IntroductionTime is definitely among the most familiar concepts that we have come across, yet it is one of the least understood. We need it in everyday life; it tells us when to wake up, eat, go to work, exercise and sleep. We simply cannot live without it, yet we are still struggling to understand what exactly it is. To the ordinary person, the concept of time is thought to flow in a direction, from the past to the present, and the present to the future. However, after looking deeper into the philosophy and science, many famous philosophers and scientists have reason to believe otherwise, for example McTaggart (1908) and Greene (2004). This report will look at the main arguments that support the flow of time, as well as arguments against the flow of time. After lots of evaluation and analysing of all the theories and arguments, a conclusion will be drawn that answers the question – does time flow in one direction?First, key terms will be defined, such as “past”, “present”, “future” and “time”. This will help us gain a better understanding of the question and topic before the actual research is presented. This will be followed by the different theories on the flow of time (for example, by Einstein and Leibniz), showing both sides of the argument to achieve an unbiased conclusion. Towards the end, the possibility of time travel will also be discussed from the findings gathered in the primary and secondary research carried out. At the end, a detailed conclusion will be given based on all the research, evidence, analysis and evaluation. This report aims to: Discuss the reasons why the concept of time can be seen as flowing in a direction and the reasons why it cannot. Analyse and evaluate the main theories and arguments put forward by the most intelligent and influential philosophers and scientists for and against the flow of time.Analyze the opinion of a philosopher professor at Oxford University (who has been emailed) on the topic (Adam Caulton).Explore the possibility of time travel to the past and/or future, looking at famous arguments and paradoxes as well as touching on the topic of hard determinism versus liberalism.Draw a clear, detailed conclusion using all the research analysis and evaluation done in the report, answering the question in the title.Defining TimeWhen asked what the definition of time is, a normal person would probably respond with something along the lines of ‘time is whatever clocks measure’. But that seems to be hopelessly operational, and leads to further questions: what, then, is a clock? It is no help to be told that ‘clocks are whatever measure time’; we want some way to break into the definitional circle. Without clocks, time would still exist but without time, clocks would not exist. So, perhaps it is better to think of clocks as measuring time, and come up with a way of understanding time independent of clocks. Upon emailing Adam Caulton (Lecturer and Tutor in Philosophy, Balliol College, Oxford), he presented a definition of time in terms of events. To define an event first, he said “what I mean by ‘event’ is … something that happens within a fairly small spatial region and over a fairly small period of time.” From this, we can infer that “a fairly small spatial region” and a “fairly small period of time” is in relation to the whole universe and the whole timeline (since the word ‘small’ is relative). So, according to this, a click of your fingers is an event, as is the collision between two objects, or an explosion.He continued on with “but we can imagine events that happen within increasingly smaller regions of space and over increasingly small periods of time. The limiting case is a pointlike thing: it is located in space and time, but has no spatial or temporal extension. Events are real — this is undeniable. Perhaps there are pointlike events — our best theories seem to suggest that.” This raises a big question: how are the events arranged? How are they ordered? According to Einstein’s theories of relativity, they are ordered in a four-dimensional continuum. Time is one aspect of this ordering. However, this notion of time is much thinner than the everyday notion. For example, it does not necessarily have a direction and it does not necessarily “flow” (this will be discussed in detail later in the report).Time Does FlowATime Doesn’t FlowThe A-series and B-seriesWhat, then, is the past, present and future? When it comes to time, philosophers are broadly divided in two groups according to their beliefs: one group believes what is known as the A Theory, and the other group follows the B Theory. A Theorists believe that time can be divided into the past, present and future – and they are all temporal properties and real distinctions one can make. For example, World War 2 has the property of ‘pastness’. Time passes as it flows from the future, into the present, then into the past. B Theorists believe that all times are equal and that there is no such thing as the ‘present’, ‘past’ and ‘future’. The ‘present’ is just the name we give to the bit of time that we are in, but all times exist equally.John McTaggart Ellis McTaggart, British metaphysician in the 19th-20th century, rejected the B-series because he thought it ruled out the possibility of change. “The B series by itself is not sufficient for time, since time involves change.” (McTaggart, 1908). McTaggart thought that change is of the essence of time and time necessarily involved change. The events that form a B-series must also form an A-series in order to count as being in time, i.e. they must pass from future to present, and from present to past, in order to change. He thought that if time exists, it had to be like the A Theory.But, he also rejected the A-series