How to travel in time: all the ways and paradoxes. Time Paradox Time Paradox You Can't Kill Yourself

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 funnel” 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, 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 sci-fi 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 over 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.

I doubt that any phenomenon, real or imagined, has given rise to more puzzling, tortuous, and impossibly fruitless philosophies than time travel. (Some possible competitors, such as determinism and free will, are somehow related to the argument against time travel.) In his classic Introduction to Philosophical Analysis, John Hospers asks: “Is it logically possible to go back back in time, say 3000 BC. e., and help the Egyptians build the pyramids? We need to remain vigilant on this matter."

It's just as easy to say - we usually use the same words when we talk about time and space - as easy to imagine. "Besides, H. G. Wells presented it in The Time Machine (1895), and every reader presents it with him." (Hospers misremembers The Time Machine: "A man from 1900 pulls the lever of the machine and suddenly finds himself in the middle of the world several centuries earlier.") To be honest, Hospers was somewhat of an eccentric who was awarded an unusual honor for a philosopher: to receive for one electoral vote for the President of the United States. But his book, first published in 1953, remained the standard for 40 years, undergoing 4 reprints.

IMPOSSIBLE MACHINE: In H.G. Wells' 1895 novel The Time Machine, an inventor travels 800,000 years into the future. A still from the 1960 film adaptation. Hulton Archive/Getty Images

To this rhetorical question, he emphatically answers "no." Wells-style time travel is not only impossible, but logically impossible. This is a contradiction in terms. In an argument that stretches four long pages, Jospers proves this by the power of persuasion.

How can we be in the 20th century A.D. e. and in the 30th century BC. e. at the same time? There is already one contradiction in this ... From the point of view of logic, No possibility of being in different ages at the same time. You can (and Jospers can't) stop and consider if there's a catch in this emphatically general phrase: "at the same time." The present and the past are different tenses, therefore they are neither the same time, nor V the same time. Q.E.D. It was surprisingly easy.

However, the essence of time travel fiction is that lucky time travelers have their own watches. Their time continues to advance as they move to a different time for the universe as a whole. Hospers sees this but doesn't accept it: "People can move backwards in space, but what does it literally mean to 'move backwards in time'?"

And if you continue to live, then what else is left for you but to become a day older every day? Isn't "getting younger every day" a contradiction in terms? Unless, of course, this is said figuratively, for example, “My dear, you are only getting younger every day,” where it is also assumed by default that a person, although looks younger every day, anyway getting older every day?

(He does not appear to be aware of F. Scott Fitzgerald's short story, in which Benjamin Button does just that. Born at seventy, Benjamin grows younger every year, until infancy and non-existence. Fitzgerald recognized the logical impossibility of this. The story has a great legacy .)

Timing is notoriously easy for Jospers. If you imagine that one day you were in the twentieth century, and the next day the time machine takes you to Ancient Egypt, he wittily remarks: “Isn't there another contradiction here? The day after January 1, 1969 is January 2, 1969. The next day after Tuesday is Wednesday (this is proved analytically: "Wednesday" is defined as the day following Tuesday)" - and so on. And he also has the final argument, the final nail in the time traveler's logical coffin. The pyramids were built before you were born. You didn't help. You didn't even look. “This event cannot be changed,” writes Hospers. - You cannot change the past. That's the key point: the past is what happened, and you can't make what happened not happen." It's still a textbook of analytic philosophy, but you can almost hear the author scream:

The entire royal cavalry and the entire royal army could not make sure that what happened did not happen, for this is a logical impossibility. When you say that it is logically possible for you to go back (literally) to 3000 BC. e. and help build the pyramids, you are faced with the question: did you help build the pyramids or not? When it happened for the first time, you didn't help: you weren't there, you weren't born yet, that was before you even stepped on the stage.

Recognize it. You didn't help build the pyramids. This is a fact, but is it logical? Not every logician finds these syllogisms self-evident. Some things cannot be proved or disproved by logic. Jospers writes more quirkily than one might think, beginning with the word time. And in the end, he openly takes for granted the thing he is trying to prove. “The whole so-called situation is riddled with contradictions,” he concludes. “When we say what we can imagine, we are just playing with words, but logically words have nothing to describe.”

Kurt Gödel allowed himself to disagree. He was the leading logician of the age, a logician whose discoveries made it impossible to even think about logic the old way. And he knew how to deal with paradoxes.

Where Hospers' logical statement was "it is logically impossible to get from January 1 to any other day than January 2 of the same year," Gödel, working in a different system, expressed something like this:

“The fact that there is no parametric system of three mutually perpendicular planes on the abscissa axes follows directly from the necessary and sufficient condition that the vector field v in four-dimensional space must satisfy if the existence of a three-dimensional mutually perpendicular system is possible on the field vectors.

