Today’s reading from baralbion‘s philosophical questions is:
The future is as unchangeable as the past. The past and future are always present, unchanged and unchanging and unchangeable (No, I’m not sure what it means either, but I’m getting there.)
Time is one of those things that seem so simple but when we look more closely turn out complicated. If you don’t think so, then take a look at this excellent article on time on The Internet Encyclopedia of Philosophy.
As that article shows, there are currently several theories of time, some straightforward, others mind-boggling in their implications. There are at least two that imply a close relationship between past and future.
The first is the “block” model of the universe. This, due to Einstein’s Theory of General Relativity, sees the universe and as 4-dimensional block, the dimensions being the three familiar ones of space and the fourth, that of time. This suggests that just as all points in the space contained within a 3-dimensional block are present simultaneously, so all points in the space-time contained within a 4-dimensional space-time block are present simultaneously. In other words, all points in time, irrespective of whether we regard them as past, present of future, are simultaneously present. That would seem to imply that the relative positions of points in space-time are fixed just as the relative positions of objects in 3-dimensional space are fixed. This in turn seems to indicate that the future is already present in the universe and is therefore fixed.
The second starts by noting that some particle interactions are apparently time-symmetric. That is, they can be described equally well by a particle moving forwards in time or by an anti-particle moving backwards in time. This would imply that the present/future can affect the past. No one claims, however, that this time symmetry occurs at the macroscopic level, i.e. the level at which we lead our lives. It does not open our way to time travel, for example.
For the time being at least, it seems that if you wish to maintain that the future is fixed or that, on the contrary, the future is continually evolving out of the present and is therefore unpredictable, all you need do is select a theory of time that supports your view.
Thinking about this, it occurred to me that the central issue for us, as we lead our lives, is the present. We talk about “the present” as though we all know what this means and its nature is obvious and uncontroversial. When we look more closely, however, problems begin to arise.
What do we know about the present? It is the stage on which our consciousness operates: I cannot be conscious in the past or in the future. My consciousness defines the present. For me, the present is the time-location of my consciousness.
As a spot definition we might say that the present is the vantage point from which we recognize two other great swathes of time: the past and the future. If I recognize a “past”, it must be time before the “now” in which I am talking about it. Likewise, if I talk about a “future”, it must be a time after the “now” in which I am talking about it. This “now”, the present, is the time sandwiched in between, the time in which I act, think and am conscious (even if dreaming or hallucinating). The only time in which I can do these things.
But what is the present? We tend to think of it as a duration, albeit short, in which everything “happens”. I write, pause, pick up my tea cup, drink, put the cup down and resume writing. To me it seems that all of this is “now”, the present. But a moment’s reflection makes us realize that it is not so.
The present is continually moving. The present in which I pick up my cup is not the present in which I drink and this is not the present in which I put the cup down again. We could record these actions with a film cine camera and we would find a set of still pictures, each the encapsulation of a “present”. The act of picking up my cup and drinking from it includes very many such “presents”, each following the others in rapid succession into the immutable past.
However, a frame from a film is not really a “present”, either. Close examination shows slight blurring which means that the frame represents, not an instant, but a duration during which time moves on. The beginning of a blur represents one “present” and its end another. We could speed up the camera so that each frame represents a smaller and smaller interval of time but the frame would always be precisely that, an interval of time, never the instantaneous present. As we home in ever closer to the mythical present it continues to escape us because “the present” actually has no duration. How, then, can the present even exist?
Could the present, then, be a series of “instants” so short as to have no duration themselves but able to form a continuous line of time by acting in series? Zeno of Elea realized that thinking this leads to paradox as shown in his famous example of the arrow that cannot move:
At any instant, the arrow is in some specific position because it cannot be in two places at once. Thus it cannot move during this instant which has no duration. Time is made up of a series of instants. The arrow cannot move during any such instant. Therefore the arrow cannot move at all.
What is the solution to this paradox? It is the recognition in modern mathematics that any time interval contains infinitely many instants. As mathematicians put it, between any two instants there is a third one. Instants have no ordering and cannot add up to an interval of time any more than a lot of zeros can add up to a number. Zeno’s paradox relied on a time interval being composed of a series of instants. Once we scotch this idea, the paradox disappears.
Far from helping us, though, this makes our problem worse: if the present is a set of instants, how can these form a continuous stream of time? The answer is that they can’t. We are still left wondering what the present is.
One answer might be that the present is not a thing but an interface between past and future, perhaps like the surface of a lake, where the water gives way to air. In that case it would have no dimension. It would be like the familiar geometrical “point” that has position but no extension. But if that is so, how can we claim to experience the present, to act in the present? You might as well talk about walking about on a geometrical point. (Did someone mention angels dancing on the head of a pin?)
If the present is the dimensionless interface between future and past, the instantaneous point at which future becomes past, then any concept that we live in the present is mistaken: you cannot be in that which has no size. This implies that we in fact live in the past. In other words, what I think is the “present” is really a memory of the recent past.
But if so, Zeno suddenly wakes up again. “If the present is an instant without duration,” he might say, “then nothing can move during it. Nothing can be done.” I cannot make a cup of tea or drink it because I am not doing but remembering these actions from the recent past. My memories cannot possibly affect the future. If there is a future (and there is, for it is that that is continuously changing into past), it must exist on its own account since I cannot affect it in any way.
If that is true, then the only conclusion is that the world is ruled by determinism, as baralbion‘s proposition implies. Somehow the future is formed without our knowledge, becomes instantiated at the interface with the past that we call the present and impinges on our consciousness as a memory.