Continuing our theme of film-related physics concepts (see the domain wall analogy from V for Vendetta) I recently saw a TV advert for the Mini Countryman which I thought nicely illustrates some of the key ideas of the Many-Worlds interpretation of quantum mechanics .
In this ad, the Minis – together with their occupants – split every time the drivers are faced with a choice about which route to take, leading to large numbers of Minis running amok.
This is the essence of the Many-Worlds interpretation of quantum mechanics which posits that every possible quantum outcome is actually realised. This obviates the need for the non-unitary evolution inherent in the usual view of the collapse of the wavefunction (state vector reduction) but at the expense of a hyper “inefficient” vision of reality as a hugely branched ‘tree’ in which all possibilities actually exist. As an observer living in such a universe the apparent collapse of the wavefunction is merely motion through a specific set of branches of this ‘tree’.
Proposed in 1957 by Hugh Everett, the Many-Worlds interpretation was initially very unpopular, a fact that apparently lead him to leave physics. It has since gained some support among physicists and its distant cousin, the Multiverse, has become popular in attempts to understand the implications of string theory and within the context of the anthropic principle.
The Many-Worlds interpretation has also entered the common unconscious via science fiction and now via television commercials, which of course means that it must be right.
PS. In fact one could also argue that this TV advert is also a nice, albeit imperfect, visualisation of the Feynman path integral approach to quantum mechanics which calculates the probability for a particle to go from point A to point B as a suitable integral over all paths joining A and B . In the advert, point A is the starting point before they reach the statue and point B is the end-point on the ferry, and all the Mini’s in between explore all the possible paths connecting A and B…except that they don’t explore all paths of course. But then again, it is just a TV ad.
PPS. There may also be some appropriate pun based on mini-superspace, the finite-dimensional version of superspace, but I can’t quite find it. If you can, please leave a comment.
 Tegmark, M. (2007). Many lives in many worlds Nature, 448 (7149), 23-24 DOI: 10.1038/448023a
 Christian Grosche (1993). An Introduction into the Feynman Path Integral Lecture given at the graduate college ”Quantenfeldtheorie und deren Anwendung in der Elementarteilchen- und Festkörperphysik”, Universität Leipzig, 16-26 November 1992 arXiv: hep-th/9302097v1