Popcorn's 'pop' is caused by escaping steam, not the shell cracking.

In 2015, French researchers Emmanuel Virot and Alexandre Ponomarenko from the École Polytechnique used high-speed cameras and sensitive microphones to study the physics of popcorn. Their study, published in the Journal of the Royal Society Interface, revealed that the popping sound is an aeroacoustic phenomenon. When a kernel reaches approximately 180 degrees Celsius (355 degrees Fahrenheit), the internal pressure climbs to about 135 pounds per square inch.The researchers discovered that the initial fracture of the hull occurs silently. The actual 'pop' happens roughly 6 to 10 milliseconds later when the pressurized water vapor is suddenly released. This rapid decompression acts like a miniature explosion, causing the air inside the cavities of the expanding starch to vibrate. This creates the distinct acoustic signature we recognize as a pop.This mechanism is remarkably similar to the physics of a volcanic eruption or the opening of a champagne bottle. The starch inside the kernel expands to nearly 40 to 50 times its original size in just a fraction of a second. This transformation from a hard seed to a white, fluffy foam is driven by the starch's transition into a gelatinous state before it rapidly solidifies upon cooling. Understanding these dynamics helps food scientists optimize kernel quality and popping efficiency.