Probably, no one would refuse to visit ancient Babylon, to see the mysterious Atlantis and dinosaurs or mammoths with their own eyes. And how many of those who, having committed a rash act, wondered how to return to the past in order to fix everything. Yes, the ability to travel in time excites the minds of people from time immemorial.

There are many stories, the most fantastic and not so, about how people returned to the past or, on the contrary, moved to the future. Is time travel still possible?

Unfortunately, scientists, relying on the laws of logic and science, convince us that today this is unrealistic. In the modern world, there are no such technologies that would not be subject to the current laws of physics. In addition, time travel itself causes a bunch of paradoxes that violate one of the most important laws of the universe - the law of causality (that is, the idea that the effect follows directly from the cause). However, scientists put forward all sorts of theories that may well be implemented in the future.

Faster than the speed of light

This follows from Einstein's famous theory of relativity. So, if an object develops a speed higher than the speed of light, then time for it will slow down in relation to the outside world. Is it possible to return to the past in this way? From a theoretical point of view, yes. After all, if a speed exceeding the speed of light becomes available, then the slowdown of time relative to the outside world will allow the object to reach its destination even before the start. However, today the speed of light is the limiting value. And no one has yet been able to surpass it.

According to Einstein's theory of relativity, in order to give an object a speed greater than the speed of light, a colossal amount of energy is needed - the mass becomes larger with increasing speed, and therefore more and more energy is needed. At the moment, such a technology that could reproduce so much energy is simply not available to mankind. Alas. Although in the distant future, everything is possible.

Through the wormhole

Wormholes, or black holes, are peculiar curvatures of reality that connect points of space and time. Moreover, such a distance between points is much shorter than in a normal medium. Black holes can connect entire universes, distant galaxies, and perhaps even completely different time periods.

However, just as in the situation with a speed exceeding the speed of light, all this remains only a theory, not fixed in practice. To date, there is no equipment, no technology, no knowledge in order to be able to go through a wormhole. Therefore, the question of whether it is possible to return to the past through a black hole remains open.

Back to the Future

Since there are no practical possibilities to move into the past today, it would be logical to ask a question about the future. After all, it is likely that in tens to hundreds of years people will still be able to come up with a way to return to the past. And if you get into such a “future”, then from there you could go back several millennia.

Regarding travel to the future, scientists are not so categorical. At least, if you take into account the laws of physics, then moving into the future seems more real. So, more than once it has already been said about experiments on a temporary stop of the vital functions of a person. Of course, today the existing technologies are still far from ideal. However, it is likely that in a couple of years such a “time capsule” will still be created. Then, by freezing the human body, it will be possible to keep it completely unaged for a huge amount of time. Humans will be able to transcend existing life spans: fall asleep and then wake up in the distant future.

Revived memories

So, as it has already become clear, today there is no way to travel through time in the truest sense of the word. However, this does not mean that a return to the past is impossible. You don't even need FTL or a wormhole to travel down the alleys of your memory. Go back in time with your own memories.

Of course, you cannot be transported to Ancient Rome or see dinosaurs, but you will be able to relive those wonderful moments that you had in the past and which seemed to be impossible to return. Distant memories fade under a pile of recent events, but if you try, you can again feel those long-faded emotions. Thus, your body will exist in the present, and the brain will travel to the past.

But sometimes even evoking the right memories is not as easy as it seems. Therefore, below are the most effective ways to return to the past with the help of memories.

old pictures

Photos are a kind of window into the past. Looking at them, you can not only delve into memories, but also relive long-forgotten emotions. Whenever you feel like going back in time, take out your photo albums or family videos. Just while watching, you should not shed bitter tears and think that all the best things in your life have already happened. Try, looking at the pictures, to remember everyone who is depicted in them (including yourself): character, habits, beliefs, where he works, what is the goal in life, whether he is satisfied with himself, why he smiles or is sad, etc.

Instead of photographs, souvenirs or other memorabilia are also suitable. Examine them and remember those moments when you got them, why and from where.

Effect: Some people believe that after viewing old photographs, they should be burned, as they interfere with moving into the future. Burn or not - it's up to you. However, the very viewing of old pictures helps not only to immerse yourself in the past, but also to understand what does not suit you in the present.

Your own romance

Another great way to go back in time is to write about how things were. It doesn't matter how the text will look, because no one will read what you wrote, except for yourself. Just sit down and write about what happened, how you felt at that moment, what worried you, etc. In this way, you will be able to experience the emotions that you write about. Just do not need to describe in detail everything that happened according to the principle: “I took a cup - poured coffee - sat by the window ...” Write about the main thing - about what worried you then and does not let go even after so many years.

Effect: This method is called the method of therapy with the help of writing. It has been around for quite some time. Psychologists believe that describing past events is good for both mental and physical health. It's also a great way to look at yourself from the outside. Well, if you're lucky, then you get a real romance.

deja vu

If you can’t get out of your head what happened to you, you think that it was the best thing in your life, you want to repeat everything again and wonder how to return to the past - then live this happy day again!

To do this, allocate one free day in the present. In the smallest detail, remember those events that you regret, and bring them to life. Even if you don't have enough members, don't be discouraged. This is where your imagination comes in handy. Just imagine that they are nearby. On this day, do everything exactly the same as then. Live the day according to the scenario of "your golden age": go to that very place, cook those same pancakes and listen to the music that your most trembling memories are associated with.

Effect: as a rule, this method helps to calm down and stop regretting what has passed. However, if immediately after the experiment it did not become easier, then you should not abuse it. Otherwise, you run the risk of becoming a faded shadow of your former self, talking to yourself and dejectedly wandering through the "places of military glory."

One Actor Theater

Another way to go back in time is to act out situations. Imagine that you are on the stage of the theater, and the play that you have to perform is a moment in your life that you would like to return to. It is best to play such a performance in the company of friends. Believe me, this is much more effective than talking on the phone for hours, retelling what happened in the manner of “and I told him ...., and he answered me ..., and then we ...”.

However, not everyone will decide on this, many will simply be ashamed. Therefore, you can arrange a "one-man theater". Anyone can become the heroes of the past days: from plasticine men to soft toys.