He talked about world axes in Einstein's space-time continuum. This was in 1949. Gödel published his greatest work 18 years earlier, when he was a 25-year-old scientist in Vienna. It was a mathematical proof that once and for all destroyed any hope that logic or mathematics could be a finite and permanent system of axioms, clearly true or false. Gödel's incompleteness theorems were built on a paradox and are left with an even bigger paradox: we definitely know that complete certainty is unattainable for us.

Walk through time: Albert Einstein (right) and Kurt Gödel during one of their famous walks. On his 70th birthday, Gödel showed Einstein the calculations that relativity allows for cyclical time. The Life Picture Collection/Getty Images

Gödel was now thinking about time - "that mysterious and contradictory concept which, on the other hand, forms the basis of the existence of the world and of ourselves." After escaping Vienna after the Anschluss via the Trans-Siberian Railway, he took a job at the Princeton Institute for Advanced Study, where his friendship with Einstein, which began in the early 1930s, became even stronger. Their joint walks from Fuld Hall to Alden Farm, watched with envy by their colleagues, became legendary. In his last years, Einstein admitted to someone that he continued to go to the Institute mainly for the sake of being able to walk home with Gödel.

On Einstein's 70th birthday in 1949, a friend showed him a surprising calculation: his field equations from general relativity turned out to admit the possibility of "universes" in which time cycles - or, to be more precise, universes in which some world lines form loops. These are "closed timelines" or, as a modern physicist would say, closed time curves (CTCs). These are looped highways without access roads. The time curve is a set of points separated only by time: the place is the same, the time is different. A closed time curve loops back on itself and therefore violates the usual rules of causality and effect: events themselves become their own cause. (The universe itself would then be spinning as a whole, which astronomers have found no sign of, and Gödel's calculation would have been extremely long—billions of light-years—but these details are rarely mentioned.)

If the attention paid to CTCs is out of proportion to their importance or likelihood, Stephen Hawking knows why: "Scientists working in this field have to hide their real interest by using technical terms like CTCs that are actually code words for time travel." . And time travel is cool. Even for a pathologically shy, paranoid Austrian logician. In this bouquet of calculations, Gödel's words are almost buried, written in a seemingly understandable language:

“In particular, if P, Q are any two points on the world line of matter, and P precedes Q on this line, there is a time curve connecting P and Q, on which Q precedes P, i.e. in such worlds it is theoretically possible travel into the past or somehow change the past.”

Note, by the way, how easy it has already become for physicists and mathematicians to talk about alternative universes. “In such worlds…,” Gödel writes. The title of his paper, published in the journal Reviews of Modern Physics, was "Solutions to Einstein's Gravitational Field Equations", and the "solution" here is nothing but a possible universe. "All cosmological solutions with non-zero matter density," he writes, referring to "all possible non-empty universes." “In this work, I propose a solution” = “Here is a possible universe for you.” But does this possible universe really exist? Do we live in it?

Gödel liked to think so. Freeman Dyson, then a young physicist at the Institute, told me many years later that Gödel often asked him, "Has my theory been proven?" Today there are physicists who will tell you that if the universe does not contradict the laws of physics, then it exists. A priori. Time travel is possible.

At point t1 T talks to himself in the past.
At t2, T gets into a rocket to travel back in time.
Let t1=1950, t2=1974.

Not the most original start, but Dwyer is a philosopher published in Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition, which is a far cry from Improbable Stories. However, Dwyer is well prepared in this area too:

“There are many stories in science fiction that revolve around certain people using complex mechanical devices to travel back in time.”

In addition to reading stories, he also reads philosophical literature, starting with proofs of the impossibility of traveling in time by Jospers. He thinks that Jospers is just delusional. Reichenbach is also wrong (this is Hans Reichenbach, author of The Direction of Time), as is Capek (Milic Capek, Time and Relativity: Arguments for the Theory of Becoming). Reichenbach argued the possibility of meetings with oneself - when the "young me" meets the "old me", for which "the same event occurs a second time", and although this seems paradoxical, there is logic in this. Dwyer disagrees: "It's conversations like this that have created such confusion in the literature." Czapek draws diagrams with "impossible" Gödelian world lines. The same can be said about Swinburne, Whitrow, Stein, Horowitz (“Horowitz certainly creates problems for himself”), and about Gödel himself, who misrepresents his own theory.

According to Dwyer, they all make the same mistake. They imagine that the traveler can change the past. This is impossible. Dwyer can come to terms with the other difficulties of time travel: reverse causality (effects precede causes) and entity multiplication (travelers and their time machines meet their counterparts). But not with this. "Whatever time travel might mean, it's impossible to change the past." Take an old T who travels the Gödel loop from 1974 to 1950 and meets a young T there.

