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 Incoming links: Cosmic microwave background temperature

Past exam of the short options paper shared by Prelims and Parts A and B of the physics course of the University of Oxford / 2012 / S2 / 3 / 3 / Solution 2026-10-25

Adiabatic expansion preserves the blackbody form while each photon's energy redshifts as

a^{- 1}

. Thus the cosmic microwave background temperature obeys

T (z) = T_{0} (1 + z)

T (z = 3) = 4 T_{0} ≃ 10.9 K .

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The COBE Far Infrared Absolute Spectrophotometer by NASA LAMBDA Created 2026-10-24 Updated 2026-11-05

Instrument overview of FIRAS, describing its differential Michelson interferometer, internal reference and external calibrated blackbody. It reports the absolute cosmic microwave background temperature inferred from the spectral comparison.

lambda.gsfc.nasa.gov/product/cobe/about_firas.html

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