This article delves into the physics behind time travel, exploring potential mechanisms, theories, and paradoxes that accompany this concept. It begins with Albert Einstein’s theories of relativity, which describe space, time, mass, and gravity. A key outcome of relativity is that the flow of time isn’t constant. Time travel has been extensively discussed in the context of general relativity, where one has closed time-like curves (CTCs).
Classical physics can be classified into various branches, but it mainly deals with energy and matter. The traditional branches of classical physics are Optics, Acoustics, Electromagnetics, and Quantum Physics. The laws of physics allow time travel, but why haven’t people become chronological hoppers?
The theoretical study of time travel generally follows the laws of general relativity. Quantum mechanics requires physicists to solve equations describing how probabilities behave along closed timelike curves (CTCs), theoretical loops in spacetime that might make it possible to travel through time.
There are parts of astrophysics that might point to time travel, such as Black holes, White Holes, Einstein-Rosen Bridge, and Worm Holes. Relativity, statistical mechanics, and quantum mechanics (things like fundamental clocks) also play a role in understanding time travel.
Some theories suggest that it might be possible to travel through time using quantum mechanics. Cosmology and quantum physics are the two important branches dealing with time travel. Many physicists believe time travel into the past is at least scientifically possible, as many argue that Einstein’s relativity has shown this. Quantum mechanics, the branch of physics that deals with subatomic particles, offers additional insights into the nature of time and the universe.
📹 Is Time Travel Possible? Here’s What Physics Says
What does physics say about time travel? Surprisingly enough it doesn’t just say it’s impossible, it’s more complicated than that.
What type of physics is time travel?
Relativity allows us to travel into the future without a time machine, either by traveling at the speed of light or spending time in an intense gravitational field. Both acts experience a relatively short amount of subjective time, while decades or centuries pass in the rest of the Universe. However, going backwards in time is harder due to insufficient knowledge and theories, as stated by Barak Shoshany, a theoretical physicist at Brock University.
What is the hardest branch of physics?
Theoretical physics is currently engaged with a number of challenging topics, including quantum gravity approaches such as M-theory, twistor theory, the non-commutative geometric approach, and Thiemann’s spin-network approach.
Is rewinding time possible?
Scientists from the Austrian Academy of Sciences (ÖAW) and the University of Vienna have discovered that it is possible to speed up, slow down, or reverse the flow of time in a quantum system. This is not time travel, but implementing or reverting to different quantum states from different points in time. In the subatomic universe of quantum physics, things considered impossible in the physical world, such as superposition, entanglement, and teleportation, seem possible. Researchers Miguel Navascués and Philip Walther have published a series of papers explaining the possibility of speeding up, slowing down, and even reversing the flow of time within a quantum system.
What are the 12 branches of physics?
Physics is a scientific discipline that aims to construct and test theories of the physical universe. It can be organized into several distinct branches, including classical mechanics, thermodynamics, statistical mechanics, electromagnetics, photonics, relativistic mechanics, quantum mechanics, atomic physics, molecular physics, optics and acoustics, condensed matter physics, high-energy particle physics, and nuclear physics.
Classical mechanics is a model of forces acting on bodies, including sub-fields for solids, gases, and fluids. It includes the classical approach, Hamiltonian and Lagrange methods, and deals with the motion of particles and the general system of particles.
Is time travel related to quantum physics?
The study of time travel follows the laws of general relativity, while quantum mechanics involves solving equations about probabilities along closed timelike curves (CTCs). In the 1980s, Igor Novikov proposed the self-consistency principle, which states that changes made by a time traveler in the past must not create paradoxes. This principle ensures that history remains consistent, preventing contradictions. However, this principle may conflict with certain interpretations of quantum mechanics, particularly unitarity and linearity.
Unitarity ensures that the total probability of all possible outcomes in a quantum system always sums to 1, preserving the predictability of quantum events, and linearity preserves superpositions, allowing quantum systems to exist in multiple states simultaneously.
Is time travel part of quantum physics?
The study of time travel follows the laws of general relativity, while quantum mechanics involves solving equations about probabilities along closed timelike curves (CTCs). In the 1980s, Igor Novikov proposed the self-consistency principle, which states that changes made by a time traveler in the past must not create paradoxes. This principle ensures that history remains consistent, preventing contradictions. However, this principle may conflict with certain interpretations of quantum mechanics, particularly unitarity and linearity.
Unitarity ensures that the total probability of all possible outcomes in a quantum system always sums to 1, preserving the predictability of quantum events, and linearity preserves superpositions, allowing quantum systems to exist in multiple states simultaneously.
Is time travel possible metaphysics?
Time dilation is a concept that describes the difference of elapsed time between two events, measured by observers moving relative to each other or differently, depending on their proximity to a gravitational mass. It posits that the faster we move through space, the slower we move through time. This allows for one person traveling at a high enough speed to have time pass at a much slower rate for them than a person who is not in motion, causing the former individual to age significantly slower.
In Einstein’s relativity, time, or change, continues to move forward for both the time-traveler and everyone else on Earth. This means that if the time-traveler engages in such a process, they would not freeze their bodily processes or uncontrollable factors about themselves; they would simply slow them down. Accordingly, they would not partake in a different now from everyone else; they would merely perceive it differently. This sort of time-travel is merely measuring different processes of change to create a new conception of time.
However, Einstein never claims that a person partakes in a different now or travels to a new dimension; if time were to suddenly stop all at once, the time-traveler would still stop in his travels at the exact same instant as everyone on Earth. This is the reason why Einstein’s time dilation is not really time-travel at all: the “time-traveler” continues to live in the same moment as everyone else.
Time-travel, as understood properly through metaphysics, is only logically plausible to a small degree. Possibilism and eternalism argue that other modes of time exist just as much as the present does, but this implies that they would be subject to change, which both theories claim is not the case. Traveling into the past with such a view of time is nonsensical, as the past cannot be set and open to change at the same time.
