The Mouse Trap Reactor is a visual representation of a chain reaction in a confined space. Useful as an analogy for an uncontrolled nuclear reaction.
This demonstration utilized 1000 mousetraps that were set-up for a chain reaction. It took 10 people 8 hours to set up the traps! As far as we know there has not been a similar reaction this big.
As in a nuclear-fission chain reaction, a neutron (the starter ping-pong ball) creates the first fission reaction. This event is simulated by the mousetrap releasing two additional ping-pong balls. These, in turn, potentially each release two more balls (neutrons) initiating a doubling of the available neutrons with each fission. As additional ping-pong balls are released, the rate of the reaction accelerates. This chain reaction is simulated by rapidly releasing ping pong balls, which in turn releases other ping-pong balls to continue the reaction.