dark matter

noun

a hypothetical form of matter invisible to electromagnetic radiation, postulated to account for gravitational forces observed in the universe.

dark matter

noun

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

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

dark matter

Unseen matter that may make up more than ninety percent of the universe. As the name implies, dark matter does not interact with light or other electromagnetic radiation, so it cannot be seen directly, but it can be detected by measuring its gravitational effects. It is believed that dark matter was instrumental in forming galaxies early in the Big Bang.

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Word History and Origins

Origin of dark matter¹

First recorded in 1985–90

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A Closer Look

�� is the universe made of? We know that galaxies consist of planets, stars, and huge gas and dust clouds—all 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 mass—in 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.

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Example Sentences

Examples have not been reviewed.

They realized that the way galaxies were moving was being influenced by something invisible called dark matter that makes up roughly a quarter of the universe.

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Although this is still a plausible hypothesis, these particles likely would not constitute the majority of dark matter in the universe.

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Some of this stuff is known as mysterious dark matter, others are things like dark comets, which as their name suggests, are far more difficult to see from Earth than something like Tsuchinshan-Atlas.

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“The obvious places to look for new physics are the places we don’t fully understand, like dark matter and dark energy,” said Dr. Andreea Font, a computational astrophysicist at Liverpool John Moores University in England.

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These primordial black holes have been theorized for decades and could even be ever-elusive dark matter, the invisible matter that accounts for 85% of the universe's total mass.

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When To Use

�� does dark matter mean?

Dark matter is speculated to be a type of matter that cannot be directly observed. It has an unknown nature, a high mass, and astronomers hypothesize that it makes up much of the universe.How is dark matter pronounced?[ dahrk mat-er ]

darkly dark meat

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