A Brief History of Time (Travel)
1. Time Travel – Time as a philosophical concept
a. Time as a straight line
b. Time as a wheel
c. Time as the fourth dimension in a four-dimensional universe ("Block Universe")
d. Time as an integral part of the Space-Time Continuum (according to Einstein's Theory of Relativity)
2. The basic concepts; a historical review
a. Contradiction and Consistency
3. Back to the past or back to the future? Some scientific approaches
a. Is there a difference?
b. Are the following possible ways of traveling through time?
4. The Paradoxes
The "Freebie" Paradox
The Butterfly Effect
The Billiard Ball Paradox
The Gemini Paradox
The Grandfather Paradox
5. So how does it really work?
6. Time Travel Scenarios in literature, cinema and TV
a. Time Travel - Single Destination, Return Trip
b. The Multiverse
c. The Causality Loop
d. Alternate Histories
Literary and Cinematic Examples
Annex A: The case of John Titor
Annex B: The Time Traveler's (beginners) Guide
Time Travel scenarios have been the inspiration for literary classics (from Mark Twain's A Connecticut Yankee in King Arthur's Court to H. G. Wells's The Time Machine) and for Sci Fi works such as Isaac Asimov's End of Eternity, and of course to special-effects packed Movies such as the Back to the Future series, the Terminator series, etc'. They are all different, but the one thing they have in common is a discussion of how the actions of time travelers in the past affect reality in the present.
In order to comprehend the very notion of Time Travel, first we need to comprehend another notion, which is not to be taken for granted, and that is that there are several perceptions of the concept of time itself.
Our basic grasp of the world sees time as a straight, unidirectional line (Time as an Arrow or as a River), which was popular, inter alia, amongst the ancient Greek philosophers such as Heraclitus, who said in the 5th century that "everything flows" and that "you cannot step twice into the same stream… We both step and do not step in the same rivers. We are and are not."
The problematic nature of this perception was demonstrated by author Jack Finney in his novel Time and Again, in which scientists debate the dilemmas posed by attempts to alter the flow of the river.
Here is a simplistic description of Time Travel in a three-dimensional world (according to the perception of time as an arrow):
The question is, can we travel "sometime else" instead of "somewhere else"? Theoretically, this should be not only possible, but also unavoidable, since time is linear.
(Image 17e, source: Philosophy 2A: Time & Space)
The Mayans, for instance, viewed time as a wheel in which every event repeats itself after a predetermined number of years (52). The Spanish conquistadores took advantage of this when they planned the conquest of the Aztec empire (Mexico) since due to a freak historical coincidence, the Aztecs thought that Hernán Cortés, commander of the Spanish forces, was none other than Quetzalcoatl, the (white) god who promised to return to his people in the 52nd year of the cycle. Incidentally, the current cycle is supposed to come to an end with the destruction of the world in late 2012 (see also The X-Files), but lately there have been claims that the Mayan calculations were wrong…
The prevailing perception before the theory of relativity:
1. Time is a fourth dimension
2. We can travel in space
3. We should also be able to travel in time
4. We are unable to travel in time, meaning that time travel indeed impossible, or that the perceptions of the time as a fourth dimension is wrong.
And this is exactly the discussion developed in the book by HG Wells' The Time Machine. "According to Wells, we can actually travel through time, and therefore this concept of the universe is wrong.
Another simplistic description of Time Travel according to Einstein's Theory of Relativity. The red axis is shorter than the green, meaning that the traveler on the red axis will less (the Gemini Paradox)
(Image 16e, source: Philosophy 2A: Time & Space)
Incidentally, according to the Theory of Relativity, a similar effect will be achieved in the event of a journey to the center of the earth, since the deeper we penetrate into the center of the earth, the more gravitation increases, therefore a journey to the center of the earth will also constitute a shortcut to the future...
In order to deal with the ideas of time and time travel, it is vital to understand two basic concepts:
Def.: To be logically committed to the assertion of some statement, S, and its denial, not-S, at the same time.
ID.: Identify the statement that being both asserted and denied.
Contradiction is a term in logics used to describe a situation where a statement, or set of statements, is logically consistent when it involves no logical contradiction. A logical contradiction is the conjunction of a statement S and it's denial not-S. In logic, it is a fundamental law- the law of non contradiction- that a statement and its denial can not both be true at the same time.
For instance, A single statement can be considered self-contradictory. For instance, "this statement is false". We have no way of determining whether this statement is true or false, therefore it is self-contradictory.
The Contradiction Principle can be used to test the veracity of statements by confronting them with a statement which has already proven true. The Contradiction Principle is used a lot in logic and in mathematical logic.
In philosophy, Contradiction is a disputed concept. Some view it as an independent, deterministic perception of reality, and others view it as a valid depiction of human thought, or a mere convention which can be changed according to the system of logic that we use.
So what is consistency? Consistency is a term in logic describing a situation that occurs when two statements do not contradict each other irrespective of their being true or false. For instance:
1. Some dogs have fleas.
2. Therefore I want a Reese's Peanut Butter Cup.
According to the Ynet Encyclopedia, causation is a term that has three main implications:
2. causes in nature - not only human actions can brighten the room, but also natural causes such as the sunrise. Terms like "creation" were used in the past also in relation to natural causes. In other words, the causes were considered to have real power to create their own effects. However, unlike in the first sense, causes in nature are not deliberate human actions, but only sufficient conditions for the outcome: the sun is is shining, therefore the room is lit. The use of a sufficient condition as an explanation of an existing situation is common, for example, in medicine.
3. Cause as an explanation - Some use the term "cause" instead of the term "explanation". That is, in every situation there are elements that are under our control, and they allow us to bring about the desired effect. According to this meaning of Cause, the same event can be explained in different ways according to its context. The primary meaning of "cause" originates in the anthropomorphic concept (attribution of human qualities to non-human factors) which was popular in the natural sciences science dating back to the 6th century BC.
Only in the time of Copernicus and Newton attempts began to explain phenomena by viewing them as individual cases of the laws of physics and mathematics. This concept, according to which a certain "power" to generate an effect lies within every cause, social science and philosophy until the 18th century.
David Hume's definition of Causality (1748):
"We may define a cause to be an object, followed by another, and where all the objects similar to the first, are followed by objects similar to the second."
