Big Rip

The Big Rip is a hypothetical cosmic ending in which accelerating expansion grows strong enough to unbind structures at every scale, from galaxies to atoms.

Dark energy: An unknown component of the universe associated with the observed acceleration of cosmic expansion. The Big Rip requires a form of dark energy whose density grows as space expands.
Heat death of the universe: A proposed cosmic future in which usable energy becomes unavailable as the universe approaches thermodynamic equilibrium. Unlike the Big Rip, heat death does not require structures to be torn apart.
Robert R. Caldwell: An American cosmologist who studied dark energy and coauthored the 2003 paper describing the Big Rip scenario. His work gave the scenario its influential formulation and name.
Dark energy equation-of-state parameter: The ratio of dark-energy pressure to its energy density, conventionally denoted by w. A sustained value below −1 is the key condition for the standard Big Rip scenario.
Phantom energy: A hypothetical form of dark energy with an equation-of-state parameter below −1. Its increasing density can make cosmic expansion accelerate without bound.
Big Crunch: A hypothetical cosmic ending in which expansion reverses and the universe collapses to a dense state. It reverses cosmic expansion rather than driving it toward unbounded acceleration.
Marc Kamionkowski: An American theoretical physicist whose research includes cosmology and the nature of dark energy. He coauthored the paper that analyzed the Big Rip's physical sequence.
Type Ia supernova: A stellar explosion with a predictable peak luminosity, used as a distance indicator in cosmology. Supernova measurements constrain expansion history but do not yet establish future phantom behavior.
Equation of state (cosmology): A relation between pressure and energy density used to characterize cosmological fluids. Its parameter distinguishes phantom energy from other proposed drivers of expansion.
Big Freeze: A proposed cosmic future of continued expansion, cooling, and increasing isolation of matter. It shares continued expansion with the Big Rip but leaves bound structures intact.

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