So, on the other day me and my colleges were discussing the following phenomena:
Pick two open bottles of beer. With the bottom of the first, hit the second on the bottleneck, in the following way: you align then vertically, and hit the first on the second from the top.
The typical event is that the second bottle starts to spit all the gas, almost completely emptying it.
Our hypotheses was that the way the bottle was hit, the eigenmodes of the bottle were excited. This eigenmodes caused a compression/extension on the beer itself, causing it to segregate from the liquid. However, we were not sure if this is the right explanation for it.
Can someone confirm this reasoning or have another suggestion to explain this phenomena?