Is the Universe Open, Closed, or Flat? Reading: Chapter 26, Cosmology

How do we go about determining the ultimate fate of the Universe?

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Tests for the Appropriate Solution and Estimates for the Best model

• Test: Topology of the Universe from the Mass and Expansion Rate of the Universe ===> Not enough mass to close the Universe, Omega(mass) < 0.3.
• Test: Topology of the Universe from Large z Observations ===> Universe is critical, has Omega(everything) = 1 and Dark Energy is dominant.
• Universe from a Snapshot of the Cosmic Microwave Background Radation, CMBR ===> Best model for the Universe.

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Global measurements of Omega (from WMAP supported by Type Ia SNe)

===> The Universe is flat

and 72 % of the Universe is Dark Energy; dark matter part of Omega ~ 23 %, and the normal matter part of Omega ~ 4.6 %. A nagging issue connected with Dark Energy is something known as the Cosmological Constant Problem.

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