Time travel is the act of moving from one part of the timelime to another in any manner other than the slow progress of moving from your date of birth to date of death.
Time Travel as a Concept In The Real World And Fiction
In Real Life, Time Travel is often considered a Bad Idea. Whether time travel is even possible is a somewhat heated debate in some circles, and the implications of it are unknown. Multiple schools of thought on how time travel works exist. Are alternate universes created with a quantum model? Can you loop back on yourself and change the future, or is the future that caused you to go back in time in the first place a constant?
However, in many continua, time travel is not only possible, but common or even central to the plot. It is important to note the particular rules of the continua's model of time travel during a visit -- the effects of time travel are often permanent and very serious. Only in the most comedic continuums is time travel used lightly.
It is a common plot device in both goodfic and badfic, and in the latter it is commonly used to spawn alternate universes, particularly to allow uncanonical romances or to allow the survival of characters that would otherwise have died.
Be wary when describing time travel to others. It tends to make people's brains hurt. Even The Doctor, who was intimately familiar with the nature of time and time travel, could only describe the former as being "a ball of timey-wimey stuff", and never could manage to explain the latter in a fashion that his companions (or the viewers) could comprehend.
Time Travel as a Narrative Error
In badfic, many narrative impossibilities may indicate accidental time travel -- in particular, the common case of a plothole. If a character travels a vast distance in an improbable amount of time, it may be plothole time travel. If a character somehow gets to a place of importance at an improbable time (especially if they could not possibly have left in time to get there), it may also be plothole time travel. If a person, due to narrative error, somehow arrives at a location before actually getting there ('He got there, but he was somehow already there'), then once again, plothole time travel. This accidental sort of time travel is very closely related to spacial travel -- these two properties being the base of all PPC portal technology, allowing agents to jump forward in a story's timeline as well as to different locations in a continua.
Other instances of time travel as an error can be found in temporal distortions. Sometimes they are caused by the tone and pacing of a target fic, and other times they are actual errors in gaguing the canonical passage of time. Missions may describe a distortion's affects in many ways. Here are just two examples, for time crunch and time stretch:
- Time crunch is a narrative moving forward at more than one second per second. When time is crunched, events seem to happen far too quickly in a story: almost as if all of the 'boring parts' were stripped out. Time crunch may look to Agents like a VCR tape on fast-forward, or even like a vast, cosmic 'disc skip' as events are jumped over.
- Time stretch is a narrative moving forward at less than one second per second. When time is stretched, events slow down to a crawl, almost as if the present events contain far too much to ever actually happen in a second's time. Time stretch may appear to agents like a dramatic slow-motion in an action movie or even like characters moving at normal speed while time itself slows down, somehow fitting too many details into each individual second.
In these cases, erroneous or unintentional time travel may be used as a charge. Temporal distortion is a related concept.
Time Paradox
Time paradox is bad and very hard to describe. For an example, if one goes back in time and then makes it so that they could (or would) have never gone back in time in the first place... Did the person go back in time, or was that future un-made and replaced with a new one? And if so, it only could have existed if that original future did too to stop the time travel... etc. etc...
In 'harder' settings, time paradoxes end in either an unending loop of paradox, or the whole timeline just ceasing to exist. In 'softer' settings, they sometimes are regarded with a cosmic shrug and "ok, moving on... wibbly wobbly timey wimey stuff..."
AUs in fiction can prevent time paradoxes when the content of a fic clashes with the events of the canon.
Agents should not cause time paradoxes because causing a time paradox is a very bad idea. Unless it gets rid of a Sue or a Sue-Wraith, and harms nothing else -- but Upstairs might still get pretty mad anyway. But it might be really cool, despite that.
Causing a time paradox (not as a plot point) can be a charge.
Narrative Time Travel and the PPC
PPC portals can be used to travel through a narrative, most of which have their own timelines. If one is at the beginning of the story, and one opens a portal to the end of the story, that person has effectively 'skipped' all of the time in the middle -- just like a plothole does accidentally. Which makes sense, because PPC portals run on plothole-based technology.
Because time in a story passes as the story reaches completion (flashbacks excepted), moving through the story chapter by chapter may move agents through space and time as the narrative moves along at its own pace. Time and location are closely linked in fiction -- in badfic, time may not even be passing beyond the narrative's present location.
Because Agents are not part of the narrative, they may be exempt from the story's particular pace through time and space. A Fic Location Follower is standard issue to Agents for this reason, so they don't get left behind when the fanfic jumps to a new scene in a new place and time. This may be bad if the narrative makes this jump suddenly, imparting significant velocity to the hapless Agents. It probably is also bad if the narrative suddenly cuts out at the end of a chapter into long and empty author's notes, dropping the agents down into the next chapter's content with a jarring stop-and-start of time and space.
Witnessing time and space stop and start probably causes some agents to go mad.
For this reason, some agents turn off their Fic Location Followers and just follow the time and spacial jumps manually with portals.
Of course, all of these circumstances will be ruled by the Laws of Narrative Comedy in the field.
Examples
In the mission "The Dark Side" (WoW x FMA), Nume, Ilraen, Barid, and Brightbeard deliberately time-traveled with the help of a bronze dragon to undo an assassination made in error. They recommend not messing up that badly.
In the mission into "Rising Darkness, Raising Light" (Ōkami), Aster, Lore, and Ray witnessed the Mary Sue Leah crunch the timeline of a video game into only two scenes involving the Sue's lust object.