#middlegame might actually be a better example of paradox space physics although none of you have read it so

[originalcontent]

Models of Time Travel

Not a comprehensive list, nor a mutually exclusive one. Feel free to add on if I’m missing anything major.

Closed Time Loop Model - There is one set timeline that the universe is meant to follow. It cannot be altered, and any attempts to alter it will likely only end up perpetuating it via unexpected consequences. Typically cause and effect are inextricably tied together. Personally, I find this model to be the most satisfying when well executed.

Revisionist Model - One can go back in time and alter events, thus replacing the timeline with one wherein history happened differently. Sometimes the entire reality is rewritten and the time traveler will either vanish or remain behind as a refugee from the prior timeline. Alternatively, everyone for the most part goes back to living their lives but with a few adjustments, a la Back to the Future.

Inevitability Model - One can go back in time and alter events, but the timeline will correct for the adjustments and the overall course of history will always remain unchanged. For example, you go back in time and prevent a murder, only to learn that the would-be-victim dies of a heart attack that very night. Classic predestination.

Paradox Model - The universe follows a set timeline, but time travel itself is revisionist, and the two are incompatible with one another. Take the example of going back in time and killing your grandmother, thus preventing your own birth, thus preventing her murderer from having ever existed. In this system, time travel is not physically impossible but it is often functionally impossible. The new timeline will inevitably be doomed, and so this model will almost always result in a return to the status quo.

Time Tourism Model - Ultimately nothing you do in the past will matter or change anything, so don’t worry about it and just do whatever.

Butterfly Effect Model - Literally anything you do in the past could have drastic and far-reaching consequences that are impossible to predict, so don’t do or touch anything.

Multiverse Model - One can go back in time and alter events, thus creating a new timeline wherein history happened differently, existing concurrently in parallel to the previous timeline. Sometimes convergence or travel between the timelines is possible; in fact it’s often the only proof that there is a multiverse rather than a revisionist universe.

Quantum Leap Model - You aren’t actually changing history at all, but rather are jumping into an alternate timeline wherein history has always been different. Or potentially remaking your own universe. Often this isn’t achieved through classic time travel but through higher level means, such resetting the parameters for your reality, or a making a powerful wish.

Local Time Loop Model - There is a set timeline that the universe is meant to follow. This timeline expects certain actions from you within a certain time frame, and if you fail to perform these actions then the timeline cannot progress as intended, so it sends you back to the start of the day/hour/year/whatever and you get to try again and again until you get it right. Sometimes there’s a person or a piece of technology that’s perpetuating the time loop, sometimes the world will be destroyed and you need to try over and over to save it, and sometimes the universe just really isn’t willing to let you get on with your life until you’re honest about your feelings. Local time loops are revisionist, but it’s usually more the universe forcing you to follow a different course rather than the reverse.

Paradox Space Model - There is a set timeline that the universe is meant to follow. This timeline expects certain actions from you within a certain time frame, and if you fail to perform these actions then you will become doomed, so hopefully another version of you did it better. Imagine that the failed iterations of a local time loop don’t reset but rather follow multiverse logic. In this model, the offshoot timelines don’t continue in parallel ad infinitum. They exist insofar as they can serve to progress the primary timeline, and will eventually cease to exist or be written over once they’re no longer relevant. That being said, even though there is only one true timeline, the others did still occur somewhere and somehow.

Entropy Model - The very act of time traveling at all causes the universe to deteriorate or to behave chaotically. People may start vanishing, natural disasters may occur, the world may fall into disarray. It’s often paired with local time loops or the revisionist model as a limiting factor that keeps one from going back and changing things forever. Often this only occurs if the timeline is doomed, such as if you failed to succeed in your time loop, or if you caused a paradox, and so it can be reversed by doing/undoing the appropriate chain of events.

Uncertainty Model - There is a set timeline that the universe is meant to follow, but there are some grey areas. A subversion of the inevitability model, which acknowledges that certain historical events are set in stone but with the corollary that anything not explicitly set in stone is free game to mess with. You can determine the outcome of various historical mysteries and unknowns by nature of them being mysteries and unknowns.

Free Will Model - For time travel to exist, elements of the past and present must be somehow concurrent, and for free will to exist, that means that people in the past must have equal agency to people in the present. Such is the nature of the rarely explored problem of what if history chooses to rewrite itself, thus destabilizing the present.

Memory Transfer - You send your memory back in time, replacing your previous self. This is typically incompatible with a closed time loop but necessary for a local time loop.

Self Replicating - You send your body back in time, existing simultaneously with your past self.

#ironically even though it's where i got the name homestuck probably isn't the best example of the paradox space model #it has a lot of closed time loop elements and then flat revisionism at the end #middlegame might actually be a better example of paradox space physics although none of you have read it so #it's the middle of the night what am i doing