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Dark energy

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Acceleration of the Universe
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Dark energy is the term for a proposed form of energy that is thought to permeate all space. Dark energy has a repulsive effect, much weaker than gravity, but falling off in strength over distance much less rapidly. The true nature of dark energy is one of the current unsolved problems in physics.

The abundance of dark matter is 22.7% of the total mass of the Universe, which is far larger than the 4.5% of mass represented by ordinary matter, such as interstellar gas. But 72.8% of the mass of the Universe is bound up in the mass-equivalence of dark energy.


Not only is the Universe expanding, its rate of expansion is increasing with time. Dark energy is the name given to the mysterious "something" that is fuelling this universal inflation. Such energy would also add to the observed flatness of the Universe.

Dark energy is the successor to such past scientific gap-fillers as caloric, phlogiston, aether and Einstein's "biggest blunder" — the cosmological constant (it's really more of a reinterpretation than a successor; dark energy appears in the Einstein Field EquationsWikipedia's W.svg as a cosmological constant, using the same symbol Einstein did). Whether it stays as it is, becomes modified into a more concrete form, or is replaced by an even stranger space filler remains to be seen.

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