I had never seen popcorn pop, so I decided to take the kernels outside of the bag and heat them over a stove. It’s a little creepy to watch them start expanding and then rupturing, but it quickly becomes amusing and subsequently delicious.
If you’re wondering how popcorn “works,” here’s the description according to about.com:
Popcorn kernels contain oil and water with starch, surrounded by a hard and strong outer coating. When popcorn is heated, the water inside the kernel tries to expand into steam, but it cannot escape through the seed coat (the popcorn hull). The hot oil and steam gelatinizes the starch inside the popcorn kernel, making it softer and more pliable. When the popcorn reaches a temperature of 180 °C (356 °F) the pressure inside the kernel is around 135 psi (930 kPa), which is sufficient pressure to rupture the popcorn hull, essentially turning the kernel inside-out. The pressure inside the kernel is released very quickly, expanding the proteins and starch inside the popcorn kernel into a foam, which cools and sets into the familiar popcorn puff.
Given my new, buttery fascination, I would push for a redesign of popcorn bags far and wide so that more people could enjoy the process. Then again, there’s probably a safety hazard attached to standing too close to the microwave for too long.