Effect: having played out your own life situations, you can, albeit temporarily, but feel yourself in the past, see from the side what happened to you and appreciate all this more deeply.

In order to briefly return to the past, you can walk through memorable places: the area from your childhood where you have not been for a long time, the school, the first place of work, the church where you got married, the lake shore where you first kissed, etc. Even if something has changed there in the past, memory will helpfully throw up images from the past. And together with them you will remember again how you felt then.

Call your old friends with whom you have long lost contact. It can be your friends from school, first colleagues at work and others. Believe me, remembering happy moments from the past is much better in the company of participants in those events.

Smells also play a big role. They are great for bringing back lost memories. After all, a person associates a lot with a certain smell. Buy the perfume you had during your summer travels and be transported back to those sunny and happy days.

Music also evokes memories. You may feel embarrassed that you once loved to listen so much as a child, but re-listening to old addictions years later can help give the impression that you are back in the past.

Ever dreamed of going somewhere else? No, not at the usual speed with which we "boringly" go forward - second by second. Or:

• faster, so that you can climb far into the future, remaining at the same age;
• slower so that you can do much more than others in the same amount of time;
• in the opposite direction, so that you can go back to the era of the past and change it, perhaps changing the future or even the present?

It may sound downright sci-fi, but not everything on this list will be purely "fantastic": traveling through time is a scientifically possible process that is always with you. The only question is how you can manipulate it for your own purposes and control the movement in time.

When Einstein proposed special relativity in 1905, the realization that every massive object in the universe must travel through time was just one of its startling consequences. We also learned that photons - or other massless particles - cannot experience time in their reference frame at all: from the moment one of them is emitted to the moment it is absorbed, only massive observers (like us) can see the passage of time. From the position of a photon, everything is compressed into one point, and absorption and emission occur simultaneously in time, instantly.

But we have a lot. And anything that has mass is limited to always traveling at less than the speed of light in a vacuum. And not only that, but no matter how fast you are moving relative to something - whether you're accelerating or not, it doesn't matter - for you, light will always travel at the same constant speed: c, the speed of light in a vacuum. This powerful observation and awareness comes with a surprising consequence: if you are watching a person moving relative to you, their clock will run slower for you.

Imagine a “light clock,” or a clock that works on the principle of bouncing light back and forth in an up and down direction between two mirrors. The faster the person moves relative to you, the greater will be the speed of light in the transverse (along) direction, and not in the direction up and down, which means that the clock will go slower.

Similarly, your clock will move slower relative to them; they will see time flowing more slowly for you. When you get back together, one of you will be older and the other younger.

Such is the nature of Einstein's "twin paradox". Short answer: assuming that you started in one frame of reference (e.g., at rest on Earth), and you end up in the same frame later, the traveler will age less, because time will pass “slower” for him, and the one who stayed at home, will face the "normal" passage of time.

Therefore, if you want to accelerate in time, you have to accelerate to near-light speed, move at that pace for a while, and then return to your original position. You have to turn around a bit. Do this and you can travel days, months, decades, epochs, or billions of years into the future (depending on your gear, of course).

You could witness the evolution and destruction of mankind; the end of the earth and the sun; the dissociation of our galaxy; the heat death of the universe itself. As long as you have enough power in your spaceship, you can see as far into the future as you like.

But going back is another story. Simple special relativity, or the relationship between space and time at a basic level, was enough to take us into the future. But if we want to go back in time, back in time, we need general relativity, or the relationship between space-time and matter and energy. In this case, we regard space and time as an inseparable fabric, and matter and energy as something that distorts this fabric, causes changes in the fabric itself.

For our Universe as we know it, space-time is rather boring: it is almost perfectly flat, almost not curved, and in no way obsessed with itself.

But in some simulated universes - in some solutions to Einstein's general theory of relativity - it is possible to create a closed loop. If space loops on itself, you can move in one direction for a long, long time to get back to where you started.

Well, there are solutions not only with closed spacelike curves, but also with closed timelike curves. A closed time-like curve means that you can literally travel through time, live in certain conditions and return to the same point from which you left.

But this is a mathematical solution. Does this math describe our physical universe? It seems not quite. The curvatures and/or discontinuities we need for such a universe are wildly inconsistent with what we observe even in the vicinity of neutron stars and black holes: the most extreme examples of curvature in our universe.

Our universe may rotate on a global scale, but the observed limits of rotation are 100,000,000 times tighter than those that allow for the closed time-like curves we need. If you want to go forward in time, you need a relativistic DeLorean.

But back? It might be better if you can't travel back in time to prevent your father from marrying your mother.

In general, summing up, we can conclude that traveling back in time will always fascinate people at the level of the idea, but, most likely, will remain in the unattainable future (paradoxically). It's not mathematically impossible, but the universe is built on physics, which is a special subset of mathematical solutions. Based on what we have observed, our dreams of righting our wrongs by going back in time are likely to remain only in our fantasies.

Every person would dream of getting into the past for a moment and correcting some mistake in it, or moving into the future to find out how life turned out. Time travel is a favorite technique of many directors and science fiction writers. There are scientists who claim that this is possible in reality.

What is time travel?

This is the transition of a person or any objects from a given moment to a segment of the future or in the past. A little time has passed since the discovery of black holes, and if at first they seemed unreal to the discoverer Einstein himself, then later astrophysicists around the world began to study them. The philosophy of time travel excited the minds of many scientists - K. Thorne, M. Morris, Van Stokum, S. Hawking and others. They complement and refute each other's theories and cannot reach a consensus on this issue.

Time travel paradox

Against travel to the distant or near past, the following arguments are given:

1. Breakdown of the relationship between cause and effect.
2. "The paradox of the murdered grandfather." If, having committed, the grandson kills his own grandfather, then he will not be able to be born. And if his birth does not happen, then someone will kill his grandfather in the future?
3. The possibility of time travel remains a dream, as the time machine has yet to be created. If it were, then aliens from the future would be present today.

