You get brainwashed whenever you go to sleep (and that’s a good thing)

What’s the weirdest thing you learned this week? Well, whatever it is, we promise you’ll have an even weirder answer if you listen to PopSci’s hit podcast. The Weirdest Thing I Learned This Week hits Apple, Anchor, and everywhere else you listen to podcasts every-other Wednesday morning. It’s your new favorite source for the strangest science-adjacent facts, figures, and Wikipedia spirals the editors of Popular Science can muster. If you like the stories in this post, we guarantee you’ll love the show.

FACT: Your brain gets an actual scrub-down when you go to sleep

By Sara Kiley Watson

We’ve all heard of brainwashing, but usually in regard to someone joining a cult or falling prey to a conspiracy theory. As it turns out, our brains frequently indulge in a much more literal form of sudsing.

Our brains are constantly floating in vats of cerebrospinal fluid (CSF), which serves to cushion these monumentally important organs as we go about our daily lives. Scientists have hypothesized for some time now that CSF also has a role in clearing out toxins.

In 2019 a team of researchers at Boston University figured out a way to image CSF inside the skull, then watched the brains and CSF of 13 healthy, young people while they slept. They found something truly bananas: When we sleep, our CSF pulses around in gigantic waves every 20 seconds or so, giving the brain a nice, nightly scrub down, scooping up toxins and disposing of them while we catch some shut-eye. It’s sort of like the brain is a loofah full of sudsy soap sitting in the middle of a tub and the waves are hands reaching out to squish it clean.

These waves may be powered by our blood flow. Neural oscillations, or brainwaves, change when we sleep, and they tend to move nice and slow during some phases. This means for a few hundred milliseconds on that brainwave loop, neurons go quiet and don’t necessarily need as much blood. When those brain cells hush down, the squishing of the loofah happens—and proteins like beta-amyloid are scooped up and flushed down the drain like the last suds of your of a bubble bath.

FACT: One of the world’s most beloved meteorites has a tragic and disturbing origin story

By Sara Chodosh

My second favorite room in New York City’s American Museum of Natural History is the Hall of Meteorites, but I’ve always found its centerpiece odd. A behemoth of a meteorite sits on a raised platform, unprotected by railings or glass—the sign even tells you that it’s okay to touch it.

It’s part of what’s known as the Cape York meteorite, and this chunk is called Ahnighito, which both is and isn’t a tribute to the Inuit people who originally used this hunk of iron to forge metal tools.

Like so many of the items in museums, it was “discovered” in the 19th century in the sense that this is when white academics first came across it. Ahnighito was being mined for iron for many centuries before that.

You’d think that this rich human history would make Ahnighito a precious item. At least precious enough not to want people touching it. It wasn’t until I read this fascinating Twitter thread from art crime professor (possibly the coolest title in the world) Erin Thompson that I understood why. The reasoning isn’t comforting, but it is fascinating. And it turns out, the story of Ahnighito is also the story of a young boy named Minik Wallace, who is possibly the most tragic historical figure I’ve ever read about. This week’s weird fact is pretty depressing—apologies for that—but it’s also incredibly important. Listen to Weirdest Thing to learn more.

FACT: Cuttlefish might have more self-control than you do

By Rachel Feltman

If you weren’t already aware, cephalopods—the class that includes octopus, cuttlefish, nautiluses, and squids—tend to be very smart. They have the largest brain to body mass ratio of known invertebrates, and have incredibly complex nervous systems. Some of them can even use tools:

Recently, scientists at the University of Cambridge marked a new milestone in the journey to understanding cephalopod intelligence: they showed that cuttlefish can pass the marshmallow test.

First conducted at Stanford in 1972, the marshmallow test is a famous experiment on self-control and the ability to delay gratification by planning ahead. The classic study features children being given the choice between a small, immediate treat (like one marshmallow) or a larger treat after a waiting period (two marshmallows). Scientists would leave the kids alone with the single marshmallow for 15 minutes, promising to double the prize as soon as they returned, and the question was whether the wee subjects would get impatient and scarf down the initial treat.

This evidence of the ability to strategically delay gratification is certainly a feather in the cap of cuttlefish everywhere, but what does the original experiment actually tell us about human behavior? It’s probably more complicated than you think. Listen to this week’s episode to get the inside scoop.

(And as promised, listeners: Here’s a video of a cuttlefish going incognito.)

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