The nature of the topic in this blog post as well as the on going lockdown imposed in the UK due to the coronavirus pandemic may lead any readers to believe that I have started suffering from cabin fever. However I can reassure you that the majority of this post was written during a week off I had when I was changing jobs which caused equal levels of mental-degredation.
The coronavirus pandemic has however given me the opportunity to write up the post online so that you too can experience the rubbish I come up with when I have too much time on my hands.
The Paradox
Backwards time travel within science fiction stories largely fall into three distint categories in terms of the rules for which the universe will follow:
Fixed Timeline Theory
The timeline cannot change, any travellers to the past were always present to begin with ensuring that nothing in the future ever changes.
Dynamic Timeline Theory
When a traveller visits the past, their actions will have an effect on the world which causes it to diverge in the future allowing for the possibility of paradoxes.
Multi-verse Theory
Any changes to the timeline by travelling to the past will have no effect on the future you travelled from. Instead, the effects are felt in a parallel universe. This ensures that any potential paradoxes are resolved for they will effect a different version of the world.
Of these three theories, fixed timeline theory is unique in that it is fundamentally built into the laws of the universe that paradoxical meddling of the past is completely impossible.
When considring the traditional Grandfather paradox for example, you are guarunteed to be prevented from killing your Grandfather, as you are alive. You being alive is fundamental proof in fixed timeline theory that your Grandfather must have survived your attempt on his life.
Every attempt you make to kill your Grandfather will fail:
- Your gun will jam
- You will miss
- The bomb will not go off
- You will be caught in the act
- You will chicken out at the last second All attempts will fail.
Fixed timeline theory is nice in the way it has this internal logic which prevents the universe from ever becoming too complicated.
Unfortunetly however, we cannot have nice things. The theory’s protection against paradox is in itself actually a paradox.
Causal Loops
The concept of a causal loop is commonly explored on the topic of time travel. A classic example of a causal loop is the struggling scientist attempting to find the secrets of backwards time travel.
Then one day his future self travels back to him and shows him the mathmatical equations that reveal how time travel is made possible, and thus, the scientist finds the secret to time travel.
The paradox here of course is that the equations for time travel do not appear to have originated from anywhere. They just seem to pop out of nowhere into this causal loop.
The only way in which the equations could have entered the universe would be through the information being injected in by a different timeline.
As there is only one timeline in fixed timeline theory, obviously it is impossible for such a causal loop to ever occur.
This in and of itself does not disprove fixed timeline theory of course. It does however prove that causal loops in fixed timeline theory are impossible, and this is where the theory begins to unravel.
All Time Travel as a Causal Loop
In the previous time travel example its relatively obvious where the data injection takes place, and it is easy to see how the data has vast consequences over the world. Let’s now consider a slightly more subtle causal loop.
We will consider the same scientist attempting to solve the time travel equation. Unlike before he’s not completely hopeless. He’s 90% of the way there to solving the time travel equations. Unfortunetly, this has been his life’s work, he has spent 40 years attempting to perfect this equation and he’s really struggling with getting the last 10% work done. His university are sick of him, his funding is about to be revoked and his bills are piling up on his doorstep. He’s about to give up and go to focus on mroe profitable ventures.
However, on the day he decides to throw the towel in, his future self comes back to visit him.
“You cannot give up now!” His future self exclaims. “I am the living proof that you were right! Time travel is possible!”
The scientist is inspired! He can’t give up now! He’s just seen the proof that he succeeds in his endevour.
He preserveres, he re-mortgages his house to save off the lack of funding being provided after his university cut him off and finally! He finishes his master work. He has uncovered the secrets of time travel after 40 years of blood, sweat and tears.
And none of this would have been possible if his future self had not come back and inspired him to continue his wor…hang on though…who inspired his future self to invent time travel? At some point somewhere one of the scientists must have been able to complete his work without being inspired, otherwise…we have stumpled upon another caucal loop.
It may not have provided the secrets to time travel, but the inspiration to continue on with his work seems to have popped into existence, just as before, with no clear genesis. This loop is much more troubling for fixed timeline theory due to the subtle nature of the data being injected.
Let me hammer that final nail in the coffin of the theory with a last damning causal loop example.
The Butterfly Effect
So far we have explored causal loops where there is a direct obvious connection between the future and past entities. Through the butterfly effect we can show that this would not be necessary to create an illegal causal loop.
In the butterfly effect, a butterfly can flap its wings in Australia and through a series of connected events cause a tornado in florida. This may seem like a far fetched analogy used to only illustrate the concept, however the chaotic nature of Earth’s weather system means that such a small event really can have a huge effect (although usually the effect would not be felt on such a larch scale until a long time after the butterfly event).
The butterfly effect is not unique to the weather system either. It is a feature of all chaotic unpredictable systems, and there are a log of systems that fall unser that cateogry. A key example pertinent to our case is the chaotic nature of human society itselt. With such a large group of people interacting in complex ways it becomes impossible to predict from day to day how people are going to act. In terms of the butterfly effect, we’re living through one of the greatest examples in our history. One bat in China gets infected with coronavirus and causes unpresedented lockdown laws across the entire globe.
So how is this relevant to time travel? Well, it shows that all things are interconnected. Everything in the past has some sort of effect on everything in the future down to a subatomic level and this poses serious problems for our time travelling scientist.
If we consider the scenario in which he invents time travel without any help from future persons and then decides to travel back in time to perform unrelated tasks, this is still a causal loop. His future self being in the past has, through the butterfly effect, modified in some small way the actions of the scientist performing his research. This same problem is present no matter the identity or significance of the time traveller too. In the same way, the future self present in the past has influenced the slef about to travel. At some point there would have to have been a version of the traveller who’s past was not influenced which would prove that there are other timelines.
This unfortunatly makes a lot of our favourite time travel stories impossible. Who knew that Harry Potter and the Prisoner of Azkaban was not possible, not because of the use of magic, but instead due to its implausible time travel mechanics. That said of course, in the world of Harry Potter, time travel is proven to be possible through J.K. Rowlings ret-con happy twitter account. Although the fact that fixed timeline theory is not possible may be disheartening (or perhaps not as you probably have bigger things to worry about), there is a silver lining to this for the possibility of real backwards time travel.
In 2009, theoretical physicist Stephen Hawking threw a party in which none of his guests turned up for.
- I would have inserted a picutre of Mr Hawking at his party but I won’t due to copyright concerns. If you do want to learn mroe about the party and see a really sad picture of Stephen Harking on his own at the party then I encourage you to google it.
This party was an experiment to see whether time travel was possible. He invited future time travellers to the party in the hope that shoudl one turn up, we would have proof that at some point in future time travel really will be possible. Given that no one did turn up it would unfortunetly suggest that time travel probably isn’t possible. Or would it?
The wonderful thing about fixed timeline theory is that it prevents dangerous paradoxes. Something that definetly cannot be said of dynamic timeline theory. With great power comes great responsibility, so any time traveller that valued their life (think Marty Mcfly in Back to the Future) would know that turning up to a party that took place centures ago such as the one that Stephen Hawking invited them to would be remarkably dangerous, expscially if they had seen no one turn up to it previously in their timeline.
Any backwards time traveller would have to perform a difficult balancint act of safety to keep the paradoxes that they create in their travels to a minimum. If however any time travellers are reading this post and feeling brave, if you could go back in time and throw that sodding bat in the bin before it becomes such a menace, it would be much appreciated.