Déjà vu is a glitch in the Matrix, it happens when they change something..

So we saw Déjà vu last night. It’s a surprisingly good film. There are, however, the usual slight inconsistencies found with any movie involving time travel. One thing it does well though, was outlining the various theories on the nature of time in a layman-friendly fashion. It fails to actually define which of these theories is correct in the Deja Vuniverse(see what I did there? God I’m good) but hey, I guess they didn’t want to be scientifically bold or whatever :P

Inspired by this, I thought we should review the possibilities, just because I have nothing better to write about.

I’ll be using two analogies through this discussion so I’ll outline first:

To discuss cause and effect, I will rely on the heavily abused ‘Grandfather’ analogy. The gist of this hypothetical argument is ‘what would happen if you were to travel back in time and kill your grandfather?’.

To help describe the various theories on the nature of time, I we will often fall back on the ‘time as a river’ analogy. I’ve stolen this from Déjà vu, who use it well. As we’ll see, this analogy isn’t perfect, especially for the more complicated theories, but hopefully it’ll give you the gist of each argument.

Before we begin, a slight caveat; this is hugely simplified. There are many other theories; those below are essentially the basis for many of those theories. And then there are some that are hyper complex to the point where they cannot be explained in written text – they inhabit the world of mathematical equations, or worse, the seemingly magically world of quantum mechanics, String Theory or Grand Unified Theory.

Theory One:
'There is no time.’

Simple really! There is no such thing as time, it’s just a perception invented by beings with limited life spans.

This isn’t really a theory as such. We know time exists in some sort of fashion, because like everything else, it’s relative (thank Einstein for that). The faster you go, the slower time is. If you have two atomic clocks and two jet planes, you can prove this. If they leave from the same point, fly for a set period of time (say, two days, measured from the ground where they departed) in opposite directions around the planet each with a clock on board and land at the same time you’ll discover something interesting. Their atomic clocks will no longer read the same time. Less time will have passed for the plane flying with the spin of the Earth (ie, flying faster). More time will have passed for the plane flying against the spin of the Earth (ie, flying slower). In this example, the difference would be (and was) in the order of millionths of a second, but you get the idea.

This simple fact of truth means that, to some extent, time travel in to the future is possible. All you need is a space ship that can accelerate to as near as light speed as possible (Ok so this is basically impossible too, but hey) and a keen crew. If they were to travel at this speed around the Earth for a year or two, they would find much more time has passed on Earth. Crazy huh.

The reason this isn’t really possible is even more complex, but it’s related to the fact that the closer to the speed of light you get, the heavier you get, and that’s why it’s impossible to hit the speed of light, regardless of how massive your engine is. It’s exponential - you could never have enough thrust to counter the increasing weight. That’s why only energy can achieve this speed, because it has no mass. (Well, theoretically. I think some arguments state that light has mass? I dunno.)

But anyway, the gist of this theory is that, because of this, there is simply no way to travel backwards in time. Nothing exists (ie wormholes or time machines) that will ever allow it. The grandfather argument is rendered mute, because you’re unable to get back to before you are born. Game Over Bitch.

Theory Two:
‘Uber River’

I have dubbed this theory the ‘Uber River’ theory (that’s quasi-German for Super River, by the way) as the gist of it is that the river of time cannot be changed, diverted, split, dammed or anything. No matter how hard you try.

Let us assume you find a way to travel back in time. You roar back from 2006 to 1932 when your Grandfather is 5. You figure a five year old cannot put up much of a fight (you sick fuck). Your jump back is plotted below via the brown dotted line that looks a bit like a trail of poo.

Once you arrive, you begin your nefarious scheme. You whip out your Sniper Rifle. You take aim at your grandfather, bashing his plastic spade around in the sand pit. You fire.

What happens next? Well, there are essentially two possibilities.

Firstly, the answer is nothing. The gun misfires, the shot somehow misses, or some kind of unforeseen and unavoidable event (or series thereof) always prohibits you from killing your grandfather. This theory is potentially dodgy, because it tends to imply some kind of cosmic fate. Cosmic fate implies the existence of some kind of God. This is not scientific. If you avoid this explanation, other potential answers are:

a) Chaos theory is a load of shit. No event can change the final outcome. This doesn’t mean there’s a God. It’s just….the way things are. Nature is just stubborn.

b) The river was always flowing this way. Your brown poo line is actually a tiny stream that flows the other way and then back into the river. It always has, and always will. Because it was always like this, you didn’t change anything. You were just following the river.

Secondly, and point b) leads us nicely to this, is that perhaps you do shoot your grandfather. His five year old head explodes like a watermelon. And nothing changes. You soon discover he was never your grandfather because your GREAT Grandparents covered up his death least they become suspects, and adopted another boy who is your true Grandfather. This is really pretty close to our first point. The idea here is that you can do whatever you want, but your actions to try and change what will happen in the future are actually what cause the future to be like that in the first place. (Spoiler follows) we see this in Déjà vu when the note they send back is sent to Doug’s partner and results in his death, which they were trying to avoid. Oops. If they hadn’t sent the note, he would not have died. See? Sucks.

Potential problem with this theory? It implies knowledge gaps – it implies it is impossible to know exactly what happened or what caused what in the past. This is kind of dubious. What if you were to travel into the past by only five minutes, to same the destination from which you left? Wouldn’t you know exactly everything that was going to happen?