This meeting, of course, is recorded in the traveler's memory twice; if the young T's reaction to meeting himself can be frightened, skeptical, joyful, etc., the old T, in turn, may or may not remember his feelings when, in his youth, he met a person who called himself the same in the future . Now, of course, it would be illogical to say that T can do something to young T, because his own memory tells him that this did not happen to him.

Why can't T go back and kill his grandfather? Because he didn't. Everything is so simple. Except, of course, things are never that simple.

Robert Heinlein, who created a lot of Bob Wilsons in 1939 kicking each other before explaining the mysteries of time travel, revisited paradoxical possibilities 20 years later in a story that surpassed its predecessors. It was titled "You Are All Zombies" and published in Fantasy and Science Fiction after a Playboy editor turned it down because he was sick of having sex in it (it was 1959). There is a story about transgenderism, a little progressive for that era, but necessary to perform the equivalent of a quadruple axel in time travel: the protagonist is his (/his) mother, father, son and daughter. The title is also a joke: "I know where I came from - but where did all you zombies come from?"

A paradox made real: In a way, the time travel loop is similar to a spatial paradox such as this one created by artist Oscar Ruthersvärd.

Can anyone surpass this? In purely quantitative terms - of course. In 1973, David Gerrold, as a young television writer on the short (and later long-running) Star Trek, published his novel Dubbed, about a student named Daniel who receives a Time Belt from a mysterious "Uncle Jim" along with instructions. Uncle Jim convinces him to keep a diary, which turns out to be convenient because life gets confusing quickly. It soon becomes hard for us to keep track of the accordion-growing cast of characters, including Don, Diana, Danny, Donna, Ultra-Don and Aunt Jane - all of them (as if you didn't know) are one person on the winding roller coaster of time.

There are many variations on this theme. The number of paradoxes is increasing almost as fast as the number of time travelers, but when you look closely, it turns out that they are the same. It's all one paradox in different costumes to match the occasion. It is sometimes called the shoelace paradox, after Heinlein, whose Bob Wilson dragged himself into the future by his own shoelaces. Or the ontological paradox, the mystery of being and becoming, also known as "Who's your daddy?". People and objects (pocket watches, notebooks) exist without a cause or origin. Jane from You Are All Zombies is her own mother and father, forcing the question of where her genes come from. Or: in 1935, an American stockbroker finds a Wellsian time machine (“polished ivory and shiny nickel”) hidden in the palm leaves of the Cambodian jungle (“mysterious land”); he presses the lever and travels to 1925, where the car is polished and hidden in palm leaves. This is her life cycle: a closed ten-year time bend. "But where did it come from in the first place?" the broker asks a Buddhist in yellow robes. The sage explains to him like a blockhead: "There was never any 'initially'."

Some of the most ingenious loops involve simply information. "Mr. Buñuel, I had an idea for a movie for you." The book on how to build a time machine comes from the future. See also: predestination paradox. Trying to change something that is about to happen somehow helps it happen. In The Terminator (1984), a cyborg killer (played in a strange Austrian accent by 37-year-old bodybuilder Arnold Schwarzenegger) travels back in time to kill a woman before she gives birth to a child destined to lead a resistance movement in the future; after the failure of the cyborg, debris remains that make its own creation possible; and so on.

In a sense, of course, the paradox of predestination appeared several millennia before time travel. Lai, hoping to break the prophecy about his murder, leaves the baby Oedipus in the mountains to die, but, unfortunately, his plan backfires on him. The idea of a self-fulfilling prophecy is old, though the name is new, coined by the sociologist Robert Merton in 1949 to describe a very real phenomenon: "a false definition of a situation that evokes new behavior that turns the original misconception into reality." (For example, a warning about a shortage of gasoline leads to panic buying, which leads to a shortage of gasoline.) People have always wondered if they could run away from fate. Only now, in the age of time travel, are we asking ourselves if we can change the past.

All paradoxes are time loops. All of them make us think about cause and effect. Can the effect precede the cause? Of course not. Obviously. A-priory. "A cause is an object followed by another..." David Hume repeated. If a child is vaccinated against measles and then has a seizure, the vaccine may have caused the seizure. The only thing everyone knows for sure is that the seizure was not the cause of the vaccination.

But we're not very good at understanding why. The first person we know to have tried to analyze cause and effect through logical reasoning was Aristotle, who created levels of complexity that have caused confusion ever since. He distinguished four separate types of causes that can be named (with allowance for the impossibility of translation between millennia): action, form, matter, and purpose. In some of them it is difficult to recognize the reasons. The active cause of sculpture is the sculptor, but the material cause is marble. Both are necessary for the existence of sculpture. The ultimate reason is purpose, that is, let's say beauty. From a chronological point of view, final causes usually come into play later. What is the cause of the explosion: dynamite? spark? robber? safe breaking? Such reflections seem petty to modern people. (On the other hand, some professionals believe that Aristotle's vocabulary was deplorably primitive. They would not like to discuss causality without mentioning immanence, transcendence, individuation, and arity, hybrid causes, probabilistic causes, and causal chains.) In any case, we it's worth remembering that nothing, on close examination, has a single unambiguous, undeniable reason.

