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Unsolved problems in physics: Is time travel theoretically and practically possible? Will such travel invoke paradoxes, such as often used in fiction?

Time travel is the concept of moving backward or forward to different points in time, in a manner analogous to moving through space. Additionally, some interpretations of time travel suggest the possibility of travel between parallel realities or universes.^[1]

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Origins of the concept

Charles Dickens' 1843 book A Christmas Carol is considered by some^[2] to be one of the first depictions of time travel, as the main character, Ebenezer Scrooge, is transported to Christmases past, present and yet to come. These might be considered mere visions rather than actual time travel, though, since Scrooge only viewed each time period passively, unable to interact with them. A clearer example of time travel is found in the popular 1861 book Paris avant les hommes (Paris before Men), published posthumously by the French botanist and geologist Pierre Boitard. In this story the main character is transported into the prehistoric past by the magic of a "lame demon", where he encountered such extinct animals as a Plesiosaur, as well as Boitard's imagined version of an apelike human ancestor, and was able to actively interact with some of them. Another early example of time travel in fiction is the short story The Clock That Went Backward by Edward Page Mitchell, which appeared in the New York Sun in 1881.

The first time travel story to feature time travel by means of a time machine was Enrique Gaspar y Rimbau's 1887 book El Anacronópete. This idea gained popularity with the H. G. Wells story The Time Machine, published in 1895, which is often seen as an inspiration for all later science fiction stories featuring time travel.

Since that time, both science and fiction (see Time travel in fiction) have expanded on the concept of time travel, but whether it could be possible in reality is still an open question.

Time travel in theory

Some theories, most notably special and general relativity, suggest that suitable geometries of spacetime, or specific types of motion in space, may allow time travel into the past and future if these geometries or motions are possible.^[3] Concepts that aid such understanding include the closed timelike curve.

Although the possibility of traveling to the future by moving at relativistic velocities is taken for granted by physicists, many in the scientific community believe that backwards time travel is highly unlikely. Any theory which would allow time travel would require that issues of causality be resolved. What if one were to go back in time and kill one's own grandfather (see grandfather paradox)? Additionally, Stephen Hawking once suggested that the absence of tourists from the future constitutes a strong argument against the existence of time travel—a variant of the Fermi paradox, with time travelers instead of alien visitors. However, the theory of general relativity does suggest scientific grounds for thinking backwards time travel could be possible in certain unusual scenarios, although arguments from semiclassical gravity suggest that when quantum effects are incorporated into general relativity, these loopholes may be closed. These semiclassical arguments led Stephen Hawking to formulate the chronology protection conjecture, suggesting that the fundamental laws of nature prevent time travel, but physicists cannot come to a definite judgment on the issue without a theory of quantum gravity to join quantum mechanics and general relativity into a completely unified theory.

The "presentist" view

Presentism holds that neither the future nor the past exist; that the matter of the universe only exists in the present moment, that time is merely a concept of man used to describe what is going on around him. This could be interpreted to mean that there is nowhere for a time traveller to go, thus rendering the whole topic of time travel null and void. However, some presentists argue that although past and future objects do not exist, there can still be definite truths about past and future events, and that it is possible that a future truth about the time traveler deciding to return to the present date could explain the time traveler's actual presence in the present.^[4] In any case, the relativity of simultaneity in modern physics is generally understood to cast serious doubt on presentism and to favor the view known as four dimensionalism (closely related to the idea of block time) in which past, present and future events all coexist in a single spacetime.

Time travel to the past

Time travel to the past is theoretically allowed using the following methods^[5]:

The equivalence of time travel and faster-than-light travel

If one were able to move information or matter from one point to another faster than light, then according to special relativity, there would be some inertial frame of reference in which the signal or object was moving backwards in time. This is a consequence of the relativity of simultaneity in special relativity, which says that in some cases different reference frames will disagree on whether two events at different locations happened "at the same time" or not, and they can also disagree on the order of the two events (technically, these disagreements occur when spacetime interval between the events is 'space-like', meaning that neither event lies in the future light cone of the other).^[6] If one of the two events represents the sending of a signal from one location and the second event represents the reception of the same signal at another location, then as long as the signal is moving at the speed of light or slower, the mathematics of simultaneity ensures that all reference frames agree that the transmission-event happened before the reception-event.^[6] However, in the case of a hypothetical signal moving faster than light, there would always be some frames in which the signal was received before it was sent, so that the signal could be said to have moved backwards in time. And since one of the two fundamental postulates of special relativity says that the laws of physics should work the same way in every inertial frame, then if it is possible for signals to move backwards in time in any one frame, it must be possible in all frames. This means that if observer A sends a signal to observer B which moves FTL in A's frame but backwards in time in B's frame, and then B sends a reply which moves FTL in B's frame but backwards in time in A's frame, it could work out that A receives the reply before sending the original signal, a clear violation of causality in every frame. An illustration of such a scenario using spacetime diagrams can be found here.

