Time Travel: Theories, Paradoxes, and Possibilities


Have you ever committed a grave mistake you wished you could take back? Its ability to go back to the past and have the chance to correct errors is one of the reasons why humans find the idea of time travel so intriguing. Many science fiction stories explore the idea of time travel, and it has become a widely popular concept in the genre. As is frequently seen in science fiction films, nothing is ever set in stone since you can always go back and change it with the help of a time machine. In movies, time travellers frequently enter a machine and, poof, vanish. Then they instantly reemerge among knights, dinosaurs, or cowboys.

What is Time Travel?

Steampunk Time Clock

The phrase “time travel” frequently conjures our most fanciful ideas of what it means to go across the fourth dimension, from millennia-jumping Victorians to phone booth-hopping time-travelling teenagers. You can travel across time without a time machine or a beautiful wormhole. The act of moving from the past into the future is an act of constantly moving through time. However, “time travel” typically refers to the ability to slow down or stop the forward motion to travel backwards.

While time travel has been a recurring theme in fiction since the 19th century, it has never been empirically proven and may still be impossible. Most people interpret time travel to mean that a person’s body, mind, and memories remain the same while their position in time is altered. No time travel would be noticeable if the traveller’s body and mind returned to their original states at the destination time. People usually consider the ability to travel to past or future destinations when it comes to time travel.

However, is time travel a reality in this universe, or is it merely a concept from science fiction? Newtonian absolute time theory, in which people advance deterministically and linearly into the future, does not make the idea of time travel possible. According to special relativity, it is also impossible since our light cones prevent it from happening. However, general relativity does open the door to the potential of travelling through time, that is, going backwards or forwards in time without regard to the regular flow of time that we experience on Earth, in a manner like how a person can travel between various points in space.

Theories of Time Travel

Time Portal Time Machine Royalty

Time travel is a common theme in fiction, although there is some theoretical support for the concept.

1. Einstein’s Special or General Relativity Theory

Most people think of time as a linear, constant concept—one which advances at a steady rate. However, Einstein demonstrated that time may change depending on where you are in space. The three dimensions that makeup space are length, width, and height. These measurements help us locate the object. Think about going to work on foot; the length of a road, the breadth of a path, and the height of the nearby buildings make up your area. However, time is a different dimension. Time is the fourth dimension that reveals our constant forward motion.

General relativity is the foundation for thinking about time and causality. The “spacetime” hypothesis developed by theoretical physicist Albert Einstein unites space and time into a unified concept that explains how they both function at a level of complexity unsurpassed by any other accepted theory. Since this theory has been around for more than a century and has been experimentally validated precisely, physicists are confident that it accurately captures the causal structure of our universe.

On the other hand, Einstein’s Theory of Special Relativity suggests that not everyone experiences time passing at the same rate. Depending on where exactly you are in space, it changes. For instance, if you are a traveller or an observer. Depending on how quickly you are travelling concerning another item, time can either speed up or slow down. Now that we are aware that time is relative to everyone, it is conceivable that there are rational explanations for time travel.

2. Wormholes Theory

An Einstein-Rosen bridge, a wormhole, is a theoretical tunnel-like structure that might link far-flung locations in spacetime. Time travel between various universe parts may be possible if traversable wormholes are present. Wormholes have yet to be shown to exist, and their stability and suitability for time travel are still up in the air. Specific general relativity solutions to Einstein’s field equations predict the existence of wormholes. These answers imply that spacetime might be folded and warped in a way that would allow a shortcut to exist between two different places. However, more work and discussion over the conditions necessary for stable and travelable wormholes are still needed.

Though they weren’t initially dubbed wormholes, the theory dates to 1916. While examining a solution provided by another physicist, Austrian physicist Ludwig Flamm discovered an alternative solution to Albert Einstein’s general relativity equations. He referred to it as a “white hole,” a hypothetical time-reversal variant of a black hole. There may exist a spacetime conduit that links the entrances of black and white holes. General relativity was utilized by Einstein and scientist Nathan Rosen in 1935 to develop the concept and suggest the presence of “bridges” between spacetime. These bridges connect two different points in spacetime, which offers the potential for a quicker route that would reduce travel time and distance. These shortcuts are commonly referred to as wormholes or Einstein-Rosen bridges.

