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Science Uncovers the Explosive Force Behind Beer Tapping

By Wesley Fenlon

Beer goes nuclear.

Even if you really, really like beer, you've probably never compared drinking a brew to the dramatic impact of a nuclear bomb. That would just be...excessive, right? Pure exaggeration. Or not.

While the act of drinking a beer doesn't have much to do with a nuclear explosion, the act of tapping a beer bottle on its top, hard and fast, does. If you've ever been the victim of a beer-tapping prank, you know the beer will basically explode out of the bottle, turning most of its contents into foam and fizzling away. Physicists say the effect is not so different from a nuclear explosion. Minus the nuclear part.

Photo credit: NPR

NPR writes that physicist Javier Rodriguez Rodriguez and his team at Carlos III University in Madrid "have figured out that a stiff hit on the bottle's top sets off miniature explosions inside the beer. These tiny blasts create mushroom clouds similar to those generated in the air by an atomic bomb."

Rodriguez said that " the laws of physics that control the development of these beer mushroom clouds are the same as [those that drive] the development of the cloud in an atomic bomb."

Rodriguez and his team filmed beers with high speed cameras to crack the case of the beer tap. Eventually, they broke down the chain reaction that was happening.

A tap to the top of a beer bottle sends a wave traveling through the beer. The glass bottle can also compress, compounding those waves. Very small bubbles in the beer pulsate as they're hammered by the waves. Eventually, they can't take the impact, so the little pockets of gas collapse into clouds of smaller bubble fragments.

Then things get exciting. Rodriguez says "The carbon dioxide has an easier time to get into the bubbles because of the increase in surface area. So they grow very, very fast." As the bubbles grow, they become lighter, so they float to the surface of the beer. "The faster the bubbles rise, the faster they grow, because the mixing with carbon dioxide is more efficient," Rodriguez says. And so the bubbles feed on their own energy, becoming an unstoppable foamsplosion. Once tapped, there's no way to stop the reaction.