In Brief
  • Cosmic Microwave Background Radiation (CMB) allows us to study the earliest days of the Universe.
  • Apparently, our Universe used to be orange.

We are certain about three things in the Universe (this is where you brace yourself for epic kernels of wisdom): it is very old, extremely large, and pitch black (save for a few stars here and there). Naturally, it wasn’t always so old or large, but did you know that the Universe didn’t use to be black either?

Cosmic Microwave Background Radiation
The Cosmic Microwave Background Radiation (CMB) is a remnant of the early universe. Image Credit: NASA

Back when the Universe was young, when the lingering affects of the big bang remained very prominent, it was unrecognizable from its present form. Not only were stars and planets absent, but the forging of atoms—which comprise stars, planets, and all matter—hadn’t even begun.

Things eventually simmered down, and the Universe finally became conducive for a plethora of things, including the feature known as Cosmic Microwave Background Radiation (CMB). To this day, it still remains (albeit less spectacularly)—allowing us to look back to the earliest moments after the big bang.

Ultimately, CMB dominated the early Universe, and, because of its properties (like its temperature and the wavelengths of light it absorbed), the Universe appeared orange for a few million years.

The video below explains both how and why, and provides an explanation for the current color (or lack thereof) of CMB. It’s also a great lesson on the electromagnetic spectrum and cosmological redshift.

WATCH: “Space Used to Be Orange!!”