Cosmic microwave background

Cosmology

Aliases: CMB, microwave background
Domain: Cosmology

Definition

The light released at recombination, arriving now stretched a thousandfold into microwaves at 2.725 K from every direction. The oldest light there is.

Open on the Glossary shelf — the interactive card, the filters, and everything alongside it.

From the Glossary database in Notion, last edited 2026-08-17. This page is the row, rendered by the build; nothing on it is written by hand.