Cosmic microwave background

The cosmic microwave background (CMB) is a form of electromagnetic radiation dating from an early stage of the universe. It is the oldest known radiation in the universe. With a traditional optical telescope, the space between stars and galaxies is completely dark but a sufficiently sensitive radio telescope reveals the CMB as a faint glow not associated with any star, galaxy, or other object.

  • The glow of the cosmic microwave background is strongest in the microwave region of the electromagnetic spectrum.
  • The CMB is an emission of uniform thermal energy coming from all parts of the sky.
  • The CMB is considered to be part of available evidence for the Big Bang theory.