The idea may sound far-fetched but the "many worlds" concept is the subject of serious debate among physicists. It is a particular interpretation of quantum mechanics, which describes the often counter-intuitive behaviour of energy and matter at small scales. Prof Cox made the comments during an interview with Radio 4’s The Life Scientific programme.
In a famous thought experiment devised by the Austrian physicist Erwin Schrodinger, a cat sealed inside a box can be both alive and dead at the same time. Or any combination of different probabilities of being both dead and alive. This is at odds with most common perceptions of the way the world is. And Schrodinger’s experiment was designed to illustrate the problems presented by one version of quantum mechanics known as the Copenhagen interpretation.
This proposes that when we observe a system, we force it to make a choice. So, for example, when you open the box with Schrodinger’s cat inside, it emerges dead or alive, not both. But Prof Cox says the many worlds idea offers a sensible alternative. "That there’s an infinite number of universes sounds more complicated than there being one," Prof Cox told the programme. "But actually, it’s a simpler version of quantum mechanics. It’s quantum mechanics without wave function collapse… the idea that by observing something you force a system to make a choice."