In an alternate universe, the arrows of time could run in the opposite direction of what we know, unfolding so that our known past exists during the far-off future of a distant world.

A pair of scientists from the California Institute of Technology and the Massachusetts Institute of Technology who suggest this concept aren't the first to do so, but they've demonstrated how this phenomenon could arise based on simpler principles than previously examined.

Using entropy as the basis for their model, the physicists have developed a way to show the spontaneous appearance of the arrows of time, and how they can flow in opposite directions.

In the multiverse, pictured above, parallel universes could exist, with time running in opposite directions. A pair of scientists from the California Institute of Technology and the Massachusetts Institute of Technology have developed a model to explain how this could happen based on simpler principles than previously examined

HOW PARTICLE ACCELERATORS COULD FIND A PARALLEL UNIVERSE Cern’s Large Hadron Collider has been operating at highest capability in recent months in search of miniature black holes. These are said to be a key sign of a ‘multiverse'. If scientists are able to detect mini black holes are at the LHC at the predicted energies, it could prove the existence of extra dimensions and by extension, parallel universes. 'Just as many parallel sheets of paper, which are two dimensional objects (breath and length) can exist in a third dimension (height), parallel universes can also exist in higher dimensions,' Cern employee Mir Faizal from the University of Waterloo told Dailymail.com. 'We predict that gravity can leak into extra dimensions, and if it does, then miniature black holes can be produced at the LHC.' The LHC's record high energy now makes it possible to look for these mini black holes, and energy gravity may be even tracked disappearing into them. The new 'gravity's rainbow' theory, which says that space and time curve differently for particles of different energy, could explain why the LHC has yet to find any of these black holes. Advertisement

In an interview with New Scientist, Sean Carroll of CIT, Pasadena and Alan Guth of MIT explain that, in the laws of physics, the direction in which time flows does not matter.

By this explanation, time which runs backwards would still go in accordance with the laws.

While humans have grown accustomed to the idea that events lead to other events in a particular order, Carroll says this is not the case.

'There's no such thing, at a very deep level, that causes [must] precede effects,' Carroll told New Scientist.

In time as we know it, entropy – a measure of disorder – increases.

On a universal scale, this means that 'the future is the direction of time in which entropy increases,' New Scientist writes.

At a much earlier point in the life of the universe, like at the time of the big bang, entropy would be much lower, the researchers explain.

In their model, which is not yet published, the researchers drop a fixed amount of particles into an infinite universe.

The individual particles each have a randomly assigned velocity, and eventually, arrows of time spontaneously come about, according to New Scientist.

Under these conditions, half of the particles will spread outward toward the edges of the cloud, increasing entropy.

The other half will move toward the centre, decreasing entropy.

Once these particles pass through the centre, they will continue on, heading outward toward the edge.

They're referring to this idea as the 'two-headed arrow of time.' If an arrow of time emerges in one direction, the same will happen in the opposite.

Regardless of the starting position, the researchers explained to New Scientist, the particles will all eventually move in the outward direction.

The model shows that entropy can grow without limit, indicating that 'time zero,' would be the point of lowest entropy.

This means that the direction of the individual arrows has no importance, because the cloud will always expand.

To make a plausible model, the researchers must work to understand the initial state, when the particles are dropped into the infinite cloud, and entropy is both growing and shrinking at the same time. But, the basis of physics on the known direction of time makes it hard to determine its behaviour under different circumstances

'The point that Alan and I are trying to make is that it's very natural in those circumstances that almost everywhere in the universe you get a noticeable arrow of time,' Carroll told New Scientist.

'Then of course, you do the work of making it realistic, making it look like our universe. That seems to be the hard part.'

The researchers say this model could apply to all of existence, including the multiverse.

But, the model is not perfect, Andreas Albrecht, of the University of California in Davis, explained to New Scientist.

'They've created a world where they can slip certain notions in very easily,' Albrecht told New Scientist, regarding the team's model of the infinite universe, but says he likes the idea of double headed time.

To make a plausible model, the researchers must work to understand the information gaps at the initial state, when the particles are dropped into the infinite cloud, and entropy is both growing and shrinking at the same time.