To accelerate time into the future is to engage in Einstein’s theory of relativity, where time moves slower for one person than all others. This leads to the recognition that time is a mere mental, rational being, entirely manmade, serving the means of measuring change. All Einstein’s theory maintains is that it may be possible to slow down one’s bodily processes by changing how one measures time, which does not clash with Thomistic metaphysics, considering all partake in the one and only mode of time that is being, i. e., now.
In conclusion, time is a construct that allows us to make sense of this world and its changes. This recognition leads us to question what allows us to measure these changes or what causes them in the first place, thus setting us on a quest to unravel the mysteries of the universe.
Which branch of science deals with time travel?
Time travel is a concept in philosophy and science fiction, often achieved through the use of a time machine. It is uncertain whether time travel to the past would be physically possible, and it may raise questions of causality. Forward time travel is extensively observed and well understood within special and general relativity frameworks. However, making one body advance or delay more than a few milliseconds compared to another is not feasible with current technology. Backward time travel can be found in general relativity solutions, such as a rotating black hole.
Travel to an arbitrary point in spacetime has limited support in theoretical physics, usually connected only with quantum mechanics or wormholes. Ancient myths depict characters skipping forward in time, such as King Raivata Kakudmi in Hindu mythology, Kumara Kassapa in the Buddhist Pāli Canon, Urashima Tarō in Japanese mythology, and Honi ha-M’agel in Jewish tradition. These stories highlight the possibility of time travel and its implications for various aspects of human life.
In summary, time travel is a hypothetical activity that could be achieved through suitable geometries or motions in space. While it is uncertain whether time travel to the past would be physically possible, it is a widely recognized concept in philosophy and science fiction.
Which branch of physics deals with time?
The branch of physics, focusing on the properties of matter and energy and their interaction, is divided into various branches. Relativity, a theorem formulated by Albert Einstein, states that space and time are relative, and all motion must be relative to a frame of reference. Physics is a crucial subject in all science, and its branches have evolved to understand every aspect of the physical world.
These branches include mechanics, optics, thermodynamics, electromagnetism, relativity, and acoustics. Each branch has gained a full title in modern times, making physics a comprehensive study of the physical world.
Does quantum physics allow time travel?
The physical feasibility of time travel remains a topic of debate, yet experimentalists can leverage quantum mechanics to simulate time travel in a laboratory setting, facilitating precise measurements. Although time-travel simulations do not permit the modification of past events, they can facilitate the development of more optimal futures by addressing issues from the past.
Which field in physics study for time?
The problem of time in theoretical physics is a conflict between general relativity and quantum mechanics. Quantum mechanics views time as universal and absolute, while general relativity views it as malleable and relative. This raises questions about the physical nature of time and why it seems to flow in a single direction, despite no known physical laws at the microscopic level. In classical mechanics, time is treated as a classical background parameter, external to the system itself.
This special role is seen in the standard formulation of quantum mechanics, where it is regarded as part of a priori given a classical background with a well-defined value. This treatment of time is intertwined with the Copenhagen interpretation of quantum mechanics and the conceptual foundations of quantum theory.
📹 Time Travel in Fiction Rundown
For ages I’ve been thinking about doing a video analyzing time travel in fiction and doing a comparison of different fictional time …
It’s also equally interesting in the Harry Potter type time travel, that the time traveler effectively has no free will over whether they will commit to the time travel or not. It is their fate no matter their conscious thoughts, they will perform the action. And that also ties in well with the HP universe’s use of prophecies, which also imply that free will to a certain extend is blurred. Potentially free will exists, but all thoughts and decisions will still lead to the same outcome – like throwing a stick in a stream – Its path down the stream may be random, but it is a certainty that it will flow down through it one way or another. It is confined chaos.
One of my favorite examples of time travel, and in my opinion the best example of time travel, comes from Steins;Gate. There are three methods of time travel in Steins;Gate: D-Mail, Time Leaping, and physical time travel. With a D-Mail, you send a text message through time, which has the possibility of changing the past. If the change isn’t big enough, then functionally nothing will change (for instance, if the thing you tell someone to do is minor or if they just ignore the text), but if it’s big enough, you can change a lot. This is a large part of the plot, the characters sending text messages to the past and it enacts huge changes. For instance, in the story, someone plans to leave, and you send a D-Mail to them telling them to stay, and they will which causes massive changes. Nobody remembers anything from a D-Mail except for the protagonist Okabe. With Time Leaping, you mentally jump back into your past body from the future. You can only jump back 72 hours, and obviously because of this restriction you can only jump back three days before the machine was created. The person who uses the machine remembers everything, and the timeline changes just by virtue of your future knowledge. If someone other than Okabe were to use it, however, Okabe wouldn’t notice any timeline change under normal circumstances, unless whoever it was did something so big that it forced the timeline to change. But time leaping itself wouldn’t cause the timeline to change on its own, it’s what the Leaper does with the future information that would cause it to change, With physical time travel, it’s exactly what it sounds like.
The game Outer Wilds has probably my favourite depiction of time travel ive seen recently (huge spoilers, go play the game first) Similarly to Groundhog Day, the main character seemingly relives the exact same 22 minutes over and over again, retaining all their memories of past loops. We find out later in the game that there is effectively a time machine linked to the main characters brain that is repeatedly sending our own memories back in time 22 minutes to their past self, creating the illusion of a time loop where in reality they have consious memories of things they have not done yet.
The problem with time travel is that space is associated with time. For example, the solar system is going around the Milky Way galaxy at 1 million miles per hour, so what happened an hour ago took place a million miles away, and what happened one day ago took place 24 million miles away, etc….So if you travelled backwards in time you would also have to travel to the exact same point in space.
