Cosmic microwave background (CMB)

Definition

The Cosmic Microwave Background (CMB) is the thermal radiation left over from the Big Bang, now observed as a faint glow in all directions in the universe. It provides key evidence for the conditions of the early universe and is crucial for understanding cosmology.

5 Must Know Facts For Your Next Test

1. The CMB was discovered in 1965 by Arno Penzias and Robert Wilson.
2. It has a nearly uniform temperature of about 2.725 Kelvin.
3. The CMB is most visible in the microwave portion of the electromagnetic spectrum.
4. Tiny fluctuations in the CMB provide evidence for the density variations that led to galaxy formation.
5. Observations of the CMB support an expanding universe model.

Review Questions

• Who discovered the Cosmic Microwave Background?
• What is the approximate temperature of the CMB?
• Why are tiny fluctuations in the CMB important for understanding galaxy formation?

Related terms

Big Bang: The theory that explains the origin of the universe as an expansion from a hot, dense state approximately 13.8 billion years ago.

Redshift: The phenomenon where light or other electromagnetic radiation from an object increases in wavelength as it moves away from an observer, indicating an expanding universe.

Recombination Era: The period in cosmological history when electrons combined with protons to form neutral hydrogen atoms, allowing photons to travel freely and leading to the creation of the CMB.