Four Times Breakfast Cereal Invaded the World of Physics

Jun 14, 2023

While physics is often used to answer questions like "how big is the universe?" and "how can we blow those dudes up?," it sometimes sets its sights a little lower. A little earlier. A little tastier.

Yep, it seems physicists enjoy the most important meal of the day as much as the rest of us, and a surprising amount of brainpower by the cleverest thinkers alive is dedicated to figuring out the complexities of Tony the Tiger's favorite food. And some of the phenomena displayed by Froot Loops might have applications in the rest of the world.

Grrrrrrrreat!

Derivatives of position are a complex series of metrics within physics to allow for as accurate a description of movement as possible — if describing an object's journey from A to B, doing so in a way that is replicable and analyzable far beyond "it was there and now it's here and took about five seconds." The first three are velocity, acceleration and jerk (i.e., how smooth or not the moments are). It's the fourth, fifth and sixth that start to get breakfasty — they’re called snap, crackle and pop. These measurements — strictly speaking, "derivatives of the position vector with respect to time" — owe their names to someone simply trying to make themselves laugh. "Snap" made total sense as a name, and two more derivatives also needed naming, and that trio of onomatopoeic gnomes have been shilling cereal since 1933. They’re part of humanity's collective psyche at this point. We fucking love breakfast.

You know how, in a bowl with only a few Cheerios left, they tend to group together? Physicists have noticed this, naming it the "Cheerios effect," and investigated its potential ramifications within the field of fluid dynamics. A 2019 paper that came out of Brown University described it thusly: "The Cheerios effect arises from the interaction of gravity and surface tension — the tendency of molecules on the surface of a liquid to stick together, forming a thin film across the surface. Small objects like Cheerios aren't heavy enough to break the surface tension of milk, so they float. Their weight, however, does create a small dent in the surface film. When one Cheerio dent gets close enough to another, they fall into each other, merging their dents and eventually forming clusters on the milk's surface."

Meanwhile, scientists from Queen Mary University in London have inverted the effect to avoid clustering and make objects in water spread out. It's all thought to have handy applications in things like meniscus dynamics and liquid nanotechnology.

We’ve all been there — you pull the inner bag out of a new box of cereal to open it, and all the raisins (if you’re healthy) or marshmallows (if you’re not) are up at the top, like the head on a glass of beer but more infuriating. You don't want to eat a bowl of 90 percent raisins then have bland-ass bran for the next two weeks. They’re mixed in the factory, surely, so why is it all separate?

A 2021 paper in Scientific Reports entitled "Size Segregation of Irregular Granular Materials Captured by Time-Resolved 3D Imaging" applied computer-aided X-ray tomography to bags of mixed nuts to solve the problem of why the Brazil nuts always end up at the top — aka the same phenomenon as raisins and marshmallows — and found that the nuts/raisins etc. only move to the top when they’re oriented upright. The uses of this knowledge are far from limited to breakfast and snacking, though, as the lead author told journalists: "This will allow us to better design industrial equipment to minimize size segregation thus leading to more uniform mixtures. This is critical to many industries, for instance ensuring an even distribution of active ingredients in medicinal tablets, but also in food processing, mining and construction."

In other words, your life might one day be saved by medication honed by science gleaned from a big bowl o’ Lucky Charms.

If there's one thing physicists love even more than breakfast, it's squishing stuff to see what happens. One team from San Diego and Sydney put Rice Krispies into compression chambers to record how boxes of cereal were treated by immense pressure. They saw vastly more complexity in how the cereal was deformed (a science word, not an offensive one) than anyone was expecting — three different types of velocity-dependent deformation and a propagating compaction band recorded visually for the first time in granular matter. It could have life-saving uses in non-breakfast contexts: Studies of "crunchy matter" are still in their relative infancy, but given the relative similarity between cereal and, say, the snow in an avalanche (brittle, porous and in huge fuckin’ numbers), this could lead to improved understanding of post-avalanche snowbank stability.

They also tested Cocoa Puffs and Cocoa Krispies in the compressor, to see what difference chocolate made. It takes more pressure to crush some cereal if it has a chocolate coating. That particular bit of knowledge probably won't save any lives, but it sounds like a fun day in the lab.

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