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The Cosmological Constant
Cosmic Microwave Background

Basic Idea: scale on the sky given by horizon/sound speed at recombination. Angular scale it subtends today tells us about spatial curvature.

Recap of relation: fixed ruler -> spatial curvature

System of interest: temperature anisotropies of CMB photons from the big bang provide a ruler

  • What they are:
    • State of the universe at 300,000 years old
    • Cosmic microwave background: best black body spectrum in nature
    • Anisotropies:
      relevant scales and players
      acoustic waves, why calculation under good control
  • Position of the first peak


  • Recent results: Boomerang and MAXIMA
  • Future measurements
    expected sensitivity and parameter dependence

Note also weak test of lambda directly

Other cosmological tests CMB is used for

Other suggested test of angular size

Some References

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Comments or Questions? Contact jcohn@astron.berkeley.edu