of the great laws of physics.