And in other words, if the first object didn’t exist, the second would never exist. (David Hume, 1748)
Immanuel Kant responded to this in his Critique of Pure Reason with a claim that the concept of Cause is a Faculty of Understanding (or one of the categories creating our perception of the world) without which cannot organize our scientific experience.
One may now ask: How many possible judgments are there? Kant believed that all the possible propositions within Aristotle's syllogistic logic are equivalent to all possible judgments, and that all the logical operators within the propositions are equivalent to the moments of the understanding within judgments.
universal, particular, singular
Unity, plurality, totality
affirmative, negative, infinite
Reality, negation, limitation
categorical, hypothetical, disjunctive
Substance, cause, community
problematic, assertoric, apodeictic
Possibility, existence, necessity
Traditional physics was mostly deterministic in nature, and was perceived mainly as the study of the link between cause and effect in the material world, until Albert Einstein presented his Special Theory of Relativity in 1905 and proved that two events, occurring within a certain time of each other from the viewpoint of one observer, may occur within a different time of each other from the viewpoint of another observer.
The introduction of the Quantum Theory in 1925 greatly undermined the traditional perception of physics. Its deterministic nature was no longer complete, but statistical. A given system no longer had to develop in a predetermined course, because different courses of development were available to it, and the laws of Quantum development could only determine the probability of development according to each of the possibilities.
Davis Lewis wrote many articles dealing with causality and the link to the paradoxes of time travel. One of them, published in 1978 at Princeton University (later in SciAm), entitled The Paradoxes of Time Travel, Lewis rejects the Chronology protection conjecture and the claim that the very existence of the paradoxes makes time travel impossible. According to him, you "can" kill your grandfather, but that doesn’t mean that if you try, you will succeed… "Time travel, I maintain, is possible. The paradoxes of time travel are oddities, not impossibilities. They prove only this much, which few would have doubted: that a possible world where time travel took place would be a most strange world, different in fundamental ways from the world we think is ours." He makes the following analogy: "An ape can’t speak a human language -- say, Finnish -- but I can... But don’t take me along to Helsinki as your interpreter: I can’t speak Finnish."
So what does that have to do with Time Travel?
"Can do" doesn't always mean we "can" do something. The very existence of a theoretical possibility doesn't make it real. This goes for Time Travel too, regardless of whether we travel back to the past or back to the future.
The following are some articles on the subject:
David Lewis, "Postscripts to Causation"
David Lewis, "Counterfactual Dependence and Time's Arrow"
David Lewis, "Counterfactuals and Comparative Possibility"
Igal Kvart, "Lewis' 'Causation as Influence'"
Michael Dummet, a philosopher from Oxford, also dealt with the questions of causality and determinism, but he used the Bilking argument. He suggested the following example: A tribal chief does a ceremonial dance to ensure the bravery of the tribal hunters and the success of a hunt (which took place two days earlier and from which the hunters have not yet returned). In other words, someone claims that by acting in a given time, he can cause an event to occur in another given time. How we prove (or disprove) the chief's claim?
a. Find out (e.g. by radio contact) whether hunters were brave.
b. If yes, ask the chief not to dance. If no, ask him to dance.
What are the possible results?
Chief does as asked
There is no reliable correlation between dancing and earlier bravery.
Chief tries to do as asked, but can’t
The hunter’s bravery is causing the chief to dance, rather than the other way around.
(Image 18e, source: Philosophy 2A: Time & Space)
Which leads us to Dummet's loophole. The Bilking argument depends on the ability to determine whether the (claimed) earlier effect has taken place, before its claimed later cause needs to happen.
And how does Dummet's loophole relate to Time Travel?
(Image 19e, source: Philosophy 2A: Time & Space)
Suppose I claim that I can influence the properties of light coming from distant galaxies, just by looking at it in the right way. If I’m right, I’m affecting events millions of years in the past (when the photons left the galaxy in question). In order to "bilk" my claim, you would have to:
(a) detect the relevant property of the photon,
(b) get a message to me, before the photon reaches me.
But since according to the Special Theory of Relativity, nothing can travel faster than the photon, bilking is impossible in this case.
Can nature exploit this loophole? There are some reasons for thinking that in quantum mechanics, it does.
See: K-Pax, Contact...
And what happens when the traveler wants to go back in time? It's also possible, according to the special theory of relativity and the time dilation effect. The closer the speed is to the speed of light, the more time will slow for the traveler. At the speed of light time’s progress will reach zero, and at FTL travel, the progress of time will be negative (ie, backward).
There's just one little catch. Einstein's theory also states that the speed of light is the maximum speed in the universe. Therefore, according to special relativity, traveling back in time is not possible. But according to general relativity, there are no restrictions on the motion of the space in which the object is moving. Space is expanding, carrying the galaxies and pulling away from Earth at a speed that can exceed the speed of light. Mathematician Kurt Gödel even discovered that general relativity equations allow, assuming that the entire universe revolves around itself, and thus sweeps space-time with it, for traveling back in time by circumventing the universe. Evidence that the universe revolves around itself are yet to be found, and even if it does, for now, the technical ability to conduce experiment to prove this does not exist.
In the 1960s' Roy Kerr, a mathematician from New-Zealand, showed that self-rotating black holes also pull space-time, and about a decade later physicist Frank Tipler used Kerr’s work to suggest a theoretical possibility of time travel by flying near a massive black hole rotatling at a high speed.
(Wormhole image, Source: http://www.st-v-sw.net/Obsidian/Martin/worm.htm)
To the past
Lots of Paradoxes
Very high speed – possibly FTL; slowing time within a given system, according to the SpecialTheory of Relativity; A spacecraft with FTL capability is yet to be built.
To the Future
No problem - a one-time unidirectional trip to the future (without going back to the past in order to change it) is fundamentally no different than a trip from New York to Los Angeles, for instance.
Accelerating time outside a given system – according to the General Theory of Relativity; Staying in a very powerful gravity field.
In both cases, the only limit is technological, and in the future a way to overcome it may be found.
1. Suspension of Time
2. Jet Lag
This phenomenon, familiar to anyone who ever took a long flight, apparently creates a time difference between the traveler’s time and the external time.
