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Dark Matter

Dateline: 12/20/99

By Alan Bruzel

If chemistry is the study of matter, then it is only natural for chemists to be curious about what kind of matter predominates in the universe. As it turns out, there is vastly more than, literally, meets the eye. In the opinion of astronomers, the universe contains ten to one hundred times more unobservable (dark) matter than it does visible matter. The amount must be inferred because dark matter neither emits nor reflects detectable energy when measured using conventional techniques.

The necessity for dark matter arose when it became apparent that the gravitational force keeping galactic clusters rotating around their common center required more mass than the combined masses of their visible stars. Dark matter has therefore been cast in the role of a halo surrounding these, and probably all, galaxies.

Many particles, familiar and unfamiliar, aspire for the role of dark matter. None has received the critics' unambiguous approval, and it may well be that several actors will collaboratively share the limelight. Thus far, there are many schools. Those in the camp of ordinary matter include dark galaxies and interstellar dust, as well as MACHOs (MAssive Compact Halo Objects) such as black holes, white dwarfs, brown dwarfs, and neutron stars. Another category comprises neutrinos possessing a measurable mass. WIMPS (Weakly Interacting Massive Particles) are also contenders, but require the discovery of new forms of matter heavier than a neutron.

What the Web Has to Say about:
Dark Matter

CyberSpace!
Origins of observations leading to postulation of dark matter.

Dark Matter
Potential dark matter candidates. From Joe Silk, Center for Particle Astrophysics, University of California at Berkeley.

Dark Matter
Cosmological consequences of dark matter. From the Center for Particle Astrophysics, University of California at Berkeley.

Dark Matter
Experiments measuring Weakly Interacting Massive Particles. From the Particle Astrophysics Group, University of Sheffield.

Dark Matter in the Universe
Scientific American article by Vera Rubin presents an in-depth assessment.

Dark Matter Mystery
Pros and cons of the leading dark matter contenders. From the Harvard-Smithsonian Center for Astrophysics.

Dark Matter Through the Web
On-going projects directed toward establishing credible dark matter candidates. See also, Theory vs. Experiment. From the Institut de Physique Nucléaire de Lyon.

UK Dark Matter Collaboration
Research originating from particle detectors placed in 1100 meter-deep UK salt mine.

What Is Dark Matter?
Article by Scott I. Chase in Usenet Relativity FAQ.

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