Question

The current peak wavelength of the CMB corresponds to a blackbody of temperature 2.74 K. What was the peak wavelength of the CMB when it was emitted? The current redshift of the CMB is z = 1100. Give your answer in microns

Answer 1

CMB frequency

The universe is filled with blackbody radiation whose temperature now is T0=2 725 0 002 K, so the frequency of the peak brightness is max 160 GHz. This cosmic microwave background (CMB) is a relict of the "big bang" creation of the universe and reveals precise values for a host of cosmological parameters.