Time travel in modern fiction is sometimes achieved by
space and time warps, stemming from the scientific theory of
general relativity.
Stories from antiquity often featured time travel into the future through a time slip brought on by traveling or sleeping, in other cases, time travel into the past through supernatural means, for example brought on by
angels or spirits.
Time slip A time slip is a
plot device in
fantasy and
science fiction in which a person, or group of people, seem to
travel through time by unknown means. The idea of a time slip has been used in 19th century fantasy, an early example being
Washington Irving's 1819
Rip Van Winkle, where the mechanism of time travel is an extraordinarily long sleep.
Mark Twain's 1889 ''
A Connecticut Yankee in King Arthur's Court had considerable influence on later writers. The first novel to include both travel to the past and travel to the future and return to the present is the Charles Dickens 1843 novel A Christmas Carol''. Time slip is one of the main plot devices of time travel stories, another being a
time machine. The difference is that in time slip stories, the protagonist typically has no control and no understanding of the process (which is often never explained at all) and is either left marooned in a past or future time and must make the best of it, or is eventually returned by a process as unpredictable and uncontrolled as the journey out. The plot device is also popular in children's literature. The 2011 film,
Midnight in Paris similarly presents time travel as occurring without explanation, as the director "eschews a 'realist' internal logic that might explain the time travel, while also foregoing experimental time Distortion techniques, in favor of straightforward editing and a fantastical narrative set-up".
Time portal A
time portal or a
time gate is a doorway in
time, employed in various
fiction genres, especially
science fiction and
fantasy, to transport characters to the
past or
future. They differ from time machines in being a permanent or semi-permanent fixture, often linking specific points in time. An influential example of such a work is the short story, "
By His Bootstraps", by
Robert A. Heinlein, which features a time gate built by aliens and plays with some of the inherent
paradoxes that would be caused by
time travel.
Communication from the future In literature,
communication from the future is a
plot device in some
science fiction and
fantasy stories.
Forrest J. Ackerman noted in his 1973 anthology of the best fiction of the year that "the theme of getting hold of tomorrow's newspaper is a recurrent one". An early example of this device can be found in
H. G. Wells's 1932
short story "
The Queer Story of Brownlow's Newspaper", which tells the tale of a man who receives such a paper from 40 years in the future. The 1944 film
It Happened Tomorrow also employs this device, with the protagonist receiving the next day's newspaper from an elderly colleague (who is possibly a ghost). A communication from the future raises questions about the ability of humans to control their destiny.
Precognition Precognition has been explored as a form of time travel in fiction. Author
J. B. Priestley wrote of it both in fiction and non-fiction, analysing testimonials of precognition and other "temporal anomalies" in his book
Man and Time. His books include time travel to the future through dreaming, which upon waking up results in memories from the future. Such memories, he writes, may also lead to the feeling of
déjà vu, that the present events have already been experienced, and are now being re-experienced. Infallible precognition, which describes the future as it truly is, may lead to
causal loops, one form of which is explored in
Newcomb's paradox. The film
12 Monkeys heavily deals with themes of predestination and the
Cassandra complex, where the protagonist who travels back in time explains that he can't change the past.
Time loop A "time loop" or "temporal loop" is a
plot device in which periods of time are repeated and re-experienced by the characters, and there is often some hope of breaking out of the cycle of repetition. Time loops are sometimes referred to as
causal loops, Stories with time loops commonly center on the character learning from each successive loop through time. In the
Piers Anthony book
Bearing an Hourglass, the second of eight books in the
Incarnations of Immortality series, the character of
Norton becomes the incarnation of Time and continues his life living backwards in time. The 2016 film
Doctor Strange has the character use the Time Stone, one of the
Infinity Stones in the
Marvel Cinematic Universe, to reverse time, experiencing time backwards while so doing. In the film
Tenet, characters time travel without jumping back, but by experiencing past reality in reverse, and at the same speed, after going through a 'turnstile' device and until they revert to normal time flow by going through such a device again. In the meantime, two versions of the time traveller coexist (and must not meet, lest they mutually destruct): the one that had been 'traveling forward' (existing normally) until entering a turnstile and the one traveling backward from the turnstile. The
laws of thermodynamics are reversed for time traveling people and objects, so that for example backward travel requires the use of a
respirator. Objects left behind by time travellers obey 'reverse thermodynamics;' for example, bullets shot or even simply deposited while traveling backward fly back into (forward traveling) guns. ==Themes==