It should be noted that according to relativity it would take an infinite amount of energy to accelerate a slower-than-light object to faster-than-light speeds, and although relativity does not forbid the theoretical possibility of tachyons which move faster than light at all times, when analyzed using quantum field theory it seems that it would not actually be possible to use them to transmit information faster than light^[7], and there is no evidence for their existence.

Special spacetime geometries

The general theory of relativity extends the special theory to cover gravity, illustrating it in terms of curvature in spacetime caused by mass-energy and the flow of momentum. General relativity describes the universe under a system of field equations, and there exist solutions to these equations that permit what are called "closed time-like curves," and hence time travel into the past. ^[8]The first of these was proposed by Kurt Gödel, a solution known as the Gödel metric, but his (and many others') example require the universe to have physical characteristics that it does not appear to have.^[8] Whether general relativity forbids closed time-like curves for all realistic conditions is unknown.

Using wormholes

Wormholes are a typed of warped spacetime which are also permitted by the Einstein field equations of general relativity, although it would be impossible to travel through a wormhole unless it was what is known as a traversable wormhole.

A proposed time-travel machine using a traversable wormhole would (hypothetically) work something like this. A wormhole is created somehow. One end of the wormhole is accelerated to nearly the speed of light, perhaps with an advanced spaceship, and then brought back to the point of origin. Due to time dilation, the accelerated end of the wormhole has now aged less than the stationary end, as seen by an external observer. However, time connects differently through the wormhole than outside it, so that synchronized clocks at either end of the wormhole will always remain synchronized as seen by an observer passing through the wormhole, no matter how the two ends move around. This means that an observer entering the accelerated end would exit the stationary end when the stationary end was the same age that the accelerated end had been at the moment before entry; for example, if prior to entering the wormhole the observer noted that a clock at the accelerated end read a date of 2005 while a clock at the stationary end read 2010, then the observer would exit the stationary end when its clock also read 2005, a trip backwards in time as seen by other observers outside. One significant limitation of such a time machine is that it is only possible to go as far back in time as the initial creation of the machine^[9]; in essence, it is more of a path through time than it is a device that itself moves through time, and it would not allow the technology itself to be moved backwards in time. This could provide an alternative explanation for Hawking's observation: a time machine will be built someday, but has not yet been built, so the tourists from the future cannot reach this far back in time.

According to current theories on the nature of wormholes, creating a wormhole of a size useful for a person or spacecraft, keeping it stable, and moving one end of it around would require significant energy, many orders of magnitude more than the Sun can produce in its lifetime. Construction of a traversable wormhole would also require the existence of a substance known as "exotic matter", which, while not known to be impossible, is also not known to exist in forms useful for wormhole construction (but see for example the Casimir effect). Therefore it is unlikely such a device will ever be constructed, even with highly advanced technology. On the other hand, microscopic wormholes could still be useful for sending information back in time.

In 1993, Matt Visser argued that the two mouths of a wormhole with such an induced clock difference could not be brought together without inducing quantum field and gravitational effects that would either make the wormhole collapse or the two mouths repel each other. ^[10] Because of this, the two mouths could not be brought close enough for causality violation to take place. However, in a 1997 paper, Visser hypothesized that a complex "Roman ring" (named after Tom Roman) configuration of an N number of wormholes arranged in a symmetric polygon could still act as a time machine, although he concludes that this is more likely than not a flaw in classical quantum gravity theory rather than proof that causality violation is possible. ^[11]

Another approach — attributed to Frank Tipler, ^[12] but invented independently by Willem Jacob van Stockum ^[13] in 1936 and Kornel Lanczos ^[14] in 1924 — involves a spinning cylinder. If a cylinder is long, and dense, and spins fast enough about its long axis, then a spaceship flying around the cylinder on a spiral path could travel back in time (or forward, depending on the direction of its spiral). However, the density and speed required is so great that ordinary matter is not strong enough to construct it. A similar device might be built from a cosmic string, but none are known to exist, and it does not seem to be possible to create a new cosmic string.

