Time Travel | As it seems, in the light of the latest scientific theories, what I thought was incredible could become reality: we could, at least at the theoretical level, travel in space-time, “fooling” the known laws of physics. Maybe not tomorrow, day after day, but definitely one day; when we will overcome the momentum of developing the necessary technology.

Governments of the world should invest in … the journey in time! The idea of irreversibly “flowing” is so deeply rooted in human consciousness that the possibility of moving back and forth into the fourth dimension, a possibility that relativity does not exclude from the theoretical point of view, seems only a scenario, Star Trek genre.

“Still, SF today is often the science of tomorrow. That is why it is our duty to study the fanciful physical theorems applied by the Star Trek crew.” If we were to study only the earthly problems, we were very limited much of our human potential. ” These words do not belong to an SF fan, but to the most famous physicist alive, Stephen Hawking.

But Hawking is the same who denied the possibility of travelling in time for years, causing heated debate among cosmologists and astronomers when they argued that Einstein’s general theory of relativity could have allowed it. Time Travel, he declared then, would allow people to change their past; they could prevent their own birth, a possibility in his ridiculous opinion. “The most obvious proof that a journey in time will never be possible is that we have not been hunted by hordes of tourists so far,” Hawking said ironically.

Recently, however, he seems to have changed his “turn”: he now claims that a journey in time is not just a feasible thing, but one in which governments should invest funds. In a preface written to the book by American astronomer Lawrence Krauss, The Physics of Star Trek, Hawking speaks openly about the bending of space, and about speeds higher than light. He states that “one of the consequences of the accelerated interstellar journey would be that it could go back in time.” He says, however, that a voyage in time will probably not be “feasible,” but the seeds of doubt seem to have been set in his mind: “If Einstein’s theory of general relativity is combined with quantum theory, it seems to be a possibility.”

The fact is that studies on the so-called “closed time-like curves” are progressing in several universities, including Cambridge and Caltech (California Institute of Technology). “It does not require a lot of money, it only needs a sufficient mental opening to consider the possibilities at first sight fantastic,” Hawking said. Quantum theory is what caused Hawking to change his mind over black holes. Considered by many as a “corridor” of access to other dimensions, black holes can, in the view of the physicist, be the “key” of the journey in time: “A black hole has a dramatic effect on time, slowing it more than anything else in the galaxy, and this makes it a kind of natural time machine. ”

Time Travel Train

A way suggested by Hawking to travel in time is to build a means of locomotion that allows us to travel very, very quickly. How fast? Well at least at a speed that would allow us to avoid the danger of being swallowed by a black hole, and anyway below the limit of the speed of light, equal to about 186,000 miles/second. This speed cannot be exceeded, but if we could move with values close to the speed of light, we could travel in the future. So, hypothetically, if we were on a train, able to go at speeds close to that of light – Hawking gave the example of a train that would cross the entire terrestrial circumference 7 times per second – time would begin to drain more slowly inside him than outside: on the train, everything would happen in a kind of “slow-motion”.

The reason for this phenomenon, explained the physicist, is precise to “protect” the speed of light, the insurmountable limit of physics. Therefore, in Hawking’s opinion, this could be a way to travel in time, or at least in the future: if that train would travel 100 years (measured by an observer on Earth) consecutive, for us, potential travellers, because of the slowing down of time, it would take only a week. Of course, making such a train is not possible at the moment, but there is something similar at the Geneva CERN: Large Hadron Collider, able to accelerate particles from 0 to 60000 mph in a fraction of a second.

Increasing power, the particles could theoretically dump in the tunnel 11,000 times per second at a speed close to that of light, reaching a value equal to 99.99% of its limit. If this happens, the journey begins in time (the phenomenon has been demonstrated by certain types of particles, called “mesons Pi“, which normally have a very short life of a fraction of a second but when determined to travel at speeds close to that of light, their lifespan increases 30 times).

Live In a Single Day As a Whole Year!

In Hawking’s view, a way to use this principle and travel in time would be to fabricate a proper astronaut and launch it into space. Equipped with properly sized engines powered by the correct amount of fuel, after about 4 years it would be able to reach 90% of the speed of light, and after another 4 years, it would start to travel over time. Another two years and the astronaut would reach 99% of the speed of light, a day spent on board corresponding to an entire year spent on Terra. Hawking imagines how a trip could be near a black hole on a space shuttle: “For the courageous people on board the shuttle, time would slow down at each orbit by 16 minutes, and they would only have eight minutes of experience “.

