I believe that the basic elements of this potential revolution – the reasons for it and its likely outcome – can already be discerned. In fact, as we shall shortly see, clear hints that time may not exist, and that quantum gravity – the unification of general relativity and quantum mechanics – will yield a static picture of the quantum universe, started to emerge about thirty years ago, but made remarkably little impact. This is one of my reasons for writing this book: these things should be better known. They are only just beginning to be mentioned in books for the general reader, and even most working physicists know little or nothing about them.
No doubt many people will dismiss the suggestion that time may not exist as nonsense. I am not denying the powerful phenomenon we call time. But is it what it seems to be? After all, the Earth seems to be flat. I believe the true phenomenon is so different that, presented to you as I think it is without any mention of the word ‘time’, it would not occur to you to call it that.
If time is removed from the foundations of physics, we shall not all suddenly feel that the flow of time has ceased. On the contrary, new timeless principles will explain why we do feel that time flows. The pattern of the first great revolution will be repeated. Copernicus, Galileo and Kepler taught us that the Earth moves and rotates while the heavens stand still, but this did not change by one iota our direct perception that the heavens do move and that the Earth does not budge. Our grasp of the interconnection of things was, however, eventually changed out of recognition in ways that were impossible to foresee. Now I think we must, in an ironic twist to the Copernican revolution, go further, to a deeper reality in which nothing at all, neither heavens nor Earth, moves. Stillness reigns.
People often ask me what are the implications of the non-existence of time. What will it mean for everyday life? I think we cannot say. Copernicus had no inkling of what Newton (let alone Einstein) would find, though it all flowed from his revolution. But we can be certain that our ideas about time, causality and origins will be transformed. At the personal level, thinking about these things has persuaded me that we should cherish the present. That certainly exists, and is perhaps even more wonderful than we realize. Carpe diem – seize the day. I expand on this in the Epilogue.
This book revolves around three questions: What is time? What is change? What is the plan of the universe? The only way to answer them is to examine the structure of our most successful theories. We must fathom the architecture of nature. What part, if any, is played by time in these theories? Can we identify the ultimate arena of the world?
These questions were forced upon physicists by the work I mentioned in the Preface. It is one of the two big (and almost certainly intimately connected) mysteries of modern physics (Box 2). Both are aspects of an as yet unbridged chasm between classical and quantum physics.
BOX 2 The Two Big Mysteries
As explained in Box 1, physicists currently describe the world by means of two very different theories. Large things are described by classical physics, small things by quantum physics. There are two problems with this picture.
First, general relativity, Einstein’s theory of gravity, seems to be incompatible with the principles of quantum mechanics in a way that Newtonian dynamics and the theory of electromagnetism, developed by Michael Faraday and James Clerk Maxwell in the nineteenth century, are not. For these theories, it proved possible to transform them, by a process known as quantization, from classical into quantum theories. Attempts to apply the same process to general relativity and create quantum gravity failed. It was this technical work, by Dirac and others, which brought to the fore all the problems about time with which this book is concerned.
The second mystery is the relationship between quantum and classical physics. It seems that quantum physics is more fundamental and ought to apply to large objects, even the universe. There ought to be a quantum theory of the universe: quantum cosmology. But quantum physics does not yet exist in such a form. And its present form is very mysterious. Part of it seems to describe the actual behaviour of atoms, molecules and radiation, but another part consists of rather strange rules that act at the interface between the microscopic and macroscopic worlds. Indeed, the very existence of a seemingly unique universe is a great puzzle within the framework of quantum mechanics. This is very unsatisfactory, since physicists have a deep faith in the unity of nature. Because general relativity is simultaneously a theory of gravity and the large-scale structure of the universe, the creation of quantum cosmology will certainly require the solution of the only slightly narrower problem of quantum gravity.
One of the themes of my book is that this chasm has arisen because physicists have deep-rooted but false ideas about the nature of space, time and things. Preconceptions obscure the true nature of the world. Physicists are using too many concepts. They assume that there are many things, and that these things move in a great invisible framework of space and time.
A radical alternative put forward by Newton’s rival Leibniz provides my central idea. The world is to be understood, not in the dualistic terms of atoms (things of one kind) that move in the framework and container of space and time (another quite different kind of thing), but in terms of more fundamental entities that fuse space and matter into the single notion of a possible arrangement, or configuration, of the entire universe. Such configurations, which can be fabulously richly structured, are the ultimate things. There are infinitely many of them; they are all different instances of a common principle of construction; and they are all, in my view, the different instants of time. In fact, many people who have written about time have conceived of instants of time in a somewhat similar way, and have called them ‘nows’. Since I make the concept more precise and put it at the heart of my theory of time, I shall call them Nows. The world is made of Nows.
Space and time in their previous role as the stage of the world are redundant. There is no container. The world does not contain things, it is things. These things are Nows that, so to speak, hover in nothing. Newtonian physics, Einstein’s relativity and quantum mechanics will all be seen to do different things with the Nows. They arrange them in different ways. What is more, the rules that govern the universe as a whole leave imprints on what we find around us. These local imprints, which physicists take as the fundamental laws of nature, reveal few hints of their origin in a deeper scheme of things. The attempt to understand the universe as a whole by ‘stringing together’ these local imprints without a grasp of their origin must give a false picture. It will be the flat Earth writ large. My aim is to show how the local imprints can arise from a deeper reality, how a theory of time emerges from timelessness. The task is not to study time, but to show how nature creates the impression of time.
It is an ambitious task. How can a static universe appear so dynamic? How is it possible to watch the flashing colours of the kingfisher in flight and say there is no motion? If you read to the end, you will find that I do propose an answer. I make no claim that it is definitely right – choices must be made, and many physicists would not make mine. If all were clear, I should not have promised a but the theory of time. In order not to interrupt the flow of the text, I make few references to the problems in my timeless description of the world. Instead, I have collected together all those of which I am aware in the Notes. Although, as will be evident throughout the book, I do believe rather strongly in the theory I propose, there is a sense in which even clear disproof of my theory would be exciting for me. The problems of time are very deep. Clear proof that I am wrong would certainly mark a significant advance in our understanding of time. In a way, I cannot lose! Whatever the outcome, I shall be more than happy if this book gives you a novel way of thinking about time, exposes you to some of the mysteries of the universe, and encourages even one reader to embark, as I did 35 years ago, on a study of time.