Would you accept the assumption that the reason for the stone's existence is the same stone a moment earlier?

“It seems that all reasoning about establishing a fact is based on relations Causes and Consequences Hume argues, but he realized that this reasoning was never easy or certain. Is it the sun that causes the stone to heat up? Is insult the cause of someone's anger? Only one thing can be said for sure: “A cause is an object followed by another one ...” If the effect not necessary follows from the cause, was it the cause at all? These disputes resound in the corridors of philosophy, and continue to resound despite Bertrand Russell's attempt in 1913 to settle the matter once and for all, for which he turned to modern science. "Strangely, in advanced sciences such as gravitational astronomy, the word 'cause' never occurs," he wrote. Now it's the turn of the philosophers. “The reason why physicists have abandoned the search for causes is that, in fact, there are none. I believe that the law of causality, like much that is heard among philosophers, is but a relic of a bygone era, surviving, like the monarchy, only because it is erroneously considered harmless.

Russell had in mind the hyper-Newtonian view of science that Laplace had described a century earlier - the universe held together - in which everything that exists is bound together by the mechanisms of physical laws. Laplace spoke of the past as reason of the future, but if the whole mechanism chugging along moves as one, why should it seem to us that any single gear or lever would be more causal than any other detail? We may think that the horse is the reason for the movement of the wagon, but this is just a prejudice. Like it or not, the horse is completely defined too. Russell noticed, and he was not the first in this, that when physicists write down their laws in mathematical language, time does not have a predetermined direction. “The law makes no difference between the past and the future. The future "determines" the past in the same sense that the past "determines" the future.

“But,” we are told, “you cannot influence the past, while you can, to a certain extent, influence the future.” This view is based on the same causal errors that I wanted to get rid of. You can't make the past not what it was - right... If you already know what it was, obviously there is no point in wishing it was different. But you also cannot make the future different from what it will be... If it happens that you know the future - for example, in the case of an approaching eclipse - it is as useless as wishing the past to be different.

But so far, contrary to Russell, scientists are more slaves of causality than anyone else. Cigarette smoking causes cancer, although no single cigarette causes any single cancer. Burning oil and coal leads to climate change. A mutation in a single gene causes phenylketonuria. The collapse of an aged star causes a supernova explosion. Hume was right: “All reflections on fact-finding seem to be based on relations Causes and Consequences". Sometimes that's all we talk about. Lines of causality are everywhere, long and short, clear and blurry, invisible, intertwining and inevitable. They all go in the same direction, from the past to the future.

Suppose one day in 1811, in the town of Teplitz in northwestern Bohemia, a man named Ludwig made notes on a line of music in his notebook. On an evening in 2011, a woman named Rachel blew a horn at the Boston Symphony Hall with a well-known effect: the air in the room vibrated, basically at a frequency of 444 vibrations per second. Who can deny that, at least in part, writing on paper caused fluctuations in the atmosphere two centuries later? Using physical laws, it would be difficult to calculate the path of influence of Bohemia molecules on molecules in Boston, even taking into account Laplace's mythical "mind that has a concept of all forces." In doing so, we see an unbreakable causal chain. A chain of information, if not matter.

Russell did not end the discussion when he declared the principles of causality to be relics of a bygone era. Not only do philosophers and physicists continue to bash their heads over cause and effect, they have added new possibilities to the mix. Now on the agenda is retrocausality, also known as reverse causality or retro-chronal causality. Michael Dammett, a notable English logician and philosopher (and reader of science fiction), seems to have started this current with his 1954 paper, "Can an Effect Precede a Cause?" . Among the questions he raised was this: Suppose someone hears on the radio that his son's ship has sunk in the Atlantic Ocean. He prays to God that his son is among the survivors. Did he commit sacrilege when he asked God to undo what had been done? Or is his prayer functionally identical to that of his son's future safe journey?

What, against all precedent and tradition, might inspire modern philosophers to ponder the possibility that effects may precede causes? The Stanford Encyclopedia of Philosophy offers this answer: Time travel. That's right, all the paradoxes of time travel and murder and birth grow out of retro causality. Effects cancel their causes.

The first main argument against causal order is that a temporal order in which temporally reverse causality is possible is possible in cases like time travel. It seems metaphysically possible that a time traveler enters a time machine at the moment t1, in order to get out of it at some former moment t0. And this seems nomologically possible, after Gödel proved that there are solutions to Einstein's field equations that allow closed paths.