My favorite time travel is from The Five Kingdoms series by Brandon Mull. After traveling back in time, you’ll find that the thing you thought you’d changed had actually always happened. In other words, it’s like Harry Potter’s time travel, except with one key distinction: you cannot travel to a time when you already existed, meaning that you can’t travel to the same time twice and can’t travel to any time that you were already born.
the “no free will” point about Harry Potter is exemplified perfectly in the movie when, without any explanation or discussion, Hermione suddenly grabs the pebbles that she throws through the window of Hagrid’s house. While it could be said that she would’ve reasoned out a solution to cause their past selves to leave the house regardless, it could alternatively be said that she had that “Eureka moment” BECAUSE she had already seen the results of it in her personal history (the vase breaking). It’s utterly brilliant, and surprisingly, it’s also completely realistic. According to the Novikov self-consistency principle (as described by Wikipedia; academic discretion is advised) “if an event exists that would cause a paradox or any “change” to the past whatsoever, then the probability of that event is zero”. In other words, you travel to the past because you traveled to the past and you do what you already did, and no more (nor less)
The major logical consistency problem in Prisoner of Askaban is the idea of responsible adults giving a 14 year-old an all-powerful time machine just so she could attend 16 hours of classes a day and then never using it again, no matter how handy it would have been to save lives and prevent horrific disasters later in the series.
I personally love the time travel mechanics of Homestuck. It follows the self-consistent loop principle to such a degree, that free will is theoretically preserved, but deviations from the basically predetermined actions result in a branching of the time line and the new branch subsequently becoming ‘doomed’. This means that the extremely intricate web of interwoven time loops which in the Alpha time line resulted in the creation of the universe and these loops is disrupted so that it doesn’t result in its own existence. So the doomed branch gradually fades away, in almost every case accompanied by everything going wrong and everyone dying one way or another until reality itself dies. Of course, this gets wildly more complicated as soon as alternate universes and other shenanigans come into the mix, but that is the gist of it.
Life is Strange has an interesting time travel mechanic too. The main character, Max, can reverse time yet she stays in the exact place she just was while the world around her goes back to how it was. For instance, in one of the scenes, she and Chloe are breaking into the principals office and trigger the alarm, Max rewinds time to when Chloe was still outside but Max was still in the office.
One great example of time travel in fiction I really like is The Fifty Year Night from Hilda, where changes in the past doesn’t create new timelines but rather change the current and only one proceeded by a time worm chasing any leftover from the “original” timeline, including the original characters who did time travel so the “new timeline” can exist without paradoxes such as two of the same person. It’s such a chaotic and kinda logical/magical way to see time travel and I love it.
I wish you would’ve covered time travel in steins gate. In this anime there are infinitely existing timelines and when you time travel essentially you are sending your consciousness into your body of whatever timeline you go to. It is a different but identical universe that happens to be at a different point in time.
The original Terminator was a good example of the “self-fulfilling prophecy” type of time travel where the events that take place were exactly what happened the “first time”. I also like this type the best. The reason I don’t like the ones where you can make changes as much is because it’s too easy to fall into a paradox if a writer isn’t careful. For example, if your future self goes back to stop yourself from taking a certain road to work. But if you were forced to take the alternate route without anyone knowledge about it then you aren’t going to know to go back in time the “second time” to alter the path. So now it’s a paradox.
My favourite time travelling type, is that once you go back in time and change anything you cause a new timeline, but that doesn’t affect you in anyway since you are from another timeline, so if you killed yourself that is a different you and it does not mean you disappear its just the ‘killer’ you is now in a different timeline than originally was; it just makes it really hard to get back to your original timeline – if not impossible.
In my opinion, Bill & Ted’s style of time travel is identical to Harry Poter’s style where the “Time traveling clone” has the same past experience as the original one. Also, I’d like to reference the “Johnny Maxwell” book series where each instance you travel, you can change the way everything works.
I think one of the best time traveling devices is the one in Stephen King’s book “11/22/63”. In it, there can only be one time line. If you travel back in time and change something, when you return to the present, the effects of what you did take effect and you change the present. But if you travel back again to change something else, now everything you did in the previous travel didn’t happen so now only what you change this time will take effect. Another cool thing about it is, that if you want to change small things that won’t really affect the world (like going back in time to watch Star Wars when it came out, and then coming back to the present), it would be very easy to do. But if you want to change something major (like killing your father and prevent yourself from ever being born), somehow you will find lot’s of hardships to do so (like your gun always jams when you go to kill your father, or you get hit by car on the way to kill him, stuff like that). That way, no time travel can “accidentally change the past”. You must actively want to do it. And even then, when you change things, the world sometimes mend’s it to go back to the normal timeline (like if you somehow manage to kill your father after many trials, you don’t disappear because actually your mom was fucking the mail man and you were never your fathers son)
I like the idea that time travel doesn’t “create” alternate timelines; all timelines already exist, but by traveling back in time, you’re actually switching to a timeline where that is what happened. So you can never change a timeline, but you can change the timeline that you’re in. If by some chance you merely go back on the same timeline, then things will progress as before, like in the Harry Potter example.
I like the steins gate, John titor theory of world lines and convergence theory. Retractor fields and such. It just makes sense that way as well. Because it imposes the idea of you can’t fit a big being into a small hole, so sending your memories as data is the best way to go back in time, sadly that would mean you can only travel between yourself and past self.
My favorite type of time travel is the one described in Ed by qtnm (highly recommended!). There the very act of time travel creates a new universe that doesn’t influence the original one. If you time traveled you can never go back to the original universe and there will be two independent copies of you simultaneously, both with a free will. So no killing grandpa paradox – from the perspective of the original universe you just disappeared, from the perspective of the new universe you just appeared out of nowhere, killed your grandpa and your second copy never get born, but it didn’t affect your existence, because from your point of view it is just continuous timeline forward and “traveling back in time” doesn’t affect your own past.
I like the time travel in Dragon Ball, where the act of time traveling creates an alternate universe/timeline. The time traveler can change the new timeline in anyway they want, but when they return to their timeline nothing is changed. The time traveler can create a better world for an alternate version of themself and their friends, but they can’t experience the better world for themself. I think it is very tragic but makes sense.
Bill and Ted actually have pretty strict self-consistency, they just play with the concept pretty fast and loose, with the audience not being aware of what the characters are aware of sometimes, or a lot of the self-consistency scenes happening off-screen. For example, Ted’s dad “lost” his keys a week prior to the characters realizing they needed it, so they just went back (off-screen and post-hoc) to when his dad did have the keys, stole them, and hid them in a nearby convenient spot for the characters to immediately find in the scene. Bill even mentions this explicitly, “Remember, Ted, we can’t forget to actually do this afterward, or it won’t have actually happened.”