Nowadays there are already people who wish to undergo the process, believing that in the future the medical solution to the problem that caused their death is found (and the small deposit in the bank will yield a handsome return). The technology is still in its infancy, but it is already being used to freeze terminally ill patients who died a clinical death, in the hope that in the future they could be defrosted after a cure for the illness that caused their death is found. The truth? I have a problem with this method every time I take out an accidentally frozen piece of fruit from the refrigerator and see what happens to it when it defrosts…
4. Various forms of suspended animation
The "Rip Van Winkle" method, or any other suspended animation method involving an almost complete stop of all bodily functions for an (almost) unlimited period of time.
All those methods have one problem in common – they only stop personal time (i. e. for the person flying/frozen/suspended).
c. So, is time travel even possible, regardless of which approach we prefer?
There are several main reasons as to why time travel is not possible in practice, even if we accept the assumption that it is possible in theory. Here are several examples:
No, because of the Laws of Physics
There are many phenomena that physics cannot explain, and yet they exist.
No, because of the paradoxes
The very existence of the paradoxes makes time travel impossible
No, due to the tremendous technical difficulties
(Breaking the speed of light barrier, finding a source of energy, securing the necessary funds)
No, because of the Chronology protection conjecture
A thousand people cannot all go out to "kill their grandfather" and fail; If it was possible, we would have already seen time travelers in droves, so (paraphrasing Fermi's paradox), where are they? (The question posed by Hawking and Sagan)
Naturally, for every Con, there is a Pro…
a. The very idea of time travel defies common sense.
The obvious response is that 20th century physics made a lot of discoveries hard to accept by common sense, yet they were all proven beyond a doubt.
b. None of the physical theories the suggestions for building a time machine are based upon have been implemented, and the way to implement those theories may be wrought with obstacles, theoretical or practical, which have not been taken into account, so that time travel will never be possible.
c. If time travel was possible, we would have been flooded with visitors from the future, but since such visits do not occur, then we must conclude that a time machine was never built.
Time travel is possible only up to the point in time in which the time machine was invented, or that amounts of the energy required for such a trip would be so huge, that it will be attempted only in exceptional and special circumstances. And even if the visitors from the future are already here, whenever they are exposed they go back and change the past, thus preventing their exposure, and so on and so forth…
d. The physical-technological-logical conditions will be such that a paradox will never be created.
For example, a person who would kill his grandmother out of scientific curiosity will never get to travel back in time, and even if it happens, he will be killed in an accident before he ever comes near her, or kill another woman by accident; if someone takes the notes of the ninth symphony to Beethoven, they will be lost on the way, or Beethoven will put them aside and forget all about them. This, by the way, is exactly what happened to the hero of Crime Traveler, who learned first hand that " time will not let you cheat"; or alternately, even if it is theoretically possible to build a time machine, it will never be done in practice due to practical obstacles (for instance, a government decision not to fund a of trillion dollars project).
That is the position of famous physicist Stephan Hawking, who suggested that the universe has defense mechanisms that prevent paradoxes, and therefore the laws of physics rule out every possibility of successfully building a time machine (see "the chronology protection conjecture").
And Carl Sagan says ("Broca's Brain", p. 172): "I do not know if time travel into the past is possible. The causality problems it would imply make me very skeptical. But there are those who are thinking about it. What are called closed time-like lines-routes in spacetime permitting unrestricted time travel-appear in some solutions to the general relativistic field equations. A recent claim, perhaps mistaken, is that closed timelike lines appear in the vicinity of a large, rapidly rotating cylinder. I wonder to what extent general-relativists working on such problems have been influenced by science fiction. Likewise, science-fiction encounters with alternative cultural features may play an important role in actualizing fundamental social change."
David Lewis, however, claims that the paradoxes are nothing but "oddities" and there is nothing about them that makes time travel impossible…
Dilemma A: A person claiming to be from the future comes up to you, and warns you that if you do or do not do something, a terrible catastrophe will or will not happen. You listen to him. The catastrophe does not happen. Then where did the person who warned come/will come from (see "Twelve Monkeys")?
Suppose you don't listen to him and the catastrophe does happen. Wouldn't that have unknown catastrophic implications on the person who came from the future?
Incidentally, such phenomena abound mainly after mass disasters; People report that while they were supposed to be at the disaster area, they stayed away at the last minute because of some mysterious warning they received, which of course also contributes to the reinforcement of conspiracy theories that abound in the wake of mass disasters (see 9/11)…
Dilemma B: Doesn't the change we made in the past, assuming we made it and back in one piece there with the information necessary to make the change, nullify the need to travel to the past and make the change in the first place? (See Paycheck)
The different paradoxes related to time travel can basically be classified into two categories: Paradoxes that violate causality and paradoxes that violate consistency.
Suppose our traveler returns to a time before his parents ever met, and discovers that unless he intervenes, they will never meet. He decides to intervene and bring them together. The reality created is entirely consistent, but causality is violated; the traveler was born not because his parents met, rather his parents met because he brought them together. Incidentally, in order for this to work, the traveler cannot botch his attempts to bring his parents together. Failure is not an option.
However, we have already seen that going back to the past does not necessarily change reality, and that the actions of the traveler in the past may be an integral part of his contemporary reality. But if consistency is maintained (the chicken or the egg, remember?). the traveler's actions may well violate the principle of causality.
It should be noted that the underlying premise of all Time Travel scenarios is that Time Travel is indeed pos. Therefore, one of the ways to settle a paradox is to show that at least one of the conditions creating is invalid...
Confused? You won't be, after you watch Back to the Future, Terminator, etc'…
The following is a summery of the main paradoxes of Time Travel and possible ways to settle them.
If I were to travel back in time and present Beethoven, for instance, with the notes of his world famous 9th symphony, or Da Vinci with the Mona Lisa, and they, in turn, copied the masterpieces and presented them as their own, then the masterpieces exist only because I went back in time and not because of their original creators (hence a "free lunch"), So who was the original creator of the masterpiece?
A man who wishes to build a time machine is visited by an older version of himself. This future self explains to him that he should not worry about designing the time machine, as he has done it in the future. The man receives the schematics from his future self and starts building the time machine. Time passes until he finally completes the time machine. He then uses it to travel back in time and gives the schematics to his past self (or tries to stop him from using the machine). So who, if anybody, will invent/has invented the time machine?