Physicist Robert Forward noted that a naïve application of general relativity to quantum mechanics suggests another way to build a time machine. A heavy atomic nucleus in a strong magnetic field would elongate into a cylinder, whose density and "spin" are enough to build a time machine. Gamma rays projected at it might allow information (not matter) to be sent back in time. However, he pointed out that until we have a single theory combining relativity and quantum mechanics, we will have no idea whether such speculations are nonsense.^{[citation needed]}

In the science fiction series Sliders, a wormhole (or vortex, as it is usually called in the show) is used to travel between parallel worlds, and one is seen at least once or twice in every episode. In the pilot episode it was referred to as an "Einstein-Rosen-Podolsky bridge", a term which may have arisen from a confusion between "Einstein-Rosen bridges" (a genuine term for Schwarzschild wormholes) and the Einstein-Podolsky-Rosen paradox (a famous thought-experiment in quantum mechanics which is unrelated to wormholes).

Wormholes are a common feature in the computer game Elite in which they are short-lived constructs created on-demand by the hyper-drive as a means of interstellar transport.

Wormholes are also seen in the computer game Freelancer, commonly referred as jump holes. They are supposed to be black hole-like formations with ultra-high gravity amounts, that work like 'portals' for players to travel instantly between different star systems.

A wormhole plays a pivotal role in many episodes and the Dominion story arc in the Star Trek series Deep Space Nine. The Bajoran wormhole (pictured above) connects points in the Alpha and Gamma Quadrant's, allowing ships to traverse a distance of 70,000 light years in just a few minutes. One of the main points of use during the series involved the invasion of the Alpha Quadrant by the Dominion. This continuing story arc dominated the final seasons of the series.

In the Stargate series, the Stargate generates a wormhole between itself and the gate at the destination, by being supplied with a threshold amount of raw electricity. Objects in transit between gates are broken down into their individual elemental components, and then into energy, and it is this "wormhole" that they travel through before being reconstructed on the other side. Nevertheless, unlike some other science fiction series, many of the technical issues facing wormhole travel are addressed.

In the Film Event Horizon, the experimental ship uses a top secret prototype stardrive. The drive folds space-time and creates an artificial wormhole extending to any point in the universe, allowing the ship to traverse great distances instantaneously.

Wormhole metrics

Theories of wormhole metrics describe the spacetime geometry of a wormhole and serve as theoretical models for time travel. A simple example of a (traversable) wormhole metric is the following:

Wormholes and time travel

A wormhole could allow time travel. This could be accomplished by accelerating one end of the wormhole to a high velocity relative to the other, and then sometime later bringing it back; relativistic time dilation would result in the accelerated wormhole mouth aging less than the stationary one as seen by an external observer, similar to what is seen in the twin paradox. However, time connects differently through the wormhole than outside it, so that synchronized clocks at each mouth will remain synchronized to someone traveling through the wormhole itself, no matter how the mouths move around. This means that anything which entered the accelerated wormhole mouth would exit the stationary one at a point in time prior to its entry. For example, if clocks at both mouths both showed the date as 2000 before one mouth was accelerated, and after being taken on a trip at relativistic velocities the accelerated mouth was brought back to to the same region as the stationary mouth with the accelerated mouth's clock reading 2005 while the stationary mouth's clock read 2010, then a traveler who entered the accelerated mouth at this moment would exit the stationary mouth when its clock also read 2005, in the same region but now five years in the past. Such a configuration of wormholes would allow for a particle's world line to form a closed loop in spacetime, known as a closed timelike curve.

It is thought that it may not be possible to convert a wormhole into a time machine in this manner: some analyses using the semiclassical approach to incorporating quantum effects into general relativity indicate that a feedback loop of virtual particles would circulate through the wormhole with ever-increasing intensity, destroying it before any information could be passed through it, in keeping with the chronology protection conjecture. This has been called into question by the suggestion that radiation would disperse after traveling through the wormhole, therefore preventing infinite accumulation. The debate on this matter is described by Kip S. Thorne in the book Black Holes and Time Warps. There is also the Roman ring, which is a configuration of more than one wormhole. This ring seems to allow a closed time loop with stable wormholes when analyzed using semiclassical gravity, although without a full theory of quantum gravity it is uncertain whether the semiclassical approach is reliable in this case.

