We all know that time doesn’t always travel in a linear fashion. It’s really more a great big blob of wibbly-wobbly timey-wimey stuff. And you don’t need to be an atheist, a scientist, or a Whovian to accept this. After all, if time really were a line extending from the beginning of Creation to the End of Days? How could we possibly explain God’s omnipresence, or his knowledge and foresight of all things? Or his ability to both provide for all circumstances and keep all that happens within his will, yet also allow our choices to direct the flow of events and influence our own history? And at the more mundane level, things like relativity, string theory, and quantum physics have demonstrated that time is not so rigid a thing.
Well, whether or not travel from one point to another within our wobbly bubble of time is possible, it is good for the Sci-Fi author to have a thorough knowledge of some of the different theories concerning how time travel could work. Even more important is knowing how to keep the theory you choose for your story straight.
Came across this graphic the other day:
These are broad categories, and they cover almost all theories of timelines and time travel. However, there are few more:
Time is flexible, but some points are fixed: This is seen again and again in the Doctor Who series, where some events can be influenced and changed, but certain points in time cannot, no matter how hard a person tries.
Time doesn’t exist, there is only now: The late Jack Vance held to this for the most part, though a couple Dying Earth stories break this paradigm. His theory was that the only moment that exists is now. What has happened in the past is gone and no longer exists. What will happen in the future has not happened yet, and does not exist. Thus, time travel is impossible because there is nowhere to go.
Time is only the 4th of 10 dimensions: In the book “Imagining the 10th Dimension” Rob Bryanton posits that in the same way that from a 2 dimensional perspective it is difficult to conceive of a 3rd dimension, and from a 3rd dimensional perspective it is difficult to conceive of 4 dimensions, so it can continue on up to the 10th. He has some reasons why the 10th is sort of the furthest you can go. But anyway, in his view, theoretically time travel would be not so much jumping back and forth on a timeline but rather jumping out to a higher dimension and then jumping back down at a different point, or using a higher dimension as the space your bridge occupies as you move to a different place. In this theory, the idea of changing time becomes somewhat irrelevant – it is what it is, but there are a multitude of other 4th dimensional “objects”, thus you could end up jumping not just from one point to another in a single timeline, but to completely separate timelines that might have absolutely no connection whatsoever to each other.
Time is a combination of elements: This is the one that Lost seemed to be presenting until the last few episodes where the whole series took a nose dive more tragic than the crash that started the whole thing. Actually, I’m not sure if anyone else came up with this idea from that show, or if I was the only one who thought this way about it. The idea is that people, places, and events all exist within time, but where and how they interact is fluid. So, you might time travel and make a change, and suddenly your brother is no longer your brother. He exists in some way, but you don’t share a history anymore. Or maybe you do, but not as siblings. This theory somewhat relies on the notion that while there are certainly an incalculable number of permutations of genetic structures, life events, and so on, a higher force imposes a level of order that causes certain patterns to arise consistently.
Time is a wheel: This isn’t really seen in Sci-Fi or applied to our world, but since I’m reading The Wheel of Time currently (2/3 of the way through book 13, one more to go!), it’s on my mind. Time is a circular thing, where people, places, and events are constantly recycled. A crisis might threaten the world, and a hero will rise up to avert it. Having done so, he dies, time goes on, and at some point in the distant future, when everyone has forgotten what happened, the same crisis will threaten again, and that hero will be reborn to once again make changes. Names and details might change slightly, but the souls are the same.
There are almost certainly many other theories people have conceived of. The key for the author is to be sure that he or she knows the theory that is being applied, knows exactly how it works, and – most importantly – is consistent in application of the theory.