Time Travel

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A Time Portal that is often used by temporal agents (aka time cops) in the 31st century.

Time travel is an incredibly popular topic and plot point found throughout all of fiction, and all mediums. Tabletop gaming certainly is no exception, with its presence being in abundance.

What is time travel?

Putting it simply, time travel is regarded as the ability to advance from one's "present" starting point to periods in the past, or even into the far future. Exactly how far one travels through time is irrelevant, it's the ability to move outside of the normal linear flow of time that defines this term.

Forms of Time travel

At their core, time travelers can be split into two primary categories: deliberate and accidental. Deliberate time travelers purposefully attempt(ed) to travel through time, whilst accidental time travelers "fell" through time involuntarily.

Specific means of breaching the time barrier can include:

• Rifts in the fabric of time.
• Machines or magical artifacts that allow one to travel through time.
• Arcane rituals that can transport or summon individuals across the gulf of time.

Such means of time traveling can also be divided into intentional and accidental versions, as well as permanent and impermanent versions.

Perhaps the two most iconic forms of time travel in general pop culture are the time traveling machine, which allows for at least a semi-controlled shifting through time, and the accidental time-rift, where a "science" experiment goes wrong and accidentally throws one or more folks through time and they have to figure out how to get home before they are stuck there permanently.

Time travelers

Time travelers are a diverse lot, and can usually be divided into one of several informal archetypes:

• The Victim; somebody who was pulled through time against their will and really, really wants to go home.
• The Immigrant; typically similar to a Victim, but decides they like their new temporal residence much better. The "gay person from the past who prefers the present for its superior gay rights" archetype is a popular sub-branch of this archetype amongst a certain audience.
• The Tourist; somebody who travels across time for the sheer pleasure of seeing incredible things, whether it's the wonders of the future or the most notable events of the past.
• The Academic; a history student who wants to answer the great questions and solve the famous mysteries by traveling back in person to see how it happened.
• The Nomad; somebody who simply doesn't feel at home in any one time zone and so travels throughout history looking for a place to belong.
• The Questor; somebody who travels through time to achieve some epic goal.
• The Impossible Thief; a time traveler who attempts to steal treasures and relics from what they consider the past.
• The Eternal Conqueror; a would-be empire builder who seeks to exploit the past, the future, or both in order to set themselves up as a powerful ruler.
• The Time Police; a person who attempts to fix time rifts and stop people from exploiting time travel for profit, often by claiming that such actions could lead to the destruction of reality.

Science

At a high level, physics pretty clearly indicates that travelling backwards in time is impossible. But in the same hand it also says that how fast you travel forward in time is governed by velocity and mass. From the perspective of things like black holes or light, they are frozen in time as the universe flashes by around them. So if you wanted to travel to the future, you could theoretically do that by orbiting a black hole for a while as time outside the gravity well passes faster for the rest of the universe than it does for you. Or if you wanted to travel to a distant star, you could accelerate to the speed of light and the closer you get to that speed, the slower time passes for you the traveler.

Think of it like this... time and mass and velocity are linked in such a way that time is a bit like a old style reel film being played on a film projector. There is a total amount of energy which this system can have in moving the projector, or radiating out from the projector in the form of gravity, and whatever's leftover gets expended in the form of time (playing the film in the projector). If you're moving stupid fast or are stupid heavy, time for you slows to a crawl.

With the recent discovery that gravity waves travel at the speed of light, the remaining question is whether pure information can travel faster. This hinges on putting particles into superposition, theoretically locking their subatomic state such that what happens to one has an effect on the other. So far experiments have been discouraging on this front.

Conundrums

Because time travel revolves around the concept of moving in a non-linear fashion through a medium that, to the best of our current knowledge, only can be moved in a linear fashion, it naturally invites a certain amount of logical conundrums and philosophical debates.

The biggest and most well-known of these conundrums is, of course, the "self-defeating time-trip" paradox. To try and put it simply; let's say that you go back in time to make sure that something doesn't happen - maybe you want to assassinate Hitler and stop the Nazis causing World War II, that's a classic example. The thing is, if you do change the timeline by succeeding... then in the changed timeline, you would have no reason to go back and change history, so you wouldn't travel back in time. Which means the change wouldn't happen... which then means you'd live in the timeline where you'd want to go back and change it... which would erase your need to change it... which would create the need to change it... and so on, and so on, ad infinitum.

If your head is starting to hurt, well, there's a reason this has been popular with big-brained scientists alongside hack sci-fi writers.

The second-most famous of the time travel conundrums is the "grandpa assassination" paradox. Namely, if you kill one of your ancestors, then you should logically erase yourself from existence, setting up a same if=then loop as the previous example.

There have been several major methods settled on as a way to resolve the aforementioned paradoxes, varying in degrees of grimdark.

The Multiverse theory is the most common, perhaps because it's the simplest. Basically, time is non-linear because it branches into parallel timelines; when you change history, you create an alternate timeline which you can then enter into from your original starting point, so it doesn't matter that your origins don't make sense in the course of this new timeline, because your roots are in an entirely different timeline, and you basically become a character in a universe-sized crossover fanfic.