Time travel and the anthropic principle

It has been suggested by physicists such as Max Tegmark that the absence of time travel and the existence of causality may be due to the anthropic principle. The argument is that a universe which allows for time travel and closed time-like loops is one in which intelligence could not evolve because it would be impossible for a being to sort events into a past and future or to make predictions or comprehend the world around them (at least, not if the time travel occurs in such a way that it disrupts that evolutionary process).^{[citation needed]}

Time travel to the future

Time travel to the future is theoretically allowed using the following methods^[5]:

Time dilation

Time dilation is permitted by Albert Einstein's special theory of relativity. These theories state that, relative to a stationary observer, time appears to pass more slowly for faster-moving bodies, or bodies that are within a deep gravity well. ^[16] For example, a moving clock will appear to run slow; as a clock approaches the speed of light it will appear to slow to a stop. This has given rise to the popular twin paradox. General relativity states that a similar effect would occur if the clock were to be close to a black hole.

Time perception can be apparently sped up for living organisms through hibernation, where the body temperature and metabolic rate of the creature is reduced. A more extreme version of this is suspended animation, where the rates of chemical processes in the subject would be severely reduced.

Time dilation and suspended animation only allow "travel" to the future, never the past, so they do not violate causality, and arguably should not be considered time travel.

Curved spacetime shell

This method of travelling to the future is unique in that it does not require travelling in space. However, it is impractical because it requires a mass on the order of the planet Jupiter. If a clump of distorted spacetime as massive as Jupiter is squeezed to be 5 meters tall and forms a funnel shape, a person who went into the bottom of it would not have to move anywhere to travel. The traveller inside the funnel would be moving 4 times faster than everything else, and the traveller would be able to see through the distorted spacetime like a window and see objects moving fast outside as if the world were in fast forward^[5]. To observers on the outside, the time traveller would appear to be moving more slowly.

Small travel

Today, the only way to "travel" to the future cannot be used to travel over long periods of time -- only less than a single second. It is so insignificant that it is usually not mentioned at all. The only people that have used this method have been astronauts. Basically, the longer a person is in orbit around the Earth, the younger the astronaut will be in relation to observers on Earth. So far, the record for traveling farthest in the future using this method is held by Sergei Avdeyev^[5]. He was in orbit 748 days (total) and traveling approximately 17,000 mph, resulting in him traveling 0.02 seconds (20 milliseconds) into the future^[17]. That means that for Sergei Avdeyev to time travel just one whole second into the future, he would need to orbit for approximately 102.47 years. A common misconception was that the Apollo astronauts traveled faster, so they held the record -- they did travel faster, but not long enough (only a few days).

Other theories

The possibility of paradoxes

The Novikov self-consistency principle and recent calculations by Kip S. Thorne^{[citation needed]} indicate that simple masses passing through time travel wormholes could never engender paradoxes—there are no initial conditions that lead to paradox once time travel is introduced. If his results can be generalised, they would suggest, curiously, that none of the supposed paradoxes formulated in time travel stories can actually be formulated at a precise physical level: that is, that any situation you can set up in a time travel story turns out to permit many consistent solutions. The circumstances might, however, turn out to be almost unbelievably strange.^{[citation needed]}

Parallel universes might provide a way out of paradoxes. Everett's many-worlds interpretation of quantum mechanics suggests that all possible quantum events can occur in mutually exclusive histories.^[18] These alternate, or parallel, histories would form a branching tree symbolizing all possible outcomes of any interaction. If all possibilities exist, any paradoxes could be explained by having the paradoxical events happening in a different universe. This concept is most often used in science-fiction, but some physicists such as David Deutsch have suggested that if time travel is possible and the many-worlds interpretation is correct, then a time traveler should indeed end up in a different history than the one he started from. ^[1]

Daniel Greenberger and Karl Svozil proposed that quantum theory gives a model for time travel without paradoxes. ^[19] In quantum theory observation causes possible states to 'collapse' into one measured state; hence, the past observed from the present is deterministic (it has only one possible state), but the present observed from the past has many possible states until our actions cause it to collapse into one state. Our actions will then be seen to have been inevitable.