But time travel doesn't exactly get rid of all the questions. “Many incoherences can clash here, including the incoherence of changing what is already fixed (causing the past), the ability to kill or not kill one’s own ancestors, and the ability to create a causal loop,” the encyclopedia warns. Writers bravely risk a couple of incoherences. Phillip Dick reversed the clock in Time Back, as did Martin Amis in The Arrow of Time.

It seems like we really are traveling in circles.

"The recent resurgence of wormhole physics has led to a very disturbing observation," Matt Visser, a mathematician and cosmologist from New Zealand, wrote in 1994 in Nuclear Physics B (an offshoot of Nuclear Physics devoted to "theoretical, phenomenological and experimental high-energy physics, quantum theory fields and statistical systems”). By all appearances, the "revival" of wormhole physics is well established, although these alleged tunnels through space-time remained (and remain) completely hypothetical. The troubling observation was this: "If traversable wormholes exist, it would appear that they can be turned into time machines quite easily." The observation is not just disturbing, but disturbing in the highest degree: "This extremely disturbing state of affairs stimulated Hawking to announce his conjecture about chronological protection."

Hawking is, of course, Stephen Hawking, a Cambridge physicist who was by then the most famous physicist alive, partly because of his long struggle with amyotrophic lateral sclerosis, partly because of the popularization of the most intricate problems of cosmology. There is nothing surprising in the fact that he was attracted to time travel.

"The Chronology Security Hypothesis" was the title of an article he wrote in 1991 for the journal Physical Review D. He explained his motivations thus: travel to the past would allow. Guessed by whom? An army of science fiction writers, sure, but Hawking was quoting physicist Kip Thorne (another Wheeler protégé) at Caltech, who was working with his graduate students on "wormholes and time machines."

At a certain point, the term "sufficiently developed civilization" became stable. For example: if we humans cannot do this, will a sufficiently advanced civilization be able to? The term is useful not only for science fiction writers, but also for physicists. Thus, Thorne, Mike Morris, and Ulvi Yurtsever wrote in Physical Review Letters in 1988: "We begin with the question: Do the laws of physics of a sufficiently advanced civilization allow the creation and maintenance of wormholes for interstellar travel?" Not surprisingly, 26 years later, Thorne became the executive producer and scientific consultant for Interstellar. “You can imagine that an advanced civilization could pull a wormhole out of the quantum foam,” they wrote in that 1988 article, and they provided an illustration with the caption: “Space-time diagram for turning a wormhole into a time machine.” They imagined wormholes with holes: a spacecraft could enter one and exit another in the past. It is logical that they cited a paradox as a conclusion, only this time it was not the grandfather who died in it:

“Can an evolved being lock Schrödinger's cat alive at event P (destroying its wavefunction to a living state) and then go back in time through a wormhole and kill the cat (destroying its wavefunction to a dead state) before it reaches P? »

They didn't give an answer.

And then Hawking intervened. He analyzed the physics of wormholes, as well as paradoxes ("all sorts of logical problems that arise with the ability to change history"). He considered avoiding paradoxes “by some modification of the concept of free will,” but free will is rarely a comfortable topic for a physicist, and Hawking saw a better approach: he proposed the so-called chronology-protected hypothesis. It took a lot of calculations, and when they were ready, Hawking was convinced that the very laws of physics protect history from possible time travelers. Regardless of what Gödel believes, they must not allow closed time curves to arise. “It seems that there is a force that protects chronology,” he wrote quite fantastically, “which prevents the occurrence of closed time curves and thus makes the universe safe for historians.” And he completed the article beautifully - in the Physical Review he could do it. He didn't just have a theory - he had "evidence":

"There is also strong evidence for this hypothesis in the form of the fact that we are not swept away by hordes of tourists from the future."

Hawking is one of those physicists who knows that time travel is impossible, but also knows that it's interesting to talk about it. He notes that we are all time traveling to the future at a rate of 60 seconds per minute. He describes black holes as time machines, recalling that gravity slows down time in a certain place. And he often tells the story of the party he threw for the time travelers - he only sent out the invitations after the event itself. "I sat and waited for a very long time, but no one came."

In fact, the idea of the chronology security hypothesis was in the air long before Stephen Hawking gave it a name. Ray Bradbury, for example, laid it out in his 1952 short story about time-traveling dinosaur hunters: “Time does not allow such a confusion - for a man to meet himself. When the threat of such events arises, Time steps aside. Like a plane falling into an air pocket." Notice that Time is an active subject here: Time does not allow, and time steps aside. Douglas Adams offered his own version: “Paradoxes are just scar tissue. Time and space heal their wounds around them, and people just remember as meaningful a version of the event as they need to.”

