Time Models

If we were to visuablise time as a line in the fourth dimension, how would the line be shaped? Would there be more than one line? Would they be linked to each other? If so, how?

Below are the different models of how time could be shaped in the fourth dimension. Different models allow different types of time travel! But remember, all of the below are simply theories, meaning, they aren't proven. So basically, all this is wild speculation!

» Single timeline; fixed history

In a model with a fixed history, time travel is possible, but the events in that timeline cannot be changed. Even if you were able to time travel to the past or future, it will just turn out that you were supposed to make that change all along. For example:

• You are told by a strange voice to walk into an elevator.
• You walk into the elevator.
• An anvil drops right where you were just standing.
• The elevator turns out to be a time machine.
• You travel back in time, to see your former self standing in front of an elevator, with an anvil hanging above your head.
• You tell your past self to walk into the elevator.
• Your past self walks into the elevator...

As you can see, the situation simply repeats itself, with no known origin and no known end.

This model has been used in various pieces of science fiction, including Time Bandits, Futurama, and The Hitch-Hiker's Guide to the Galaxy.

» Single timeline; malleable history

This is one of the most preferred time models for fiction writers, as it allows their time travellers to go back and forth through time quite harmlessly, without changing too much. Also, if they do cause a significant change, the timeline can be restored back to appriximately how it was before the time travelling took place.

Scientifically, however, shows that this model (although handy) is extremely illogical and inaccurate. Chaos theory dictates that in a complex system such as our universe (the Earth's weather system is complex enough), small changes can trigger big consequences in the long run.

» Single timeline; sensitive history

This is like the above timeline, only this time, the time traveller is faced with the full-blown realities of chaos.

In this model, time travel is possible, but extremely risky. No matter what you do, just by time travelling, you change history. And you can never set it back the way it was.

» Multiple timelines

This model includes multiple parallel universes. Variations of this model include:

• Everytime someone time travels to the past, a new universe is created. The time traveller can never return to their original parallel universe.
• There are a multitude of parallel universes which a time traveller can hop back and forth between.

This model is extremely useful, as it eliminates various paradoxes and problems caused by single timeline models.