And other researchers, including Fernando De Felice, professor of physics at Padova University, believe that some black holes “hide” in the cars of the time. Indeed, black holes are stars whose matter is concentrated in an infinitesimal point called “singularity,” where time and space deform to the point where the trajectory of a particle bends over itself, creating a situation called the “time loop “. Basically, De Felice explains, the moving particle, even travelling in the future, would meet with herself in the past. And the hypothesis would be that, by entering a black hole, you would wake up in a kind of ring where the future would meet the past, so even going ahead, sooner or later, you will come back also at the starting point. The risk would be “just” to be made of the “massager” of the giant gravitational forces.

How Could You Build a Time Machine?

According to De Felice, the simplest way would be to create a so-called “wormhole”, a tunnel that connects spaces in two separate space-time regions, and passing through this tunnel would be equivalent to a journey in time. Unfortunately, despite the long-lasting studies of the properties of such a wormhole, it is not yet clear how it would be possible to create one. And if some speculative theories on quantum gravity theory state that space-time has a complicated structure similar to a foam composed of wormholes of the size of 10-33 cm, that is, a billion times smaller than an electron, however, only a few physicists believe it is possible to “manipulate” one of these microscopic wormholes and increase it to human usable dimensions.

According to William A. Hiscock, a physics professor at Montana State University, the journey in the future could be accomplished using Einstein’s Special Relativity Time Dilution, which argues that a clock, even biologically, moves slower as Touch the speed of light. As such, leaving Terra on board an astronaut who manages to accelerate to reach speeds close to that of light, a journey could be made to the centre of our galaxy, returning to 40 years (measured time on the shuttle ). On Terra, in the meantime, it will have been 60,000 years, so the astronaut would wake up in the future. Unfortunately, such a voyage would require an enormous amount of energy, impossible to obtain with the current technology.

As Hiscock sees it, even more, complicated is the journey back in time. There are many solutions to Einstein’s General Relativity Equation that allow a person to follow a line of time that would make her meet herself or a parent in a previous age, but the problem is to decide if these solutions do not are just bizarre mathematical results: no experiment has so far demonstrated that such a journey in time could happen in our universe, the teacher says. However, he adds, some theorists have done some studies about the possibility of manipulating matter and space-time geometry so that “horses that can spin around the time” can be created.

The Imprudent Time Traveler

The famous “grandfather paradox”, first described by René Barjavel, author of books in Le voyageur imprudent (1943), imagines a situation where a nephew would return over time and would kill his grandfather before he meets the grandmother before they have the opportunity to produce descendants. In such a case, the nephew could no longer be born, so how could he return to his grandfather in time ?! There is also a theory in this respect; some physicists claim that any event would produce a new parallel universe in which history would evolve in an independent manner. In other words, by changing an event we did not change history, we just got into two parallel realities.

Recently, the grandfather’s paradox seems to have been solved by a group of MIT researchers in Boston, led by physicist and computer scientist Seth Lloyd. Faced with the other theoretical attempts made so far, Lloyd has resorted to an “effect” so far ignored. He started from teleportation, a famous Star Trek process where people are transferred from one place to another instantly (in the laboratory anyway, some photons have already been teleported) and quantum mechanics; “trick” was the use of the so-called post-selection principle, thanks to which only the particles that have been teleported can be brought back to the original condition, thus making a journey back in time. Such a car would not require any distortion of space or time.

Last but not least, in the researchers’ approach, there is a more specific intention than the time travel: the post-selection effect used by Professor Lloyd is at the heart of research on the quantum computer, and in this direction, some possibilities. Japanese Michio Kaku, a physics professor at City University in New York, is also convinced that running a time machine would require the use of an enormous amount of energy, but believes that black holes could solve the problem through wormholes.

“The distance between two points on a sheet of paper is a straight line, but if we bend the paper until the two points coincide …”. In fact, the first one who imagined this possibility was not even a physicist, but Lewis Carroll in his “Alice in Wonderland”. “In the pages of his novel, Carroll makes Alice travel in time passing through a magnifying glass. If a star collapses under its own power, it does not fall into a precise point, but in a neutron circle, just like Alice’s magnate. What would happen if you were trying to cross a black hole? Am I falling like Alice in Wonderland or are we destroying? We do not know that, but one day we will send a rocket in the middle of a black hole in search of a possible journey in time. “

Facts: famous travellers over time

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