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Nurana Rajabova looks for a way of seeing time as if from the outside.
Admittedly, the idea of time travel has always given me a smirk. I suppose that is because to me it has always sounded like a fantasy that could never be actualized. Hence, entertaining the idea of its possibility felt like a waste of time. Nonetheless, as I encounter this concept more and more often these days, especially as a part of intellectual conversations and philosophical speculations, I must admit that somehow time travel keeps me wondering. My momentary contemplations, however, do not necessarily focus on whether it is practically possible to travel to a certain point in the past or in the future. Rather, they help me deep dive into the nature of time itself.
Defining time may, at first, seem quite straightforward. After all, we are all familiar with the idea of time in the sense of duration and its measurement. However, what time is in its essence is a much more difficult question, with a long history of philosophical disputes and still no agreed definition.
Our most common intuition tells us that time is a passing phenomenon. What this entails is that space (or the physical universe) is in a fixed or static position and time, like a film running through an old projector if you will, comes and passes through the universe. As time comes, it brings all the changes with it. In other words, the universe changes through time.
Alternatively, one can also see this relationship between time and space in the reverse way. As my friend once said, “Time is not passing. We are the ones passing through time.” In this sense, time can be imagined as a static line consisting of past, present and future points. However, unlike the previous view, in this case the one in motion is believed to be space (or physical reality). In other words, space and everything in it move along the line of time. As it progresses the points it leaves behind are deemed to be the past, the point it is standing on is considered to be the present, and the points that it has yet to encounter are the future.
In both of these views, time and space are seen as separate entities with the potential to intersect at a certain point. It is only this intersecting point that has real existence. Outside of this intersecting point, time on its own without space conjoined to it, has no reality whatsoever. Note that the intersecting point is always the present. The points (or times) we refer to as past and future, being outside of this intersection, are not in existence. Hence, they are not real. To put it differently, time becomes real only at the point it meets space. Any point outside that is not existent.
Secondly, in such an understanding of time, there is a non-permanence or succession factor: the present comes into existence when the past is gone. When the present is in existence, the past is not, any longer. Similarily, the future also can come into existence only when time meets space and the future becomes the present. In other words, the future becomes real when it becomes the present. Therefore the future, in its commonly understood sense, is never actually in existence.
Lastly, another key factor in this view is motion. That is, be it the universe passing through time or time passing through the universe, there is a motion that makes their meeting possible and only as a result of this motion the present happens to exist and be real.
This view of time is known in philosophy as presentism. It is the view that only the present exists. The past has been but is no longer, while the future will come to be but is not yet. This view in fact dates back to ancient thinkers, one of them being Heraclitus (c.500 BC) who famously said: “You cannot step twice into the same river, for other waters and yet others, go flowing on… Everything flows and nothing abides; everything gives way and nothing stays fixed.” (Wheelwright, 1960)
Presentism fits well with our conventional view of time, which understands time in terms of a perception of change; as John Locke put it, somewhat archaically, “When that succession of ideas ceases, our perception of duration ceases with it” (An Essay Concerning Human Understanding, 1689, p.174). The Scottish Enlightenment philosopher David Hume expressed a somewhat similar understanding of time when he wrote: “As it is from the disposition of visible and tangible objects we receive the idea of space, so from the succession of ideas and impressions we form the idea of time… Wherever we have no successive perceptions, we have no motion of time, even though there be a real succession in the objects” (A Treatise of Human Nature, 1738, p.35).
Given that I am examining the idea of time in the context of time travel, naturally the main question that arises for me is: what does this view of time tell us about time travel? Can time travel be considered possible, given this understanding of time? The short answer for me is: it cannot. The reason is obvious. Let’s suppose I build a machine to take me to some point in the past. Unfortunately, according to the presentist view of time, the past does not meet physical reality any longer, consequently it does not exist. Therefore, travelling to any point in the past is not possible.This argument also holds for time travel into the future. The universe has not yet intersected with the future moment I want to visit, therefore the circumstances that would make that possibility real do not exist. Hence, travelling to any point in the future is not possible either.
Now, does that mean the nature of time absolutely forbids the possibility of time travel? It seems so. But all hope may not be lost yet. There could be a way. However, for time travel to be possible the presentist concept of time would need to be negated, since we can travel only to a point that exists. Consequently, for us to be able to travel to any moment in the past or in the future, it would be necessary for those moments to be in existence alongside the present; to be within the boundaries of where time meets space. This could happen only if time and space were in a static relationship to each other, such that, let us say, the line of space runs in parallel to or is superimposed upon the line of time. In other words, time travel is possible only if all the times of physical spatial reality all exist, not just those in one’s present. This view in philosophy of time is known as eternalism, and it says that the past, the present and the future all exist somehow ‘all at once’.
Lost In The Flow of Time, Dror Rosenski 2021
Arguably, the first defender of eternalism of whom we are aware was the ancient Greek philosopher Parmenides. He explained his philosophy with the following words: “There remains, then, but one word by which to express the [true] road: Is. And on this road there are many signs that What Is has no beginning and never will be destroyed: it is whole, still, and without end. It neither was nor will be, it simply is – now, altogether, one, continuous… Permanence is basic. No things come to be or, slipping into the past, cease to be. Past, present, and future are distinctions not marked in the static Is. Time and becoming are at best secondary, at worst illusory, as our understanding of the world confirms” (trans. Philip Wheelwright, 1960).
Clearly eternlism defies our most intuitive and commonsensical view of time. But consider it this way. Imagine consciousness as a pair of binoculars through which you can only see a narrow frame. Through seeing and feeling yourself only in a certain instant, you get the idea, if not the illusion, of the present. You feel like in this particular instant you are in a different time from the past which is already gone as well as the future which is yet to come – whereas, if you took the binoculars away, you would see it all: Time would appear to be timeless, as all the points of existence would coexist alongside the present, including those deemed to be past and future to those of limited vision. Of course, fortunately or unfortunately, you can never take away those binoculars thanks to the limited capacity of human perception. We all live with the perception of time, whereas, in reality, time may be something our mind makes up due the narrow frame it’s able to perceive and is unable to break free of.
As we can see, the eternalist understanding of time allows for time travel to be possible. Moreover, it also may allow for the theoretical possibility of seeing the future. It’s not possible for anyone, even God I dare say, to really see something that does not exist. If we accepted eternalism to be true, we could argue that the future exists, and perhaps that any potential prophets and clairvoyants simply had wider binoculars than ordinary people, enabling them every once in a while to catch a glimpse of future events hidden from the rest of us.
To conclude, the idea of time travel may always remain a fantasy, with no possibility of being actualized in the physical world, yet it can serve an important purpose for us by unleashing a different understanding of time. More often than not, we take time to be a phenomenon with real existence only in the present. This theory of time absolutely negates the possibility of time travel. However, time travel could be a logical possibility if we stretch our understanding of time to take it as an ‘eternal’ phenomenon, regardless of how counter-intuitive or paradoxical that sounds. If we do, we also choose to view time’s passing as an illusion the mind comes up with thanks to its narrow capacity to perceive beyond a certain frame.
© Nurana Rajabova 2021
Nurana Rajabova holds an MA in philosophy from University College Dublin.