Steins gate and donnie darko are probably some of the most interesting pop-media timetravel options to discuss. Donnie darko uses a tangent universe to travel time, effectively you travel in sace and/or time, but there needs to be a universe that is locally tangent in space or time. And steins gate opens the flood gates into the concept of converging and diverging time lines, relying on the similarity requirement to make time travel possible. Effectively saying time is constantly moving forward but there are infinite universes. Similar timelines are jumpable, but universes have become samples from a “random field” effectively allowing both determinism to exist from a single point of reference (such as the main character) but from the view of all timelines it is completely stochastic. Both are extremely interesting concepts, and rely on physics to a lesser degree than enders game, but way more than any other film/book/show i have seen so far.
When people bring up timeturners, they often think “why didn’t people just go back and kill Voldemort before he did anything bad?” My answer to that is the dumb wizards not understanding how timeturners work, going back and failing. And the smart wizards don’t bother because since Voldemort is alive and well right now, it clearly wouldnt work.
My favorite type of time travel is the kind that immediately splits the timeline because of the butterfly effect. In other words, you aren’t going to the past and changing things, you are jumping into an alternate dimension that is identical to a past version of your world, and then functionally living there. If you are using a method that lets you return to your own timeline, you can pick up where you left off, but all you’ve really done is hop into a similar dimension, do some stuff, and then return home, where nothing has changed. Or you can jump to the past, do some stuff, and then wait for the future to live out the rest of your days in this new world where another version of you already exists.
The time travel in the comic book “Planetary” works slightly in the same way as “Primer”, in that you can only go back so far as the first Time Machine was turned on. What’s interesting in “Planetary” is that they’re concerned about every traveler from every future showing up simultaneously the moment that the first machine is turned on, potentially destroying free will.
My favorite infinite time-loop is from “The Twelve Monkeys” Bruce Willis, our unlucky time traveler, is shot and killed after being sent into the past to prevent a deadly plague. A young kid, whom we learn is Willis’s character while younger, witnesses the killing. As Willis is dying, he recognizes himself as a kid, and memories of seeing a man killed in the Airport flood through his mind. The young man somehow survives the devastation of the world-wide plague, only to be sent back in time to the Airport as an adult to prevent the plague from ever starting. The adult dies, is witnessed by the kid. Lather, rinse, repeat. The cycle never ends for Willis.
Some really fun scifi work in the fact that the self-consistency demand itself gives you great power. Say you need to guess a decryption key. Make a time machine and go back and tell yourself the guess was wrong if it was…then only consistent solution is the right guess (or something going weird and wrong so better be sure there is a correct answer).
An interesting time travel ish story is “The Jaunt” by Stephen King. Takes place in the future, where interstellar travel is possible via teleportation portals that people use like an airport. To use the portals you must pass through while in a sedated state; as the short story goes on they reveal the background of the invention of the machine and how it came to be discovered that a person must be unconscious to safely “jaunt”. Won’t spoil the story, suffice it to say that it involves the perception of time being affected by teleportation, and King puts a really dark and genuinely frightening edge into what transpires as primarily a sci-fi short story. Very haunting ending and thought provoking! Good stuff
Here’s another one for you: Homestuck. If you make a logically consistent loop, you’re fine, and nothing happens other than a loop-de-loop in the timeline. But if you don’t, it’s more like making a duplicate of the universe as it was in the past, then jumping to that. It’s like copying a word from a document, holding ctrl-z for a while, pasting the word in, and saving it as a new file. So you can’t change the past – but you can copy it and change the copy.
What I liked about the Harry Potter time travel was the fact that you got to see what was causing all these events, truths behind scenarios. Of course it’s a literal proof of fate. That there’s nothing you can do to fix a past mistake because it’s destined to occur. It makes sense, and is easy to comprehend.
A sudden jump to past has (among other things) also a locational problem: it you jump just ten minutes back in time the Earth wasn’t at that same location then and you’d end up to be in space. While time-jumping you should somehow be able to very accurately follow the movement of the Earth too: two meters too low and you’ll be under ground; ten meters too hi and you’ll be falling down and die.
I love the explanation of Harry Potter time travel given in a fanfic called The Methods of Rationality. Basically HP Time travel DOES allow you to change the past, but that obviously leads to an unstable progression of timelines where your “new past self” will make slightly different choices and still go back in time, leading to new variations of choices, until you land on a stable set of choices where your overlapping selves actions line up such that your actions when time traveling cause your past self to mirror those actions in turn. Harry even tries to take advantage of this and prove that N=NP by instantly finding the prime factors of a large number. He has a classmate multiply two prime numbers with values between 1-100 to use as a target number, then makes a plan to send a piece of paper back in time to himself. The logic he intends to follow follows this progression: “If the paper from the future is blank, I will write down 1 x 2 and send it back in time to myself. If the product of the two written numbers is not equal to the target number, increment the first number to the next prime and send it back in time to myself. If the first digit’s next prime would be larger than 100, drop the first digit back to 1, increment the second number to the next prime, and send it back in time to myself. If the product of the two digits is equal to the target number, send those two digits back in time to myself” The idea being that the only stable time loop would be the one that contained the prime factors of his target number.
Stargate Episode 1964 had a really interesting episode where, no major spoilers, an elite team called SG-1 uses a wormhole device, a stargate, to travel to distant planets in exploration. However, if the wormhole collides with a Solar Flare in just the perfect way, it sends the wormhole back in time. One of the best Episodes of the TV Show.
“A Christmas Carol” is arguably the first Time Travel Story in the sense that we usually think of: a person traveling by some (impossible) means to arbitrary points in the past/future. There were some previous stories in which someone saw a vision of the future, but that’s really just a form of prophecy… and Rip-VanWinkle-style stories where someone just skipped time, which doesn’t even break the laws of physics. Dickens essentially invented a whole genre of SF.
