dark matter (redirected from Accelerated expansion)

dark matter

n.

Matter that emits little or no detectable radiation of its own, postulated to account for gravitational forces observed on astronomical objects and to be part of the missing mass.

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dark matter

n

(Astronomy) Astronomy matter known to make up perhaps 90% of the mass of the universe, but not detectable by its absorption or emission of electromagnetic radiation

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dark matter

Matter that emits little or no detectable radiation. Gravitational forces observed on many astronomical objects suggest the significant presence of such matter in the universe, accounting for approximately 23 percent of the total mass and energy of the universe. Its exact nature is not well understood, but it may be largely composed of varieties of subatomic particles that have not yet been discovered, as well as the mass of black holes and of stars too dim to observe. Also called missing mass.

A Closer Look What is the universe made of? We know that galaxies consist of planets, stars, and huge gas and dust cloudsall of these objects are observable by the radiation they give off, such as radio, infrared, optical, ultraviolet, x-ray, or gamma-ray radiation, and all can be observed using various kinds of telescopes. But there are reasons to suspect the existence of far more matter than this, matter that is not directly observable. Evidence for such dark matter comes from observations of certain gravitational effects. For example, astronomers have found that galaxies rotate much faster than they would be expected to rotate based solely on their observable massin fact, they should be flying apart. One explanation for this apparent anomaly is to assume that the galaxies have much more mass than we can see, and this invisible mass holds them together gravitationally. Various theories of the composition of this invisible dark matter have been proposed, from exotic yet-to-be discovered particles to planet-sized objects made of ordinary matter that are too small or far away to be detected by present-day instruments. But none of these theories are entirely satisfactory, and the fundamental question of what makes up most of the universe remains unanswered.

Thesaurus

Noun

1.

dark matter - (cosmology) a hypothetical form of matter that is believed to make up 90 percent of the universe; it is invisible (does not absorb or emit light) and does not collide with atomic particles but exerts gravitational force matter - that which has mass and occupies space; "physicists study both the nature of matter and the forces which govern it" cosmogeny, cosmogony, cosmology - the branch of astrophysics that studies the origin and evolution and structure of the universe weakly interacting massive particle, WIMP - a hypothetical subatomic particle of large mass that interacts weakly with ordinary matter through gravitation; postulated as a constituent of the dark matter of the universe

Translations

dark matter

n (Astron) → dunkle Materie, Dunkelmaterie f