Metastability

During a metastable state of finite lifetime, all state-describing parameters reach and hold stationary values.

Metastability is common in physics and chemistry – from an atom (many-body assembly) to statistical ensembles of molecules (viscous fluids, amorphous solids, liquid crystals, minerals, etc.)

The abundance of states is more prevalent as the systems grow larger and/or if the forces of their mutual interaction are spatially less uniform or more diverse.

Non-equilibrium thermodynamics is a branch of physics that studies the dynamics of statistical ensembles of molecules via unstable states.

Extremely pure, supercooled water stays liquid below 0 °C and remains so until applied vibrations or condensing seed doping initiates crystallization centers.

Adenosine triphosphate (ATP) is a highly metastable molecule, colloquially described as being "full of energy" that can be used in many ways in biology.

An entire mountainside of snow can suddenly slide due to the presence of a skier, or even a loud noise or vibration.

[7] A metastable state is then long-lived (locally stable with respect to configurations of 'neighbouring' energies) but not eternal (as the global minimum is).

Some energetic states of an atomic nucleus (having distinct spatial mass, charge, spin, isospin distributions) are much longer-lived than others (nuclear isomers of the same isotope), e.g.

[8] The isotope tantalum-180m, although being a metastable excited state, is long-lived enough that it has never been observed to decay, with a half-life calculated to be least 4.5×1016 years,[9][10] over 3 million times the current age of the universe.

Transitions from metastable excited levels are typically those forbidden by electric dipole selection rules.

This slow-decay property of a metastable state is apparent in phosphorescence, the kind of photoluminescence seen in glow-in-the-dark toys that can be charged by first being exposed to bright light.

Molecular vibrations and thermal motion make chemical species at the energetic equivalent of the top of a round hill very short-lived.

For instances, having the wrong crystal polymorph can result in failure of a drug while in storage between manufacture and administration.

Gilbert Simondon invokes a notion of metastability for his understanding of systems that rather than resolve their tensions and potentials for transformation into a single final state rather, 'conserves the tensions in the equilibrium of metastability instead of nullifying them in the equilibrium of stability' as a critique of cybernetic notions of homeostasis.