## Time Travel Is Mathematically Possible, Say Researchers

Time travel has always created curiosity among people and much so for scientists who have been working over the years to solve or refute the theory. In fact at some point of time in our lives, the thought of travelling to a different time would have flashed through our minds too. And if mathematicians from the University of British Columbia and the University of Maryland are to be believed, then this dream of ours might have just got wings that’s at least for now.

According to the paper titled “**Traversable acausal retrograde domains in spacetime (TARDIS)**” that published in IOPScience Classical and Quantum Gravity journal recently, experts have developed a mathematical model of a ‘time machine’ that could manipulate the space-time continuum enough to travel backwards through time.

“People think of time travel as something as fiction,” says study author, theoretical physicist and mathematician, Ben Tippett from the University of British Columbia. “And we tend to think it’s not possible because we don’t actually do it. But, mathematically, it is possible.”

Mr Tippet along with his co-author and astrophysicist David Tsang from University of Maryland describe the TARDIS machine as a ”bubble” of space-time geometry that carries whatever’s inside it backward and forward through space and time along a circular path through spacetime.

Mr Tippett and Mr Tsang have used Einstein’s theory of general relativity to come up with their mathematical model ‘TARDIS’ in order to prove the theoretical possibility of time travel. In other words, the idea is that an object can travel through time if it reaches the speed of light.

In general relativity, curvature of space-time account for the curved orbits of the planets. If space-time was not curved, planets and stars would move in straight lines. So, space-time geometry becomes curved near a massive star, which in turn makes the straight trajectories of nearby planets to bend to follow the curvature around the star.

“The time direction of space-time surface also shows curvature,” Mr Tippett says.

“There is evidence showing the closer to a black hole we get, time moves slower. My model of a time machine uses the curved space-time – to bend time into a circle for the passengers, not in a straight line.

“That circle takes us back in time.”

So, if space-time is curved, and we run time along it at the same time, then theoretically the bend can be turned into a loop, making time travel possible.

“Since the 1950s, there have been many other proposals for space times which allow people to travel backward in time,” Mr Tippett says. “My work was to model a ‘time machine,’ where passengers inside of a box of limited size could travel along a circle through space and time, returning to their own pasts.

“The shape of spacetime was used to turn the direction of the arrow of time inside of the box in space and time. I then used Einstein’s theory to analyze this strange spacetime, and determine what would be required to build such a thing.

However, while time travelling is possible – at least in theory, Mr Tippett believes that scientists have yet to discover the right materials to bring a time machine to life and doubts that anyone will ever be able to build a machine to make it work.

“HG Wells popularised the term ‘time machine’ and he left people with the thought that an explorer would need a ‘machine or special box’ to actually accomplish time travel,” Mr Tippett said.

“While is it mathematically feasible, it is not yet possible to build a space-time machine because we need materials — which we call exotic matter — to bend space-time in these impossible ways, but they have yet to be discovered,” he added.