because of something now known as ‘McTaggart’s Paradox’. It is true that the A properties are mutually exclusive; nothing can have pastness, presentness and futurity all at once – that is a contradiction. The obvious response to this would be that nothing has all three properties at the same time; it starts with having futurity, then presentness, and finally pastness. But McTaggart goes one step beyond: if an event is in the future, then it will be in the past. This means it has second order temporal properties: it has present futurity (currently in the future), and future pastness (will be in the past). When it is in the past it will have past futurity (used to be in the future). But again, we get a contradiction. No event can have both future pastness and past futurity – that would mean it is and is not in the future, which does not make sense. So again we say it does not have these properties at the same time, it currently has future pastness and then it will have past futurity, which is to say it has third order temporal properties. But again, some of the third order temporal properties are contradictory so we have to go to fourth order and fifth order, and so on, creating an infinite loop. No matter how many levels you pursue them to, the contradictions of McTaggart’s Paradox always come back. For this reason, McTaggart rejected the A-series and therefore concluded that time does not flow (or even exist) if it does not follow the A or B Theory. McTaggart’s beliefs are the beginning of the modern metaphysics of time, although McTaggart’s Paradox is not thought of being a great argument anymore because of how much theories have developed.Einstein’s Special Theory of RelativityFrom a human’s perspective, it seems to be quite obvious that time is flowing. However, even though physicists have tried really hard, none of them have come up with any evidence or proof supporting the flow of time. In fact, when reframing some of Einstein’s words from his Special Theory of Relativity, evidence is provided for the other side of the argument – that time does not flow. To understand this, we will imagine a loaf of bread being the entirety of spacetime. Therefore, the slices making up this loaf are the ‘nows’ of an observer; each slice represents certain space at a certain moment of time from the observer’s perspective. The union obtained by placing the slices together, in the order in which the observer experiences them, fills out a region of spacetime. If we take this perspective to a logical extreme and imagine that each slice depicts all of space at a given moment of time according to one observer’s viewpoint, and we include every slice from the ancient past to the distant future, the loaf will encompass the whole universe throughout the whole of time – the whole of spacetime. Every event, regardless of when or where, is represented by some point in the loaf. This is schematically illustrated in Figure 1, however the perspective is somewhat confusing. The ‘outside’ perspective of the figure, from which we are looking at the whole universe (all of spacetime), is a fictitious vantage point, one that none of us will ever be able to seen from. We are all within spacetime. Every experience we ever have occurs at some location in space at a moment of time. And since Figure 1 is supposed to show all of spacetime, it encompasses the totality of such experiences. If you could zoom in and closely examine all the comings and goings on planet Earth, you would be able to see every little thing from the past, present and future. Given the coarse resolution of Figure 1, you cannot actually see these moments, but you can see the schematic history of the Earth. Obviously, Figure 1 is an imaginary perspective; it stands outside of spacetime – which is impossible. It is the view from nowhere and nowhen. Even though we cannot actually step beyond spacetime and take in the full sweep of the universe, Figure 1 provides a very strong means of analysing and clarifying the basic properties of space and time. As a main example, the intuitive sense of time’s flow can be easily and vividly portrayed in this framework by a variation on the movie-projector metaphor. We can imagine a light that illuminates one time slice after another, momentarily making the slice come alive in the present – making it the momentary now – after which it lets it go instantly dark again as the light moves on to the next time slice. Right now, in this way of thinking about time, the light is illuminating the slice in which you, sitting on planet Earth, are reading this word. But again, while this image seems to match our experience, scientists have not been able to find anything in the laws of physics that embodies a moving light like this. They have not found any physical mechanism that singles out moment after moment to be momentarily real as the mechanism ‘flows’ toward and into the future. In actual fact, it is quite the contrary. While the perspective of Figure 1 is unquestionably imaginary, there is very convincing evidence that the spacetime loaf – the totality of spacetime, not slice by single slice – is real. An implication of Einstein’s work is that special relativistic reality treats all time as equal. Although the notion of ‘now’ plays the prime and central role in our view of the universe, relativity subverts our intuition and declares our universe an egalitarian one in which every moment of time is as real as any other. Einstein argued that every part of the spacetime loaf in Figure 1 exists on the same footing as every other, suggesting that reality embraces past, present and future equally and that the flow we envision bringing one section to light as another goes dark is nothing but an illusion.