The theory could resolve some of the

This is because, instead of a collapse in which quantum particles 'choose' to occupy one state or another, they in fact occupy both, simultaneously

Imagine a world where dinosaurs hadn't become extinct, Germany had won World War II and you were born in an entirely different country.

These worlds could exist today in parallel universes, which constantly interact with each other, according to a group of US and Australian researchers.

It may sound like science fiction, but the new theory could resolve some of the irregularities in quantum mechanics that have baffled scientists for centuries.

The team proposes that parallel universes really exist, and that they interact. That is, rather than evolving independently, nearby worlds influence one another by a subtle force of repulsion. They show that such an interaction could explain everything that is bizarre about quantum mechanic

WHAT THEY CLAIM: Professor Wiseman and his colleagues propose that: The universe we experience is just one of a gigantic number of worlds. Some are almost identical to ours while most are very different; All of these worlds are equally real, exist continuously through time, and possess precisely defined properties; All quantum phenomena arise from a universal force of repulsion between 'nearby' (i.e. similar) worlds which tends to make them more dissimilar. Advertisement

The team from Griffiths University and the University of California suggest that rather than evolving independently, nearby worlds influence one another by a subtle force of repulsion.

They claim that such an interaction could explain everything that is bizarre about how particles operate on a microscopic scale.

Quantum mechanics is notoriously difficult to fathom, exhibiting weird phenomena which seem to violate the laws of cause and effect.

'The idea of parallel universes in quantum mechanics has been around since 1957,' said Howard Wiseman, a professor in Physics at Griffith University.

'In the well-known 'Many-Worlds Interpretation'', each universe branches into a bunch of new universes every time a quantum measurement is made.

'All possibilities are therefore realised – in some universes the dinosaur-killing asteroid missed Earth. In others, Australia was colonised by the Portuguese.'

'But critics question the reality of these other universes, since they do not influence our universe at all.

'On this score, our 'Many Interacting Worlds' approach is completely different, as its name implies.'

The Many Worlds theory was first proposed by Hugh Everett, who said that the ability of quantum particles to occupy two states seemingly at once could be explained by both states co-existing in different universes.

Instead of a collapse in which quantum particles 'choose' to occupy one state or another, they in fact occupy both, simultaneously.

IS OUR UNIVERSE A HOLOGRAM? UNIVERSE COULD BE A MERE PROJECTION The holographic model suggests gravity in the universe comes from thin, vibrating strings. These strings are holograms of events that take place in a simpler, flatter cosmos The universe is a hologram and everything you can see - including this article and the device you are reading it on - is a mere projection. This is according to a controversial model proposed in 1997 by theoretical physicist Juan Maldacena. Until now the bizarre theory had never been tested, but recent mathematical models suggest that the mind-boggling principle could be true. According to the theory, gravity in the universe comes from thin, vibrating strings. These strings are holograms of events that take place in a simpler, flatter cosmos. Professor Maldacena's model suggests that the universe exists in nine dimensions of space, and one of time. In December, Japanese researchers attempted to tackle this problem by providing mathematical evidence that the holographic principle might be correct. The holographic principle suggests that, like the security chip on a credit card for example, there is a two-dimensional surface that contains all the information needed to describe a three-dimensional object - which in this case is our universe. In essence, the principle claims that data containing a description of a volume of space - such as a human or a comet - could be hidden in a region of this flattened, 'real' version of the universe. In a black hole, for instance, all the objects that ever fall into it would be entirely contained in surface fluctuations. This means that the objects would be stored almost as 'memory' or fragment of data rather than a physical object in existence. Advertisement

Like Everett, Professor Wiseman and his colleagues propose the universe we experience is just one of a gigantic number of worlds.

They believe some are almost identical to ours, while most are very different.

All of these worlds are equally real, existing continuously through time, and possessing precisely defined properties.

They suggest that quantum phenomena arise from a universal force of repulsion between 'nearby' worlds which tend to make them more dissimilar.

Dr Michael Hall from Griffith's Centre for Quantum Dynamics added that the 'Many-Interacting Worlds' theory may even create the extraordinary possibility of testing for the existence of other worlds.

'The beauty of our approach is that if there is just one world, our theory reduces to Newtonian mechanics, while if there is a gigantic number of worlds it reproduces quantum mechanics,' he says.

Dr Michael Hall from Griffith's Centre for Quantum Dynamics says the 'Many-Interacting Worlds' theory may even create the extraordinary possibility of testing for the existence of other worlds

'In between it predicts something new that is neither Newton's theory nor quantum theory.

'We also believe that, in providing a new mental picture of quantum effects, it will be useful in planning experiments to test and exploit quantum phenomena.'

'For us at least there is nothing inherently implausible in the idea,' added Professor Wiseman.

'For fans of science fiction it makes those plots involving communication between parallel worlds not quite so far-fetched after all.'

The ability to approximate quantum evolution using a finite number of worlds could have significant ramifications in molecular dynamics, which is important for understanding chemical reactions and the action of drugs.