The cosmic microwave background (CMB) is the radiation leftover from the Big Bang, the moment of the universe's creation. This faint glow of light, which permeates all of space, provides crucial insights into the early history and evolution of the universe.

The podcast episodes "Ep. 2: Why We Can Exist" and "How climate change is affecting global timekeeping" both discuss the CMB and its importance in understanding the universe. The first episode explains how the fundamental forces of nature behaved differently in the hot, dense early universe, and how the CMB radiation contains remnants of this time. The second episode mentions plans for the Simons Observatory, which will map the CMB in unprecedented detail to further our understanding of the universe's origins and evolution.