Popcorn is more than just a delicious snack—it’s a marvel of physics.
When you toss a handful of kernels into a hot pan or microwave bag, you witness a tiny explosion, a burst of transformation that turns hard golden grains into fluffy white morsels.
But have you ever stopped to wonder why popcorn pops?
Or why it makes that signature pop sound?
Thanks to groundbreaking research by French physicists Emmanuel Virot and Alexandre Ponomarenko from the École Polytechnique, we now have a clearer understanding of the physics behind popcorn’s transformation.
Their study, published in the Journal of the Royal Society Interface, dives deep into the mechanics of how and why popcorn pops—and reveals some surprising insights along the way.
The Only Funny Corn?
As far as cooking goes, popcorn is arguably the only funny corn. Imagine tossing an ear of sweet corn on the grill—nothing exciting happens.
Glass gem corn is stunning to look at, but boiling it just feels like a crime against beauty. But popcorn?
It jumps, it pops, it performs tiny acrobatics right in front of your eyes. And the secret lies in its unique structure.
Unlike other varieties, Zea mays everta—the scientific name for popcorn—is the only type of corn capable of popping. Its secret?
A hull that is significantly more compact than other types of corn.
This airtight shell allows for immense pressure buildup, ultimately leading to that explosive transformation we know and love.
To put this to the test, Virot and Ponomarenko heated up some microwavable Zea mays everta on a hot plate while capturing the entire process with a high-speed camera running at an astonishing 2,900 frames per second.
What they discovered was both expected and unexpected.
At 170°C (338°F), only about 34% of the kernels popped. But once the temperature hit 180°C (356°F), the magic happened—96% of the kernels exploded into the airy, crunchy snack we crave.
“We found that the critical temperature is about 180 degrees Celsius, regardless of the size or shape of the grain,” Virot explained in an interview with AFP.
What Actually Happens Inside a Popping Kernel?
We all know that heat makes popcorn pop, but what’s really happening inside?
The study explains that when the temperature exceeds 100°C (212°F), the water content inside the kernel boils, creating superheated steam.
The hull traps the steam, and pressure continues to build.
Once the pressure reaches a critical threshold, the hull fractures explosively. But the real magic happens inside—
- The sudden expansion causes the starch granules within to undergo a rapid transformation.
- For a split second, the kernel’s insides turn into a gooey, molten starch mess, much like a caterpillar inside a chrysalis.
- But almost immediately, the starch solidifies into the spongy, irregular shape we recognize as popcorn.
This rapid shift from liquid to solid is why no two pieces of popcorn look the same.
Under a microscope, their surfaces are covered in tiny, hardened starch bubbles, frozen mid-expansion.
The Surprising Truth About the “Pop” Sound
If you thought the pop sound came from the hull cracking, think again.
Virot and Ponomarenko discovered that the sound actually happens after the explosion.
Using a microphone synced with their high-speed footage, the researchers found that the pop is caused by the sudden release of water vapor from inside the kernel.
Much like the sound of a champagne cork popping or a volcano erupting, the noise comes from resonating empty cavities inside the popped kernel as the steam escapes and the pressure rapidly equalizes.
This means that the pop of popcorn is not just an explosion—it’s also a miniature sonic event caused by pressure waves and trapped gas escaping in rapid succession.
A Gymnast in Disguise?
Now for one of the strangest findings: Popcorn jumps when it pops. But why?
The study found that as the starch bursts from the hull, a “starch leg” is momentarily formed.
This acts like a miniature springboard, launching the kernel into the air.
The researchers compare this to the way a gymnast pushes off the ground to execute a flip.
In scientific terms, popcorn occupies a midway point between explosive plants and jumping animals—it uses a combination of fracture mechanics (like seed pods bursting open) and biomechanical movement (like frogs or crickets jumping).
Can You Prevent Unpopped Kernels?
The one thing that ruins a good bowl of popcorn? Unpopped kernels.
But is there a way to avoid them?
Unfortunately, the answer isn’t what we want to hear.
Virot explained that unpopped kernels are often defective—they have tiny flaws in their hulls that prevent pressure from building properly.
Additionally, if a kernel sits in the pan too long, the hull can develop a tiny hole, allowing steam to escape before the internal pressure reaches the critical level needed for popping.
So if you’re left with a handful of unpopped kernels, don’t blame the heat—blame the corn itself.
Or better yet, try switching to a high-quality brand with a higher percentage of well-sealed kernels.
The Science (and Magic) of Popcorn
Popcorn is more than just a snack—it’s a perfect storm of physics, chemistry, and biology wrapped up in a tiny golden package.
From the precise temperature needed for optimal popping to the surprising cause of the iconic pop sound, it turns out that every kernel of popcorn is a mini-experiment waiting to unfold.
And the next time you make a bowl of popcorn, take a moment to appreciate the science behind it.
Because in every jump, in every explosion, in every pop—there’s an entire world of physics at play.
Sources: LiveScience, Journal of the Royal Society Interface
