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dark matter

a hypothetical form of matter invisible to electromagnetic radiation, postulated to account for gravitational forces observed in the universe.
Origin of dark matter
1985-90 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for dark matter
  • Such visible evidence of gravity bending light in space may help scientists map otherwise invisible dark matter.
  • Now find out as the film shows the birth of a star from hydrogen, helium gas and dark matter.
  • dark matter cannot be photographed, but its distribution is shown in the blue overlay.
  • The spectrometer is designed to look for evidence of antimatter and dark matter.
  • Dark flow was named in a nod to dark energy and dark matter-two other unexplained astrophysical phenomena.
  • Once upon a time, dark matter was the strangest, hardest to fathom material in the universe.
  • Studying neutrinos means better understanding the sun, other stars, and maybe even the properties of mysterious dark matter.
  • She deduced from her observations that galaxies are pervaded by dark matter, invisible to our telescopes.
  • In fact, dark matter seems to act as a scaffold on which visible matter is arranged.
  • The bad news is that it doesn't say anything about gravity or dark matter or dark energy.
British Dictionary definitions for dark matter

dark matter

(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
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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dark matter in Science
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.

Our Living Language  : What 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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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dark matter in Culture

dark matter definition

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.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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