One really interesting time looper game is Outer Wilds (heavy spoilers for the game ahead btw) The premise of the time travel is based on how black hole/white hole wormholes happen to spit people out a tiny bit in the past. Then, masks were made that can take information into a wormhole that gives 22 minutes of past travel, and link it to… well, either people or even machinery. 9 million timelines later, they find what they were looking for, and the second part of whatever was going on takes place which takes you (as well as a buddy) into the loop, causing for some REALLY interesting timelines. It still works like the groundhog day looper, but you can also turn off the loop (and turn it back on again) and also, the mechanism powering the loop can be used to power something else. The premise of the time loop roping more people into it, though, is a really interesting premise, especially as the other people can remember the interactions with each other or go about other things!
There’s two Marvel Comics mutants with the ability to self-duplicate. Jamie Maddrox, the Multiple Man, generates copies of himself. If the copies die, he doesn’t suffer harm any more than an amoeba is harmed if one of the other amoebas it divided into dies. The other, Gardner Monroe aka Flashback, didn’t generate duplicates — he pulled future versions of himself back into his present. When one of his future selves was killed during a fight (ironically by his team leader using the duplicate as a human shield, apparently thinking they were expendable like Maddox’s copies), Flashback had a full-blown panic attack. He knew that at some point in his future, he would disappear and never reappear, having died at the moment in the past he’d been pulled back to (and that his present self had just witnessed). But he had no idea if it would happen in the next second, or hour, or month, or year.
One of my favorite time travel films is the anime “The Girl Who Leapt Through Time.” It has an interesting plot, good characters, and a reasonably plausible depiction of reverse time travel. The physics aren’t explained (nor are they relevant), but the consequences of going back in time are dealt with in a way that feels solid and intelligent.
personally, i like the Steins;Gate version of time travel, based off of ‘John Titor’s’ claim of divergence values, using the many worlds theory. If you haven’t seen the show, three people make a time machine out of a microwave that sends SMSs back in time, and instantly changes the world line. The main character can remember each individual timeline though, leading to the creation of a more effective machine that can take his current memories into the mind of an earlier point in time, also changing the world line. This also plays into Titor’s divergence model because to stop a sweeping event like a forceful takeover of the earth, you need to alter the world lines enough to be able to change the outcome. It works out a lot better in the anime, so watch that if you want a full explanation. It’s almost to primer levels of insanity.
The Harry Potter form of internally consistent time travel might appear the most logically neat, but it somewhat ignores the completely illogical inconsistency when viewed from outside the time loop, the famous bootstrap paradox popularised by that episode of Capaldi’s Doctor Who (Who write Beethoven’s symphonies?) It creates a series of events that, logically, have no instigating moment, no ‘start’, a perfect loop with no beginning or end. Harry went back in time and ends up saving himself from the dementors because he saw his future self do so. The Harry that he saved will then go on to fill his role while he moves on in the timeline, and so on and so forth, eternally. But in this scenario there could never have been a ‘first’ Harry to go back in time, because without him going back to save himself, he would have received the dementor’s kiss and been unable to. So while perhaps the most logically elegant in regards to not dealing with branching timelines, it is also one of the most infeasible forms of time travel, as it is a form of time travel that could never ‘begin’.
Take a look at Dark – it’s Harry Potter style time travel with an even more heavy-handed sense of fate, because you traveling back in time to STOP yourself from traveling in time actually created the events to cause you to travel back in time in the first place. Also . . . never considered A Christmas Carol a time travel experience before – nice.
I watched Stein’s;Gate and went to this article, and it was interesting thinking about how it fits in this rundown. Its interesting to see how the events of the past change when you come from the future, but still without making paradoxes. You create a new timeline but with the memories of the old one, and this allows you to pretty much fit yourself into any kind of time travel present in the second scenario presented here, where you affecting the past changes it. Take D-mail. The act of sending a text message to the past literally changes it so the future is overwritten but with you and your memories of the change intact. This is like “visiting the past” and allowing the butterfly effect (often mentioned in the show) to change the course of history as per how the text functions. Then with shifting consciousness to the past. You have now effectively traveled to your place in the past except with the knowledge and experiences of the future as it would pan out, much like in Groundhog’s day, with Bill Murray leaping around. The show is much easier to comprehend than many time travel stories by simply broadening the scope of how the time travel functions to simply splinter reality into “worldlines,” and from what I can tell, its made it easier to comprehend some of the more complex time travel stories by simply asking, “how does this line up with worldlines?” Its an interesting show and a great gateway into time travel concepts. Watch it, please. Maybe do a article on it. That would be great.
I just realised Back to the Future could’ve had a seriously spooky chapter. Emmett and Marty sometimes take photos with them which have characters vanish from the image, but the photo itself still exists. There would need to be a timeline where someone felt compelled to take a pointless photo, not knowing it was of a ghost from the original version of the past. Imagine Marty notices a confusingly blank photo being taken by a family member, and he’s reminded of his own family photos where he nearly vanished from history. He alerts Emmett, and we eventually learn that the erased person was Marty’s best friend from school, who Emmett unknowingly erased on his first time travel experiment, also setting up his own unlikely friendship with Marty. The entire trilogy was already an alternative timeline.
I love the time travel in Misfits and Dark. As you said, there’s a logic to it even if there isn’t an exact science. The actions of the characters have impactful consequences on the past, future and present and characters must do certain things in order to keep the timeline going. The only thing that bothered me about it I the fact that in those universes time travel becomes a sort of “time loop” with no beginning or end and the characters are destined to follow the same trajectory of events over and over with no hope of a break in the timeline. It seems impossible for any breaks in the timeline to occur because all the characters are given the same information and experiences in every loop, you can almost watch the story from any point, and it would eventually make sense and repeat itself.
To me back to the future is as logical as harry potter time travel, you have to stop thinking about it like multiple timelines but rather as a single timeline, the timeline goes as followed, the main character is born, years pass, mc goes back in time and does things, mc goes back to the future. He didnt change anything, he just followed the timeline
I love the HP time travel aswell, it looks a lot like the Attack on Titan (AoT) time traveling which essentially has one storyline that will be followed and you can’t change that (spoiler) Eren knew that he will lose the final fight and he knew he had to do the fight. Even if he didn’t he’d like still do it? It’s kinda weird but super cool!!
wow so i’m currently writng afiction which deals with time travel a little bit and i had to come up with a “fictional theory” for time travel and this article really helpedme to understand the different factos and rules that need to be established in order for it to make a difference to the story. Thank you so much!!
