If you're a fan of Doctor Who, Back to the Future, Legends of Tomorrow, or just science fiction, you have already wondered if it is possible, scientifically, to travel in time, or if it’ll become possible in the coming years. Answer...

Time travel implies power through space-time that defines our reality, to go either in the future or in the past. Many fictional works evoke the probability of time travel, and have made multiple viewers or readers dream for generations. Having a Time-Turner as Hermione in order to follow several programs simultaneously to college? Amazing ! Having the opportunity to go anywhere in time as Hiro Nakamura and live or participate in key events of history? Unbelievable ! Being able to travel where we want in space and time with a TARDIS? Awesome ! However, the question that always arises is that of the consequences of time travel. Also, if many works tell us that we should not change the "fixed points of the Universe" (as Pompeii, if you have the reference) or it is better to avoid crossing ourselves from the past or members of our family. But in general we forget the basic question : can you really travel through time? And how ?

Wormholes

This is one of the most enigmatic points of science today, and one of the best arguments of those who think that one day we will travel through time. But first, what is it? Discovered in 1916 by the scientist Ludwig Flamm, and again in 1935 by the eminent Einstein and Rosen, the wormholes are defined by our dear Wiki as "Hypothetical objects that would connect two distinct layers or two distinct regions of space-time and manifest themselves on one side, like a black hole, and on the other hand, as a white hole (or white fountain)" . To represent them simply, one can imagine the space-time as an object in two dimensions: a sheet of paper, for example. Imagine you fold the paper into three or four in length, so as to form a kind of accordion, and once all folded, drill a hole in your sheet. The hole will be present on every fold of your page, and you would be able to go through all these folds, if you were an ant, for example. So you have your wormhole.

Obviously a real wormhole would -if one could travel through it- go from one space-time A to a space-time B. Today, there are 3 types of wormholes, which are more mathematical solutions than concrete objects :

The Schwarzschild Wormhole, impassable ;

The Reissner-Nordstrøm Wormhole, passable but in one direction, may contain a Schwarzschild wormhole;

The Lorentz Wormhole negative ground, passable in both directions.

Seen like this, traveling through time by wormholes seems ideal, and really easy. The problem ? You must first go into a black hole, hoping that this theory of wormholes exist, and that there will be a white fountain on the other side to greet you. A black hole, just so you know, is a point in the universe where matter is compressed to the point of becoming so dense that even light is not going through. In addition, its 'compact' side gives it a gravitational field so intense that it is impossible to escape. Yeah, not so friendly.

So to travel back in time through a wormhole, you would require :

1-That wormholes are not a scientific hypothesis

2-Find a wormhole "passable" and therefore that could lead you to another point in space-time

3 Being able to cross a black hole without injury

4-That white fountains are not a hypothesis either

5-Being able to travel to another space-time without knowing where you are going, and taking the risk of not being able to go back (if the wormhole is only passable in one direction)

Conclusion : for the moment, travel in space-time through wormholes is a rather wobbly solution. But let's see the rest!

Travel beyond the speed of light

As mentioned in another article on the aerodynamics, the speed of light is the highest known speed. The unsurpassable. The immeasurable. The hurdle. Travelling at this speed comes, roughly, to run 7 and a half times around the earth in one second. Nothing less. But this speed is obviously limited, although it seems infinite to us. Light travels at "only" 1,079,252 848.8 km / h. So, I guess you learn nothing by saying that if a cosmic object is far from us, we see it with a certain delay. In fact, we perceive as the time it takes the light to reach us, depending on its distance. For example, we still see the moon with a second late, since it is located, on average, 384,467 km from us. This means that we will never look at it "live", we always look at the moon as it was one second before. Similarly, if a civilization from the Andromeda galaxy (located just 2.2 million light years from us) is watching us, they would see the Earth 2.2 million years ago. Thus, these aliens would not see us, but they would see our ancestor Lucy, Australopithecus. And it would be the same if we were watching them in our turn. We would see their planet 2.2 million years ago.

Also, if you wanted to go back in time, you’ll just have to ... travel beyond the speed of light! And ten years ago, scientists have discovered an optical phenomenon that spreads, in certain circumstances, faster than light : superluminal speed. Thus, in 2011, scientists from the University of Science and Technology of Hong Kong have studied this phenomenon, to see if it was really possible to exceed the speed of light. They then investigated the properties of photons, these elementary particles electromagnetic wave component (these are the particles exchanged in the absorption or emission of light by the material). These small "packets" of elemental energy have therefore been the subject of attention from the team of Professor Du Shengwang. These scientists first measured the maximum speed of a photon. To achieve this, "the team of Professor Du Shengwang generated a pair of photons, and spent one of them in a group of rubidium atoms cooled laser," says the study report. They then discovered that it was impossible that a photon travels faster than light, regardless of their environment. So, they (unfortunately) proved that the superluminal speed is in fact an optical effect created by a collection of effects of quantum nature.

The consequences of time travel

For now, it does not seem possible to travel through time. But if it was, what are the real consequences?

Many think they could change the course of history, avoid disasters, prevent two people to meet and so prevent them to rise the worst tyrant of all time. But the problem is that all this is only theory, often fictitious. In fact, if we could travel in time, we would do probably only be… spectators of all these events.

To say that we could go back in time, for example, suppress someone, and then return to our time is only fiction. Or we would deny the importance of every human being. For if we, small ants, do not feel so important to the proper functioning of the world, we are. So if you go back in time to murder your worst enemy when he was a child, you would change completely the reality, and you could never go back to your "time". In fact, even if one does not notice the change of a tiny grain of sand, it makes all the difference. And, ironically, it is in this that The Flash's adventures (him, again?) with Flashpoint are realistic. First he returns in the past only to save his mother. But, returning "to the present”, he realizes that this has changed the life of everyone around him (sometimes on a pretty bad way). Therefore, he decides to return to his childhood to let her get killed. But even this time ... All is regrettably not perfect!

To take another example and not speak only to superhero fans, I think it is also what is expressed in Doctor Who, with the story of "fixed points". Pompeii is a very promising example of sense (largely because it's one of the only times when the Doctor broke the rules, behaves like a human, and this is what will be worth it to regenerate in the body of the man he saved), but we can take many other examples. When he returned in the Rose's parents past, he forbade her to save his father, because he shows her that it would change the whole course of things. And it is the same with Clara's parents, who he leaves die, because he knows that, without their disappearance, Clara would not be the same, or they would have never met.

And in the same way, the journey into the future could not escape the rule, because changing the future would mean that a lamp lights before we have pressed the switch ...

Also, forgive me to disappoint you, but the time travel is, for now, humanly impossible. And the consequences, if they are not scientifically observable, are also unclear. But we can always hope that our descendants will find the keys to the space-time, and will have the opportunity to travel wherever they want in the universe and time. And why not even at home, to observe human beings in the 21st century ...

(I'm sorry, I am told that I have no right to say more about visitors of the future who are living ... hm, aren’t living, yet, in our time.)

As an alternative, we suggest you to wait for a mad man in a blue box to land in your garden, or for a charming "captain" to kidnap you in his invisible ship. Meanwhile, my friends, I leave you with an interesting little video on the subject, and I advise you to always try to broaden your curiosity, your culture, your knowledge, while remaining aware that we are… totally ignorant !