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WandaVision: What Is Cosmic Microwave Background Radiation?

Contains spoilers for WandaVision episode 4

Episode 4 of WandaVision has arrived, and with it, Kat Dennings' return to the MCU fold. Her character, Darcy Lewis, was last seen in Thor: The Dark World, and has apparently really come into herself since her "the hammer's called Meow-Meow" days.

Darcy's big day starts with a tense car ride, and peaks with her hopping around S.W.O.R.D.'s chain of command, gaining enough sway that the organization will bring her a decades-old television but not a cup of coffee. The reason: She's spotted a broadcast signal caught in a fuzz of CMBR, or "cosmic microwave background radiation." But what is cosmic microwave background radiation? And more importantly, what other sitcoms does it hide?

Like a lot of science fiction technobabble, CMBR has roots in science fact regardless of its hand-wavy television deployment. As explained by University of Chicago's Erik M. Leitch in Scientific American, it really is what the show describes, broadly speaking. As he explains, it's "the residual heat of creation — the afterglow of the big bang — streaming through space these last 14 billion years like the heat from a sun-warmed rock, reradiated at night."

But let's not get caught up in a hodgepodge of pointless reality. What's really exciting is the importance of cosmic radiation in the Marvel universe, and what it could signify for the MCU going forward.

Marvel's cosmic radiation does some fantastic stuff

For one thing, we know that in the MCU, the Big Bang led directly to the formation of the Infinity Stones, one of which — the Mind Stone — is canonically responsible for Vision's brain and Wanda's bevy of superpowers. We've seen the Stones give off "a power surge of ridiculously cosmic proportions" already in Endgame, accompanying both "the Snap" and that time when Thanos destroyed the Stones. It could be that the Infinity Stones' direct relationship to the creation of the universe means that they emit the same energy as the Big Bang. If that's the case, then Wanda's powers, which also derive from the Stones, should do the same.

In the context of the larger Marvel universe, "cosmic radiation" has a storied history. Most notably, it's what Reed Richards, Sue and Johnny Storm, and Ben Grimm mosied through on a stolen rocket, resulting in their transformation into the Fantastic Four.

In more glass-is-half-empty news, Marvel's First Family aren't the only ones with cosmic energy hanging around their necks. The Fantastic Four frequently butts giant heads with Galactus, Marvel's big ol' bucket-headed homage to the song "Food, Glorious Food" and another result of the Big Bang. Galactus is famously enthusiastic about doling out "the Power Cosmic," a nigh-unbeatable primordial force of creation and destruction with more uses than a Bat Belt. We already know that the MCU is actively moving toward the Fantastic Four, and it could be that the radiation from the Infinity Stones — or Wanda herself — will play a part in their creation.

As always, WandaVision leaves us with more questions than answers, but calling audiences' attention to cosmic radiation seems like a sure sign of bigger things to come.