Time travel is honestly a really complicated subject, I’m glad there’s someone else who thought about this. Something I’m still wondering about is paradoxes and relating. Such as, if you invent a time machine and give it to yourself in the past before you invented it, you probably won’t give it to yourself, so you don’t have a time machine in the past because your motive is gone. If you do happen to get in a paradox, does time stop, do you disappear, or does the universe somehow fix your paradoxical problem? If it does, does it simply remove you from existence? Create a branching path in time? Anyways, let me wrap up. You create incredible articles, and I’m glad someone else thinks about this stuff.
Great article. And I agree. I also like the Harry Potter version of time travel where, if you went back in time, you have always been there. I recall this as being the version of time travel employed on the TV series “Lost.” Indeed, one episode from the fifth season even has the title which sums this up nicely: “Whatever Happened, Happened.”
Homestuck also had some really interesting time travel, sort of a spin-off of the harry potter version, but the people traveling through time DO get free will… sort of as an example, if the harry potter scenario happened in homestuck, harry would be able to just not save himself at all if he wanted… but it would create a “doomed timeline”, one that guarantees that everyone in it will die… mostly (and since homestuck also has a multiple “universes” thing going on, it also has a thing where anyone in a doomed timeline is completely unable to interact with other universes) theres a few other wrinkles to it as well, like the fact that characters that died in doomed timelines can still be relevant later since all characters that are truly dead go to an afterlife of sorts, or the fact that a character ended up in a doomed timeline but was able to go back to save the main timeline (and be the reason the main timeline gets saved) as a result, it creates a thing where anyone that does time travel can usually do it safely, but they have to keep track of anything they see their time-traveling future self doing, or get fucked by creating a doomed timeline — …aaaand i just remembered a Certain controversial plot thing called “the retcon” (its not the same as the author retconning the story, this just is an in-story event that people call “the retcon”) that’s basically an entirely different type of time travel, its closer to the usual way “multiple timelines” is done, and while there are no obvious incongruencies or paradoxes, a lot of people didnt like it because it undid a whoooooole bunch of character development (and its.
What I would find interesting is a story containing two people capable of travelling through time, but with different rules for time travel each. Say one of the two can freely change the past and redirect the course of history but they can only travel back in time by possessing the body of their old self. Then the other of the two can hop to any point in history with their current body, but can never change the course of history as any timeline deviation they manage to cause converges back into the normal timeline. And so the two of them could work together (and there could even be a budding romance..?) in order to prevent something from happening.
The theory of the Stein Gate anime is i think the very best explaining more about time travelling based on science fiction. LIke the attractor field that is condradicting the other part of this article because you cant change the future in the same attractor field(group of world lines). The anime make sense try perusal it you will understand me
The Undertale model is interesting, because it ties up its loose ends in a different way to Groundhog Day, for instance, while having that same type of logical, internal consistency. In the Undertale model, rather than creating new timelines by going back in time, you simply cut the timeline where it was, erase it completely from existence back to where you started and start time anew, with only yourself and vague echoes of memories in some (particularly determined) other folks knowing what happened before. When you yourself are acted upon by this same force in the late game, being the most determined (or in this case second most determined) entity in the world, you are capable of remembering everything that happened, just as Flowey, who acted with knowledge of your own resetting did when you were in control. Thus — internally and logically consistent. I like to refer to this as a ‘time collapse’, where the time is ‘added’ to the present, rather than properly deleted.
Here’s two types of time travel I like to think a out: a first-person linear timeline, and a near-universal history-changing timeline. The first-person linear timeline is when a character, travelling through time, cannot be effected by changes in their timeline that they make. This was kind of what avengers endgame did. Each character still follows a course of linear, unchanged time, despite interacting with their past. It’s basically like saying “we can go to the past and interact with things there, but it won’t effect my past, because that’s already happened linearly from my perspective”. With the near-universal history-changing timeline, any change made to the past is carried into the future, branching into new timelines. Unless the writer includes a perspective through which these changes can be observed, then it would be like nothing happened at all. No-one would know anything changed, because no-one would know anything to be any different from what it once was.
I like how time travel works in the H.G. Wells novel, The Time Machine. You go wherever you want in time, but you don’t move in space without moving the machine: it’s not a teleporter. You can do whatever you want. When you go back, you keep anything in the machine. The machine can be taken apart, like any other. When you leave, you are gone in the present for the amount of time you leave, but you can come back to when you left, negating that. You remember what happened when you return.
One of my favorite ideas for time travel was in the comic “Live With Yourself” where a guy lives with three different versions of himself (him as a baby, him as a middle aged man, and then him as an old man). The actions work in a chain system, so if something affects the present version, it will have an immediate effect on the middle age version and a less/greater effect on the old man. It was a really great comic, but it got a little too complicated as of late for me to continue reading it.
It’s been a long time since I’ve watched Bill and Ted, but I’m pretty sure that it works more like the HP version than any others. they’re just aware of it and take advantage of it since they have the phone booth. like when they need something they don’t have access too, they just make a plan to get it later and use the time machine to put it where they can access it then. This would mean their future selves had already been where they were in the present planting whatever thing they needed where ever they needed it planted.
My personal favorite implementation of time travel is in the Zero Escape trilogy. Instead of people physically traveling through time, only their consciousness travels through time, swapping their minds between one timeline and another, but only when that person is in mortal danger. Actions are constantly made throughout the series across dozens of different timelines that all build together to the sole purpose of creating specific timelines to avoid massive disasters, intentionally putting people in situations where they need to make specific choices so that multiple outcomes of that situation can exist. There’s also a minor plot point that I really love with people in a “doomed” timeline having to accept the fact that the past won’t just change, because it’s already happened, so they have to keep living their own lives to the best they can. The games also include their own interpretation of Back to the Future, which questions where the original version of Marty in the new timeline he created (the “cool” timeline) went when the Marty we know who changed the past took his place, and uses its time travel to assert that the two Martys swapped places, with the original “cool” Marty going back in time, changing the past to create the outcome of the “boring” timeline that the Marty we know is from.
