Shedding light on dark matter
Article Abstract:
Metcalf and Silk have proposed that observations of the gravitational effects of matter on the light from distant supernovae will help in distinguishing between microscopic and macroscopic forms of matter. They have included recent developments in the characterization of type Ia supernovae, together with analysis of the gravitational effect of different distributions of matter. The proposal for a fundamental test of the dark matter could be a significant step forward in understanding the composition of the Universe.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1999
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Universal peekaboo
Article Abstract:
A combination of findings from several observations strengthens the case for a positive cosmological constant. The likely impact of a positive cosmological constant on the Universe would be eternal, accelerating expansion. Measurements of very small ripples in the radiation remaining from the hot Big Bang are starting to indicate a Universe which is geometrically flat. Pushing the observations of supernovae to greater distances should make it possible to establish definitively whether the Universe is accelerating.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1999
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Less expansion, more agreement
Article Abstract:
Astronomers are beginning to achieve a better level of accuracy in their knowledge of the value of the current rate of expansion of the Universe, H0. The determination of H0 needs independent measurements of the recession velocities and distances of extragalactic sources, and uncertainty arises because of the inaccurate set of extrapolations required by distance measurements. It now seems that work by Allan Sandage and Gustav Tammann, indicating H0 of 66, may be quite reliable.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1999
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