Is It Possible to Create a Time Machine?
First, we would like to note that there are two scientific thoughts about the possibility of inventing the time machine in the future: the first says that the discussed apparatus will be invented, and the second claims the opposite. Let us try to analyze these points of view.
Justifying their position on the impossibility of creating a special apparatus to transfer through time and space, the opponents of this theory argue that if the discussed apparatus were ever invented, then now we would have plenty of tourists from the future. This is quite logical. However, we do not observe this, hence the time machine will not be invented.
In their turn, the adherents of the possibility of the existence and invention of the time machine in the future, answer this question with the following proposition. The future can form several branches. For example, you changed something in the past and when you come back, you find out in your time that everything has changed, but not for everyone else ... An alternative branch of time appears in which everyone lives normally (because they do not know what you are changing).
I really like a classic American cinema, and in particular, the film "Back to the Future 2;" who did not watch be sure to look. In the film, it goes precisely about the question of the bifurcation of time and space.
In the movie, the protagonist travels in time and almost prevents the relationship of his parents, thereby "erasing" himself. In science, this phenomenon is known as the "grandfather paradox", which says: "If you could travel through time and kill your grandfather, would you cease to exist without a chance to be born?"
Possible Variants to Travel
1. Physical (which is based on Einstein's general theory of relativity):
A) When moving at a speed close to the speed of light, the time for the moving object practically stops, while all other objects in the universe continue to age. It is proved that the higher the travelling speed of the object, the slower the time goes for it; This concerns both objects of biological origin (man) as well as human inventions (a timer was thrown from a skyscraper and marked simultaneously with a timer on the ground; the time of the thrown timer differed from the "fixed timer" for microseconds but differed!). That proves time deceleration with speed increasing.
B) Being in the region of a black hole’s gravity. In theory, time will stop altogether, and if you fall into the gravitational field, you will be able to see the development and death of the surrounding universe just in a few subjective minutes, whereas in fact, many billions of years will pass. "Eternity" for such an observer will end with the collapse of the universe.
A) Metabolism break with subsequent recovery (for example, cryopreservation – the instantaneous freezing of a biological object, the experiments in this direction are currently under way).
B) The hibernation of warm-blooded animals is also a kind of "journey into the future". The body ages, but three months of winter pass insensibly.
The implementation of travel to the past is much more difficult than in the future, but there are several theoretical ways to get into "yesterday:"
1. With the help of "wormholes," the hypothetical existence of which is assumed by Einstein's General Theory of Relativity. They are some tunnels connecting our time-space with another time. There is a small complication: Einstein's equations say that a wormhole will have collapsed before the time traveler will enter it, if it is not held by the matter with a negative energy density (whose existence has already been proved). That is, in theory, you can get to the past in this way, but "where?" and "at what time?" is still unknown.
2. Deutsch-Politzer proposition. This "machine" “works” through the subjective perception of a person, its principle of work is as follows: while you are remembering the past, you are in the past.
In general, our reality is equal to our sensations. Looking at the Sun, we see it as it was about 8 minutes ago. We look at a tree and see it as it was one quadrillion of a second ago. These feelings are the basis of our "now," despite their coming from the past. Thanks to the restoration of these sensations, we create our own subjective past.
Universe Is a Natural Time Machine
The documented and publicly available facts of time travelers in our time are absent.
In fact, a journey through time can be done from the point of view of the observer. Astrophysicist Neil Degrasse Tyson at a press conference at the University of Miami said: "Do you know what is the best thing? If you now, go to the galaxy at number M100, which is at a distance of 65 million light-years from here. What is so cool about that? The light from the asteroid that led to the extinction of dinosaurs is only now approaching this galaxy. That is just unimaginable! Thus, being now in that galaxy, you would have outrun the light, you could get your telescope, and watch the extinction of dinosaurs. It is just indescribable! Thus, the Universe is something like the Time Machine. You see things not as they are now, but as they once were."
You can go to the past only in theory, but you can see it. It remains to wait for spacecraft that can instantly transfer us into neighboring galaxies so that we can at least not participate but watch our past.