Two mouths are present in wormholes, and a throat connects them. Most likely, the mouths would be spheroidal. The throat could take a longer course than a more direct route would require, or it could be a straight stretch. Although wormholes are predicted mathematically by Einstein’s theory of general relativity, none have been seen thus far. It is possible to detect a hostile mass wormhole by observing how its gravitational field affects nearby light. Some general relativity solutions permit the presence of wormholes with black holes at each end. A wormhole cannot be produced by a naturally occurring black hole, which is the result of the death of a star.

Wormholes might link two distinct areas of the same universe and possibly two other universes. Scientists propose that it may be possible to travel through time by manipulating one end of a wormhole in a specific manner. Adding “regular” matter might be enough to destabilize a wormhole, even as adding exotic matter could stabilize it so that human passengers may pass through it without danger. Wormholes cannot be stabilized or enlarged, even if detected, due to limitations in existing technology. However, in the hopes that technology will one day be able to use them, scientists are still researching the idea of a means of space travel.

3. Grandfather Paradox Theory

Inconsistencies contradicting the timeline’s history are produced when something goes back in time, known as the “Grandfather Paradox.” The scenario where a person travels to the past and kills their grandpa to avert their birth is the most frequently used example of this paradox. However, the situation involving a person’s grandma is not the only case where this paradox is applicable. Over the years, philosophers and physicists have conjured up a variety of fascinating examples of grandfather paradoxes.

For instance, the “Hitler paradox” argues that if someone went back in time and killed a young Hitler, all knowledge of Hitler would be lost, eliminating the motivation for doing so in the first place. Another illustration is a signal being sent backwards in time by an electronic circuit to turn itself off, which results in the circuit receiving the signal before it is even sent. Or there’s Polchinski’s Paradox, in which a pool ball travels through a wormhole and emerges in the past before hitting its younger self, preventing it from travelling through the wormhole. The grandfather paradox, despite its name, is just one of many paradoxes that all deal with logical and historical inconsistencies that arise when a time traveller takes any action that alters not only their past but also the pasts and possibly futures of anyone who is in any way connected to the modified event. The Grandpa Paradox states that it is feasible to stop one’s birth by going far enough back in time to reach a point where one can murder one’s, own grandpa.

4. Multiverse Theory

Physics researchers have attempted to bridge the gap between the galactically massive Einstein’s Theory of General Relativity and the physics of the tiniest universe-building components, quantum physics, for almost a century. However, they kept coming up against a problematic requirement: their theories could only be valid if our world is one among many in a multiverse. For instance, a multiverse is necessary for Erwin Schrödinger’s equation, which describes how a quantum wave collapses. And a multiverse is an essential component of string theory, which asserts that the world is formed of incredibly tiny vibrating energy threads. The problem is that no one can demonstrate the multiverse’s existence, let alone what it looks like or whether we can communicate with it.

The concept of a particle existing in multiple possibilities until measured, as described by Erwin Schrödinger’s equation for the quantum wave function, has been a mystery as it is unclear why the wave collapses upon measurement. In 1955, American physicist Hugh Everett proposed the Many Worlds Interpretation, which suggests that all possibilities manifest themselves instead of the wave collapse. However, only one chance is experienced consciously. The others will diverge into various timelines. Additionally, the cosmos constantly splits into new timelines since it is all a part of a single superposition probability wave.

Other multiverse ideas suggest that there are universes outside of our chronology, but they are too far away for us to observe them. These are predicted by the mathematics of the String Theory or the Eternal Inflation Theory, which asserts that the multiverse is constantly expanding and creating new “bubble universes.” Still, they are so far away that we are unlikely ever to encounter them. They could be membranes or floating “branes” that are individually characterized by a set of additional dimensions. Alternatively, they could be infinite probability bubbles created by the inflationary stretching of space and time, often known as “Quantum Foam” or “space foam,” which produces a quantum spacetime; each bubble has the potential to expand into an entire universe.

5. Novikov Self-Consistency Principle

Igor Dmitriyevich, a Russian physicist, created the Novikov self-consistency principle in the middle of the 1980s. It is sometimes referred to as the Novikov self-consistency conjecture and Larry Niven’s law of conservation of history. Novikov intended it to resolve the paradoxes associated with time travel, which are, in theory, allowed in some general relativity solutions that contain what are referred to as closed timelike curves. According to the principle, the chance of an event that would result in a paradox or any “change” to the past is zero if it exists. In this way, time paradoxes could not be made.

