The Isotropic CMB: Present Data

• peeling away foregrounds from signal
• frequency spectrum (Mather+ 1994, Fixsen+ 1996, Fixsen 2009)
• CMB in context of cosmic photon backgrounds (Hill+ 2018)
• temperature
• polarization

Decoding the CMB Epoch: a Scattering Problem

• the present transparency of the U to the CMB
• the CMB as a scattering problem
• lightning review of scattering
  • cross sections
  • scattering rates
• photon scattering by cosmic matter
• surface of last scattering

The Atomic Age

• microphysics: recombination of hydrogen (mostly)
  • ionized (plasma) to neutral (gas)
  • opaque to transparent