Time travel - esoteric

Time is considered as a process of movement of consciousness in three-dimensional space. The human senses are capable of perceiving only four-dimensional space, but it is part of multidimensionality, where there is no connection between cause and effect. The generally accepted concepts of distance, time and mass do not work there. In the Field of Events the moments of the past, present and future are mixed and any material, astral and metal masses undergo changes instantly.

Through the astral, time travel is real. Consciousness can go beyond the physical shell, moving and overcoming the laws of the universe. S. Grof suggests that a person can be guided by his consciousness and mentally travel through space and time. At the same time, violating the laws of physics and acting as a kind of natural time machine.

Time travel - fact or fiction?

In the "Newtonian universe" with its uniform and rectilinear time, this would be unrealistic, but Einstein proved that time is different in different places in the universe, and can accelerate and decelerate. When time reaches a speed close to the speed of light, it slows down. From a scientific point of view, time travel is real, but only into the future. Moreover, there are several ways to move.

Is time travel possible?

If you follow the theory of relativity, then moving at a speed close to the speed of light, you can bypass the natural flow of time and move into the future. It accelerates significantly compared to someone who does not travel and remains motionless. This confirms the "twin paradox". It consists in the difference in the speed of the flow of time for the brother who went on a space flight and the brother who remained on Earth. The movement in time will consist in the fact that the traveler's clock will lag behind.

According to scientists, black holes act as time tunnels and being near their event horizon, that is, in an area of ​​extremely high gravity, makes it possible to reach the speed of light and move in time. But there is a simpler and easier way - to stop the metabolism of the body, that is, to conserve at sub-zero temperatures, and subsequently wake up and recover.

Time travel - how to do it?

1. Through wormholes. "Wormholes", as they are also called, are some tunnels that are part of the General Theory of Relativity. They link two places in space. They are a consequence of the "work" of exotic matter, which has a negative energy density. It is able to twist space and time and create the prerequisites for the emergence of these very wormholes, a warp drive that allows you to travel at a speed exceeding the speed of light, and.

2. Through the Tipler cylinder. This is a hypothetical object that is the result of solving the Einstein equation. If this cylinder has an infinite length, then by rotating around it, it is possible to move in time and space - into the past. Later, the scientist S. Hawking suggested that this would require exotic matter.

3. Methods of time travel include traveling with the help of gigantic cosmic strings formed during the Big Bang. If they rush very close to each other, then the spatial and temporal indicators are distorted. As a result, a nearby spaceship can fall into segments of the past or future.

time travel technique

You can travel physically or astrally. The first way to move is available to the elite, who own the knowledge of druids, ferrilths, etc. With the help of ancient spells that invoke the Mists of Kalen, which modern scientists have called the "Cloud of Time", you can get into the moments of the past or future, but this requires a lot of training, tempering the spirit and body, do not disturb the harmony with nature.

Moving in time with the help of magic is subject to clairvoyants, psychics. They use the method of astral travel - viewing by a beam. Through special techniques and rituals, they move into the past in a dream, changing events in the way they need. When they wake up, they find real changes in the present that are the result of the travel time. This can be achieved if you develop imaginative thinking, be able to influence objects with the power of thought, for example, move objects, heal people, accelerate the growth of plants, etc.

Evidence of time travel

Unfortunately, there is no real evidence of such movements yet, and all the stories told by contemporaries or those who lived earlier cannot be confirmed. The only thing that is somehow related to the topic is the Large Hadron Collider. There is an opinion that there, at a depth of 175 meters underground, a time machine is being built. In the "ring" of the accelerator, a speed is generated that is close to the speed of light, and this creates the preconditions for the formation of black holes and movement to the moments of the past or future.

With the discovery of the Higgs boson in 2012, real time travel is no longer a fairy tale. In the future, it is planned to isolate such a particle as the Higgs singlet, which will be able to neutralize the links between cause and effect and move in any direction - both in the moments of the past and the future. This is the task of the LHC, and it is not opposed to the laws of physics.

Time travel facts

There are many photographs, historical notes and other data confirming the reality of such episodes. Cases of time travel include one story evidenced by a 1955 calendar found on an airstrip in Caracas, Venezuela in 1992. Eyewitnesses of those events claim that a DC-4 plane then landed at the airport, which disappeared in 1955. When the pilot of the ill-fated flight heard on the radio what year they were in, he decided to take off, leaving a small calendar "as a keepsake".

Many of the photographs that are considered evidence of temporary movements have long been debunked. Some of the most widely known photographs actually have nothing to do with the fact of time travel. We will look at a photo that shows a man dressed, supposedly not in the fashion of that time (1941), in stylish sunglasses and a camera in his hands, reminiscent of the famous Polaroid.

Actually:

The best movies about time travel

At one time, such films as Kin-Dza-Dza, We are from the Future, and The Butterfly Effect produced a boom in domestic cinematography. Time Travel Syndrome is the genetic disorder of the protagonist in The Time Traveler's Wife. Of the foreign paintings, one can note "Groundhog Day", "Harry Potter and the Prisoner of Azkaban". Time travel films include Lost, The Terminator, Kate & Leo.

The idea that you can get into the past or the future gave rise to a whole genre of chrono-fiction, and it seems that all possible paradoxes and pitfalls have long been known to us. Now we read and watch such works not for the sake of looking at other eras, but for the confusion that inevitably arises when trying to disrupt the flow of time. What tricks over time underlie all chrono-operas and what plots can be assembled from these building blocks? Let's figure it out.

Wake up when the future comes

The easiest task for a time traveler is to get into the future. In such stories, you don’t even have to think about exactly how the time stream works: since the future does not affect our time, the plot will hardly differ from a flight to another planet or to a fairy-tale world. In a sense, we are all already traveling through time - at a rate of one second per second. The only question is how to increase the speed.

In the XVIII-XIX centuries, dreams were considered one of the fantastic phenomena. A lethargic dream was adapted for traveling into the future: Rip van Winkle (the hero of the story of the same name by Washington Irving) slept for twenty years and found himself in a world where all his loved ones had already died, and he himself had been forgotten. Such a plot is akin to the Irish myths about the people of the hills, who also knew how to manipulate time: the one who spent one night under the hill returned after a hundred years.

