Views on Time Travel

Time-travel has always been a fascination for mankind. We have always in our cultures tried to play god, by wrestling with the amount of control we have over our surroundings. Ever since the concept of time travel was conceived, we have seen it as a means to control our circumstances, or even change them, by changing the cause and thereby the effect. However, there are issues to consider. I intend to talk about time travel, and when time-travel is possible by using the paradoxes involved in time travel, the Novikov principle, seen through the perspective of the butterfly effect.

First of all, let us think about a simple problem. Consider this. You go back in time, and kill your grandfather before he met your grandmother. Now if you did this, you would prevent one of your parents, and by extrapolation, yourself from being born. But if you were never born, how would you travel back in time to cause this event to happen? This is called the grandfather paradox.

Now think of this problem – that of a man who travels back in time to discover the cause of a famous fire. While in the building where the fire started, he accidentally knocks over a kerosene lantern and causes a fire, the same fire that would inspire him, years later, to travel back in time. Here’s another one, that of a man who travels back in time and impregnates his grandmother. She would, as a result, give birth to the man's father, to whom will be born the man himself. This man would have to travel back in time in order to ensure his own existence. This is called the predestination paradox, which is a paradox of time travel that is often used as a convention in science fiction. It exists when a time traveller is caught in a loop of events that "predestines" him or her to travel back in time. This paradox is in some ways the opposite of the grandfather paradox.

A variation on the predestination paradox which involves information, rather than objects, traveling through time is similar to the self-fulfilling prophecy, which is is a prediction that, in being made, actually causes itself to become true. A man receives information about his own future, telling him that he will die from a heart attack. He resolves to get fit so as to avoid that fate, but in doing so overexerts himself, causing him to suffer the heart attack that kills him.

The common thread running through the above three examples is that the normally accepted definition of causality is reversed, wherein the effect becomes the cause of the effect, which is the cause and so on. In the first example, the person would not have traveled back in time but for the fire that he or she caused by traveling back in time. Similarly, in the third example, the man would not have overexerted himself but for the future information he receives. In the second example, the man's very existence would be pre-determined by his time traveling adventure. This also raises the paradox of which came first – the time travel or his existence.

In fiction itself, this concept has been dealt with quite often, most prominent examples being the story of Oedipus Rex and Achilles. Lord Krishna, too is a famous example. In filmdom, I don’t even have to tell you about The Terminator and its sequels, which rely almost totally on this paradox as the centre of their story. One could argue, as many did in the case of the Terminator’s particular paradox, that if the soldier sent back in time did not impregnate Sarah Connor, John Connor would still be born. The very simple counter-argument here is that only if the soldier who came back impregnated her, she would believe what was going to happen in the future and bring her son up, training him to be a fighter.

The “Back To The Future” series also exploits this concept to a huge extent. But here, again, there is a glaring loophole. If the scientist and the boy went to the past and altered something, obviously the boy would be missing in the present. In this case, the altered future would involve another version of the boy, in which case the boy that left to the past is an extra in the space-time continuum. Strange, isn’t it?

Obviously with such buildup about loopholes and paradoxes, one must think I’m getting somewhere. Well, I am. I present to you, the Novikov Self- Consistency Principle. This was postulated by Dr. Igor Novikov in around 1985 to solve, or rather explain the problem of paradoxes in time travel. Simply put, the principle states that any event which could give rise to a paradox exists, then that event has a probability of zero.

To prove his theory, Novikov did not rely upon conventional paradoxes like the grandfather paradox. He relied upon a scenario with a more mathematical/statistical bent. He considered the scenario of billiards ball being fired into a wormhole in such a way that it would go back in time and collide with its earlier self, thereby knocking it off course and preventing it from entering the wormhole in the first place.

It was found during the course of this experiment that there were many trajectories that could result from the same initial conditions. For example, the billiard ball could knock itself only slightly astray, resulting in its going into the past slightly off course, which results in its earlier self only being deflected slightly. He found that this “sequence” of events which is actually a causal loop (read predestination paradox) is completely consistent, and does not result in a paradox. Further, he saw that the probability of such consistent events was nonzero, and the probability of inconsistent events was zero, so no matter what a time traveller might try to do he/she will always end up accomplishing consistent non-paradoxical actions. In other words, no action a time-traveller takes will significantly alter the course of history.