Time travel is simultaneously my favorite and least favorite concept used in any story. It’s for one simple reason: How are the paradoxes avoided? So far, “closed loop” and “alternate world lines” are the best case uses. A combination of both takes careful finesse, but if done right you have a very well constructed and researched story. While Prisoner of Azkaban still makes the most non-paradoxical sense, I would argue that Steins;Gate makes the most use of scientific time travel theory. It explores nearly every aspect of time travel and the dangers of such. To me it continues to stand as my example of how time travel should be handled in any fictional story if you want it to be compelling.
i think best example will be Steins;Gate. it does both many different timelines/worldlines also if you think about it Steins;Gate had a self consistent Time travel which consisted creation and ending of many new worldlines. But when main character reaches stein;Gate timeline it is only with the help of future him. thus making two worldlines agin. one where he succeed and one where he fails the zero.
It’s funny you mention self-contained time loops as the most consistent when they are the most vulnerable to bootstrap paradoxes, not to mention this only works to a certain extent; Harry and his friends were deliberately not trying to alter the experiences of their time clones, but then, what if they did decide to do that? Or failed? Then we’re either back to the grandfather-paradox that you dislike other stories for, or they pull a Back to the Future and time itself breaks just by encountering your past self. I feel one of the best bootstrap paradoxes and most well-recognized movies of all times wasn’t mentioned for some reason; the Terminator. The Terminator has a phenomenal bootstrap paradox of John Connor sending his best friend Kyle Reese back in time to protect John’s mother Sarah from a time-travelling robot, only for Kyle to fall in love with Sarah and become the father of John Connor. John could not be born without Kyle being sent to the past and Kyle could not be sent to the past without John being there to send him. The Legend of Zelda: Ocarina of Time has even crazier shennanigans, where you can freely travel back and forth between times, planting a seed in the past causes a plant to be there in the future, but simultaneously it has a bootstrap paradox where you as an adult learn a song from a man who learned it from a boy. You then have to travel back in time to play that song near the man, who in turn learns the song fom you, revealing you were the boy who taught the man the song all along.
This is one of my favorite youtube articles. I love it and I always come back to see it again. It would be enteresting for you to do a 2nd part with the new shows and movies that play with timetravel! PD: My favorite kind of timetravel is the one in HP and Dark, where everything is destined to happen once you jump back and forward into time!
I can’t believe you left off 12 Monkeys from this narrative. It’s my favorite for the same reason why you liked The Prisoner of Azkaban, although I think 12 Monkeys leaves a larger impact on the viewer, especially as it relates to the theories of time travel. I still believe it’s the most accurate interpretation of time travel we’ve seen on screen (given if time travel was possible of course).
my favourite version of time travel is in Time Travellers Wife, which is basically a bigger version of the Harry Potter time travel. The main character has no control over his powers and accidentally travels to random points in his life, interacting with future and past versions of himself but never actually changing the timeline because his entire life is already predetermined and everything has already happened or always will happen no matter what. It results in a really interesting narrative structure that tells his lifestory in a non-consecutive way whilst being very logical and never having to explain any complicated time travel rules
But.. but… Harry Potter and the Cursed Child! Yes, Prisoner of Azkaban’s closed loop time travel is perfect… but then bloody godforsaken Cursed Child comes along with completely inconsistent alternate timeline mess contradicting the earlier books. They even use the same Time Turners. Yet this time with multiple alternate timelines.
One thing I’ve always wondered with time travel and going into the future, is that if you do go to the future, then wouldn’t that mean that your life would just be put on pause until you reappear? Like when Marty and Doc go to the future, their 1985 selves are now technically no longer continuing to live their lives in 1985, so they wouldn’t be able to see their future selves because they disappeared in 1985 to go to the future! It seems like most movies kind of implant a “rule” where anytime someone travels into the future, the timeline, like, “assumes” they’ll be traveling back to where they started, which is a really weird thing for the timeline to do, isn’t it?
Can you watch Steins Gate? It’s a time-traveling anime and I’m kind of confused of which category that type of time traveling belongs to. Primarily because it’s kind of unique compared to most of the other films you mentioned in this article. And I don’t know if you watch anime but this anime series Focus heavily on the science of time travel. Well at least as much can be for fictional science.
Oh, man, I love time travel stories! I own a copy of “Time Travel & Infinity,” which has six episodes from the second “The Outer Limits” series, and “A Stitch in Time” is my favorite episode, with Amanda Plummer playing a time-travelling serial killer who murders other serial killers; she waits until the criminal on Death Row is executed in the present, then she goes back in time to a point in that serial killer’s life before he commits his first murder and she kills him then, thus sparing all of his victims while ensuring that his absence in the present isn’t missed. So in the present, the FBI starts looking into all of these cold cases with men who were mysteriously murdered decades in the past, and there aren’t any criminal records on these victims (because our time traveller killed them before they could turn bad). And everything that the time traveller does in the past changes something in the present, like the detective who’s leading the investigations on all these cold cases had a friend who was murdered by another serial killer, but when the time traveller goes back and kills that guy, the detective’s friend walks into the FBI office to say hi to the detective, like she had been alive all along (because now, she was and had been). And when the FBI starts closing in on our time traveller in the present (because she accidentally left some fingerprints on a lamp at another one of her murder scenes in the 1960’s), she just jumps in the time machine, goes back to that murder scene, wipes away the fingerprints that she left behind moments after she left them, and then she goes back to the present, and suddenly the FBI’s not breathing down her neck anymore because she retroactively got rid of the evidence that would have gotten her caught.
I know most people said it in the Comments but I’m gonna say it anyway. You really need to watch Steins Gate it explains multiple different time travel theories in a perfect way, it’s confusing but yet it’s amazing, the Harry Potter time travel it’s explained, memory sending back in time, text messages back in time, world line changing and sending yourself physically back in time as well, butterfly effects etc… And it’s done in a amazing way with a fantastic story as well.
