So you want to be a time traveler? Well if you ever get your hands on a time machine, find a magical portal, or discover you can time travel at will, you are in luck! I’m going to be releasing a series to explain the benefits and pit falls of time travel, so you’ll be ready to take that harrowing trip through time and space.
Time Paradox and World Lines
There are however many considerations to take into account before starting a trek through time and space. One of the most regarded problems involves the potential of creating a time paradox. Famously, there is the idea that if one were to go back in time and cause the death of one’s own grandfather, than the question of the one going back in time becomes a paradox. How would that person have come to exist to go back in time to cause the death of their grandfather if they never existed in the first place. Theories abound concerning time paradoxes. One way of handling these paradoxes is the theory of world lines or parallel universes. Say you went back in time and did cause the death of your own grandfather. Instead of challenging your own existence, you have merely changed one world line where you would never be born. However the world line you came from would still exist in parallel to the changed world. It might be trick though returning to that world line. In this way you could say that both world lines exist and remain unalterable and self contained. Of course the number of such world lines would have to approach an infinite number. Events that would normally cause a paradox are simply gateways which link such world lines together. If such an event occurs, the world line shifts appropriately.
Let’s get a little help from anime now shall we. In Steins;Gate Okabe Rintarou has a very bizarre experience and finds himself searching for answers. Familiar with John Titor, a real figure who claimed to have come from the future, Okabe seeks information out online and discovers something strange, John Titor is relatively unknown. All of Okabe’s previous information and books on Titor are missing and no one else seems to know of him. He finds John Titor has recently appeared online in what looks something like 4chan and Okabe reads and joins the discussion.
John Titor: “You mean the so-called Grandfather Paradox, right? There’s no such thing. It’s possible to meet yourself in the past. If you do, you simply move world lines. Let me begin by saying that time isn’t a single line, moving from past to future. It’s comprised of an infinite number of parallel lines, like rivers, called ‘world lines.’ For example, let’s say a serial killer was to murder you today. If I came from the future and prevented it, the world would diverge into two streams: a world in which you survive and a world in which you died.”
This pretty much follows what I discussed before. Time moves in an endless number of streams leading towards many different futures. The idea is that these world lines all exist within the fabric of space and time. To travel back in time is to move backwards in the stream. In order to reach a different future, one would have to go back to point where the path to that future began and make the subsequent changes.
John Titor: “You all seem to have fixed ideas about the nature of time. Time isn’t a single line, moving from past to future. Let’s say I were to go back in time and kill someone we’ll call ‘A.’ This alters something called the divergence number, and the world line moves to a world without A. When there’s a world line shift, people’s memories are altered. In other words, memories of the world line where A existed are deleted, and replaced with memories of a world line where A doesn’t exist.”
John Titor is explaining what might happen if someone were to attempt to change the future. He posits that when the divergence number is altered by an event, such as someone being killed in the past, the present would shift world lines to a world where that person had been killed. This shift would be instantaneous and everyone would completely forget the events of the previous world where that person had lived. The shift would go unnoticed and life would continue as if nothing unusual had happened at all.
So don’t be too worried about creating a time paradox, because world line theory has got you covered!