Maybe it's a bit like magic. Scholars tend to refer to laws of physics. Gödel believed that a healthy, paradox-free universe is only a matter of logic. "Time travel is possible, but no one can kill themselves in the past," he told a young visitor in 1972. “Initiality is often neglected. The logic is very strong." At some point, the security of the chronology became part of the basic rules. It has even become a cliché. In her 2008 short story "Region of Dissimilarity", Rivka Galchen takes all these concepts for granted:

"Fiction writers have come up with similar solutions to the grandfather paradox: murderous grandchildren inevitably stumble upon some kind of obstacle - non-working guns, slippery banana skins, their own conscience - before carrying out their impossible deed."

“Region of dissimilarity” is from Augustine: “I felt myself far from You, in the region of dissimilarity” - in regione dissimilitudinis. He does not fully exist, like all of us, chained to a moment in space and time. “I contemplated other things below You, and I saw that they are not completely there, and they are not completely absent.” Remember, God is eternal, but we are not, much to our regret.

The narrator Galchen befriends two older men, maybe philosophers, maybe scientists. It doesn't say exactly. These relationships are not well defined. The narrator feels that she herself is not very well defined. The men speak in riddles. “Oh, time will tell,” one of them says. And also: "Time is our tragedy, the matter through which we have to wade in order to become closer to God." They disappear from her life for a while. She follows the obituaries in the papers. Mysteriously, an envelope appears in her mailbox - diagrams, billiard balls, equations. She recalls the old joke: "Time flies like an arrow, and fruit flies love bananas." One thing becomes clear: everyone in this story knows a lot about time travel. A fateful time loop - still the same paradox - begins to emerge from the shadows. Some rules are clarified: "contrary to popular movies, traveling to the past does not change the future, or rather, the future has already been changed, or rather, it is still more complicated." Fate seems to gently pull her in the right direction. Can one escape fate? Remember what happened to Lai. All she can say is: "Of course, our world is subject to rules still alien to our imagination."

The paradoxes of time travel regularly occupy the minds of not only scientists who comprehend the possible consequences of such a movement (albeit hypothetical), but also people who are completely far from science. Surely you have argued with your friends more than once about what will happen if you see yourself in the past - like many science fiction authors, writers and directors. Today, the film with Ethan Hawke in the lead role, Time Patrol, based on the story of one of the best science fiction writers of all time, Robert Heinlein, was just released. This year has already been a success of several films relating to the theme of time like "Interstellar" or "Edge of Tomorrow". We decided to speculate what potential dangers might await the heroes of temporary sci-fi, from killing their predecessors to splitting reality.

Text: Ivan Sorokin

Paradox of the dead grandfather

The most common, and at the same time the most understandable of the paradoxes that overtake the time traveler. The answer to the question “what will happen if you kill your own grandfather (father, mother, etc.) in the past?” may sound different - the most popular outcome is the occurrence of a parallel time sequence, erasing the culprit from history. In any case, for the temponaut himself (this word, by analogy with "astronaut" and "astronaut", sometimes refers to the pilot of the time machine), this does not bode well at all.

Movie example: The whole story about teenager Marty McFly, who accidentally travels to 1955, is built on preventing an analogue of this paradox. Having accidentally conquered his own mother, Marty begins to literally disappear - first from photographs, and then from tangible reality. There are many reasons why the first film in the Back to the Future trilogy can be considered an absolute classic, but one of them is how neatly the script sidesteps the idea of potential incest. Of course, in terms of the scale of the idea, this example can hardly be compared with the well-known plot from Futurama, as a result of which Fry still becomes his own grandfather, accidentally destroying the one who was supposed to become this grandfather; in the end, this event had consequences that literally affected the entire universe of the animated series.

Pulling yourself by your hair

The second most common time travel plot in cinema: going to a glorious past from a terrible future and trying to change it, the hero ends up causing his own (or everyone's) troubles. Something similar can happen in a positive context: the fairy-tale assistant who directs the plot turns out to be the hero himself, who came from the future and ensures the correct course of events. This logic of the development of what is happening can hardly be called a paradox: the so-called time loop is closed here and everything happens exactly as it should, but in the context of the interaction of cause and effect, the human brain still cannot but perceive this situation as paradoxical. This technique is named, as you might guess, in honor of Baron Munchausen, who pulls himself out of the swamp.

Movie example: In the space epic Interstellar (spoiler alert) there are a huge number of plot twists of varying degrees of predictability, but the emergence of a “closed loop” is almost the main twist: Christopher Nolan’s humanistic message that love is stronger than gravity does not receive its final form until at the very end of the film, when it turns out that the spirit of the bookshelf, protecting the astrophysicist performed by Jessica Chastain, was the hero Matthew McConaughey, sending messages to the past from the bowels of a black hole.

