Why does a beer overlow when someone hits the top of a beer with the bottom of theirs?

Question

Why does a beer overlow when someone hits the top of a beer with the bottom of theirs?

In: Other

Answer 1

Because it causes the bottle to almost intantly move down, but the beer tends to stay where it was. This causes a considerable decompression between the beer and the bottom of the bottle, favoring the formation (and expansion) of bubbles, which will rise and form the foam that you see.

Basically umit’s the sped up version of shaking the bottle

P.s. sorry for my english