Note that if the "free lunch" is indeed in the form of an artistic masterpiece, eventually it will be worn out and degraded to a degree that will make it impossible to give to its creator, and then someone will have to create it all over again…
Resolved Using Consistent Histories
If the recipient of the notes is not the person they were meant for, he will throw the time traveler out on his butt or throw the notes away without looking at them
Resolved Using Alternate History
Changing the past in one key point
Resolved Using the Multiverse/Quantum Mechanics or Relative-State Interpretation
Someone in some universe will write/paint the original work…
The ninth symphony was composed by a Beethoven from the traveler's universe and he, the traveler, passed it on to a Beethoven from a parallel universe, and another traveler passed it on to another parallel universe, and so on and so forth, so that at least one Da Vinci will have painted the Mona Lisa, and at least one inventor will have invented the time machine…
One of my favorite examples is Back to the Future, where Marty McFly performs the song "Johnny B. Goode" at a high school dance in 1955, after the band's guitarist (named Marvin Berry) injures his hand. Astounded by Marty's performance, Marvin calls his more famous cousin Chuck Berry, who listens in on "the new sound [he's] been looking for".
"For want of a nail the shoe was lost.
For want of a shoe the horse was lost.
For want of a horse the rider was lost.
For want of a rider the battle was lost.
For want of a battle the kingdom was lost.
And all for the want of a horseshoe nail…"
This proverb describes a situation where permitting some small undesirable situation will allow gradual and inexorable worsening. The rhyme is thus a good illustration of the "butterfly effect", and ideas presented in chaos theory, involving sensitive dependence on initial conditions; the initial condition being the presence or absence of the horseshoe nail.
The term "butterfly effect" is related to the work of Meteorologist Edward Lorenz, and is based in chaos theory and sensitive dependence on initial conditions. Lorenz later proposed that such phenomena could be common, say in meteorology.
But famous inventor Nikola Tesla noted as early as in 1893: "A single ray of light from a distant star falling upon the eye of a tyrant in bygone times may have altered the course of his life, may have changed the destiny of nations, may have transformed the surface of the globe, so intricate, so inconceivably complex are the processes in Nature".
And how does that relate to time travel? Simple, assuming we make it back to the past, any change we make in it, as slight as it might be, will have destructive repercussions on our future. Hence the strict warning against making such changes
Resolved Using Consistent Histories
There are two possible ways to resolve this paradox:
a. Just change nothing (see again "the butterfly effect" or the chronology protection conjecture)
b. Every change we make will result in getting back not to our future, but to one of countless futures created completely at random in the aftermath of the change.
Which creates two new dilemmas - how do we find the right path back to "our" future, and what will happen to us in "our" future if we don't make it back (see the parallel universes solution).
Resolved Using Alternate History
The change will create an alternate history
Resolved Using the Multiverse/Quantum Mechanics or Relative-State Interpretation
The change will be in a parallel universe
In Ray Bradbury's short story "A Sound of Thunder" we see what happens when you travel in time to the past to hunt a Ti-Rex and you accidentally step on a butterfly...
A concept similar to that of the Grandfather paradox, with one slight difference – we are dealing with inanimate object.
Let's imagine a theoretical pool table, with one pocket connected by a wormhole to the other pocket, situated one second in time ahead of it. I.e., a ball rolling into first pocket exits from second pocket one second earlier. What would happen to the ball?
a. a miss;
b. the ball will emerges from the wormhole and collides with itself, driving itself into the pocket through which it has just traveled, without diverting itself;
c. the billiard ball will be knocked into the pocket by this collision, entering the wormhole because when it earlier emerged from that wormhole it collided with itself and knocked itself into that wormhole (a consistency paradox);
d. we are meant to miss, but the ball exiting the second pocket will collides with itself, and change course so that it rolls back into the first pocket, etc' (a "free lunch");
(image 15e, source unknown)
Resolved Using Consistent Histories
The exiting ball will hit the entering ball, knocking it slightly, but only after it exits the machine…
According to the Consistent Histories, this paradox is relatively easy to resolve, if you account for the mass and the speed of the billiard ball and view the wormhole as a time machine. One solution possible is that the entering ball will not knock its exiting self out of the machine completely, but will only will hit it slightly and divert it only after it exits the machine, and therefore will not prevent itself from entering the machine, etc' etc'. But since there is no way predict the ball's behavior without actually performing the experiment, this solution is based only on probabilistic calculations
Resolved Using Alternate History
Resolved Using the Multiverse/Quantum Mechanics or Relative-State Interpretation
Hugh Everett's Relative-State Interpretation
According to Einstein's Theory of Relativity, if one member of a pair of identical twins were to orbit the earth at close to light speed for a few hours, when he returned to earth, if ever, he might find that his twin had aged several years. Therefore the twins will still be twins, but they will no longer be of the same age, hence the paradox.
Resolved Using Consistent Histories
Resolved Using Alternate History
Resolved Using the Multiverse/Quantum Mechanics or Relative-State Interpretation
The Twin stays in the parallel universe
For those who are interested, the Gemini paradox was the subject of agent Scully's Masters Thesis.
In Asimov's short story "My Son, the Physicist", one possible way to resolve this paradox is demonstrated.
And see Orson Scott Card's Ender quardrology, which is based upon this principle
A new and most interesting interpretation of the Gemini paradox also be found in Audrey Niffenegger's The Time Traveler's Wife.
We have seen the enemy and they are us...
("The Pogo Paradox". See: Star Trek- Voyager, Relativity, 5X24)
If I decided to go back in time and kill my grandfather before he has a chance to conceive my mother or my father, what would happen?
1. I would no longer exist.
2. If I no longer existed, then I could not have killed my grandfather so he would be able to conceive my mother or my father. This would lead to my existence, again allowing me to kill my grandfather. Thus, a time loop is created in which I am perpetually killing my grandfather and being born…
Resolved Using Consistent Histories
"the chronology protection conjecture"
Nature has already adopted all the necessary means in order to prevent the occurrence of the paradox, and the laws of nature will prevent the occurrence of something without a cause; Hawking called this "the chronology protection conjecture", however, if hundreds of people will decide, for the sake of science, to go back to the past to in order to kill the grandmother or the grandfather of the inventor the time machine (or someone else's), it would be strange if all of them fail for various reasons in the name of the chronology protection conjecture. Is it really practical to attribute such mysterious powers to the universe?