The science fiction writer Larry Niven made his own suggestion about paradox avoidance in his essay The Theory and Practice of Time Travel. He argued that as long as time travel exists, history will change, and will only become static when a timeline is reached in which no time travel exists and thus no further changes can be made (unless it is on a course that is repetitive or will never become static, but there is no evidence of this). Assuming there is only a single dimension of time, the timeline we perceive must be the one that exists after all changes (if any) are made, and thus we will never perceive the invention of time travel, since it will have already destabilised itself out of the timeline by the 'time' we would have reached it.^{[citation needed]} However, few if any physicists or philosophers have taken seriously the possibility of "changing" the past except in the case of multiple universes, and in fact many have argued that this idea is logically incoherent (see this discussion between two philosophers, for example), so this idea is not usually seen outside of science fiction.

Using quantum entanglement

Quantum-mechanical phenomena such as quantum teleportation, the EPR paradox, or quantum entanglement might appear to create a mechanism that allows for faster-than-light (FTL) communication or time travel, and in fact some interpretations of quantum mechanics such as the Bohm interpretation presume that some information is being exchanged between particles instantaneously in order to maintain correlations between particles.^[20] This effect was referred to as "spooky action at a distance" by Einstein.

Nevertheless, the rules of quantum mechanics curiously appear to prevent an outsider from using these methods to actually transmit useful information, and therefore do not appear to allow for time travel or FTL communication. The fact that these quantum phenomena apparently do not allow FTL/time travel is often overlooked in popular press coverage of quantum teleportation experiments. How the rules of quantum mechanics work to preserve causality is an active area of research.

Time travel in fiction

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Types of time travel

Time travel themes in science fiction and the media can generally be grouped into two main types and a third, less common type (based on effect—methods are extremely varied and numerous), each of which is further subdivided. These type classifications do not address the issue of time travel itself, i.e. how to travel through time, but instead call to attention differing rules of the time line.

There are also numerous science fiction stories allegedly about time travel that are not internally consistent, where the traveler makes all kinds of changes to some historical time, but we do not get to see any consequences of this in our present day.^{[citation needed]}

Immutable timelines

Time travel in a type 1 universe does not allow any paradoxes, although in 1.3, events can appear to be paradoxical.

In 1.1, time travel is constrained to prevent paradox. If one attempts to make a paradox, one undergoes involuntary or uncontrolled time travel. Michael Moorcock uses a form of this principle and calls it The Morphail Effect. In the time-travel stories of Connie Willis, time travelers encounter "slippage" which prevents them from either reaching the intended time or translates them a sufficient distance from their destination at the intended time, as to prevent any paradox from occurring.

In 1.2, the Novikov self-consistency principle asserts that the existence of a method of time travel constrains events to remain self-consistent (i.e. no paradoxes). This will cause any attempt to violate such consistency to fail, even if extremely improbable events are required.

In 1.3, any event that appears to have caused a paradox has instead created a new time line. The old time line remains unchanged, with the time traveller or information sent simply having vanished, never to return. A difficulty with this explanation, however, is that conservation of mass-energy would be violated for the origin timeline and the destination timeline. A possible solution to this is to have the mechanics of time travel require that mass-energy be exchanged in precise balance between past and future at the moment of travel, or to simply expand the scope of the conservation law to encompass all timelines. Some examples of this kind of time travel can be found in David Gerrold's book The Man Who Folded Himself, The Time Ships by Stephen Baxter and the (1994) film Star Trek: Generations.

Mutable timelines

Time travel in a Type 2 universe is much more complex. The biggest problem is how to explain changes in the past. One method of explanation is that once the past changes, so too do the memories of all observers. This would mean that no observer would ever observe the changing of the past (because they will not remember changing the past). This would make it hard to tell whether you are in a Type 1 universe or a Type 2 universe. You could, however, infer such information by knowing if a) communication with the past were possible or b) it appeared that the time line had never been changed as a result of an action someone remembers taking, although evidence exists that other people are changing their time lines fairly often. An example of this kind of universe is presented in Thrice Upon a Time, a novel by James P. Hogan. In film, the Back to the Future trilogy also seems to feature a single mutable timeline.

