Back to the future: Five concepts of time travel, reflected in pop culture

We have collected five concepts of time travel, reflected in pop culture, and try to explain if they could ever become reality.

Turn back time, like in Christopher Nolan’s “Tenet”

The plot of the “Tenet” is based on the artistic assumption of the creators of the picture that time can be inverted. That is, to move along the same time axis, but in a different direction. It is not a parallel dimension or a return to the past. An inverted person does not get younger, but all processes around him are going in the opposite direction. For example, oxygen is exhaled and carbon dioxide is inhaled – therefore an oxygen mask is needed. In the inverted time axis, the explosion cools objects, rather than ignites them – the opposite entropy occurs. 

Despite the fact that Nobel Prize laureate in physics Kip Thorne contributed to the creation of the film, upon careful analysis, the concept of time inversion does not stand up to criticism. The theoretical scientific basis of the film is based on several concepts: antiparticles, CPT invariance, one-electron universe. 

Ilya Deriy, an employee of the Center for Nanophotonics of the National Research University of Information Technologies, Mechanics and Optics, explains: An antiparticle to a particle is the same particle, the moduli of the main parameters of which – mass, charge – are equal to the moduli of the particle parameters, but differ in sign. If particle “a” has mass m, then “anti-a” will have mass -m.

CPT invariance implies the symmetry of physical laws when changing a particle to an antiparticle and changing the sign of time. The theory of a one-electron universe is a hypothetical model of the universe in which all electrons are one electron located alternately at different points in space.

Without going into the details of complex mathematical calculations and equations, it can be said that there are at least three main obstacles on the way back to the future or forward to the past. Speaking about “Tenet”, one can recall one of them – the principle of causality. It consists in a simple question: “If I kill my grandfather, will I die too?” Nolan’s film responds elegantly, “How do I know?” 

The director decided not to flirt with unpleasant logical paradoxes. Another plus in Nolan’s piggy bank – people in inverted time just go towards us, changing, for us – the past, for them – the future, but we do exactly the same thing, just the opposite. Moreover, at a certain point in time, we always have the same result. This is similar to how films were played on film in old cinemas. 

Whatever it is, the picture at 12:05 will always be the same. In order not to break the logic, it is necessary to accept the requirement that “everything” exists “always”. Plus or minus does not contradict anything if we take it for granted that there is a time loop that has always existed, because in this case the principle of causality is not violated. 

We just walk in a circle and everything is arranged in such a way that the starting point always coincides with the ending point. Model,

Technology portal to the past, like in the novel “11/22/63” by Stephen King

English teacher Jacob Epping learns that in the back room of an ordinary diner there is a portal to the past, which operates according to several strict laws. A person always moves at the same time, on the same day – 11:58 on September 9, 1958. Regardless of the duration of the trip in the past, in the present it will take only 2 minutes. 

It is possible to influence and change events that have already occurred in the past, but if you use the portal again, this will cancel all changes. By the way, the past resists change – the larger the traveler’s influence on events, the more it resists. Jacob uses the portal to try to prevent the assassination of John F. Kennedy on November 22, 1963.

In this case, one can recall the Heisenberg uncertainty principle. He says that quantum particles do not have a specific momentum and coordinate. These two characteristics simply take on a value in a certain interval. And the smaller this gap for one of the variables, the larger it is for the other. 

The following conclusion suggests itself: even if it turns out to turn the past backwards, this principle will not change. And various quantum processes will always happen with a certain degree of randomness. That is, the past will no longer be the same as it was before we remember it. And the further in time we go, the more we will feel this effect. 

It is somewhat similar to the butterfly effect, when a minor impact on the system can cause unpredictable consequences not only in the system itself, but also in a completely unexpected place.

Creation of a temporal field, as in the novel “The End of Eternity”, Isaac Asimov

The book describes the organization “Eternity” existing outside of time and space, which gained the ability to travel in time after breakthrough research in mathematics and physics was carried out on the basis of the temporal field generator. 

Based on these studies, it was possible to stretch a negligibly narrow temporal field into the future, when the sun turned into a supernova. It was the use of supernova energy that allowed “Eternity” to expand the field and place members of the organization in different centuries in order to keep an eye on “time” – ordinary people and prevent catastrophes. 

Theoretically, the use of supernova energy is possible provided that it can be integrated into the developed device. You also need to remember about banal energy considerations. 

Let’s say there is a ball that is rolling down a hill. To return it to the top, it must first be stopped, and then also rolled to the peak. What if the same ball is not just rolling down a hill, but flying at a breakneck speed in outer space? It is necessary to spend energy not only to stop it, but also to stop all the processes that occur inside, the existence of many of which we do not even mean. This will have to spend a huge amount of energy, which, in my opinion, humanity does not yet have. 

Temporality is a special characteristic of temporal processes, which consists in the assumption of the temporal nature of phenomena. In the novel, this is an intertemporal cavity formed by an inexplicable paradox. 

Timeloop like in Duncan Jones’s “Source Code”

US intelligence agencies have developed the Source Code program . It allows you to place the consciousness of the agent in the body of any person in the last eight minutes of his life. The task of the main character Colter Stevens is to prevent the train explosion that happened the day before, destroying the bomb, and find out who created it. This will help find and neutralize another explosive device that has not yet been activated. 

The program is a skillful imitation, which means that it is impossible to change the course of events and evacuate the train. In this case, the activation of the “Source Code” leads to the creation of new timelines due to manipulations with quantum physics.

The time loop is a favorite plot move for many screenwriters and writers. The most striking example of this is the cult film Groundhog Day, where the hero is forced to live the same day over and over again. In real life, this term owes its appearance to the Austrian scientist Kurt Gödel. 

He wrote a paper on general relativity, where he proposed a solution to the Einstein equation by considering the role of the gravitational potential. It follows from Gödel’s solution that the universe can have a special structure, where the flow of time is looped. In theory, this could lead to time travel. Modern physicists believe that this solution has no practical meaning. 

If we add to the assumption about the temporal looping of the theory from quantum physics that there are parallel realities, then theoretically, time travel to alternative realities gets rid of all paradoxes. However, scientists did not even try to develop a mathematical apparatus that would take into account such an assumption. 

A natural portal to the past, as in the TV series “Dark”

The series takes place in the fictional city of Winden, located next to a nuclear power plant. Below it is a system of caves where a wormhole is found, allowing time travel 33 years into the past and into the future. 

In Dark, the approach to time travel and its consequences is quite realistic – it is impossible to change the course of history. Once in the past, a person cannot change destiny, only contribute to the predetermined future. 

All events will happen, and time loops will continue to exist. This is due to the  principle of causality , which was also used in “Tenet” – if event A caused event B, then A happened before B. The principle of the wormhole under Winden resembles the Einstein-Rosen bridge. The show also features a “particle of god” as a must-have for time travel. In reality, this concept resembles the Higgs boson. 

The Higgs boson is an elementary particle responsible for inert mass. It serves as a measure of the body’s inertia, that is, it determines the degree of its resistance to external influences. The more inert body mass, the slower and weaker the body reacts to the action of external forces.

The Einstein-Rosen Bridge is a wormhole, a hypothetical time travel vehicle that connects two points at any distance from each other in time and space. The implication is that space and time in this concept have neither end nor edge. That is, a particle trapped in a hole can continue its path to the future or past as far as desired. 

The concept of wormholes is consistent with general relativity, but no practical study or scientific work has proven their existence in real life. So far, they exist only on television screens.