The Bill Murray Paradox

Plots about looped time loops have already become a separate subgenre of sci-fi about temponauts for some time - both in literature and in cinema. It is not surprising that almost any such work is automatically compared to Groundhog Day, which over the years has come to be seen not only as a parable of existential despair and the desire to appreciate life, but also as an amusing exploration of the possibilities of behavior and self-development in extremely limited conditions. The main paradox here lies not in the very presence of a loop (the nature of this process is not always touched upon in such plots), but in the temponaut's incredible memory (it is she who is able to provide any movement of the plot) and the equally incredible inertia of those around him to all the evidence. that the protagonist's position is truly unique.

Movie example: Detractors have dubbed "Edge of Tomorrow" something like Groundhog Day with aliens, but in fact the script for one of the best science fiction films of the year (which, by the way, was superbly successful for this genre) handles its loops much more delicately. The paradox of perfect memory is bypassed here by the fact that the protagonist writes down and thinks through his moves, interacting with other characters, and the problem of empathy is solved by the fact that there is another character in the film who at some point had similar skills. By the way, the occurrence of a loop is also explained here.

Deceived expectations

The problem of not meeting expectations is always present in our lives - but in the case of time travel, it can hurt especially badly. Usually this plot device is used as an embodiment of the proverb "Be careful what you wish for" and works according to Murphy's laws: if events can develop in the worst possible way, then everything will happen. Since it is difficult to assume that a time traveler is able to predict in advance what the tree of possible outcomes of his or her actions will look like, the viewer rarely doubts the plausibility of such plots.

Movie example: One of the saddest scenes in the recent rom-com "Future Boyfriend" looks like this: Domhnall Gleeson's temponaut tries to go back in time to the time before the birth of his child and ends up coming home to a complete stranger. This is corrected, but as a result of such a collision, the hero realizes that more restrictions are imposed on his movements along the temporary arrow than he thought before.

Aristotle with smartphone

This paradox is a special case of the popular sci-fi trope "advanced technology in a backward world" - only the "world" here is not another planet, but our own past. It is not difficult to guess what the introduction of a conditional pistol into the world of conditional batons is fraught with: the deification of aliens from the future, destructive violence, a change in the way of life in a particular community, and the like.

Movie example: Of course, the Terminator franchise should serve as the most striking example of the destructive influence of such an invasion: it is the appearance of androids in the United States in the 1980s that ultimately leads to the emergence of artificial intelligence Skynet, which literally destroys humanity. Moreover, the main reason for the creation of Skynet is given by the protagonists Kyle Reese and Sarah Connor, due to the actions of which the main Terminator chip falls into the hands of Cyberdyne, from the depths of which Skynet eventually emerges.

The hard part of remembering

What happens to the temponaut's memory when, as a result of his own actions, the temporary arrow itself changes? The gigantic stress that must inevitably arise in such a case is often ignored by science fiction authors, but the ambiguity of the hero's position cannot be ignored. Well, there are a lot of questions here (and all of them do not have an unambiguous answer - to adequately check the answers to them, you need to literally get a time machine in your hands): does the temponaut remember all events or only part of them? Do two parallel universes coexist in the temponaut's memory? Does he perceive his changed friends and relatives as different people? What happens if you tell people from the new timeline in detail about their counterparts in the previous timeline?

Movie example: There is at least one example of such a state in almost every time travel movie; from a recent one, Wolverine from the last series of X-Men immediately comes to mind. The idea that as a result of the success of the operation, Hugh Jackman's character will be the only one who can remember the original (extremely gloomy) course of events, is voiced several times in the film; in the end, Wolverine is so happy to see all his friends again that memories that can hurt even a person with an adamantium skeleton fade into the background.

scary you #2

Neuroscientists are quite actively studying how people perceive their appearance; an important aspect of this is the reaction to twins and twins. Typically, such meetings are characterized by an increased level of anxiety, which is not surprising: the brain ceases to adequately perceive the position in space and begins to confuse external and internal signals. Now imagine how a person must feel, seeing himself - but of a different age.

Movie example: The interaction of the protagonist with himself is perfectly played out in Rian Johnson's film Looper, where the young Joseph Simmons is played by Joseph Gordon-Levitt in cunning makeup, and the elderly, who arrived from the near future, is played by Bruce Willis. Cognitive discomfort and the inability to establish normal contact is one of the important themes of the picture.

Unfulfilled predictions

Your opinion about whether such events are paradoxical depends directly on whether you personally adhere to a deterministic model of the universe. If there is no free will as such, then a skilled temponaut can safely bet huge amounts of money on various sports competitions, predict the results of elections and award ceremonies, invest in shares of the right companies, solve crimes, and so on. If, however, as is usually the case in films about time travel, the actions of the temponaut are still able to change the future, then the function and role of predictions based on a kind of insight from a stranger from the future are as ambiguous as in the case of those predictions that are based solely on on logic and past experience (that is, similar to those that are used now).