This "hit" method never gets old

With the help of dreams, the writers of that time explained any fantastic assumptions. If the narrator himself admits that he has dreamed of outlandish worlds, what is the demand from him? Louis-Sebastien de Mercier resorted to such a trick when describing a "dream" about a utopian society ("Year 2440") - and this is already a full-fledged time travel!

However, if the journey to the future needs to be plausibly justified, it is also not difficult to do this without contradicting science. The cryo-freezing method famed by Futurama could theoretically work - which is why many transhumanists now try to preserve their bodies after death in the hope that future medical technologies will allow them to be revived. True, in fact, this is just Van Winkle’s dream adapted to modern times, so it’s hard to say whether this is considered a “real” journey.

faster than light

For those who want to seriously play with time and delve into the wilds of physics, travel at the speed of light is better suited.

Einstein's theory of relativity makes it possible to compress and stretch time at near-light speeds, which is used in science fiction with pleasure. The famous “twin paradox” says that if you rush through space at near-light speed for a long time, a couple of centuries will pass on Earth in a year or two of such flights.

Moreover, the mathematician Gödel proposed a solution for Einstein's equations in which time loops can appear in the universe - something like portals between different times. It was this model that was used in the film "", first showing the difference in the flow of time near the horizon of a black hole, and then throwing a bridge into the past with the help of a "wormhole".

Einstein and Gödel already had all the plot twists that the authors of chrono-operas are now thinking up (filmed on iPhone 5)

Is it possible to get into the past in this way? Scientists strongly doubt this, but their doubts do not interfere with science fiction writers. Suffice it to say that only mere mortals are forbidden to exceed the speed of light. And Superman can make a couple of revolutions around the Earth and go back in time to prevent the death of Lois Lane. Why is there the speed of light - even sleep can work in the opposite direction! And at Mark Twain, the Yankees received a crowbar on the head and at the court of King Arthur.

Of course, flying into the past is more interesting - just because it is inextricably linked with the present. If the author introduces a time machine into a story, he usually wants to at least confuse the reader with time paradoxes. But most often the main theme in such stories is the struggle with predestination. Is it possible to change one's own destiny if it is already known?

Cause or effect?

The answer to the question of predestination - like the very concept of time travel - depends on how time works in a particular fantasy world.

The laws of physics are not a decree for terminators

In reality, the main problem with traveling into the past is not the speed of light. Sending anything, even a message, back in time would violate a fundamental law of nature: the principle of causality. Even the most seedy prophecy is already, in a sense, time travel! All scientific principles known to us are based on the fact that first an event occurs, and then it has consequences. If the effect is ahead of the cause, it breaks the laws of physics.

To “fix” the laws, we need to figure out how the world reacts to such an anomaly. This is where science fiction writers give free rein to the imagination.

If the genre of the film is a comedy, then there is usually no risk of “breaking” time: all the actions of the characters are too insignificant to affect the future, and the main task is to get out of their own problems

It can be said that time is a single and indivisible stream: between the past and the future, a thread is stretched, as it were, along which you can move.

It is in this picture of the world that the most famous loops and paradoxes arise: for example, if you kill your grandfather in the past, you can disappear from the universe. There are paradoxes due to the fact that this concept (philosophers call it "B-theory") states that the past, present and future are as real and unchanging as the three dimensions we are used to. The future is still unknown - but sooner or later we will see the only version of events that must happen.

Such fatalism gives rise to the most ironic stories about time travelers. When an alien from the future tries to fix the events of the past, he suddenly discovers that he himself caused them - moreover, it has always been so. Time in such worlds is not rewritten - a causal loop simply appears in it, and any attempts to change something only reinforce the original version. This paradox was one of the first to be described in detail in the short story "On His Own Footsteps" (1941), where it turns out that the hero was carrying out a task received from himself.

The heroes of the gloomy series "Darkness" from Netflix go back in time to investigate a crime, but involuntarily they are forced to do the things that lead to this crime.

It happens even worse: in more “flexible” worlds, a careless act of a traveler can lead to a “butterfly effect”. Intervention in the past rewrites the entire time stream at once - and the world not only changes, but completely forgets that it has changed. Usually only the traveler himself remembers that everything was different before. In the trilogy "", even Doc Brown could not follow Marty's jumps - but he at least relied on the words of a friend when he described the changes, and usually no one believes such stories.

In general, single-threaded time is a confusing and hopeless thing. Many authors decide not to limit themselves and resort to the help of parallel worlds.

The plot, in which the hero finds himself in a world where someone canceled his birth, came from the Christmas film It's a Wonderful Life (1946)

The bifurcation of time

This concept not only allows you to get rid of contradictions, but also captures the imagination. In such a world, everything is possible: every second it is divided into an infinite number of reflections similar to each other, differing in a couple of little things. The time traveler does not really change anything, but only jumps between different facets of the multiverse. Such a plot is very popular in TV shows: in almost any show there is a series where the characters find themselves in an alternative future and try to return everything to normal. On an endless field, you can frolic endlessly - and there are no paradoxes!

Now in chrono-fiction, the model with parallel worlds is most often used (frame from Star Trek)

But the most interesting thing begins when the authors abandon the "B-theory" and decide that there is no fixed future. Maybe uncertainty and uncertainty is the normal state of time? In such a picture of the world, specific events occur only on those segments on which there are observers, and the rest of the moments are just a probability.

An excellent example of such "quantum time" was shown by Stephen King in "". When the Gunslinger unwittingly created a time paradox, he almost went insane because he remembered two lines of events at the same time: in one he traveled alone, in the other with a companion. If the hero came across evidence reminiscent of past events, the memories of these points formed into one consistent version, but the gaps were like in a fog.

The quantum approach has recently become popular, partly due to the development of quantum physics, and partly because it allows us to show even more intricate and dramatic paradoxes.

Marty McFly almost erased himself from reality by preventing his parents from meeting. I had to fix it right now!

Take, for example, the film Loop of Time (2012): as soon as the young incarnation of the hero performed some actions, an alien from the future immediately remembered them - and before that, fog reigned in his memory. Therefore, he tried not to interfere once again in his past - for example, he did not show his young self a photograph of his future wife, so as not to disrupt their first unexpected meeting.

