Time Travel Types · 7:39pm Mar 16th, 2017
As promised in the most recent chapter of YAHES 2, I give to you my Time Travel Classification System.
Mode of Time Travel:
Physical: You and/or objects travel to the future or past. Most commonly seen form of time travel. Messages from the future count for this type as long as it isn't a psychic message.
Mental: Only your mind travels in time either to your own body or another person's. Type of time travel seen in time loops.
Result of Time Travel:
Alternate Universe Split: This result creates a new universe where the changes happened, rather than changing the current universe.
Return to Home: After the time travel is complete, the traveller returns to his own universe, leaving the new one to develop on its own. Seen in Dragon Ball Z when Future Trunks returns to his own timeline after saving Goku and creating a new one.
Return to New: After the time travel is complete, the traveller visits the relative present day of the new universe; returning home requires the ability to move sideways in time. Taking The Slow Path counts for this version of AUS. Seen in Chrono Trigger whenever someone changes history (one such new universe seen in Chrono Cross).
Temporal Overwrite: This result changes the universe it happens in.
Memory Shift: The results of the time travel creates new memories in the traveller reflecting the changes s/he has made to the timeline. Seen in the movie Frequency whenever John changes his father's decisions in a way that impacts the timeline.
Time Orphan: When the traveller returns to the future he has no knowledge of the resulting changes of the timeline, which can include the traveller no longer existing. Seen in Magic: the Gathering when Sarkhan saves Ugin's life 1280 years in the past, then returns to a present where he was never born on Tarkir.
Immutable Fate: The time travel has no actual result.
Already Changed: The time traveller, whether or not s/he knows it, has caused the situation s/he went back in time to change or going back in time must be done because it was done; alternately known as the Stable Time Loop. Seen in Harry Potter and the Prisoner of Azkaban when Harry and Hermione save Buckbeak and Harry saves their past selves.
Unable to Change: No matter what the time traveller does, the timeline remains unchanged. This is either due to the traveller being unable to accomplish anything or because time manages to snap back to the original path on its own. Seen in the Sailor Moon/Ranma 1/2 fic Fist of the Moon.
Destruction Paradox: The time travel destroys things.
Destabilization: When the time travel changes something, its existence begins to unravel, getting rid of the object or person in question. Seen in Back to the Future, when Marty's family starts fading because of his interference.
Total: The time travel erases the universe immediately. Rarely used due to it making for a very short story.
Now, these results don't have to be used alone. For example, not only does Back to the Future use Destabilization-class Destruction Paradox, but also Time Orphan-class Temporal Overwrite. This is best shown in the second movie, where Old Biff still disappeared when the changes he wrought to time overwrote himself (Destabilization) but the changes remained (Temporal Overwrite), but because it didn't overwrite Marty he was fine, though he didn't have any memories related to the new timeline (Time Orphan). Doc though it might have been Alternate Universe Split (Return New), but that doesn't apply if you started in the original universe's future. You'd just wind up in that universe's version of the present, rather than the altered present like they did.
Now for a bit of terminology (Borrowing a bit from the tabletop game Continuum).
"Uptime" and "downtime": If time were a river, it's known to be easier to travel down stream (Past to Future), ergo to travel to the relative future would be to go "downtime," and going backwards against the flow would be "uptime." Using these terms allows one to use "past," "present," and "future" to apply solely to the person's own timeline, rather than the universe's.
A sample conversation between time travellers would read thus:
"It happened uptime. My past, your future."
"Ah, I see. I'll be seeing you later, then."
"I was glad of your help."
Or something like that.
Most results are shown from travelling uptime, because it's harder to show how changing something downtime would affect something further downtime when the time traveller generally returns uptime to their home time.
The episode "It's About Time" used "Immutable Fate (Already Changed)" style of time travel, but then came the season five finale, which featured something different. In "The Cutie Re-Mark," the changes to the present were wrought uptime through Starlight's manipulations while she remained without knowledge of what had changed, which seems like "Temporal Overwrite (Time Orphan)" save that the Cutie Map still existed. This likely means that the time travel resulted in new universes that had ties to the original, and Twilight was merely returning downtime into the new reality, thusly the time travel result was, instead, "Alternate Universe Split (Return New)."
The changes are likely inherent to the method of travel (simple spell vs. artifact-empowered spell), so if someone used a powerful enough spell, they could rewrite the present without anyone being the wiser.
There are, however, some loopholes in stories featuring Immutable Fate. In some of these worlds, you mere can't change what is established, like in Kingdom Hearts. Which means you could change things that aren't known. This has limited application, but could be used to give you that one trump card by adding it to the battlefield uptime from the fight without anyone knowing otherwise (like the time travel battle in Bill and Ted). There's also an example in Dragon Ball Xenoverse 2, wherein Future Trunks shifts things slightly in his past by meeting Future Gohan. Future Gohan still dies, but he goes to his death with hope in the future he's giving his Trunks.
Informative indeed. Thanks for posting it. I may be referring to this blog in the future.