Air cannon

What can you do here
Beat the rubber surface of the cannon with your hand. Observe the behaviour of the objects in front of the cannon. To divert the shot in vertical direction, lift or lower the barrel, simultaneously pushing the black button.

How does it work
Beating rubber surface causes the air being pushed out of the barrel through the hole. On the edge of the hole there is friction, which makes the air layer closest to the edge rotate. As a consequence, an air ring – a whirlpool – is formed, of a shape similar to famous Cracow’s pretzel. The ring of whirlpools is a very stable structure and it moves in the air almost as a solid body. 

Interesting facts
Smoke rings can sometimes be formed by active volcanos. Similar rings, formed underwater, are often used by dolphins to communicate with one another.