The "quantum" approach is also visible in "": since the Doctor warns satellites about special "fixed points" - events that cannot be changed or bypassed - it means that the rest of the fabric of time is mobile and plastic.

However, even the probabilistic future pales in comparison with worlds where Time has its own will - or it is guarded by creatures that lie in wait for travelers. In such a universe, laws can work in any way - and it's good if you can negotiate with the guards! The most striking example is the langoliers, who, after every midnight, eat yesterday along with everyone who was unfortunate enough to be there.

How the time machine works

Against the background of such a variety of universes, the technique of time travel itself is a secondary issue. Since the time of the time machine, they have not changed: you can come up with a new principle of operation, but this is unlikely to affect the plot, and from the outside, the journey will look about the same.

Wells' time machine in the 1960 film adaptation. That's where the steampunk is!

Most often, the principle of operation is not explained at all: a person climbs into a booth, admires the buzz and special effects, and then gets out at a different time. This method can be called an instant jump: the fabric of time seems to be pierced at one point. Often, for such a jump, you first need to accelerate - pick up speed in ordinary space, and the technique will already translate this impulse into a jump in time. So did the heroine of the anime "The Girl Who Leapt Through Time", and Doc Brown on the famous DeLorean from the "Back to the Future" trilogy. Apparently, the fabric of time is one of those obstacles that storm with a running start!

DeLorean DMC-12 is a rare time machine that deserves to be called a machine (JMortonPhoto.com & OtoGodfrey.com)

But sometimes the opposite happens: if we consider time as the fourth dimension, in the three ordinary dimensions the traveler must remain in place. The time machine will rush him along the time axis, and in the past or future he will appear at exactly the same point. The main thing is that they do not have time to build anything there - the consequences can be very unpleasant! True, such a model does not take into account the rotation of the Earth - in fact, there are no fixed points - but in the extreme case, everything can be attributed to magic. This is how it worked: each revolution of the magic clock corresponded to one hour, but the travelers did not move from their place.

The most severe of all such "static" travels were treated in the film "Detonator" (2004): there the time machine squandered exactly one minute for a minute. To get to yesterday, you had to sit in an iron box for 24 hours!

Sometimes a model with more than three dimensions is interpreted even more cunningly. Let us recall Gödel's theory, according to which loops and tunnels can be laid between different times. If it is correct, you can try to get through additional dimensions to another time - which the hero "" took advantage of.

In earlier fiction, a "time vortex" worked on a similar principle: a kind of subspace where you can get into it on purpose (on Doctor Who's TARDIS) or by accident, as happened with the crew of the destroyer in the movie The Philadelphia Experiment (1984). Flying through the funnel is usually accompanied by dizzying special effects, and leaving the ship is not recommended, so as not to get lost in time forever. But in fact, this is still the same ordinary time machine, delivering passengers from one year to another.

For some reason, lightning always strikes inside temporary funnels and sometimes credits fly

If the authors do not want to delve into the jungle of theories, the anomaly of time can exist on its own, without any adaptations. It is enough to enter the wrong door, and now the hero is already in the distant past. Is it a tunnel, a pinhole or magic - who will take it apart? The main question is how to get back!

What can't be done

However, usually science fiction still works according to the rules, albeit fictional, - therefore, restrictions are often invented for time travel. For example, one can say, following modern physicists, that it is still impossible to move bodies faster than the speed of light (that is, into the past). But in some theories there is a particle called "tachyon", which is not affected by this restriction, because it has no mass ... Maybe consciousness or information can still be sent to the past?

When Makoto Shinkai takes on time travel, he still comes up with a touching story of friendship and love ("Your Name")

In reality, most likely, it will not work to cheat like that - all because of the same principle of causality, which does not care about the type of particles. But in science fiction, the "informational" approach seems more plausible - and even more original. It allows the hero, for example, to be in his own young body or go on a journey through other people's minds, as happened with the hero of the Quantum Leap series. And in the Steins;Gate anime, at first they only knew how to send SMS to the past - try to change the course of history with such restrictions! But plots only benefit from limitations: the more difficult the task, the more interesting it is to watch how it is solved.

A hybrid phone with a microwave to connect with the past (Steins;Gate)

Sometimes additional conditions are imposed on ordinary, physical time travel. For example, often a time machine cannot send anyone back in time before the moment when it was invented. And in the anime The Melancholy of Haruhi Suzumiya, time travelers forgot how to go into the past beyond a certain date, because on that day a catastrophe occurred that damaged the fabric of time.

And here the most interesting begins. Plain jumps into the past and even time paradoxes are just the tip of the chrono-fiction iceberg. If time can be changed or even corrupted, what else can be done with it?

Paradox upon paradox

We love time travel for its confusion. Even a simple leap into the past generates twists like the butterfly effect and the grandpa paradox, depending on how time works. But using this technique, you can build much more complex combinations: for example, jump into the past not once, but several times in a row. This creates a stable time loop, or Groundhog Day.

Do you have deja vu?
"Haven't you already asked me about this?"

You can loop for one day or several - the main thing is that everything ends with a “reset” of all changes and a journey back to the past. If we are dealing with linear and unchanging time, such loops themselves arise from causal paradoxes: the hero receives a note, goes to the past, writes this note, sends it to himself ... If time is rewritten every time or creates parallel worlds, it turns out to be an ideal trap : a person experiences the same events over and over again, but any changes still end up resetting to the original position.

Most often, such plots are devoted to attempts to unravel the cause of the time loop and break out of it. Sometimes the loops are tied to the emotions or tragic fates of the characters - this element is especially loved in anime ("Magical Girl Madoka", "The Melancholy of Haruhi Suzumiya", "When Cicadas Cry").

But "groundhog days" have a definite plus: they allow, due to endless attempts, sooner or later to succeed in any endeavor. No wonder Doctor Who, having fallen into such a trap, recalled the legend of a bird that for many thousands of years grinded away a stone rock crumbly, and his colleague managed to bring an extraterrestrial demon to white heat with his “negotiations”! In this case, you can destroy the loop not with a heroic deed or insight, but with ordinary perseverance - and along the way, learn a couple of useful skills, as happened with the hero of Groundhog Day.

