FIGURE 11.3 At each moment, ‘now’ is that moment.
Admittedly, different snapshots of the observer perceive different moments as ‘now’. But that does not mean that the observer’s consciousness — or any other moving or changing entity — moves through time as the present moment is supposed to. The various snapshots of the observer do not take it in turns to be in the present. They do not take it in turns to be conscious of their present. They are all conscious, and subjectively they are all in the present. Objectively, there is no present.
We do not experience time flowing, or passing. What we experience are differences between our present perceptions and our present memories of past perceptions. We interpret those differences, correctly, as evidence that the universe changes with time. We also interpret them, incorrectly, as evidence that our consciousness, or the present, or something, moves through time.
If the moving present capriciously stopped moving for a day or two, and then started to move again at ten times its previous speed, what would we be conscious of? Nothing special — or rather, that question makes no sense. There is nothing there that could move, stop or flow, nor could anything be meaningfully called the ‘speed’ of time. Everything that exists in time is supposed to take the form of unchanging snapshots arrayed along the time-line. That includes the conscious experiences of all observers, including their mistaken intuition that time is ‘flowing’. They may imagine a ‘moving present’ travelling along the line, stopping and starting, or even going backwards or ceasing to exist altogether. But imagining it does not make it happen. Nothing can move along the line. Time cannot flow.
The idea of the flow of time really presupposes the existence of a second sort of time, outside the common-sense sequence-of-moments time. If ‘now’ really moved from one of the moments to another, it would have to be with respect to this exterior time. But taking that seriously leads to an infinite regress, for we should then have to imagine the exterior time itself as a succession of moments, with its own ‘present moment’ that was moving with respect to a still more exterior time — and so on. At each stage, the flow of time would not make sense unless we attributed it to the flow of an exterior time, ad infinitum. At each stage, we would have a concept that made no sense; and the whole infinite hierarchy would make no sense either.
The origin of this sort of mistake is that we are accustomed to time being a framework exterior to any physical entity we may be considering. We are used to imagining any physical object as potentially changing, and so existing as a sequence of versions of itself at different moments. But the sequence of moments itself, in pictures like Figures 11.1—11.3, is an exceptional entity. It does not exist within the framework of time — it is the framework of time. Since there is no time outside it, it is incoherent to imagine it changing or existing in more than one consecutive version. This makes such pictures hard to grasp. The picture itself, like any other physical object, does exist over a period of time and does consist of multiple versions of itself. But what the picture depicts — namely, the sequence of versions of something — exists in only one version. No accurate picture of the framework of time can be a moving or changing picture. It must be static. But there is an inherent psychological difficulty in taking this on board. Although the picture is static, we cannot understand it statically. It shows a sequence of moments simultaneously on the page, and in order to relate that to our experience the focus of our attention must move along the sequence. For example, we might look at one snapshot, and take it to represent ‘now’, and a moment later look at a snapshot to the right of it and think of that as representing the new ‘now’. Then we tend to confuse the genuine motion of our focus of attention across the mere picture, with the impossible motion of something through real moments. It is easily done.
But there is more to this problem than the difficulty of illustrating the common-sense theory of time. The theory itself contains a substantive and deep equivocation: it cannot make up its mind whether the present is, objectively, a single moment or many — and hence, for example, whether Figure 11.1 depicts one moment or many. Common sense wants the present to be a single moment so as to allow the flow of time — to allow the present to sweep through the moments from past to future. But common sense also wants time to be a sequence of moments, with all motion and change consisting of differences between versions of an entity at different moments. And that means that the moments are themselves unchanging. So a particular moment cannot become the present, or cease to be the present, for these would be changes. Therefore the present cannot, objectively, be a single moment.
The reason why we cling to these two incompatible concepts — the moving present and the sequence of unchanging moments — is that we need them both, or rather, that we think we do. We continually invoke both of them in everyday life, albeit never quite in the same breath. When we are describing events, saying when things happen, we think in terms of a sequence of unchanging moments; when we are explaining events as causes and effects of each other, we think in terms of the moving present.
For example, in saying that Faraday discovered electromagnetic induction ‘in 1831’ we are assigning that event to a certain range of moments. That is, we are specifying on which set of snapshots, in the long sheaf of snapshots of world history, that discovery is to be found. No flow of time is involved when we say when something happened, any more than a ‘flow of distance’ is involved if we say where it happened. But as soon as we say why something happened, we invoke the flow of time. If we say that we owe our electric motors and dynamos in part to Faraday, and that the repercussions of his discovery are being felt to this day, we have in mind a picture of the repercussions beginning in 1831 and sweeping consecutively through all the moments of the rest of the nineteenth century, and then reaching the twentieth century and causing things like power stations to come into existence there. If we are not careful, we think of the twentieth century as initially ‘not yet affected’ by the momentous event of 1831, and then being ‘changed’ by the repercussions as they sweep past on their way to the twenty-first century and beyond. But usually we are careful, and we avoid that incoherent thought by never using the two parts of the common-sense theory of time simultaneously. Only when we think about time itself do we do that, and then we marvel at the mystery of it all! Perhaps ‘paradox’ is a better word than mystery, for we have here a blatant conflict between two apparently self-evident ideas. They cannot both be true. We shall see that neither is true.