The futuristic movie Looper has hit the cinemas nationwide, which sees people sent into the past for assassination by hitmen. But is there a neutron of possibility of such a frightening future? A leading time travel expert suggests the film's plotline may not be that outlandish.

It is 2074 and time travel has been invented but outlawed. Rather than disposing of enemies with a spade and car boot coffin, the mob send their tied up victims back into the past, where contract killers known as Loopers execute the unwilling time travellers in an untraceable way. Financially rewarding but morally draining, it is a cat and mouse lifestyle distinguished by suicide as Loopers are sent back to 'close the loop' on their past selves.

The movie, already being described as one of the best science fiction movies ever, throws up some thought provoking questions; Will people ever be able to weave inbetween the past and the future? Will paradoxes always spoil the time bending party? Could humanity ever be trusted to cope with the moral responsibilities time travel would demand?

Surprisingly, the concept of time travel is anchored in real physics and we speak to time travel expert Dr Ronald Mallett, to discover what plot elements of Looper are plausible. Dr Mallett made the headlines with a breakthrough blueprint for a working time machine using light.

Many in the scientific community believe that backwards time travel is highly unlikely, due to the potential problems of causality. In Looper, Joe (played by Bruce Willis) is sent 30 years into the past, so is this the first suspension of disbelief required on behalf of movie-goers? Maybe not according to Dr Mallett.

"Time travel to the future and past is really possible based on Einstein's theories of relativity. There are experiments that show time travel into the future has already been achieved and there has been recent theoretical work that has proved time travel into the past is possible".

According to the Professor, travel into the future is 'relatively' simple as space and time are intrinsically linked. If we were to travel towards the speed of light on a super-fast rocket, our heart beats and metabolism would slow down. When we returned to earth, decades would have passed on earth during a time that have might only been a year in the spacecraft.

However, in Looper, Joe is sent back in time, a far greater space/time bending feat surely?

Dr Mallett offers a solution for retro-travel.

"Einstein says light can also create gravity. My breakthrough was that if gravity can affect time and light can affect gravity, then light can manipulate time. If you generate a circular pattern of light using a ring laser, the loop pattern of light can cause a twisting of both space and time. Think of a cup of coffee. The coffee is space and your spoon is the circulating light beam. As you stir, the coffee (space) swirls around; space is being 'twisted'. According to Einstein's theory, everything you do to space also happens to time (spacetime) and therefor the light should manipulate time. If the twisting of space becomes strong enough, time will eventually get twisted into a loop.

In Looper, 'Closing the loop' describes an assassination of a Looper's past self, sealing their fate in 30 years (could almost be called delayed suicide) but this terminology also has its roots in physics terminology meaning the creation of a 'closed loop in time' in order to go back into the past.

Most of us could imagine the amazing potential of time travel and the opportunities it would provide but like anything of scientific importance, the danger of it being misused are so great, it is unlikely time travel machines would be made available to the general public. In Looper, time travel is outlawed and the film highlights how manipulation of time could have murderous consequences but Dr Mallett believes once the cat is out of the bag, it would be unstoppable...

"The question of ethics with time travel is a very important one. In Looper, they make a good point that if time travel to the past is created, it might be outlawed in the future. If it is outlawed then the only people who can use it are outlaws. The problem is you can't outlaw physics and some governments would feel there would be an advantage to manipulate time. Real politics will always trump ethics. Even though we personally feel it shouldn't happen, it will happen."

Any time travel movie has to either deal with or ignore those paradoxical consequences thrown up and Looper does both. If we went back into the past and did something to our future self, how would that affect our future self? This cause and effect is explored in one sequence when a Looper is tortured off screen, and then his future self begins to experience severe body disfiguration in real-time. Is such a temporal cause and effect possible? Dr Mallett thinks it could be.

"If you were to travel back you really could alter the past in a way that would make reality change. It's hard for us to get your heads around that you actually could alter everyone's reality by altering the past".

But what about the fact that, as Stephen Hawking once said, the absence of time travel tourists suggests time travel will never be invented? Dr Mallett has an answer for this too.

"One of the things that was nice in Looper was that assassinators were not able to go back to any time beyond a thirty year interval. The reason we don't get visitors from the past is that it is the time machine itself that is creating the affect. When you turn on the device, the device starts twisting space and time right then, so if you leave it on continuously for ten years, then you could send information all the way back ten years but not before it was switched on. Time travel into the past is definitely possible but only after the time machine is created."

So far we have solutions to a few of the fourth dimensional puzzles but what about the grandfather paradox? If Bruce Willis did successfully kill his past self he would not have existed to be sent back in the first place right?

The parallel universe theory, based in reality of quantum mechanics, suggests need to think outside of our own universe...

"The principle of parallel universes was originally invented to apply quantum physics to the entire universe. It was later applied to the problem of time travel paradoxes. Suppose every decision you made (for example, whether you decide to have a hamburger or tuna sandwich for lunch) splits the universe into two. It turns out if you go back you arrive in a past universe. In that parallel universe, Joe's future self could manipulate what happens, it is just he would be in a weird universe in which he had never been born. It is how the Grandfather Paradox could be solved. Time travel to the past is possible but the universe you arrive in is not the universe you came from. This is not pure theory; quantum mechanics shows that an electron can exist in infinite states at the same time. It is not unreasonable to imagine this on a universal level".

Finally, Looper asks, what would you do if you were sitting in front of yourself? Would you give yourself a stock market advantage or suggest inventing a bagless vacuum cleaner? That advantage may all be in your head according to Dr Mallett.

"You would have a sort of schizophrenia. Everything you do would change the future; even if you just bumped into something, you would have altered the future of everyone in that universe. It would be lonely too. Things that were in your head would not be remembered by anyone else. Even if you thought you could give yourself information about the stock market it would not be useful for you because, since you have arrived you have altered things in uncontrollable ways."

Looper can be watched in cinemas nationwide. For a simple guide to time travel, Dr Mallett's book Time Traveller: A Scientist's Personal Mission to Make Time Travel a Reality, is available online.

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