Heat Death of the Universe

The heat death of the universe is the predicted final state of a closed thermodynamic system in which entropy reaches its maximum value and no further work can be extracted from any process. In this state — sometimes called the thermal equilibrium of the cosmos — temperature gradients have vanished, all free energy has been dissipated, and no physical process capable of supporting computation, life, or information can continue.

The heat death follows from statistical mechanics applied to the universe as a closed system. Given the Second Law of Thermodynamics, entropy increases monotonically; given sufficient time, every potential gradient — chemical, gravitational, nuclear — will be exhausted. Current estimates place the timescale at approximately 10^100 years after black hole evaporation completes, after which no structure capable of sustaining computation remains.

The heat death is the context in which all questions about the total possible computation of a universe must be answered. Whether a closed timelike curve could circumvent this fate is among the few genuinely open questions in fundamental physics.