The Science of Time Travel and the Implications of Killing People before they were Born

I wanted to write a story in which people mixed with dinosaurs. Seeing as Sir Arthur Conan Doyle had the idea of a lost world and Michael Chrichton had the idea of using recovered dinosaur DNA first, it really left me no alternative but to send my characters back in time. Yes, I was going to have to use time travel. It is not one of my favourite themes of the science fiction genre. I enjoyed Doctor Who when I was younger, but like so many time travellers he kind of avoided the science of his/ her method of getting about. In fact, this is the case with most such stories going right back to H. G. Wells’ ‘The Time Machine’.

When I started writing ‘Mesozoic’ I wanted the dinosaurs and other prehistoric animals to be as accurate as possible. Although I had enjoyed some of the Jurassic Park movies, I was acutely aware that what the film makers were presenting were monsters, not dinosaurs. They existed to thrill and scare the audience, but I doubted that they would actually behave in the manner suggested on the screen. My dinosaurs were going to be a little more like animals and a lot less like cinema monsters. However, if I was going to take that approach in my writing towards the animals then it seemed, for the sake of integrity at least, that I should approach the subject of time travel and its many paradoxes as well.

I quickly discovered that time travel appears to be impossible in our universe. It did not take me long to realise this fact. The laws of physics work against the idea. Arthur Eddington’s concept of the asymmetry of time suggests that there is an obvious direction of time and it is forwards not backwards. His theory sets up one of the many contradictions of time travel. Processes that exist at the microscopic level are time-symmetric, if the direction of time were reversed the description of those processes would remain true. However, on a macroscopic level this is not the case. Imagine watching a recording of a ball being thrown, bouncing, and then coming to a stop. If you watch the same images in reverse, then it looks equally realistic. This process of the images is time-symmetric, however, the actual process of the ball being thrown, bouncing, and coming to a stop is not. This is because the ball acquires kinetic energy when it is actually thrown, but that energy is dissipated to the point where it no longer exists, and the ball comes to a rest. This process cannot be reversed in the physical world.

One of the advantages of working in fiction is being able to appeal to artistic licence. Okay, I said that I wanted to maintain a degree of accuracy, but when the universe stops you from achieving something then a writer has to turn to imagination, or in this case what was theoretically possible. At some point I had decided that my time machine was going to travel from point A to point B. Both the start and the end of the journey were fixed, as opposed to flying through space in a TARDIS. It was probably when I was reading about closed time-like curves (CTC) created through the use of gravitational fields. It appeared more logical that such a system would work much better with a fixed point of origin, such as a time travel station in the future, and a fixed terminal point in the past.

The idea of distorting the fabric of space-time with gravitational fields to create a route from one point in time to another has been the subject of much discussion, fortunately for me. I was able to read many fascinating accounts about it. I admit, much of the science was beyond me, especially the equations used to examine some of the more abstract concepts. I grasped the logic of the idea though. Moving people through time remained problematic, however. It was one thing to create a CTC but how do you move a body down it? It appeared to me that the forces necessary would prove to be destructive if the body retained its mass. The answer was to remove that mass. I favoured the idea of creating a capsule in which my characters would travel. The capsule was surrounded by a field of gluons, an elementary particle that has no mass. In theory, I believed, this would render the capsule and the people inside it in a state of zero mass also. The capsule was then transported down the CTC by photons that travel at the speed of light. Effectively, this meant that the actual journey from the future to the past would happen almost instantaneously, well from the point of view of the people in the capsule that is. Being in a massless state would also save them from exposure to the phenomena associated with travelling at the speed of light, which would more normally result in total destruction for an object with positive mass.

Okay, so I had got my characters from the future to the past with no adverse reactions, now what if any of them were killed while several million years back in history? A reader actually did raise this point with me because some of the characters in Mesozoic die. It is one of the classic paradoxes of time travel, can you be killed before you are born? I am ashamed to admit that although I was working on an answer to this problem, I never got around to completing it before I finished writing the book. My resolution was basically this; that time is not strictly linear from one point of origin, the creation of the Earth, to one point of terminus, the destruction of the Earth. I adopted the concept that more than one timeline was possible. For example, a character travels back in time to study dinosaurs and gets stepped on by a large sauropod. The consistency paradox suggests that this is a contradiction; being killed before you were born. However, what if, at the point of being stepped on and killed, a new timeline begins. The old timeline is no longer followed. It ran from the beginning of time to when the character was born, continued up until they returned to the Jurassic Period and became a stain on the foot of a large dinosaur, and then continued again from that point to a human world where the character no longer existed. Instead of running direct from point A to point B it took a detour, moving point B further back in time and making the terminus now point C. This happens to each and everyone of the characters who die in Mesozoic. Instead of a clear and straight progression of the timeline you get a series of junctions where new versions of the timeline are created.

TimeLine

It is a bit simplistic, but the diagram above does illustrate what I mean. I am not sure of what the consequences of making time so relative to each individual character would be? Clearly, if such catastrophic events were experienced by several time travellers the timeline itself would be repeatedly changed. It maybe that more than one timeline is capable of existing concurrently. Imagine if the timeline did not exist in the singular but was a combination of many different possibilities instead?

Another reader asked me if I was planning on making Mesozoic into a series of novels? At the time I was not but considering this problem with time travel and causation gives rise to some interesting questions. I may very well start trying to find the answers, as long as they include dinosaurs as well!

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