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A lightweight universe?

Authors
  • Bahcall, N A
  • Fan, X
Type
Published Article
Journal
Proceedings of the National Academy of Sciences of the United States of America
Publication Date
May 26, 1998
Volume
95
Issue
11
Pages
5956–5959
Identifiers
PMID: 9600898
Source
Medline
License
Unknown

Abstract

How much matter is there in the universe? Does the universe have the critical density needed to stop its expansion, or is the universe underweight and destined to expand forever? We show that several independent measures, especially those utilizing the largest bound systems known-clusters of galaxies-all indicate that the mass-density of the universe is insufficient to halt the expansion. A promising new method, the evolution of the number density of clusters with time, provides the most powerful indication so far that the universe has a subcritical density. We show that different techniques reveal a consistent picture of a lightweight universe with only approximately 20-30% of the critical density. Thus, the universe may expand forever.

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