The stable time loop method instead makes it that you can't change the flow of history; rather, your actions instead turn out to be necessary to cause history to take the path that you know, with your involvement simply being part of the secret true history that the common masses don't know.

Then there's the "self-correcting history" method, which is broadly similar to the stable time loop. Basically, the rough events of history are set in stone, but you can cause minor ripples. If you assassinate Hitler, there will still be a World War II, but some of the finer details may change - maybe a more competent Nazi leader takes over, maybe the Holocaust isn't made so high-priority that it eats up valuable resources intended for the front resulting in it killing far fewer people, maybe Germany becomes united under a militant communist regime instead of a fascist one. Either way, there's still going to be a big bloody war.

One of the rarest methods is the "living paradox" method. Basically, if you alter time in a manner that would logically erase you from existence, then your existence is erased, but you remain - a living ghost from a time that never was, an anomaly in the fabric of time itself. This may have serious metaphysical effects, or just give you an excuse to wangst.

These are just some of the many ways people have explored the repercussions of time travel. One particularly interesting scenario can be seen in Red Dwarf, where one episode of the sixth season has the Boyz travel back in time in search of a fresh supply of curry and accidentally prevent the assassination of JF Kennedy in Dallas. Skipping forward a year in time to escape the cops, they find themselves in an abandoned Dallas, where newspapers reveal that due to surviving his assassination, Kennedy was eventually impeached and forced to leave the president's office in disgrace after his numerous affairs were revealed; this led to the mafia blackmailing Hoover to take the position in his place thanks to their having pictures of Hoover at a transvestite orgy, which in turn led to America not preventing Communist Russia from building missile silos in Cuba, resulting in mass panic and flight from America's major population centers. This in turn led to Russia winning the space race, and the erasure of the Jupiter Mining Corporation from existence, so they can't travel back to their own time. They attempt to fix this, but instead botch things so now Booth instead goes to a floor where he can't get a proper shot. How do they solve this? By finding the disgraced Kennedy on his way to prison and convincing him to travel back in time and assassinate himself as the legendary "gunman on the grassy knoll".

Scenarios

There are a lot of different reasons why somebody might travel back in time, leading to a few popular scenarios in stories.

Our frenemies over on TVTropes describe the two most common time travel scenarios as "Set Right What Once Went Wrong" and "Set Wrong What Once Went Right".

The former is the most common scenario for a deliberate time travel and even many accidental ones; going back in time to try and mitigate some disaster or calamity. It can be as small scale as saving just one life to as large as preventing an apocalypse.

The latter is the antithesis to the former; it's about a villainous character or organization traveling through time to rewrite history to their liking, usually prompting the protagonists to follow them to stop it from happening. Supervillains undoing their defeats, neo-Nazis trying to ensure that Hitler wins World War II, and white supremacists trying to keep the American Confederacy from falling are the most common examples of this scenario.

Examples

• H. G. Wells' novel The Time Machine is one of the first cases of time travel to ever exist is ACTUALLY one of the first stories to have a controllable time machine in a modern sense of this word; before that most time travelers were transported to past and future by some supernatural shit or through lethargic sleep (only for the future). The plot is about a nameless narrator taking his time machine to a distant future in order to prove his scholarly thesis.
• Warhammer 40,000: There's been plenty of examples of time travel between the mere nature of the Warp itself distorting the flow of time, Necrons like Orikan the Diviner who can traverse time through their own arcane means (likely involving enslaved C'tan), and even the Ordo Chronos, an entire branch of the Inquisition dedicated to preserving the nature of time.
• Star Wars: a very arcane aspect of the Force is the “Nexus of the Force,” a place that is particularly strong in the force. If it’s the Cosmic Force, especially anywhere that the Ones are involved, time and space are wierd. One specific nexus, the World Between Worlds, allows a force user to jump to different periods in time and alter said events. Very briefly used by Ezra Miller to rescue Ashoka from her duel with Vader, then the only known entrance to the Nexus was destroyed so that Palpatine couldn’t get his hands on it. We don’t get much more exploration on the concept other than that time paradoxes are possible and dangerous.
• Star Trek: While it has happened a couple times throughout the series, none are quite as infamous as the fourth movie, in which the crew of the Enterprise have to travel to 1970's San Francisco to procure humpback whales for their present, where the cries of the whales can cancel out the frequency of a probe that's causing severe ecological damage to the earth and all whales have been long extinct.
• Homestuck: A comic about a reality changing video game that gives some of the players time travel powers. Making the story even more complicated is the existence of a chat program that can send messages forward and back in time, which creates tons of confusion when two people can have conversations in reverse order from each other's perspective or even get into arguments with their own past/future self. In this story time travel avoids paradoxes with a rule that if you change the past or fail to do something your future self already did, you end up in a doomed timeline where you and all your friends are destined to die and somebody will have to travel back in time to make sure the past and future happen the way that they already did happen.
• Army of Darkness: Pretty much baked into the premise of both the movie (hapless store clerk who's fought the nightmares of an ancient book gets thrown to medieval times) and the game that spawned from it.
• Doctor Who: Nothing further needs to be said.

See also

• Chronomancy - The specific magical field of time travel.
• Chronomancer - A practitioner of Chronomancy.
• Time Wizards - An RPG kinda about time travel.