A circumscribed Universe
Article Abstract:
There is some evidence which suggests that the Universe is infinite. However, researchers have realised that if the Universe's curvature is negative then it can be finite. It may be possible to measure its shape and size. Knowing whether it is finite affects theories about its origin and also determines whether it will eventually collapse. If the density of the Universe is less than Einstein's equation which defines the critical density of the universe then it is finite and will continue to expand. It will collapse if it has larger than the value of Einstein's equation.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1998
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Well of darkness
Article Abstract:
Galaxy clusters were thought the contain large amounts of dark matter sharply concentrated near the center of their potential well. However Tyson and colleagues have inferred a smoother and less central concentrated distribution of the dark matter in one cluster, using a new method to interpret the effects of gravitational lensing. The inference of a core structure for 0024+16 differs from the universal prediction and also differs in the direction opposite to that observed by the new simulations.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1998
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Missing energy and cosmic expansion
Article Abstract:
Inflationary cosmology proposes a flat universe and supports the missing energy explanation for the lower value of the sum of the ordinary matter and the dark matter than the critical density required for a cosmologically flat universe. Missing energy is the energy density of vacuum state. The missing energy varies as the universe expands and the ordinary or dark matter energy density decreases inversely with volume for cosmological constant, alpha = 1.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1996
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