Chaos (derived from the Ancient Greek Χάος, Chaos) typically means a state lacking order or predictability. In ancient Greece, it meant the initial state of the universe, and, by extension, space, darkness, or an abyss^[1] (the antithetical concept was cosmos). In modern English, it is used in classical studies with this original meaning; in mathematics and science to refer to a very specific kind of unpredictability; and informally to mean a state of confusion.^[2] In popular culture, the word can occur with all three meanings.

[edit] Chaos in mythology, literature, and religion

In Greek mythical cosmogony, particularly in the Theogony (Origin of the Gods) of Hesiod (8th–7th century BC), Chaos is the original dark void from which everything else appeared. First came Earth and Eros (Love), then Erebus and his sister Nyx (Night). These siblings produced children together which included Aether, Hemera (Day), Nemesis, and Charon.^[3] Other cosmogonies, such as that of Pherecydes of Syros (6th century BC), also have the gods being born from Chaos, but in a different way.

Some similar ideas appear in Vedic cosmogony. The book of Genesis in the Bible refers to the earliest conditions of the Earth as "without form, and void",^[4] while Ovid's Metamorphoses describes the initial state of the Universe as a disorganised mixture of the four elements:

Rather a rude and indigested mass:
A lifeless lump, unfashion'd, and unfram'd,
Of jarring seeds; and justly Chaos nam'd.
No sun was lighted up, the world to view;
No moon did yet her blunted horns renew:
Nor yet was Earth suspended in the sky,
Nor pois'd, did on her own foundations lye:
Nor seas about the shores their arms had thrown;
But earth, and air, and water, were in one.
Thus air was void of light, and earth unstable,
And water's dark abyss unnavigable.^[5]

[edit] Scientific and mathematical chaos

Mathematically, chaos means deterministic behaviour that is very sensitive to its initial conditions.^[6] In other words, infinitesimal perturbations of initial conditions for a chaotic dynamic system lead to large variations in behaviour.

Chaotic systems consequently look random. However, they are actually deterministic systems governed by physical or mathematical laws, and so are completely predictable given perfect knowledge of the initial conditions. In other words, a chaotic system will always exhibit the same behaviour when seeded with the same initial conditions - there is no inherent randomness in this regard. ^[7] However, such perfect knowledge is never attainable in real life; slight errors are intrinsic to any physical measurement. In a chaotic system, these slight errors will give rise to results which differ wildly from the correct result. A commonly used example is weather forecasting, which is only possible up to about a week ahead,^[8] despite theoretically being perfectly possible at any level (ignoring the effects of the uncertainty principle).

Edward Lorenz and Henri Poincaré were early pioneers of chaos theory, and James Gleick's 1987 book Chaos: Making a New Science helped to popularize the field. A number of philosophers have used the existence of chaos in this sense in arguments about free will.

More recently, computer scientist Christopher Langton in 1990 coined the phrase "edge of chaos" to refer to the behaviour of certain classes of cellular automata.^[9] The phrase has since come to refer to a metaphor that some physical, biological, economic, and social systems operate in a region where complexity is maximal, balanced between order, on the one hand, and randomness or chaos, on the other.

[edit] Notes

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