Resolved Using Alternate History
If your body goes back to the in the form of particles, you will be able to kill your grandfather and still be born, and no defense mechanism will be able to prevent this, since the "younger" version of the sum of the particles making you does not depend on the "older" version
Resolved Using the Multiverse/Quantum Mechanics or Relative-State Interpretation
The grandfather I killed is a grandfather from a parallel/alternate
universe and his death will have no effect on "my" universe (if I ever make it back there)…
Well, so traveled back in time and killed your grandfather. If you did it in a parallel universe, it's no biggie; when you get back to "your" universe", you will notice no change at all.
In that case the question arises, so why did we bother? After all, we will never be able to kill "our grandfather" anyway, and even if we succeed, who can guarantee that we will be able to make it back to "our" universe?
Alternately, just like a trip to the future can be a trip to one of countless possible futures, so can a trip to the past can be a trip to one of countless possible pasts, and no change made by the traveler will affect his "real" universe. This is more or less the underlying principle of the successful TV show "Sliders".
In other words, according to this interpretation, every trip to the past is actually a trip to the past of a parallel universe, an identical one except for one small detail - the sudden appearance of the traveler himself. This parallel universe is sometimes referred to as "another timeline", but one thing is clear, the grandfather that the traveler killed is not his own grandfather, but the grandfather of his counterpart in the parallel universe, which means that his counterpart will indeed not be born and will not be able to travel to a parallel universe an kill a someone else's grandfather…
Incidentally, this is a possible resolution not just to the grandfather paradox, but to all the paradoxes of time travel, although there is those who claim that traveling to a parallel universe is not time travel.
Author Alfred Bester offers a slightly different explanation to the paradox in his short story The Men Who Murdered Mohammed:
The following are some possible blueprints for building a time machine.
a. Paul Davies's Time Machine
In his book entitled "How to build a Time Machine", based on the following article, scientist Paul Davis has the following suggestion for A Wormhole Time Machine in Three Not So Easy Steps:
2. Stabilize the wormhole. An infusion of negative energy, produced by quantum means such as the so-called Casimir effect, would allow a signal or object to pass safely through the wormhole. Negative energy counteracts the tendency of the wormhole to pinch off into a point of infinite or near-infinite density. In other words, it prevents the wormhole from becoming a black hole;
3. Tow the wormhole. A spaceship, presumably of highly advanced technology, would separate the mouths of the wormhole. One mouth might be positioned near the surface of a neutron star, an extremely dense star with a strong gravitational field. The intense gravity causes time to pass more slowly. Because time passes more quickly at the other wormhole mouth, the two mouths become separated not only in space but also in time.
b. Yakir Aharonov's Time Machine
If that doesn't work, there is always Yakir Aharonov's time machine. The machine, which is based not only on quantum theory but also on general relativity, is a massive sphere that can rapidly expand or contract. Einstein's theory predicts that time will speed up for an occupant of the sphere as it expands and gravity becomes proportionately weaker, and time will slow down as the sphere contracts. If the machine and its occupant can be induced into a superposition of states corresponding to different sizes and so different rates of time, Aharonov says, they may 'tunnel' into the future. The occupant can disembark, ask physicists of the future to explain the mysteries of quantum mechanics and then bring the answers-assuming there are any-back to the present. Until then, like Plato's benighted cave dwellers, we can only stare at the shadows of quanta flickering on the walls of our cave and wonder what they mean.
Aharonov emphasizes (as do I, as do I) that anyone planning a time machine must remember it must also be "a space machine", because the Earth is moving through space at a high and complex speed due to its revolving around itself and around the sun, the movement of the sun around the center of our galaxy, and the movement of the galaxy in the universe. Which means that our time machine will also be required to move through space as a spacecraft, and just as important, to very precisely select the stopping point in space/time - (so that it doesn’t collide with a wall or take a four stories high plunge).
c. Ronald Mallett’s time machine
Ronald Mallett (New Scientist, May 19th 2001) thinks he has found a practical way to make a time machine. Mallett isn't mad. None of the known laws of physics forbids time travel, and in theory, shunting matter back and forth through time shouldn't be that difficult.
d. John Titor's time machine
According to John Titor, a self-proclaimed time traveler from the future, there are six main components to the time machine:
Two magnehousing units for dual micro singularities
An electron injection manifold to alter mass and gravity micro singularities
A cooling and X-ray venting system
Gravity sensors, or a variable gravity lock (VGL)
Four main cesium clocks
Three main computer units
Incidentally, this description appears to have been taken from Dr. Michio Kaku's Hyperspace.
So now everything is clear, and the only thing left to do is to build the time machine, charge it with as much negative energy as possible (to compensate for the amount of positive energy required to operate the machine itself), and take off…Well, of course there are still some small technical problems to be solved, but it is only a matter of time.
Time travel scenarios popular in cinema and literature can generally be classified into several main categories as described in the following chart:
(image 13e, mine)
Note that in a three-dimensional representation or a cross-section, point D will overlap point B and point C will overlap point A, which proves that 1. The return is to the point of origin, and 2. A one-time one-way trip does not pose any problems of logic.
(Image 20e, source: http://www.mjyoung.net/time/index.htm)
(Image 21e, source: http://www.mjyoung.net/time/index.htm)
Here too you can see the overlapping of points in the three-dimensional or vertical representation, enabling as to view this chart as representing the parallel universe scenario.
Please note that nowhere has it been written or argued that the passage of time in parallel or alternate universes is identical. On the contrary, in most examples of this kind there is no correlation between the rate of the passage of time in two parallel universes, which only complicates things, as attested by Colonel Sheppard of Stargate-Atlantis, Colonel Mitchell of Stargate SG-1, Captain Picard of ST-TNG, Captain Sisco of ST-DS9, Colonel O'Neill of Stargate SG-1, Captain Hunt of Andromeda (though his case a little different), etc’…
We can find an interesting example of dealing with the question of relativity of time between parallel universes in the Narnia series. Chronologically, "The Lion…" is actually the second in the series ("The Magician's Nephew" is the first); In Caspian, the children returning to Narnia are younger than they were during their first visit ("The Lion"...), but they return to Narnia to a much later period, and finally return home to the same point of departure; confused? It's all right, the children were confused too...
