key term - Cosmic microwave background

Definition

The cosmic microwave background (CMB) is the thermal radiation left over from the Big Bang, filling the universe almost uniformly. It provides a snapshot of the infant universe approximately 380,000 years after its birth.

5 Must Know Facts For Your Next Test

1. The CMB was discovered in 1965 by Arno Penzias and Robert Wilson.
2. The temperature of the CMB is approximately 2.725 K.
3. The CMB shows tiny fluctuations which correspond to density variations in the early universe.
4. It provides strong evidence for the Big Bang theory.
5. The anisotropies in the CMB have been used to determine key cosmological parameters, such as the Hubble constant and dark matter density.

Review Questions

Related terms

Big Bang Theory:

The prevailing cosmological model describing the origin and evolution of the universe from a singularity approximately 13.8 billion years ago.

Anisotropy: Variations in physical properties or quantities when measured along different directions; in cosmology, it refers to small variations in temperature observed in the cosmic microwave background.

Hubble Constant:

A measure of the rate at which the universe is expanding, typically expressed in kilometers per second per megaparsec (km/s/Mpc).