Julian Barbour - The End of Time - The Next Revolution in Physics

Strange as a timeless theory may seem, it has the potential to be very powerful. Boltzmann’s work highlighted two difficulties inherent in any theory of time – initial conditions must be imposed arbitrarily; and dull, unstructured situations are far more probable than the interesting structured things we find all around us. Interestingly structured Nows are an extreme rarity among all the Nows that can be. If the mist does pick out time capsules in Platonia, it must be very selective. Since all possible structures are present in Platonia, the vast majority of Nows do not contain any structures at all that could be called records. Even then, the apparent records will be mutually consistent in only a tiny fraction of what is already a tiny fraction. Only our habitual exposure to the time capsules we experience blinds us to the magnitude of the phenomenon that needs to be explained. Stars in real space give us only an inkling of how thinly time capsules are spread. Any scheme that does select them will be very powerful. But more than that, it will be more fully rational than classical physics, with its need to invoke a very special initial condition, can ever be. Once the law that governs the distribution of the mist over Platonia has been specified, nothing more remains to be done. The mist gathers where it does for only two reasons: the structure of the law and the structure of Platonia.

So where is the mist likely to gather? The mathematics needed to answer this question will certainly be difficult, but there are some hints (which I shall elaborate in the final chapters). They suggest that mist is likely to be distributed along thin, gossamer-like filaments that bifurcate and form a tree-like structure (Figure 6).

A tendency to bifurcation is deeply rooted in quantum mechanics. In principle, it could happen in both directions along a filament. However, the Nows we experience all seem to have arisen from a unique past. There seems to be no branching in that direction. Within quantum mechanics, as presently formulated in space and time, this fact is not impossible, but it is as puzzling as the low entropy that so exercised Boltzmann. It does seem improbable. I suspect that everything will look different if we learn to think about quantum mechanics in Platonia. For one thing, the arena has a very different shape. This is why I was keen to show you at this early stage the diagrams of Triangle Land (Figures 3 and 4) and my representation of Platonia (Figure 5). It opens out in one direction from nothing. I suspect that the branching filaments of mist in Figure 6 arise because they reflect this overall, flower-like structure of Platonia. If that is so, the great asymmetries of our existence – past and future, birth and death – arise from a deep asymmetry in being itself. The land of possible things has one absolute end, where it abuts onto mere nothing, but it is unbounded the other way, for there is no limit to the richness of being.

Who knows what experiences are possible in the oases of richly structured Nows strung out along the trade routes that cross the deserts of Platonia? The plurality of experience is remarkable and suggestive. In any instant, we are aware of many things at once. Through memories we are, as it were, present simultaneously in many different Nows in Platonia. Richness of structure permits this. One grand structure contains substructures that are ‘pictures’ – simplified representations that capture the essential features – of other structures. Our memories are pictures of other Nows within this Now, rather like snapshots in an album. Each Now is separate and a world unto itself, but the richly structured Nows ‘know’ about one another because they literally contain one another in certain essential respects. As consciousness surveys many things at once in one Now, it is simultaneously present, at least in part, in other Nows. This awareness of many things in one could well exist in a much more pronounced form in other places in Platonia.

Figure 6.The conjectured filamentary distribution of mist in Platonia. The instant you experience now is marked NOW. To its left lie Nows of which you have memories in NOW. There is no bifurcation in this direction, matching our conviction that we have a unique past. In the other direction there is a branching into different alternative ‘futures’ of NOW. In all of them, you think you have advanced into the future by the same amount from NOW. These different filaments are ‘parallel worlds’ that seem to have a common past, to which NOW belongs. Note that the filaments have a finite width, unlike a Newtonian string of successive instants. All around NOW, along the filament and to either side of it, are other Nows with slightly different versions of yourself. All such Nows are ‘other worlds’ in which there exist somewhat different but still recognizable versions of yourself. In other filaments are worlds you would not recognize at all.

The picture of ourselves dividing into parallel Nows may be unsettling, but the phenomenon itself is familiar. We are used to being in different Nows and being slightly different in all of them – that is simply the effect of time as it is usually conceived. The account of Lucy’s leaps emphasized that the differences in ourselves between Nows are far greater than we realize within consciousness. Huge numbers of microscopically different Nows could give identical conscious experience. As we shall see, quantum mechanics forces us to consider Nows everywhere, not just those on one path. It unsettles by division, seeming to threaten dissolution and personal integrity. But it simultaneously binds us into the far mightier whole of everything that can be, doing so much more decisively than any Newtonian scheme can do. For the Nows that are likely to be experienced are the ones that are most sensitive to the whole of Platonia.

I think this is sufficient introduction. I could go on to talk about free will, the future, our place in the universe, religion, and so on. If the theory is correct, it must change the way we think about these things. However, without some real understanding of the arguments for a timeless universe, I feel further discussion would lack a solid basis. I therefore postpone these issues to later in the book, especially the epilogue. My aim so far has been to outline the scheme and to show that it is truly timeless and at least logically possible.

First Outline(p. 36) The philosopher best known for questioning the existence of time and its flow was John McTaggart, who is often quoted for his espousal of the ‘unreality’ of time and the denial of transience. The following argument of his is very characteristic of professional philosophers:

Past, present, and future are incompatible determinations. Every event must be one or the other, but no event can be more than one. If I say that any event is past, that implies that it is neither present nor future, and so with the others. And this exclusiveness is essential to change, and therefore to time. For the only change we can get is from future to present, and from present to past.

The characteristics, therefore, are incompatible. But every event has them all. if [an event] is past, it has been present and future. If it is future, it will be present and past. If it is present, it has been future and will be past. Thus all the three characteristics belong to each event. How is this consistent with their being incompatible? (McTaggart 1927, Vol. 2, p. 20)

Some thoughts here certainly match my own thinking, especially that ‘exclusiveness is essential to change’, but McTaggart’s arguments are purely logical and make no appeal to physics. Abner Shimony (1997)—to whom I am indebted for several discussions—compares McTaggart’s position with mine, but I think he has not quite understood my notion of time capsules, so I do not feel that his arguments force me to accept transience.