Incidentally, the other books also describe meetings of their heroes with the heroes of "The Lion..." who apparently did manage to return to Narnia. But whether they returned to Narnia or to events occurring during the quartet's stay Narnia, but not described in "The Lion…" is unclear. Only C S. Lewis has the answers. One thing is certain - the professor in whose house they stayed was there as a child and, if he is still alive, he sits in the desolate house and yearns for the day he will find his way back…
A more scientific attempt to explain in detail the subject of multiple universes can be found in Michael Crichton's "Time Line".
The scientific basis for the existence of parallel or multiple universes (Multiverse) exists, at least in theory. According to the principles ofquantum mechanics, there is an unlimited number of possible universes, but every decision or action can brings us only to one of them (or to only one future, if you will). But is the number really unlimited?
According to scientists, one of the strangest phenomena in quantum theory is the fact that we can determine whether certain events in the sub-atomic level will happen (for example, if an electron emitted from an atom will become positive or negative) only on a probabilistic level, because this is a completely random phenomenon.
One of the boldest explanations for this phenomenon was suggested as far as in 1957 by Hugh Everett, then a graduate student of physics. He suggested the possibility that at any moment in which a random process occurs at the sub-atomic level, the universe splits into two (or more), and in each of those nearly identical universes, a different result of the event is obtained. For example, if an electron can in a particular situation become positive or negative with an equal probability, the universe splits at that moment into two universes which are identical in every respect according to that electron, which is positive in one and negative in the other. The scientist performs taking the measurement also splits into two along with the entire universe, so every one of his "copies" will have a different result of the measurement…
A macroscopic creature as a human, who has learned to survive thanks to the determinism controlling nature, will find it very difficult to accept the fact that there are laws of nature that are not contingent on two considerations, probability and randomness, but every theoretical experiment and discussion reconfirms the phenomenon.
Physics at the turn of the twentieth century - what we today call "classical" physics - viewed the universe to be a comfortable, predictable sort of place. The laws of physics could readily forecast the motions of the stars and planets as well as a falling stone. The universe seemed to run like an elegant clock, and everything in nature behaved according to a set of straightforward rules. Many physicists believed that there wasn't much work left to do in basic physics except fill in a few minor details.
When the theory of quantum mechanics was developed to explain the behavior of atoms and subatomic particles in the late 1920's and early 1930s, it produced much excitement and no small degree of agitation in the world of physics.
Experimental predictions based on the theory were remarkably accurate. But the foundation of the theory rested on principles that scientists who came of age in the late nineteenth century found extremely hard to accept.
According to quantum mechanics, a subatomic particle can sometimes be in two places at the same time; electrons can "tunnel" through otherwise insurmountable energy barriers; two particles separated by light-years of space can somehow recognize each other's quantum states without communicating. Neils Bohr, one of the pioneers of quantum theory, once said, "Anyone who isn't shocked by quantum mechanics doesn't understand it".
Quantum mechanics upset the classical order by asserting that the fundamental particles that make up all matter obeyed a set of rules that were essentially statistical in nature. Quantum theory makes mathematically precise predictions, but they are predications about probabilities. For example, quantum theory can predict with great precision the probability that an electron will carom off in some particular direction after a collision with another particle, but it cannot predict which direction the electron will actually move after the collision. Albert Einstein was particularly disturbed by the probabilistic nature of quantum theory. He summed up his objections to the theory in his oft-repeated phrase, "God does not play dice with the universe".
The many-worlds interpretation of quantum mechanics was an attempt to restore strict determinism to the world of physics. For simplicity, let's say there is a fifty-fifty chance of an electron having one of two distinct energy values (let's call them A and B), and we measure the electron's energy and discover it is B. Then, according to the many-worlds theory, there is another universe where the energy of the electron is measured as A. This universe is in fact created when we measure the energy of the electron. It might look like God has simply tossed a coin and it came up A, but in this parallel universe he also tossed the coin and it came up B.This is a pretty strange assertion, but it does remove the probability aspect of quantum theory, because all possible outcomes for a measurement or experiment do in fact occur. They just occur in other universes.
And what does that have to do with time travel?
If time travel means, in fact, travel to another universe, there is no point in trying to go back to the past and make changes, as they will not be reflected in "our" universe. Even sending a researcher to the past to learn about historical events is futile, since the researcher will be travel to a different universe and will never be able to return to our universe to tell us about his observations, which wick anyway be observations of another universe (as seen in two successful TV shows based on the same principle - "Sliders" and "Quantum Leap").
Stories of travel to parallel universes are very common in literature, and interestingly, some of the most prominent examples exist in what is defined as children's literature, such as "Alice in Wonderland" and "The Chronicles of Narnia" (filmed in several versions, the latest in 2007), Last but not least is Neil Gaiman, who had two novels ("Neverwhere" and "Coraline") based on such scenarios adapted to the Big Screen. All stories of this kind have a similar beginning - Someone, usually a child, opens a door (or a window, for that matter), goes through in spite of all warnings, and finds himself in a parallel universe, where he must undergo al kinds of adventures and hardships until he finds his way back.
Another preferred method of time travel is the quantum mirror, a device of unclear origin and specification, but apparently a kind of a super-computer, made Naquadah, which can also serve as an illustration aid to Hugh Everett's multiverse theory. It is equipped with a "remote" that allows the traveler to choose the desirable dimension. I found two versions of this miraculous invention.
1. According to Stargate, the quantum mirror is a device capable of transferring a person to an alternate reality with a touch. The closer the chosen dimension, the closer the alternate reality is to ours, etc'. Practice can improve the accuracy in reaching the desired destination.
Point of View
There But For the Grace of God
2. The same principle was used in Sliders, but we saw only the Remote in action.
Quantum Mirror Hypothesis
This theory, sketched cryptically in Whitley Strieber's best-selling "Communion", casts the aliens as a large-scale quantum manifestation, the act of observation somehow granting them reality. Likewise, humans would seem just as enigmatic and strange to them.