In summary, Uber River theory states what is demonstrated by the red lines along the bottom of the time line above. Either, a) time rejoins the normal course (the main river) at some point, or, b) those mini lines are actually what happened. The river isn’t straight like the line depicted, but weaves all over the place, with heaps of doubling back etcetera. Either way, no change can be made to that river.

Déjà vu explained this theory by saying it was the mighty Mississippi river. You throw a pebble into it. Nothing happens, because nothing you can do can divert that river. It might ripple (tiny changes to the past, but no chaos theory), but the flow and direction and speed remain constant.

But what if you didn’t just throw a pebble into it? What if you dropped 16,000 tonnes of dirt into the river? Theory 3!

Theory 3:
Confusing, twisty river.

This theory is initially straight forward. You do something that changes the past. As such, the future changes. You kill Granddad, so you are never born. The future unfolds in a massively different way. Chaos theory – you have diverted the river along another path (ie, you piled huge mounds of dirt into it). However, this raises the single most confusing question with time travel.

What happens to you, once your grandfather is dead? And as a result, what further effects will it have on the future and the past?

A) You immediately cease to exist. Because you were never born, you never went back and killed your grandfather. You see the issue here. If you weren’t born, you didn’t kill him. So you WERE born. So you DID kill him. So you were NOT born. So he didn’t die. So you WERE born. So you did kill him. So you were NOT born…

Basically, you’ve fucked it. Time is stuck in this dirty loop, because it’s only one river. You can change where it goes, but that’s it. It cannot become two rivers. As such, you cannot kill your grandfather, and continue to live in the world where he is dead (ie, you can’t exist in 1932 once you pull that trigger).

B) Nothing happens to you. You DO continue to exist in this new future. Your existence is independent of the flow of time once you leave it to rejoin at a different point. This is commonly believed to be more plausible, if only because no one knows what happens in the first example. Does the universe implode or something? However, it does imply that time is kind of meaningless again. This makes some people shitty.

Theory 4:
River Split or Fjord theory.

This is a fun theory. This picture sums it up nicely I think.

Hee hee. Notice that there are no dotted lines? That’s because for every change, for every decision, for every action, a brand new time line is created. It is independent of the others. They are infinite and they co-exist. This is the parallel dimension theory. Where something different has happened. When you kill your pops, a new line is created. Because the original line, where you came from, still exists, you are still able to come back and kill him, so we don’t get that fucked up ARRGGHH loop of repetition with the chicken/egg problem.

There are some potential issues with this:

a) It is hella complex. No real math or scientific theory can justify or explain the existence of parallel universes successfully. This doesn’t mean much, because humans are inherently stupid and mentally limited, but it’s worth considering.

b) You’re no longer really just time travelling, you’re editing parallel universes. If you went back to stop World War 2 ever happening, you don’t really stop it. You create a new universe in which it doesn’t happen. In an infinite number of other universes, millions of people still die in WW2. So why bother?

c) Oh, also, there can be no theory of souls in this universe, not in the biblical religious sense, anyway. Because there an infinite number of you. Of everyone. You are NOT a special child of God. You are NOT a snowflake.

[SPOILERS FOLLOW]

Déjà vu uses (we deduce) either 3B or 4. The thing is, we know Doug tried at least once to alter the past. And we know he failed at least once. The movie both chokes and excels around this single, important point. If it is 3B, then the river can be diverted, but it is difficult to do so. It is like a rock in the path of the river that you wish to avoid. Your initial attempt shifts it slightly, but the water still hits the rock. So you try again, and again, each shift moving it further to the side, until it misses that rock totally. Ta da, future changed.

Or it’s 4A. Any one of a million different decisions or butterflies flapping their wings etc have created parallel universes. You have created/ended up in one that avoids that rock.

I like the 3B possibility. That’s cool. You can try again and again, and maybe you’ll succeed, because it’s possible, it’s just hard. That’s a very human idea. 4 is gay because it’s just one of the zillion different outcomes. It makes you seem kind of insignificant. Either way, they did kind of choke by not really highlighting what was done differently the second time through. Right up until they board the ferry at the end of the film, nothing has gone differently. Why does everything suddenly change? It’s never explained. You could argue that’s up to the viewer to think about you’re wrong. It’s a cop out. The rest of the movie is spent showing you how identical and unavoidable everything else is. Then all of a sudden, it can be changed.

Wtf.

@_@

Notes:

My money says you will never see time travel to the past. Nor will your great, great, great, great, great, great, great grandkids. The wormholes (Einstein-Rosenburg Bridges? I cannot be arsed checking) mentioned in Déjà vu are the only existing theory that even remotely presents it as feasible. AFAIK, these work by assuming time is a dimension, like space is. A wormhole is a path between to rucked parts of this dimension. We already know this kind of distortion is possible with normal space (that’s why light bends around stars, because the very existance of nature is distorted around that star by the force of gravity. Light isn’t bending, it’s travelling straight through a bent pierce of the universe;) so it stands to reason it may be possible with time. That’s essentially what happens when you go really fast as dicussed earlier anyway. But, we are yet to see or prove the existance of a bridge between any two points (the wormhole).