The Theories of Time

You can’t figure out how timelines work without some rules to guide you.

I’ve given these rules a lot of thought. The problem with time travel in fiction is that the story will frequently make up the rules as it goes along. After all, time travel is (probably) impossible in real life, so why not? My main problem is that the rules that would be consistent with one series would not make any sense with another. So I’ve decided to create what I call the Three Theories of Time to govern how I judge how the timeline would be affected. They are based on what I consider to be the most logical, rational outcome of what would happen if time travel were possible.

The Theories

The First Theory of Time (aka, moving into the past):

Any information, whether that be energy or matter, that moves against the natural flow of time, creates a new timeline branching from the earliest point involved if any changes are observable. The previous timeline continues to exist but largely remains inaccessible.

Anytime information goes back in time, it would branch the timeline (one in which the information wasn’t received, and one in which it was) with all events continuing forward as reactions to that information.

If the information, on arriving in the past, does not create any observable changes, then the timeline does not split and instead merges over itself.

For example, suppose somebody sent a radio signal into the past, pretending to be the White Star Line and ordering the RMS Titanic to alter its course, with the intention of preventing it from sinking. If the signal arrives in 1912, it would be picked up by the Titanic and acted on. This would branch Timeline A into Timeline B, in which the Titanic never struck an iceberg in 1912 and the subsequent disastrous loss of life never happened. In the future, where would be no cause for sending the signal (since the Titanic didn’t sink there in this history).

However, if that same radio signal instead arrives in 1012, there would be no radios to receive it. Its presence does not branch the timeline because the observable events in this timeline remain exactly the same.

This theory covers the Grandfather Paradox.

The Second Theory of Time (aka, moving into the future):

Any matter that moves into the future is considered missing from the universe until it reappears at its arrival point.

This is not to be confused with time dilation. During time dilation, the traveller experiences a slowing of time relative to an observer. From the traveller’s viewpoint, the rest of the universe accelerates forward in time. Time travel into the future, in this situation, requires the traveller to either move instantaneously into the future or, if not instantaneous, exist outside the normal space-time continuum.

The Third Theory of Time (aka, looping time):

If a section of the timeline is looping on itself, then that section of the space-time continuum (the local continuum) exists outside the rest of the universe, and thus do not affect the timeline.

Information from one instance of the loop may “leak” into the next instance of the loop.

The local continuum may or may not remain in sync with the universe.

The timeline records all affected matter and energy as ceasing to exist until the loop is broken.

(The Fourth Theory of Time has been temporarily removed for review. It concerns how quickly changes in the past affect the present and future.)

How Many Dimensions?

For the purposes of consistency, I will be using the following explanation of the different dimensions in the universe.

This universe has three spatial dimensions that everyone can perceive — length, width, and height.

The timeline is the fourth dimension. Everything in the universe typically moves in the same direction on this dimension, leading to the concept of the timeline containing the past, present, and future. Most depictions of time travel are the movement back and forth along this dimension.

Of particular note is that if you cannot freely travel among higher dimensions, then you would be unable to access other timelines once you’ve departed them. They’ll still exist, but still be unreachable.

All timelines for a given universe exist along the fifth dimension. Access to this dimension would be required to travel to timelines that have been rendered inaccessible due to timeline branching. In my reviews, I refer to this dimension as the timescape.

Changelog

• May 2024: Original article, including the first three theories.
• June 2024: Added explanation of dimensions.