In "Edge of Tomorrow" aliens use time loops as a weapon - to calculate the perfect battle tactics

Another way to build a more complex structure from ordinary jumps is to synchronize two segments of time. In the movie "X-Men: Days of Future Past" and in "Time Scout", the time portal could only be opened at a fixed distance. Roughly speaking, at noon on Sunday, you can move to noon on Saturday, and an hour later - already at one in the afternoon. With such a restriction, an element appears in the story about a journey into the past, which, it would seem, cannot be there - time pressure! Yes, you can go back and try to fix something, but in the future, time goes on as usual - and the hero, for example, may be late to return.

To complicate the traveler's life, you can make time jumps random - take away control over what is happening from him. In the TV series Lost, such a disaster happened to Desmond, who interacted too closely with a temporary anomaly. But back in the 1980s, the series Quantum Leap was built on the same idea. The hero constantly found himself in different bodies and eras, but did not know how long he would last in this time - and even more so he could not return "home".

We twist the time

The heroine of the game Life is Strange faces a difficult choice: to undo all the changes that she made to the fabric of time to save her friend, or to destroy the whole city

The second technique with which to diversify time travel is to change the speed. If you can skip a couple of years to find yourself in the past or the future, why not, for example, put time on pause?

As Wells showed in the story "The Newest Accelerator", even slowing down time for everyone except yourself is a very powerful tool, and even if you stop it completely, you can secretly penetrate somewhere or win a duel - and completely unnoticed by the enemy. And in the web series "Worm" one superhero was able to "freeze" objects in time. With the help of this simple technique, it was possible, for example, to derail a train by placing an ordinary sheet of paper in its path - after all, an object frozen in time cannot change or move!

Enemies frozen in time are very convenient. In the Quantum Break shooter, you can see this for yourself

The speed can also be changed to a negative one, and then you get the counterwinds familiar to readers of the Strugatskys - people living "in the opposite direction." This is possible only in worlds where the "B-theory" works: the entire time axis is already predetermined, the only question is in what order we perceive it. To further confuse the plot, you can launch two time travelers in different directions. This is what happened to the Doctor and River Song in the Doctor Who series: they jumped back and forth through the eras, but the first (for the Doctor) their meeting for River was the last, the second - the penultimate one, and so on. To avoid paradoxes, the heroine had to be careful not to accidentally spoil his future to the Doctor. Then, however, the order of their meetings turned into a complete leapfrog, but the heroes of Doctor Who are no strangers to this!

Worlds with "static" time give rise not only to counter-motors: creatures often appear in science fiction who simultaneously see all points of their life path. Thanks to this, the Trafalmadorians from Slaughterhouse Five treat any misadventures with philosophical humility: for them, even death is just one of the many details of the overall picture. Doctor Manhattan from "" because of such an inhuman perception of time, moved away from people and fell into fatalism. Abraxas from The Endless Journey regularly messed up grammar, trying to figure out which event had already happened and which would happen tomorrow. And the aliens from Ted Chan's story "The Story of Your Life" had a special language: everyone who learned it also began to see the past, present and future at the same time.

The movie "Arrival", based on "The Story of Your Life", begins with flashbacks ... Or not?

However, if countermeasures or Trafalmadorians really travel in time, then with the abilities of Quicksilver or the Flash, everything is not so obvious. After all, in fact, it is they who are accelerating relative to everyone else - how can we assume that the whole world around is actually slowing down?

Physicists will notice that the theory of relativity is called that way for a reason. It is possible to speed up the world and slow down the observer - this is the same thing, the only question is what to take as a starting point. And biologists will say that there is no fantasy here, because time is a subjective concept. An ordinary fly also sees the world "in slow-mo" - so quickly its brain processes signals. But you can not limit yourself to the fly or the Flash, because in some chrono-operas there are parallel worlds. Who prevents them from letting time pass at different speeds - or even in different directions?

A well-known example of such a technique is the Chronicles of Narnia, where there is no formal time travel. But time in Narnia flows much faster than on Earth, so the same heroes fall into different eras - and observe the history of a fairy-tale country from its creation to its fall. But in Homestuck, which is perhaps the most confusing story about time travel and parallel worlds, two worlds were launched in different directions - and the contacts between these universes had the same confusion that the Doctor had with River Song.

If clock faces haven't been invented yet, the hourglass will do too (Prince of Persia)

kill time

Any of these devices can be used to write a story that would make even Wells' head crack. But modern authors are happy to use the entire palette at once, tying time loops and parallel worlds into a ball. Paradoxes with this approach accumulate in batches. Even with one jump into the past, a traveler can inadvertently kill his grandfather and disappear from reality - or even become his own father. Perhaps, he mocked the “paradox of causality” best of all in the story “All you zombies”, where the hero turns out to be both his own father and mother.

Based on the story "All You Zombies", the film "Time Patrol" (2014) was made. Almost all of his characters are the same person.

Of course, paradoxes must be somehow resolved - therefore, in worlds with linear time, it is often restored by itself, by the will of fate. For example, almost all first-time travelers decide to kill Hitler first. In worlds where time can be rewritten, he will die (but according to the law of meanness, the resulting world will be even worse). Asprin's attempt in "Time Scouts" will fail: either the gun will jam, or something else will happen.

And in worlds where fatalism is not respected, you have to monitor the safety of the past yourself: for such cases, they create a special “time police” that catches travelers before they do trouble. In the film Looper, the role of such police was taken over by the mafia: the past for them is too valuable a resource to be allowed to spoil it.

If there is no fate, no chronopolice, travelers run the risk of simply breaking time. At best, it will turn out like in Jasper Fforde’s “Thursday Nonetoth” cycle, where the time police played to the point that they accidentally canceled the very invention of time travel. At worst, the fabric of reality will collapse.

As Doctor Who has repeatedly shown, time is a fragile thing: a single explosion can cause cracks in the universe across all eras, and an attempt to rewrite a “fixed point” can collapse both the past and the future. In Homestuck, after such an incident, the world had to be recreated, and in all eras they mixed together, which is why the events of the books can no longer be combined into a consistent chronology ... Well, in the manga Tsubasa: Reservoir Chronicle, the son of his own clone, erased from reality, had to replace himself with a new person, so that in the events that have already happened there was at least some character.

