Article: A brief theory of iterative time

The Predestination Paradox

The best way of explaining the idea of iterative time is to use the Predestination Paradox.

Our hero receives the plans for a Time Machine. They build the Time Machine, create a new copy of the plans and send these back to their previous self.

The result is a self sustaining the loop. It's a paradox because it's hard to see where the plans actually come from. Nobody seems to design the Time Machine at all.

That's the classic Predestination Paradox. An event only happens because it triggers its own cause in the past.

Iterated time

However, let's tweak this model to introduce iteration. Supposing our hero is lazy and can't be bothered to draw up a fresh set of plans after they've made the time machine. Instead, they simply send the existing plans back to their previous self. Let's assume that it takes the hero a year to create the time machine using the plans. This means that in each iteration of the loop, the plans are getting twelve months older and the timeline that the hero lives in is becoming subtly different.

If you think about it, the diagrams have to be experiencing a different sort of time to that of the hero, because they're somehow remembering their existence of each loop into the past and ageing by a year in every iteration. After a while, the plans will become too hard to read and the hero will be unable to use them to build the time machine. The loop will collapse and the time machine will never be invented.

Let's call the time that's experienced by the plan "meta-time". Whereas normal time records the history of events in three dimensions, meta-time records the events in the fourth. Whenever a time traveller goes into the past, they make changes to history, and the record of those changes is stored in meta-time. They remember that their grandfather lived so, for them, he did, irrespective of whether anyone else in the universe would agree. Every journey through time results in a slightly different version of history.

Interation and the Predestination Paradox

I'll now use this theory to explain the Predestination Paradox.

Imagine that there's a previous timeline where the hero doesn't get the plans. This is the original iteration which will generate the loop.

In this iteration, the hero comes up with the idea of the time machine independently and spends their entire life making it a reality.

Unfortunately, by the point they're finally in a position to draw up the plans, they're too old to survive the journey into the past.

They then send the plans back in time to their previous self, which generates a new timeline where they develop time travel when they're young.

This replaces the previous timeline and generates a self-perpetuating loop. Providing their later selves are dilligent enough to ensure that they draw up a fresh set of plans before they send them back, the loop is stable. The paradox isn't an issue, because although the designs for the time machine seem to come from nowhere in the current timeline, they were actually created in the previous one.

The record of the two timelines is stored in meta-time.

It's also possible to use this approach to resolve the Grandfather Paradox.

A person goes back in time and inadvertently kills their own grandfather, destroying the chain of events that lead them to be born.

If they're never born, they can't go back in time to kill their grandfather.

If they don't go back in time to kill their grandfather, they're born and the cycle repeats.

The reason that this is a paradox is that there's an inherent contradiction, because there seems to be two incompatible versions of the grandfather's and time traveller's histories.

There's one timeline where the grandfather isn't killed and the time traveller is born.

There's another timeline where the grandfather is killed and the time traveller isn't born.

It doesn't make sense using the classic system, but if you use iterative time, it's perfectly reasonable.

History is flipping back and forth between through two different iterations. Each version of the timelines destroys itself causing the other one to exist.

In computing terms, it's an infinite loop.

Do
	If time traveller exists:
		Time traveller goes back in time
		Kill grandfather
		Kill time traveller
		
	If time time traveller is dead
		resurrect grandfather
		resurrect time traveller
Loop

It may seem crazy for time to be vibrating like a string, but it's no madder than the idea of Shrodinger's cat who's both alive or dead before someone opens the box. Why can't there be two versions of history which switch around repeatedly?

If you invoke quantum effects, you can assume that each loop will be subtly different. The events that led to the time traveller's birth and the grandfather's death will be subject to slight variations and given enough iterations, it's likely that something will change in one of the timelines. If the change happens in the grandfather's time period, the time traveller will might slip on a leaf and fail to push his grandfather in under the bus.

If the change happens in the interval between the grandfather's survival and the time traveller's birth, something might happen to stop the time traveller being born or gaining access to a time machine. A different sperm might fertilise an egg and a slightly different version of the time traveller will be born who will visit their grandmother instead. In each of these cases, the loop will collapse. Given that the time traveller can't exist in the past without making gazillions of insignificant changes, their very presence will generate instabilities and the chances that something will change to stop the loop become increasingly likely. If the time vibration causes damage, it might even increase the chances of these instabilities happening, in which case, you'll end up with a self-repairing history and a form of chronology protection. It doesn't really matter, because with meta-time, paradoxes either generate multiple timelines which resolve into a single history or which flip between a number of different states.

I'm not saying meta-time exists in the real world, of course, and the truth is that anyone who gives the matter a bit of thought can come up with their own solutions to the classic time travel paradoxes. They're so easy to resolve, it seems illogical to use them as a justification for believing that time travel is impossible. The question of whether time travel is possible depends entirely on the nature of the universe and the nature of time, and last I'd heard, these were still up for debate.