Astrophysics

Endless Expansion?

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Science  18 Aug 2000:
Vol. 289, Issue 5482, pp. 1109
DOI: 10.1126/science.289.5482.1109b

A few years ago, astronomers determined that distant supernovae were receding from the center of the universe much faster than before. The cause of this accelerating expansion of the universe remains unclear. An antigravitational repulsive force caused by an increasing density of vacuum energy has been fingered as a likely culprit; as the distance between objects grows, the density of matter decreases, allowing the increasing density of vacuum energy to dominate and eventually to produce cosmic loneliness.

Barrow et al. start their calculations with a homogeneous and isotropic universe with no curvature and then consider the changes in expansion rate over time when two forms of matter, a perfect fluid and a quintessence field, are allowed to evolve. They find that it is possible for the density of vacuum energy to decrease over time and for the density of matter to increase, leading to a deceleration of the expansion. Thus, there may yet be opportunity to observe and to interact with our extragalactic neighbors during the next few billion years. — LR

Mon. Not. R. Astron. Soc. 316, L41 (2000).

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