Whatever the validity of the quantum hypothesis
(which, admittedly, smacks of New Age gibberish), there is a body of testimony
suggesting that the aliens aren't nearly as sagely and all-knowing as they are
usually made out to be in science-fiction media. Abduction stories are replete
with absurd episodes such as aliens displaying overt mystification with articles
of clothing and other accessories. The entities encountered by Betty and Barney
Hill appeared genuinely startled by the fact that Betty's teeth were removable
while Barney's were not. Is this really the behavior one would expect of an
inconceivably advanced alien race on an anthropological internship on Earth?
Whitley Strieber describes at least two apparent aliens wearing ridiculously inept facsimiles of human attire as if in an attempt to "fit in". And then there is the story of the alien who clumsily tried to put on an abductee's high-heeled shoes, and yet another account in which an alien donned a cowboy hat in what might have been a misguided attempt to appear rural and unthreatening.
Somehow these the only examples I've found for the use of this device, perhaps an indication of its quality…
This scenario usually contains 4 clearly marked stages:
1. The Hero feels that a moment in time is repeating itself;
2. The Hero tries to find out the reason for the loop and convince others of its existence;
3. The Hero finds out what needs to be done in order to break the loop;
4. Time is restored (and nobody remembers anything).
(Image 22e, source: http://www.mjyoung.net/time/index.htm)
Is alternate history a form of time travel?
The issue of whether alternate history can be considered Science Fiction is a very controversial one in the SF world. Proponents argue that this alternate history stories actually take place in a parallel universe or parallel dimension (just ask Stargate’s Colonel Mitchell, he will explain the difference to you...) The scientific basis for this is of course Hugh Everett’s theory of parallel universes, which greatly influenced many Science Fiction stories dealing with alternate worlds.
There's a substantial difference between "alternative worlds", in which history corresponds to our own (to a point) and "parallel" worlds or dimensions - worlds apart, each with its unique and independent history and its own. There is also a "secret history", in which an old conspiracy directed the course of history without our knowledge (see the Illuminati series by Robert Wilson, and a new and updated version of this scenario, "Da Vinci Code" by Dan Brown).
The first alternate history story of the - 20th century, which is also the first alternate history story in the German language, written in 1900 by a Jewish science fiction author of Hungarian descent, Theodore Herzl. The story, "Bonaparte the Entrepreneur", describes a reality in which Napoleon Bonaparte became a successful businessman instead a general, in a world where reactionary forces defeated the Revolution, and in 1815 became destitute. Herzl was very intrigued by stories like this, and he also wrote a story called "the Left Bell", in which he showed how a man’s life would have change had he rang one door bell instead of the other (sound familiar? Hint: See "Revolving Doors") and the also "the Mind Reader", The story of telepathy who can read the minds of people around hom and control them.
Because the only question, as we know, that we should never ask in History is "What if... " dealing with alternate history became a very popular occupation among Science Fiction writers (and not just them). The idea is to take a historical event with an already known outcome, change something at a crucial point (Point of Diversion) and try to see what would happen because of the change. As a short exercise, here is a selection of common "What if..." questions
So what would have happened if…
1. Nazi Germany had won the Second World War (and more importantly, had succeeded in occupying England)…
2. The South had won the Civil War/the South and the North were united against communal enemy…
3. The USSR had taken over the USA…
4. The industrial revolution happened in a different time or a different place…
5. Cortes had not succeeded in defeating the Aztecs…
6. Jewish history had spiraled out of control…
7. The Dinosaurs had not become extinct…
8. Christianity as we know it had not become the ruling religion in Europe…
9. Aliens have invaded Earth…
So how does that relate to tine travel?
Suppose the change at the Point of Diversion was made by a time traveler…
Is Time travel possible in a two-dimensional universe?
Infinity and the Mind: The Science and Philosophy of the Infinite
The Fourth Dimension: A Guided Tour of the Higher Universes
See: A two-dimensional passage model of time for time travel by Jack W. Meiland
In spite if all the disagreements, it seems that most scientists agree that the existence of paradoxes is an indication of the tremendous difficulties facing anyone who ever decides to make the tome travel dream come true. Meanwhile, apparently, time travel will remain in the realm of Sci Fi, at least for the time being…
The examples are analyzed according to the following criteria:
1. Is it a book (B), a Movie (C) or a TV show (T)?
2. According to the scenario described, is a time machine necessary? If not, how is time travel achieved?
3. If a Machine is necessary, what is its technical specification, and how does it work?
4. What are the presumptions which allow for time travel and dealing with paradoxes?
5. Does the traveler meet his younger (or older) Self?
6. Does the time traveler return to the "Point of Origin"? And if so, how?
|13 Going on 30|
|Adjustment Bureau, the|
|All you Zombies|
|Army of Darkness|
|Back to the Future|
|Bearing an Hourglass|
|Bill & Ted's Bogus Journey|
|Bill & Ted's Excellent Adventure|
|By his Bootstraps|
|Cat who Walks Through Walls, the|
|Connecticut Yankee in King Arthur's Court, a|
|Edge of Tomorrow|
|End of Eternity, the|
|Ender Quadrilogy, the|
|Flight of the Navigator|
|For All Time|
|From Time to Time|
|Harry Potter and the Prisoner of Azkaban|
|Hot Tub Time Machine|
|Kate & Leopold|
|Lake House, the|
|Last Action Hero, the|
|Men in Black III|
|Number of the Beast, the|
|Pastwatch: the Redemption of Christopher Columbus|
|Philadelphia Experiment, the|
|Planet of the Apes|
|Planet of the Apes - the New Movie|
|Planet of the Apes - the original Movie and its Sequels|
|Race Through Time *Man Who Used to be Me, the|
|Somewhere in Time|
|Sound of Thunder|
|Star Trek 2009)|
|Star Trek Generations|
|Star Trek IV: The Voyage Home|
|Star Trek: First Contact|
|Time After Time|
|Time and Again|
|Time Line - the Movie|
|Time Line - the Novel|
|Time Machine, the - the Movie|
|Time Machine, the - the Novel|
|Time Traveler's Wife|
|Timerider: the Adventures of Lyle Swann|
|X-Men: Days of Future Past|
Every self-respecting Sci Fi show on TV has at least one episode dealing with time travel, and some shows have all their episodes dedicated to time travel scenarios.
