A study reveals a system that makes time travel mathematically possible, although only in theory.

Original poster for 'The Time Machine', 1960

“People think of travels in the time like some of fiction“. Ben Tippett likes science fiction like everyone else; but unlike most, he is also theoretical physicist and a mathematician, and on Twitter he defines himself as a “doctor of space and time.” What gives authority to this professor from the University of British Columbia (Canada) to issue this diagnosis: “We tend to think that it is not possible because in fact we do not do it. But mathematically, it is possible“.

And it shows. Specifically, in a theoretical study signed in collaboration with the astrophysicist at the University of Maryland (USA) David Tsang, and published in the journal Classical and Quantum Gravity. But beware: the keyword is “theoretical“. What often happens with physicists is summed up in an old joke: If you ask them if a horse could run faster than light, they might say yes. But if you ask them to explain it, maybe they start like this: “suppose a totally spherical horse without friction…”.

Travel to the past to change it, or to the future to know it, is a fantasy natural in a thinking species enslaved by time. And it has been one of the favorite arguments of the Science fiction ever since HG Wells coined the expression “time Machine”In his homonymous novel of 1895. But even if it was the British biologist and writer who popularized it, a fact that is not so well known is that the first appearance in literature of a vehicle to travel through time is due to the Madrid-Valencian diplomat and writer Enrique Gaspar and Rimbau in his 1887 novel The anachronópete.

Naturally, the abstruse name chosen by Gaspar could not triumph in any way. But for a country like ours that does not stand out for its scientific record (even though it has enlightened genius and often unjustly forgotten inventors), it is curious that the time machine is a spanish invention. Although it is a machine that does not exist.

Travel on paper

At least it doesn’t exist in reality. But on paper, the question is different. The truth is that Tippett and Tsang not the first theoretical exploration that manages to submit to the equations to make that old fantasy come true. “My mathematical model works on the same principles and has the same limitations as others previously proposed”, Tippett admits to EL ESPAÑOL.

A perfectly functioning time machine, but only in theory.

A perfectly functioning time machine, but only in theory.

However, their system yes he has one peculiarity. Others devised before work by means of rather strange devices; for example, the so-called Cilindro de Tipler is a cylinder of infinite length, something that is not easily found in any hardware store. In contrast, Tippett’s scheme uses a bubble. “We think this is closer to the concept of a time machine that anyone has,” he suggests.

But all of them must move within the limits of their own playing field, the general relativity enunciated by Albert Einstein. In 1915, the German physicist described the space time as a fabric of reality which explains the gravitational attraction. In a common simile, a bowling ball on a trampoline produces a depression. If we toss a marble as if it were a roulette ball, the depression will make it spin in a curved path.

This phenomenon is what explain the orbits, like those of the satellites around the Earth or that of the Earth around the Sun. fabric of space-time, that we can not see, is curved by the action of large masses such as that of a planet or a star. The existence of this tissue and its deformation remained confirmed with the announcement in February 2016 of the detection of gravitational waves by the experiment LIGO; These ripples in the fabric of space-time are created by a great cosmic cataclysm, like the merger of two black holes, and they spread like when we shake a tablecloth.

But this deformation does not only affect space: the tissue also includes time, which is a fourth dimension added to the three space ones. If we bend that fabric enough, we can form a loop with it. And since time is also part of it, we can create what physicists call a closed time curve, a kind of time loop.

Time loop

The proposed scheme places a first observerout of the time machine, with his normal life and his passing of time in a linear way. But next to him is a second observer, inside of temporary bubble, describing a circle in space-time. “It is a box that travels forward and then backward in time, along a circular path through space-time“Sums up the study. Tippett thinks it appropriate to describe it as a system hop-on/hop-off (jump in / out), like those tourist buses of cities that run circular lines. “The observers enter the box at time zero, when the box is not moving and there is no difference between the outside and the inside.”

When they start to happen strange things is when the box begins to move to speeds greater than light, something necessary for travel to the past. The time traveler would see his companion do your normal things, but periodically I would see him begin to undo everything you’ve done, such as when a video is rewound. As for the outside observer, he would probably rub his eyes as he saw his partner appear out of nowhere and unfold into two versions, one whose clock advances in time and another that goes back, until both unite and mutually annihilate each other. Outside observers would watch in rapture as the time travelers inside the box evolve backwards in time, unraveling eggs and separating the milk from the coffee, ”the researchers write.

A peculiarity of the machine is this: if the traveler wanted to travel a century back, he would first have to travel a century into the future, since the road is a loop; something like taking a circular bus line to get to a stop before ours, forcing us to go around the entire route. But at least the time traveler would not die of old age or boredom waiting to reach his destination: moving at the speed of light, his clock ticks more slowly. Tippett points out that it would also be possible to make a cut-paste of loop fragments to get paths with other forms and avoid the complete turn. “The result would seem like a Water slide“, He says. In this way, for example, it could be possible to travel into the future for only a few minutes and then go back years into the past.

Tippett and Tsang have called their machine concept Traversable Acausal Retrograde Domains In Spacetime, translatable as “retrograde acausal domains traversable in space-time”. But almost the full name is the least of it; the really important thing is that the acronyms form the acronym TARDIS, named after the time machine from the veteran and popular British television series Doctor Who.

A pity that from theory to practice there is a unbridgeable abyss. Among the many obstacles, Tippett notes that it is not easy at all fabricate those space-time ties. Scissors and zeal are not enough: “to bend space-time in those impossible ways we need what we call exotic matter, and this is something that has not yet been discovered.” A euphemism to come to say that in reality it does not exist; but on paper we can always draw it.