Tuesday, 28 August 2012

Splitting Reality – The Many-Worlds Theory

Let your soul stand cool and composed before a million universes. 
– Walt Whitman 
Through books, TV and film, the idea of parallel worlds is a widely recognised phenomena in our culture today. From a quantum physics perspective, it’s instructive to understand the origin of this idea.

As explained in a previous article, Schrodinger came up with his famous cat in a box experiment to illustrate what he believed was the absurdity of the Copenhagen interpretation. The Copenhagen interpretation is the theory of physicist Niels Bohr, that states a quantum matter exists in all states at once (a wave) until forced to chose one state when observed (a particle). Ironically it’s Schrodinger’s cat thought experiment, intended by him to deride Bohr’s theory, which has become the preferred way to explain the Copenhagen interpretation.

An alternative idea that grew from this was Hugh Everett’s 'Many-Worlds' theory. He agreed with the wave ideas of Bohr, however he argued that rather than an object being forced to become a particle when it was observed, it actually created a split in the universe to allow for each possible outcome. A disturbing example that illustrates how this could work, is when someone is nearly killed crossing a road. In the Many-Worlds theory the universe splits at that moment – in one reality the person dies and in the other reality the person lives. Using this model in any given moment, the universe is constantly splitting like the branches of a tree for each new potential outcome and creates an infinite number of parallel realities.  

Whilst the Many-Worlds theory isn’t the only one to promote the idea of parallel worlds to explain the behaviour of objects at the quantum level, it has attracted serious interest and research in recent years. Keep this in mind when you next cross that road – you could be about to split the universe in two.

The below video is a useful visual explanation of the Many-Worlds theory.