Click here for a short list of examples from some successful TV shows or choose your favorite show from the following list:
|Adventures of Brisco County, the|
|Ashes to Ashes|
|Life on Mars|
|Terminator: the Sarah Connor Chronicles|
|Time Tunnel, the|
Although there is debate over the exact date it started, on November 02, 2000, a person calling themselves Timetravel_0, and later John Titor, started posting on a public forum.
In his posts, he claimed to be a time traveler from the year 2036, sent to 1975 to obtain an IBM 5100 computer, allegedly having the capability to debug old software (a senior IBM engineer confirmed that the specific model does exist and was manufactured and sold by IBM, with that specific capability, which was not public knowledge).
Titor also claimed that on his way back, he "stopped over" in 2000 to examine the effects of Y2K, and that's also when he started to publish his posts. He insisted that John Titor is indeed his real name, but gave several conflicting versions regarding his age (according to one of them, he was two years old in 2000, whatever that implies...)
One of the first things he did was post pictures of his time machine and its operations manual. As the weeks went by, more and more people began questioning him about why he was here, the physics of time travel and his thoughts about our time. He also posted on other forums including the now non-existent Art Bell site. In his posts John Titor entertained, angered, frightened and even belittled those who engaged him in conversation.
On March 21, 2001, John Titor told us he would be leaving our time and returning to 2036. After that, he was never heard from again. Speculation and investigation about who John Titor was and why he was online continues to this day.
Although it may be easy to dismiss all this as science fiction, most people who read his posts agree that there is something very haunting about John Titor and what he said. In addition, and open to more debate, he also made a series of predictions and comments that eerily seem to be coming true.
The reader is advised to keep two things in mind:
1. John appeared to answer nearly every question that was asked of him over the 4-month period he was online. Because of that, many people neglected to read the previous posts and asked similar or exact questions he had already answered. It may offer a glimpse of what a time traveler goes through when having the same conversation again and again.
2. These posts were written before 9/11, the Discovery accident and the second gulf war. Many people believe John may have known of these events and dropped clues without actually referring to them. It's also widely agreed that he made several predictions about future physics discoveries that have materialized as he stated.
So what did John Titor predict? Below are some selected examples. Some of them relate to the period starting in 2004, allowing us to examine their authenticity. Incidentally, note that there is nothing original or new ...
First, Titor claimed that Hugh Everett's Relative-State Interpretation or the Many Worlds theory will become scientifically proven as true, making all of the time travel paradoxes redundant, especially the grandfather paradox.
In the early 2000's CERN will lay the foundations for time travel. In the autumn of 2001 after Titor had left, CERN released a statement indicating the creation of mini black holes was possible.
An upcoming civil war in the United States having to do with "order and rights" is described as beginning in 2004, with civil unrest surrounding the presidential election of that year. This civil conflict that he characterizes as "having a Waco type event every month that steadily gets worse" will be "pretty much at everyone's doorstep" and erupts by 2008.
As the West becomes increasingly unstable, in 2015 (not 2012, as foreseen by the Maya and mentioned in the X-Files), Russia launches a nuclear strike against major cities in the United States (which is the "other side" of the civil war from Titor's perspective), China, and Europe. The United States counter attacks. The US cities are destroyed along with the AFE (American Federal Empire) and the country won. The European Union and China were also destroyed.
America will wage war on Iraq, claiming Iraq has nuclear weapons (Titor made this statement years before a war with Iraq was considered. He also claimed no weapons of mass destruction would be found).
Korea, Taiwan and Japan will be annexed by China.
By the year 2036 Yahoo and Microsoft will cease to exist, however, Napster followres continue to download music from the Internet;
Mad cow disease will be a health issue in America, but it will be under-played. AIDS and Cancer remain without a cure.
Despite some allegedly alarming events which seem to indicate this fulfillment of this prediction, we can relax, It is now mid-2013, and President Obama has started his second term in Office without declaring Martial Law in the U.S…. What will be the fate of the other forecasts? Time will tell.
And what does that say about John Titor? Is he a man of the present who has the ability to predict the future, but chooses to hide behind the claim that he was from the future? (By the way, technically he came from 1975, which is the past...) Is he a fictitious character created by a crook or a group of crooks, or maybe just a hoax? Or is he really a time traveler? And maybe the future he describes is really only one of many possible ones, and the processes leading to its change are already underway?
By the way, one thing I could not find - a photograph of the man who calls himself John Titor. Too bad ...
1. What should I pack for the trip in time?
a. Nothing, only organic matter may travel through time, prepare to arrive butt naked (which is just fine, if you're Schwarzenegger or the Terminatrix.
b. Whatever you want, everything goes.
2. Should I buy a one way or a return ticket?
Don't be tempted by crooks who try to sell return tickets. The responsibility for the return is entirely your own.
3. Will knowledge of the future help me in the past?
The answer to that should be obvious, but apparently that's not always true. Assuming you make it to your destination in one piece, you'll have a hard time proving that you are not a monster/a lunatic, and that the simple objects you brought with you, if any, are not magical tools or satanic weapons, and you will most likely be killed by some religious zealot before you do. In any case we recommend that you prepare a list of solar and lunar eclipses, volcanic eruptions and other natural catastrophes, to be memorized and used when necessary.
4. And if I miss the ride back?
Best case scenario, you'll have to stay in the past as a God or a prophet. Worst case scenario, see the answer to question 5.
5. What if I get killed in the past?
Stop bellyaching, if you get killed in the past, you will have killed your whole future progeny, including your parents, and you will not be born, and if you are not born, how did you travel in time? Not getting killed out of your own time is highly recommend; By the way, it is also recommended that you don't kill anyone, at least not before you double check that the victim is not some ancestor (because killing him will result in the death of your progeny, etc'). By the way, we are proud to say that no such incident will have happened in any of our company's tours.
6. And if I get to the future?
Our extended warranty does not cover the future.
7. Which organized tours do you offer?
The choice of organized tours is limited, for obvious reasons. We recommend butterfly watching.
8. And If I happen to stray off the marked trail?
Don't bother to come back, you'll have nowhere to come back to.
9. You requested the name and phone number of a contact person in case of an emergency. Does it have to be a first-degree blood relative?
No, you may choose anyoneyou wish, except a twin sibling.
For the presentation click here.