Cosmic Microwave Background

Discovered by: Arno Allan Penzias and Robert Woodrow Wilson, awarded the 1978 Nobel Prize in Physics.

What is it? Electromagnetic radiation as a remnant from an early stage of the universe.

Why is it important? CMB is landmark evidence of the Big Bang origin of the universe. [Image - Quantum Doughnut, Public Domain, https://commons.wikimedia.org/w/index.php?curid=12958270]