Movie example: Despite the fact that only "mental" time travel appears in "Minority Report", the plot of this film serves as a vivid illustration for both models of the universe: both deterministic and free will. The plot revolves around the prediction of yet uncommitted crimes with the help of "clairvoyants" who are able to visualize the intentions of potential killers (a situation of extreme determinism). Toward the end of the film, it turns out that visions are still able to change in time - accordingly, a person to some extent determines his own fate.

I was yesterday into tomorrow

In most of the world's major languages, there are multiple tenses for events in the past, present, and future. But what about the temponaut, who yesterday could observe the death of the Sun, and today he is already in the company of dinosaurs? What tenses to use in speech and writing? In Russian, English, Japanese and many other languages, such functionality is simply absent - and you have to get out in such a way that something comical inevitably happens.

Movie example: Doctor Who, of course, belongs to the field of television, not cinema (although several television films can be found in the list of works related to the franchise), but the series cannot be left out here. The Doctor's confusing use of different times became a cause for bullying even in pre-Internet times, and after the revival of the series in the mid-2000s, the authors decided to deliberately emphasize this detail: now the on-screen Doctor is able to connect his non-linear perception of time with the peculiarities of the language (and at the same time laugh at the resulting phrases) .

multiverse

The most fundamental paradox of time travel is not in vain directly related to a serious conceptual discussion in quantum mechanics, based on the acceptance or rejection of the concept of a “multiverse” (that is, a collection of multiple universes). What actually needs to happen the moment you "change the future"? Do you remain yourself - or do you become a copy of yourself in a different timeline (and, accordingly, in a different universe)? Do all the timelines co-exist in parallel so that you just jump from one to the other? If the number of decisions that change the course of events is infinite, then is the number of parallel universes infinite? Does this mean that the multiverse is infinite in size?

Movie example: The idea of multiple parallel timelines is usually not adequately portrayed in films for one simple reason: writers and directors become afraid that no one will understand them. But Shane Carratt, the author of The Detonator, is not like that: to understand the plot of this film, where one non-linearity is superimposed on another, and in order to fully explain the movements of the characters in time, it is necessary to draw a diagram of the multiverse with intersecting timelines, only after considerable effort has been applied.

TIME PARADOX

(twin paradox, relativity theory when finding time intervals shown by two clocks A And IN, of which watches . everything was at rest in an inertial frame of reference, and the clock IN flew away from A, made a trip and returned to A. A contradiction arises when . And a period of time has passed t, then by moving with post. v hours IN a period of time will pass

I. D. Novikov.

Physical encyclopedia. In 5 volumes. - M.: Soviet Encyclopedia. Editor-in-Chief A. M. Prokhorov. 1988 .

See what the "PARADOX OF TIME" is in other dictionaries:

time paradox

This page needs a major overhaul. It may need to be wikified, expanded, or rewritten. Explanation of the reasons and discussion on the Wikipedia page: For improvement / November 7, 2012. Date of setting for improvement November 7, 2012 ... Wikipedia

twin paradox- laiko paradoksas statusas T sritis fizika atitikmenys: engl. clock paradox; twin paradox vok. Uhrenparadoxon, n; Zwillingsparadoxon, n rus. twin paradox, m; time paradox, m; clock paradox, m pranc. paradoxe de l'horloge, m; paradoxe… … Fizikos terminų žodynas

clock paradox- laiko paradoksas statusas T sritis fizika atitikmenys: engl. clock paradox; twin paradox vok. Uhrenparadoxon, n; Zwillingsparadoxon, n rus. twin paradox, m; time paradox, m; clock paradox, m pranc. paradoxe de l'horloge, m; paradoxe… … Fizikos terminų žodynas

The paradox of the murdered grandfather is a proposed paradox concerning time travel first described (under this title) by science fiction writer René Barjavel in his 1943 book Le Voyageur Imprudent. The paradox lies in ... ... Wikipedia

Thought experiment considering a disk rotating at near-light speed. In the modern sense, it shows the incompatibility of some concepts of classical mechanics with the special theory of relativity, as well as the possibility of different ... ... Wikipedia

The Einstein Podolsky Rosen paradox (EPR paradox) is an attempt to indicate the incompleteness of quantum mechanics using a thought experiment, which consists in measuring the parameters of a micro-object indirectly, without affecting this ... ... Wikipedia

Books

Svarga. Paradox of time, Marina Zagorodskaya. Humanity is increasingly thinking about time travel. But what will be the consequences? Will this affect the development of civilization as a whole? What awaits the time traveler in the past?…