It presupposes that there is either only one timeline or that any alternate timelines, as proposed by the many-worlds interpretation of quantum physics, are inaccessible. Given these presumptions, it is possible to see the requirement that time travel not result in inconsistent results as a tautology. This self-evident truth cannot be untrue. The Novikov self-consistency principle, however, is meant to go beyond just the stipulation that history must be consistent and makes the additional nontrivial assumption that the universe obeys the same local laws of physics in circumstances involving time travel as it does in regions of spacetime that lack closed timelike curves. The self-consistency principle’s presumptions can be applied to hypothetical situations involving intelligent time travellers and inanimate objects like billiard balls.

Time Travel Paradoxes

Astronomy Desktop Space

Although going back in time defies one of the most fundamental tenets of physics, causality, Einstein’s theories of relativity do not explicitly exclude it. Here are some paradoxes that have caused both scientists and fans of time travel movies alike many restless nights over the years because they are naturally brought about by the principles of cause and effect being ignored in the case of time travel.

1. Predestination Paradox

When a time traveller’s activities influence past events and ultimately contribute to the event he is seeking to stop from happening, a predestination paradox develops. Predestination paradoxes assert that whatever has occurred must continue to occur and that events always unfold similarly. You’ve created a predestination paradox by trying to influence the past. The assumption that the version of events you have experienced is already constructed into a self-consistent interpretation of reality and that trying to change the past will only result in you paying out your part in making an event in history, not modifying it, is one method to approach this kind of dilemma.

Predestination paradoxes, sometimes known as causal loops or causality loops, are time-travelling paradoxes frequently employed as conventions in science fiction. It happens when a time traveller finds himself entangled in a chain of circumstances that “predestines” him to return in time. In some ways, this paradox is the opposite of the grandfather paradox, in which the time traveller kills his grandpa before either of his parents is born to prevent time travel by erasing his existence. In this scenario, a time traveller would only be playing his part in shaping history, not changing it, if he attempted to change the past.

2. Bootstrap Paradox

In a Bootstrap paradox, an item, person, or piece of knowledge is transported back in time. It creates an unending loop without development and with no apparent origin. Since ontology is an area of philosophy that deals with the nature of being or existence, it is also known as an ontological paradox. The phrase “pull oneself over a fence by one’s bootstraps,” which refers to doing an impossible or improbable endeavor, is where the word “bootstrap paradox” comes from.

In this case, by grasping your bootlaces and pushing upwards to pull yourself over a fence.

Robert A. Heinlein, a science fiction author, popularized the term “bootstrap paradox” after describing the time travel paradoxes that Bob Wilson runs into after activating a time portal in his narrative. For example, Wilson travels to the future and receives a notebook from his future self. Wilson then returns in time and uses the knowledge in the notebook to position himself as a kind tyrant. Wilson copies the information into a fresh notebook and throws away the old one when it looks worn. Later, he reflects that there was only ever one notebook and that the one that has just been created is the one that will be given to him in the distant future.

3. Let’s Kill Hitler Paradox

The Killing Hitler paradox can make you question your reason for going back in time to kill him, just as the Grandfather Paradox can create a paradox in which your birth is prevented. Killing Grandpa might only have a small “butterfly effect,” but killing Hitler would affect everyone on the globe, even if just because you studied him in school. If you were successful, there wouldn’t have been a need for time travel in the first place, which leads to the contradiction itself. Hitler’s acts wouldn’t be remembered in history, and you wouldn’t be motivated to try if you killed him.

A hypothetical situation known as the “Let’s Kill Hitler” time travel dilemma is frequently used to highlight the difficulties and contradictions involved with time travel. It’s not a request to kill Hitler in the literal sense; instead, it’s a thought experiment to examine the effects of changing historical events. The inherent paradoxes and difficulties of altering the past through time travel are demonstrated by this paradox. Time travellers may wind up defeating themselves and creating a paradoxical loop if they successfully stop the things that prompted them to travel through time in the first place.

The nature of time, free will, and causation are all issues brought up by this thought experiment. It highlights the difficulties and probable logical inconsistencies that emerge when considering the prospect of changing the past through time travel. Even though it’s an intriguing topic, it’s vital to remember that time travel is still a theory, and its paradoxes are primarily conceptual.

