The famous modern scientist Stephen Hawking argues that time travel is impossible. "Otherwise," Hawking said, "travelers would have been with us for a long time." However, some colleagues disagree with him.
Many researchers of this topic give an explanation of why we have not yet met the time travelers who invented the corresponding machine somewhere in the distant future. For example, they assume that time travel is possible only forward, that is, into the future, which we are not, of course, for our descendants. Or, for example, a created time machine is capable of transferring people into the past, but only into the very near-by. And, apparently, we are not there for travelers either.
By the way, most of the supporters of the probability of time travel are sure that the movement of people will not be carried out by means of any unit, but by means of a certain environment. For example, using the so-called black holes.
Black holes are former stars that exploded, unable to withstand the pressure of their own huge mass. Due to this, gravity (or attraction) in them is so strong that no object can leave the black hole. And any object that is dangerously close to the hole immediately disappears into it. What's going on in the darkness of holes still remains one of the most controversial topics in scientific circles. However, there are theories according to which, at the very center of black holes, space and time change places, which means that space travel becomes time travel. That is, anyone who gets there can be in the past or the future. But even if we assume that this theory is correct, we still face an insoluble problem. Namely, according to the assumptions of some scientists, a black hole simply destroys everything that falls into it. So time travelers will die on the way to their cherished goal.
American physicist Kip Thorne suggested that time travel will become possible when humanity finds some holes or tunnels in space. According to Thorne's theory, these tunnels arise between two objects that are distant from each other, which exist in different time planes. It is through these tunnels that people will be able to move in time.
Another American scientist Richard Goth believed that time travel would be carried out by means of cosmic strings. These strings, according to the physicist, were formed in space many billions of years ago, that is, when the universe was still in its infancy. Cosmic strings are so thin that their thickness is much less than the size of the smallest particle - an atom. However, the gravitational field of the strings is very powerful. Therefore, if you combine these strings or bring one of them closer to the same black hole, you get a kind of corridor. This is where it will be possible to travel in time.
Another American, Frank Tipler, suggested that in the future, it would be possible to create some kind of cylinder-shaped object that would allow people to travel into the past. This cylinder should be launched into space and given rotation. In order to be several years back, the pilots of the spacecraft must fly around the cylinder several times. The more times they go around the cylinder, the more distant they will be in the past. However, all the same Stephen Hawking again destroyed all human dreams. He stated that in order for time travel with such a cylinder to be possible, the length of the cylinder itself must be infinite. And what is infinity today is even difficult for us to imagine.
If we imagine that someday scientists will discover places or objects with the help of which it becomes possible to travel in time, many obstacles await users of this "attraction". For example, it may be the so-called “murdered grandfather paradox”. It was first described in his book by the French writer Rene Barzhavel. The paradox is as follows. For example, a time traveler went back in time and accidentally or intentionally killed his grandfather before he met his grandmother. If you trace the entire subsequent chain of events, it turns out that the traveler himself was never born into the world. This paradox is very clearly shown in the movie "Back to the Future", when the main character goes to the past. His future father and his future mother just can't dock. Therefore, the image of their future son in the photograph is gradually disappearing.
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Many scientists fully agree with the possible existence of such a paradox. However, according to them, it can be circumvented. For example, there are many hypotheses that the past cannot be changed. And, therefore, that same grandfather still survived the attempt on his life and remained unharmed. Or another version, which also takes place in the "Back to the Future" trilogy. This version assumes the existence of several parallel times. That is, by killing his grandfather, the time traveler will not disappear, but create a different reality.
While the time machine remains the lot of science fiction writers. But who knows, maybe a few years will pass, and people will still be able to travel in time. And now our task is only one thing - to make the present happy.
Yulia Popova