Some heroes of the Tsubasa multiverse exist in at least three incarnations and come from other works of the same studio

Fans' favorite pastime is to draw for the most intricate pieces of chronology

Sound crazy? But for such madness, we love time travel - they push the boundaries of logic. Sometime, it must be, even a simple leap into the past could drive an unaccustomed reader crazy. Now, chrono-fiction truly shines at long distances, when the authors have room to turn around, and time loops and paradoxes are layered on top of each other, giving rise to the most unimaginable combinations.

Alas, it often happens that the construction develops under its own weight: either there are too many jumps in time to make sense to follow them, or the authors change the rules of the universe on the go. How many times has Skynet rewritten the past? And who can say now how time works in Doctor Who?

On the other hand, if chrono-fiction, with all its paradoxes, turns out to be harmonious and internally consistent, it is remembered for a long time. This is what bribes BioShock Infinite, Tsubasa: Reservoir Chronicle or Homestuck. The more complex and intricate the plot, the stronger the impression left on those who got to the end and managed to look at the whole canvas at once.

* * *

Time travel, parallel worlds and the rewriting of reality are inextricably linked, which is why almost no science fiction work can do without them now - whether it's fantasy like "Game of Thrones" or science fiction exploration of the latest theories of physics, like in "Interstellar". Few plots give the same scope for imagination - after all, in a story where any event can be canceled or repeated several times, everything is possible. At the same time, the elements that make up all these stories are quite simple.

It seems that over the past hundred years, the authors have done everything that is possible with time: they let them go forward, backward, in a circle, in one stream and in several ... Therefore, the best of these stories, as in all genres, are based on characters: on the one who came again from ancient Greek tragedies to the theme of the struggle with fate, on attempts to correct one's own mistakes and on the difficult choice between different branches of events. But no matter how the chronology jumps, history will still develop in only one direction - in the one that is most interesting to viewers and readers.

From the era of Queen Victoria to the present day, the concept of time travel has fascinated the minds of fantasy lovers. What is it like to travel through the fourth dimension? The most interesting thing is that time travel does not require a time machine or something like a "wormhole".

You must have noticed that we are constantly moving in time. We move through it. At a basic level, time is the rate at which the universe is changing, and whether we like it or not, we are subject to constant change. We get older, the planets move around the sun, things are destroyed.

We measure the passage of time in seconds, minutes, hours and years, but this does not mean at all that time flows at a constant speed. Like water in a river, time passes differently in different places. In short, time is relative.

But what causes temporary fluctuations on the way from the cradle to the grave? It all comes down to the relationship between time and space. A person is able to perceive in three dimensions - length, width and depth. Time also complements this party as the most important fourth dimension. Time does not exist without space, space does not exist without time. And this couple is connected in a space-time continuum. Any event that occurs in the universe must involve space and time.

In this article, we will look at the most real and everyday possibilities. travel through time in our universe, as well as less accessible, but no less possible paths through the fourth dimension.

The train is a real time machine.

If you want to live a couple of years a little faster than anyone else, you need to master space-time. Global positioning satellites do this every day, three billionths of a second ahead of the natural course of time. In orbit, time passes faster because the satellites are far from the mass of the Earth. And on the surface, the mass of the planet drags time with it and slows it down on a relatively small scale.

This effect is called gravitational time dilation. According to Einstein's general theory of relativity, gravity bends spacetime, and astronomers use this consequence when they study light passing near massive objects (we wrote about gravitational lensing here and here).

But what does this have to do with time? Remember - any event that occurs in the universe involves both space and time. Gravity not only pulls together space, but also time.

Being in the flow of time, you will hardly notice a change in its course. But rather massive objects - like supermassive black hole alpha Sagittarius, located in the center of our galaxy - will seriously distort the fabric of time. The mass of its singularity point is 4 million suns. This mass slows down time by half. Five years orbiting a black hole (without falling into it) is ten years on Earth.

The speed of movement also plays an important role in the speed of our time. The closer you get to the maximum speed of movement - the speed of light - the slower time passes. The clocks on a fast moving train will be one billionth of a second late at the end of the journey. If the train reaches a speed of 99.999% of the speed of light, in one year in a train car, you can be transported two hundred and twenty-three years into the future.

In fact, hypothetical journeys into the future in the future are built on this idea, sorry for the tautology. But what about the past? Is it possible to turn back time?

Time travel to the past

The stars are relics of the past.

We found that travel to the future happens all the time. Scientists have proven this experimentally, and this idea is at the heart of Einstein's theory of relativity. It is quite possible to move into the future, the only question is “how fast”? As for traveling into the past, the answer to this question is to look into the night sky.

The Milky Way galaxy is about 100,000 years wide, which means light from distant stars has to travel thousands and thousands of years before it reaches Earth. Catch this light, and in fact, you just look into the past. When astronomers measure cosmic microwave radiation, they look into space as it was 10 billion years ago. But is this all?

There is nothing in Einstein's theory of relativity that would rule out the possibility of traveling to the past, but the very possibility of a button that could take you back to yesterday violates the law of causality or cause and effect. When something happens in the universe, the event creates a new endless chain of events. The cause is always born before the effect. Just imagine a world where the victim would die before a bullet hits her in the head. This is a violation of reality, but despite this, many scientists do not exclude the possibility of traveling into the past.

For example, it is believed that going faster than the speed of light can send people back into the past. If time slows down as an object gets closer to the speed of light, could breaking that barrier turn back time? Of course, when approaching the speed of light, the relativistic mass of the object also increases, that is, it approaches infinity. It seems impossible to accelerate an infinite mass. Theoretically, warp speed, that is, the deformation of speed as such, can deceive the universal law, but even this will require an enormous expenditure of energy.

What if time travel to the future and past depends less on our basic knowledge of the cosmos than on existing cosmic phenomena? Let's take a look at a black hole.

Black holes and Kerr rings

What is on the other side of a black hole?