4. The Twin Paradox

The twin paradox is a thought experiment that illustrates the odd way Albert Einstein’s theory of relativity’s concept of time dilation manifests itself in contemporary physics. Relativity states that time dilation occurs when two frames of reference that move apart from one another experience time differently. Using Lorentz transformations, a fundamental component of relativity, this can be determined with pinpoint accuracy. Paul Langevin first proposed this paradox in 1911, focusing on the concept that acceleration was the primary factor behind the difference.

The Twin Paradox, possibly the most well-known thought experiment in relativity theory, has revived interest thanks to Paul Davies. In this paradox, one of the two twins leaves the planet and returns to a distant star at a speed almost equal to the speed of light. According to special relativity, a clock that is watched while moving past an observer at high speed appears to run more slowly. Many literatures examine this paradox, but very few resolve it. The general theory of relativity is thought necessary to explain the paradox. The accelerations that the traveller experiences are accidental and can be determined by special relativity alone.

5. Polchinski’s Paradox

American theoretical physicist Joseph Polchinski put out a time paradox scenario in which a pool ball enters a wormhole and exits at the other end in the past, just in time to strike its younger counterpart and prevent it from entering the wormhole in the first place. Since nothing in Einstein’s General Relativity excludes the idea of time travel, closed timelike curves (CTCs), or tunnels across spacetime, scientists take Polchinski’s dilemma seriously. Furthermore, it offers a superior research technique for scientists to consider the puzzle because it is founded on the laws of motion rather than the indeterministic concept of free will.

The billiard ball would cause a strike that alters the route of its younger version, but not enough to prevent it from entering the wormhole to avoid the inconsistencies Polchinski outlined. This answer relates to the “timeline-protection hypothesis,” according to which a probability distortion would occur to prevent a paradox. This also explains why, if you tried to travel back in time and kill your grandfather, something would always happen to prevent it, maintaining a consistent version of events.

Joe Polchinski presented Kip Thorne with this intriguing paradox in 1990. Fernando Echeverria and Gunnar Klinkhammer were similarly intrigued by the contradiction, and they investigated the physics behind potential ball trajectories and collisions. In various instances, the future form of the ball either succeeds in striking the previous version with enough force to prevent it from entering the wormhole or fails to do so. Following applying quantum mechanics to these scenarios, Thorne and Klinkhammer concluded that, while numerous outcomes from Polchinski’s setup are possible, the probability of a non-paradoxical outcome is very high. This is consistent with the Novikov self-consistency principle, according to which there must be a 100% chance of a non-paradoxical result.

Most Compelling Evidence of the Possibility of Time Travel

Vintage Rudder Sextant Sailing

For ages, daydreams, pop culture, and discussion have all explored the idea of being able to go back in time or forward in time. A potential method for man to travel across time was explained by a grimly predictable present that contains quantum mechanics, the Higgs Boson, and other science-related hypotheses. The history of time travel in our society has also repeatedly crossed the line into non-fiction, making convincing arguments that time travel is authentic.

1. A Small Time Machine Watch

Chinese archaeologists in Shangsi County found a massive tomb in December 2008 that was thought to contain Si Qing’s undamaged, 400-year-old coffin. However, before they even managed to open the lid and discover what was inside, they found something even more incredible than a long-dead bag of bones in the ground near the tomb: a tiny golden object in the shape of a watch that couldn’t have been older than a century, with the time frozen at 10:06 and the word “Swiss” engraved on the back.

People believed that time travel was responsible for how it ended up buried in the ground of an old, unexplored tomb. Scientists wondered how the tiny watch ended up in a casket from the Ming Dynasty from the 15th to the 16th century. The discovery gets more intriguing given that Geneva had a ban on flashy jewellery at the time, making the possibility that it is a watch plausible given that watches were viewed as vital, functional accessories rather than ornaments. Before 1780, there was no evidence that watches were ordinary throughout Europe.

2. The Internet and John Titor

The most well-known of these online futurists went by John Titor. The tale of John Titor, a man who asserted to be from the year 2036 and who supported his ludicrous claim with several prophecies, was one such subject that surfaced on various online message boards. Some were ambiguous, while others were highly detailed. According to Titor, the United States would be divided into five smaller territories, nuclear weapons would decimate the environment, the infrastructure would be wrecked, and most other superpowers would have been wiped off. He also provided some in-depth information regarding his time machine, but they have yet to attempt to build their own.

