Heat death of the universe

A proposed far-future state in which the universe approaches thermodynamic equilibrium, leaving no usable energy to sustain large-scale physical processes.

Second law of thermodynamics: The principle that the total entropy of an isolated system does not decrease. Its statistical tendency toward higher entropy underlies the proposed cosmic endpoint.
Statistical mechanics: The framework that explains macroscopic thermodynamics through the statistical behavior of microscopic states. It clarifies why high-entropy states dominate the proposed cosmic future.
Big Crunch: A hypothetical cosmic fate in which expansion reverses and the universe collapses to a dense state. It replaces endless dilution with a recollapsing universe.
Stellar evolution: The sequence of physical changes a star undergoes during its lifetime. Star formation and stellar burning eventually cease as usable fuel becomes scarce.
Dark energy equation of state: A relation between dark energy’s pressure and density that helps determine its cosmic effects. Its value and possible evolution affect whether accelerated expansion continues indefinitely.
Thermodynamic equilibrium: A state in which macroscopic properties no longer change because driving gradients have disappeared. Heat death is the universe’s proposed approach to this condition.
Thermodynamics: The study of heat, work, energy, and the macroscopic laws governing their transformations. Its concepts of equilibrium and available work define what heat death means.
Big Rip: A hypothetical fate in which accelerated expansion eventually tears apart bound structures. It predicts disruption before equilibrium rather than a gradual exhaustion of usable energy.
White dwarf: A dense stellar remnant supported against collapse by electron degeneracy pressure. White dwarfs are among the long-lived remnants expected after ordinary star formation ends.
Cosmological constant: A constant energy density of empty space that can drive accelerated cosmic expansion. A true constant supports one influential version of the heat-death forecast.

Linked from 7 pages