Loop around a black hole long enough and gravitational time dilation will send you into the future. But what if you landed right in the mouth of this space monster? About what will happen when diving into a black hole, we have already wrote, but did not mention such an exotic variety of black holes as Kerr ring. Or the Kerr black hole.

In 1963, New Zealand mathematician Roy Kerr proposed the first realistic theory of a rotating black hole. The concept includes neutron stars - massive collapsing stars the size of St. Petersburg, for example, but with the mass of the Earth's Sun. We have included neutron holes in the list of the most mysterious objects in the Universe, calling them magnetars. Kerr theorized that if a dying star collapsed into a spinning ring of neutron stars, their centrifugal force would prevent them from becoming a singularity. And since a black hole would not have a singularity point, Kerr figured it would be perfectly possible to get in without fear of being torn apart by gravity at the center.

If Kerr black holes exist, we could pass through them and exit into a white hole. It's like the exhaust pipe of a black hole. Instead of sucking in everything that is possible, the white hole will, on the contrary, throw out everything that is possible. Perhaps even in another time or another universe.

Kerr black holes remain a theory, but if they do exist, they are portals of sorts, offering a one-way trip to the future or past. And although an extremely advanced civilization could develop in this way and travel through time, no one knows when the “wild” Kerr black hole will disappear.

Wormholes (wormholes)

Curvature of space-time.

Theoretical Kerr rings are not the only possible shortcuts to the past or future. Sci-fi films, from Star Trek to Donnie Darko, often deal with the theoretical Einstein-Rosen Bridge. These bridges are better known to you as wormholes.

Einstein's general theory of relativity allows for the existence of wormholes, since the theory of the great physicist is based on the curvature of space-time under the influence of mass. To understand this curvature, imagine the fabric of space-time as a white sheet and fold it in half. The area of ​​the sheet will remain the same, it will not deform, but the distance between the two points of contact will obviously be less than when the sheet was lying on a flat surface.

In this simplified example, space is depicted as a two-dimensional plane, and not four-dimensional, which it actually is (recall the fourth dimension - time). Hypothetical wormholes work similarly.

Let's move to space. The concentration of mass in two different parts of the universe could create a kind of tunnel in space-time. In theory, this tunnel would connect two different segments of the space-time continuum with each other. Of course, it is quite possible that some physical or quantum properties prevent such wormholes from arising on their own. Well, or they are born and immediately die, being unstable.

According to Stephen Hawking, whose ten most interesting facts from his life we ​​recently presented to you, wormholes can exist in quantum foam - the smallest medium in the universe. Tiny tunnels are constantly being born and broken, linking separate places and times for short moments.

Wormholes may be too small and short-lived to move a person, but what if one day we will be able to find them, hold them, stabilize and increase them? Provided, as Hawking points out, that you are prepared for feedback. If we wanted to artificially stabilize the space-time tunnel, the radiation from our actions could destroy it, just as the backlash of a sound could damage a speaker.

We're trying to squeeze through black holes and wormholes, but is there another way to travel through time using a theoretical cosmic phenomenon? With these thoughts, we turn to physicist J. Richard Gott, who outlined the idea of ​​a cosmic string in 1991. As the name suggests, these are hypothetical objects that may have formed early in the development of the universe.

These strings permeate the entire universe, being thinner than an atom and being under strong pressure. Naturally, it follows from this that they give gravitational pull to everything that passes near them, which means that objects attached to the cosmic string can travel through time at incredible speed. Pulling two cosmic strings closer together, or placing one of them near a black hole, creates what's called a closed time-like curve.

Using the gravity produced by two cosmic strings (or a string and a black hole), a spacecraft could theoretically send itself into the past. To do this, one would need to make a loop around the cosmic strings.

By the way, quantum strings are very hotly debated right now. Gott stated that to travel back in time, one must make a loop around a string containing half the mass-energy of an entire galaxy. In other words, half of the atoms in the galaxy would have to be used as fuel for your time machine. Well, as everyone is well aware, it is impossible to go back in time before the machine itself was created.

In addition, there are time paradoxes.

The paradoxes of time travel

He killed his grandfather - he killed himself.

As we have already said, the idea of ​​traveling into the past is slightly clouded by the second part of the law of causality. Cause precedes effect, at least in our universe, which means it can spoil even the most well-thought-out plans for time travel.

To begin with, imagine that if you travel 200 years into the past, you will appear long before you were born. Think about it for a second. For some time the effect (you) will exist before the cause (your birth).

To better understand what we are dealing with, consider the well-known grandfather paradox. You are an assassin who travels through time, your target is your own grandfather. You sneak through a nearby wormhole and approach a living 18-year-old version of your father's father. You raise your gun, but what happens when you pull the trigger?

Think. You are not yet born. Even your father hasn't been born yet. If you kill your grandfather, he will not have a son. This son will never give birth to you, and you will not be able to travel back in time on a bloody task. And your absence will not pull the trigger, thereby denying the entire chain of events. We call this a loop of incompatible causes.

On the other hand, one can consider the idea of ​​a serial causal loop. Although it makes you think, it theoretically eliminates time paradoxes. According to physicist Paul Davis, such a loop looks like this: a mathematics professor goes into the future and steals the most complex mathematical theorem. After that, he gives it to the most brilliant student. After that, the promising student grows and learns in order to one day become a man whose professor once stole a theorem.

In addition, there is another model of time travel that involves skewed probability when approaching the possibility of a paradoxical event. What does this mean? Let's get back into the shoes of your girl's killer. This time travel model could virtually kill your grandfather. You can pull the trigger, but the gun won't fire. The bird will chirp at the right moment, or something else will happen: the quantum fluctuation will not allow the paradoxical situation to take place.

And finally, the most interesting. The future or past that you are going to may simply exist in a parallel universe. Think of it as a paradox of separation. You can destroy anything you want, but it will not affect your home world in any way. You will kill your grandfather, but you will not disappear - perhaps another “you” in a parallel world will disappear, or the scenario will follow the paradox schemes we have already considered. However, it is quite possible that time travel will be disposable and you will never be able to return home.

Completely confused? Welcome to the world of time travel.