Although it is still unknown if John Titor is a natural person or a time traveller, his early internet appearances undoubtedly captured the attention of scientists worldwide. Some people have started searching the internet for actual, non-conspiracy theory evidence of time travel. To locate proof of time travellers, Robert Nemiroff and Teresa Wilson from the physics department at Michigan Technological University have searched the web for references to the information posted before it should have been possible. The theory is that they might discover evidence of time travellers if they utilize sophisticated Google tools to target their searches to periods before events occurred.

The research has yet to produce any tangible proof of time travellers. Nemiroff and Wilson’s Cornell paper suggests that although the negative results reported here may indicate that time travellers from the future are not among us and cannot communicate with us over the modern internet, they are no proof. It may be physically impossible for time travellers to leave any lasting remnants of their stay in the past, including even non-physical ones. Natural scientists believe that time travel is possible.

3. Mobile Phones Spotted in Old Movies

The internet is the best detective in the world. Catfish have launched a grass-roots industry for tracking down internet fraudsters, Reddit has identified criminal suspects, and the web’s collectively inquisitive minds have discovered evidence of time travel in the most improbable locations. For instance, a brief excerpt from a bonus feature on the Charlie Chaplin movie The Circus on DVD. Everyone panicked when the video with annotations was released to YouTube. It makes sense, considering that there looked to be a mobile phone user in the background of a crowd gathered for the 1928 Grauman’s Chinese Theatre film debut.

Since then, historians asserted that the object is an ancient hearing aid that appears like a phone rather than a modern cell phone used by a time traveller. However, in the 1948 film Fort Apache, Henry Fonda and Shirley Temple had the bright idea to check their stagecoach route on an iPhone. Remarkably, they have 3G reception in the desert, considering this was well over 50 years before such technology was even developed. People often assume that either or both of those Hollywood actors are time travellers, which makes sense given that they have access to all the latest technology long before the rest of us.

4. The Gian Hadron Collider

The Large Hardon Collider, 17 miles in circumference, 574 feet below ground, and the most potent atom-shatter ever made, allowing protons to collide at nearly the speed of light, is the most intricate thing ever made by humans. It’s so powerful that both scientists and tabloids were a bit worried that it might result in the birth of a wormhole or a black hole, rips in spacetime that could wipe out all of existence. Or permit time travel. The Higgs boson particle was discovered without the end of the world, and the collider has been turned on several times without collapsing.

According to Stephen Hawking’s claim regarding time travel, we haven’t yet been overrun by visitors from the future, but this could be because they can only travel back as far as the invention of time travel. The LHC may be our first step toward time travel. Therefore, we should all be on the lookout for folks wearing glitzy attire, donning advanced Google Glass, and speaking profanity we don’t understand. While Weiler and his collaborator Chui Man Ho’s theory centres on the Higgs singlet. This particle was predicted to be produced by the discovery of the Higgs boson. It can enter an additional fifth dimension where it can travel forward or backwards in time and reappear in the future or past.

5. The Montauk Project Conspiracy Theory

Conspiracy theorists often use The Philadelphia Experiment as a springboard for additional claims regarding time travel studies. The Montauk Project is supposedly a string of top-secret American government initiatives exploring “exotic” experiments, including time travel at Camp Hero or Montauk Air Force Station in Long Island. Camp Hero and Montauk Air Force Station locations are real, and the American military often engages in secret US government initiatives. Preston Nichols, an American novelist who asserted to have retrieved suppressed memories of his involvement with time travel research, appears to be the originator of the Montauk Experiment tales.


Many individuals are currently debating and discussing time travel, sometimes known as “jumping into another timeline.” Even though most people don’t think it’s possible, there is time travel evidence that makes us pause and consider whether it’s true. Many individuals find it fascinating to jump between multiple timelines to see what the world will look like in 5, 10, or even 20 years. Despite initially appearing simple, time is one of our universe’s most enigmatic elements, according to modern physics. Even with this new understanding, some scientists wonder whether time exists or is merely a “stubbornly persistent illusion” As Einstein famously said, Einstein altered our understanding of the idea. Whatever time is, physicists have discovered some intriguing methods to control it, leading them to think about crossing it in novel ways.