Larry Niven suggests that in a type 2.1 universe, the most efficient way for the universe to "correct" a change is for time travel to never be discovered, and that in a type 2.2 universe, the very large (or infinite) number of time travelers from the endless future will cause the timeline to change wildly until it reaches a history in which time travel is never discovered. However, many other "stable" situations may also exist in which time travel occurs but no paradoxes are created; if the changeable-timeline universe finds itself in such a state no further changes will occur, and to the inhabitants of the universe it will appear identical to the type 1.2 scenario.^{[citation needed]} This is sometimes referred to as the "Time Dilution Effect."

Gradual and instantaneous

1. The most commonly used method of time travel in science fiction is the instantaneous movement from one point in time to another, like using the controls on a CD player to skip to a previous or next song, though in most cases, there is a machine of some sort, and some energy expended in order to make this happen (Like the DeLorean in Back to the Future or the phonebooth and the circuits of time in Bill and Ted's Excellent Adventure). In some cases, there is not even the beginning of a scientific explanation for this kind of time travel; it's popular probably because it is more spectacular and makes time travel easier.

2. In The Time Machine, H.G. Wells explains that we are moving through time with a constant speed. Time travel then is, in Wells' words, "stopping or accelerating one's drift along the time-dimension, or even turning about and traveling the other way." To expand on the audio playback analogy used above, this would be like rewinding or fast forwarding an analogue audio cassette and playing the tape at a chosen point. This method of gradual time travel fits best in quantum physics, but is not as popular in modern science fiction. Perhaps the oldest example of this method of time travel is in Lewis Carroll's Through the Looking-Glass (1871): the White Queen is living backwards, hence her memory is working both ways. Her kind of time travel is uncontrolled: she moves through time with a constant speed of -1 and she cannot change it. This would make Lewis Carroll the inventor of time travel. T.H. White, in the first part of his Arthurian novel The Once and Future King, The Sword in the Stone (1938) used the same idea: the wizard Merlyn lives back in time, because he was born "at the wrong end of time" and has to live backwards from in front. "Some people call it having second sight".^{[citation needed]}

Time travel, or space-time travel?

An objection that is sometimes raised against the concept of "time travel ships" in science fiction is that they often assume that the time traveler will remain in the same spatial position in the Earth's frame of reference, as opposed to some other frame. The idea that a traveller can go into a machine that sends him or her to 1865 and step out into the exact same spot on Earth might be said to ignore the issue that Earth is moving through space around the Sun, which is moving in the galaxy, and so on. However, this argument is somewhat confused according to special relativity, since relativity rejects the notion of absolute time and space, meaning that the speed of the Earth and Sun would themselves depend on your frame of reference, so that there is no single point in space today that is objectively the "same place" that the Earth was at some point in the past. It would always be possible to find at least one frame where the Earth's position today is the same as the Earth's position at the past or future date that is the time traveler's destination, and this frame cannot be considered any more or less valid than any other according to relativity. Also, since there is no basis in physics for the notion of a time traveler disappearing from one location in spacetime and reappearing in another (all the time travel schemes proposed in physics involve the traveler's world line remaining continuous and unbroken, as with time travel via a trip through a wormhole), there cannot be any basis in physics for saying a fictional time traveler "should" reappear at any particular location in space.

Still, the idea that the Earth moves away from the time traveler when he takes a trip through time has been used in a few science fiction stories, such as the 2000 AD comic Strontium Dog, in which Johnny Alpha uses "Time Bombs" to propel an enemy several seconds into the future, during which time the movement of the Earth causes the unfortunate victim to re-materialize in space. Other science fiction stories try to anticipate this objection and offer a rationale for the fact that the traveler remains on Earth, such as the 1957 Robert Heinlein novel The Door into Summer where Heinlein essentially handwaved the issue with a single sentence: "You stay on the world line you were on." In his 1980 novel The Number of the Beast a "continua device" allows the protagonists to dial in the six (not four!) co-ordinates of space and time and it instantly moves them there—without explaining how such a device might work. The television series Seven Days also dealt with this problem; when the chrononaut would be 'rewinding', he would also be propelling himself backwards around the earth's orbit, with the intention of landing in the same place (in space) that he originated.^{[citation needed]}

References

Time Travel Research Center © 2005 Cetin BAL - GSM:+90 05366063183 - Turkey/Denizli

Time travel

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