Now getting back to our discussion. The Novikov principle, however, makes an assumption that only one timeline can exist, or as a corollary, multiple timelines cannot be accessed. However, this does not make total sense, because when the time-traveller returns from his travels to the same timeline, he will have returned, in the event of a single timeline, in a changed state, albeit minor. This is where the butterfly effect comes in. But before that, let us lay down the logic. If the traveller comes back changed, there are a few things to be considered. First of all, if he has changed, he has to have an innate knowledge of where exactly he will return, this knowledge caused by the events he has undergone himself after the point in time he changed. This, again, is absurd because the human mind can know based only on what it has seen or atleast perceived. Thus, this kind of knowledge would, if at all existent, be deeply subconscious and incapable of manifesting itself in the short while that it takes for the traveller to return.

Second of all, when the time-traveller left, he would have left a life behind. Now, one timeline seems to explain that he merely comes back and takes his place in the timeline after this travels. However, once you think about it, it seems absurd, because once the time travel is over, who exactly takes the place? Is it th entity who traveled back in time and changed something, or is it the entity who grew up through time? To make things clearer, let us involve the Novikov principle in an example. Suppose I realise I would like to see myself when I’m fifteen and travel back in time and do so. Thus, a distinct memory has to be implanted in my 15-year-old mind about seing myself and how I would look from the future, when I’m 22 (scary thought that is). So now when I come back to the present, would I still see myself, that 15 year old, who has grown to be 22, or has time frozen, waiting for me to come back and resume functioning, or will things just be normal? The entire proposition seems to ambiguous, since it stands to reason that once time-travel is introduced, the traveller begins to exist, outside time.

Moreover, the Noviko principle only seems to be covering its tracks when it says that no matter what action the traveller takes, nothing significant will happen changing the course of time. This is where, as I said earlier, the butterfly effect comes in. The butterfly effect is a phrase that encapsulates the more technical notion of sensitive dependence on initial conditions in chaos theory. Small variations of the initial condition of a dynamic system may produce large variations in the long term behavior of the system. Essentially, if crossing a street when I was 16 was prevented, I might be in a very different position than I am today. In other words, and on a more philosophical note, everything is relevant to everything else. The concept refers to the idea that a butterfly's wings might create tiny changes in the atmosphere that ultimately cause a tornado to appear (or, for that matter, prevent a tornado from appearing). The flapping wing represents a small change in the initial condition of the system, which causes a chain of events leading to large-scale phenomena.

Given a system and a large enough time frame, slight variations in the initial conditions can cause huge variations in later conditions in the system. Now, the novikov principle suggests that only minute changes are possible in time travel, but the net result cannot be avoided, as per laws of probability. My major argument against that is that initial conditions do play a huge role. Moreover, not many real-life phenomena subscribe to probabilistic laws. For example, the binomial theorem in probability says that there is equal probability of heads and tails occuring on a toss. However, this does not mean that in 100 tosses, there will be 50 heads and 50 tails. Such an event is extremely rare, so much so that it might be a poisson event. Thus I state that the butterfly effect holds good.

There is another point I’d like to make. I would say that time travel is unambiguous and feasible only if there exist parallel universes and multiple timelines. Only if we find a way to transverse universes and timelines can time-travel be possible. What I mean is when you travel back in time and kill your grandfather, you do so in (or your actions result in the creation of) a parallel universe in which you will never be conceived as a result. However, your existence is not erased from your original universe. Thus, after the time travel is over, the act of the completed journey results in you returning to another parallel universe, where you resume life as before, without any hiccups. Another possibility is, along the lines of David Deutsch, that if backwards time travel is possible, it should result in the traveler ending up in a different branch of history than the one he departed from. This view could subscribe to the Novikov principle in that no significant change can be made to a timeline, if the change maker is from that timeline. However, a parallel universe and thus a parallel timeline can be changed by one who is not from that timeline.

This makes perfect sense logically, but is this practically possible? It is a widely regarded theory that trvelling back in time means travelling faster than light. However, I don’t believe this to be the case, since travelling faster than light very simply means you ge to see things before others do, and is not actual time-travel. Thus, I subscribe to the views I have put down here, and further state that such technological advancements might not be round the corner, and don’t seem likely, but then again, when Jules Verne wrote about the Nautilus in 20000 Leagues Under The Sea, submarines did not exist. Will man ever time-travel? It is unlikely, but as the saying goes, you never know. Only Time will tell.