If you were to travel into the past, you might as well find a different past from the one you remember. Think about it; The future is probabilistic, as it exists in quantum superimposition and collapses each time we experience one specific present. Why wouldn’t the past be the same? Why couldn’t it be true that as far as the universe is concerned, every present may have a superimposition of potential pasts leading to it? We like to think of time as a zipper where the past was already determined, but in fact it might be our minds experiencing random possibilities in logical order from a field of super-impositions that goes both ways.
A different time travel I really like is in “The day of time travel”. There is only one timeline, but any and everything people do effect it immedietly, you kill your grandpa? He dies, but because you were not born (because he died) he just dies without a cause, there is still a gunshot wound for excample, but no one shot him.
The Harry Potter time travel is how I always imagined time travel would have to work, if it were possible (which it of course, isn’t). You can’t change the past, since all of those changes have already happened – they were in the past. Their effects have already taken place. Everything fits – whatever you do, that timeline will happen, no matter if you make a conscious decision to try redirect it or help it along it’s course, as all changes you will make won’t actually be changes.
I love the time travel used in Steins;Gate. It manages to stay consistent while exploring the concept of changing world lines. Not only that, the method of time travel is extremely unique, using a phone to text back in time. The limitations are very clear, but there’s still the mystery of manipulating world lines since the protagonist is the only one who can remember previous lines. Super interesting time travel stuff, probably one of my favorite representations so far.
the thing with back to the future is that it’s nominally about time travel, but it’s also subtly about parallel dimensions, or more to the point, about traveling through parallel dimensional planes via time travel(though it isn’t treated that way within universe). It’s not deterministic, but it is consistent within the rules it creates for time travel. by the way, it’s not precisely about time travel, but there’s a movie that came out a few years back about a camera that took pictures from the future. the characters tried to change the future by making sure that the photos couldn’t possibly exist via altering what was visible in the camera’s lense. it was actually really interesting, you might like it.
I think there are many more examples of the type of time travel in Harry Potter with logical consistency, not only HP. Also, I would really love if there was a follow up to this article taking about time travel in Tenet, Endgame, and the time travel systems of Astiritsa. I feel like time travel in Astiritsa is unique (I’ve never seen something like it before), and it would be really cool to explain.
That scene in Looper with the legs has always annoyed me, like he was running along and found he had no legs but he hadn’t had legs for 30 years so a wheelchair should have appeared! The other one that the time travel makes no sense to me (and I haven’t read the book so don’t know if it’s the same) is Miss Peregrine’s Home for Peculiar Children (spoilers ahead) it begins in 2011 or 2012 where the main characters grandfather is murdered, he then time travels back to the 1940’s and is pursued by the murderer who then dies in the 1940s which somehow means his grandfather never died? Like he’d already committed the murder before time travelling, how does dying in the past undo it?
There is this German YouTuber who made a movie called “Gott würfelt nicht nur einmal” that is also about time travel. But there the protagonist can kinda reset time to certain points and redo everything he has done from that point. In the beginning he uses that to correct minor mistakes in his life, like if one pick up line doesn’t work, he would try another one and so on. That’s probably my favourite, because it also manages to be consistent and there is always only one version of yourself.
Do a part 2 that includes Dark and Bodies. Bodies (netflix limited series from UK) is particularly interesting to me because one character is his own great great grandfather. A boy who was a teenager in 2023 gets older and then goes back in time to 1890, marries and has a son. That son has a son who has a son, etc, I forget how many generations but eventually that original teen boy is born from that direct lineage. And when he goes back in time he knows he will be starting the bloodline that results in his birth. Which also means he is sleeping with his own great great grandma.
I really like the approach of timer travel in harry potter. If you were going back to certain point, well that already happened before you even think about it. But if you change your mind and didn’t, well it never happened. Your conscience of whether you are going back or not is even already predetermined. So fate is already truly cemented. If you think you can win over fate by “jokes on you i’ll time travel in other time instead” or trying to change your actions in any way, that’s what actually already happened. What the fate has actually done. So no matter what you do, you’re still following the script
The tv show milo Murphy’s law… some people can change the past but some people also can’t which is completely messed up. One time they went to the future, and almost got caught but just time travelled a few minutes earlier and the same thing happened as the prisoners of Azkaban but other times it isn’t like that and every time they time travel to one time and place they just keep adding and adding how many of them there are in that new time and space. There are also people that do end up changing the past like them saying oh we stopped ww5 and they ask what happened to 3, and 4? And they just say your welcome. I mean it is a children’s show but really, are you that lazy to completely change up the time travel every episode?
Looper is the movie that makes the least sense about time travelling given that the characters create alternative time lines by travelling to the past yet they are still affected by the actions from the past as if they were still in the same original timeline they came from. You should have included both Predestination and Dark in this article given that both work under the same premise as Harry Potter and the stories occur in unalterable universes in which future cannot be changed even if you try to by travelling to the past because whatever you do in the past, it will only account to make the future remain in the same way it already was.
One thing I never got about the Terminator time-travel lore, is that if the act of time-travel leads to a different branch of history, it stands to reason that the branch from which the traveller was sent does not alter. So why would anyone or any machine bother to try and create an alternate universe, the existence of which they can never be aware and which has no bearing on their own. It’s kind of like going back in time to kill Hitler and creating an alternative universe in which Hitler was killed. Nobody in this universe would be aware that you had done that – in fact it may have already been done multiple times. This kind of time-travel can only be for personal gain.
Ann McAffrey’s “Dragonriders of Pern” uses the same sort of Harry Potter time-travel logic. And lampshades it, when the A.I. system AIVAS directly tells one of the characters that their extraordinarily-long jump backward in time WILL work, “because it already has, and here is my data to prove that”.
My favorite time travel is legacy of kain, it’s not that time travel isn’t possible it’s that most events do not shift. When you time travel very little can affect the time line it’s like dropping a pebble in a stream, but it doesn’t change much. What really changes things is actions of killing individuals with real power or subverting ones destined choice.
I got a lays ad before this article and it was a map ad with the farms planted around the U.S sympalised with lays flags and when they were planting a flag somewhere in california it came down to the real farm and the farmer said “lookout kids, their doing one of those map ads” and i laughed way to hard.