Mike recently posted a fascinating article about the science why a beer foams over so dramatically when a bottle is struck on the top. This party foul more commonly known as “icing” a beer is a complicated and interesting bit of science that Mike reported on being solved by Spanish scientists.
Yet Mike isn’t the only one here with an enthusiasm for physics. What happens to that beer bottle when the liquid inside the bottle isn’t carbonated? The answer is quite surprising and dramatic.
The Slow Mo Guys show exactly what happens at 2500 frames per second. The bottom of that bottle is blown right off the rest of the bottle in a hail of glass and liquid. While this is an impractical if not astounding trick to show off to friends and family the what of this phenomena isn’t as compelling as the why? Why is it that if I strike the top of a beer bottle filled with beer it erupts like mentos shoved into cola but if the beer bottle is filled with water the bottle destroys itself so dramatically?
The answer is that nature abhors a vacuum. Abhors it so strongly that it willing to shatter glass to eradicate it. The layman’s interpretation of events is that when the bottle is struck the glass moves downward as a result of the force of the impact. The liquid inside the glass is constrained by the bottle but not anchored to the bottle. Thus it moves independently of the bottle at the few moments after impact. As the bottle moves but the liquid doesn’t a vacuum is formed at the bottle of the bottle. The liquid then begins to move as a result of the impact and implodes the vacuum. The force of the liquid rushing to the bottom of the bottle is intense and if powerful enough will shatter the bottom of the bottle expelling glass and liquid both.
This effect is mitigated by carbonation which instead excites the liquid creating the effect of a geyser of beer rather than breakage. So if you are going to attempt this feat on your own at home (which we do not encourage without proper safety gear) make sure you have filled the bottle with a non-carbonated liquid like tap water, that you leave an adequate amount of space at the top of the bottle so the liquid can shift when the bottle is struck, and that you don’t do it at a place where the liquid and glass shards can be problematic.
But isn’t science fun?