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Paul Davies is an internationally acclaimed physicist, writer and broadcaster, now based in South Australia. He obtained a Ph.D. from the University of London and has worked at the universities of London, Cambridge, Newcastle upon Tyne and Adelaide. He is currently Professor of Natural Philosophy at the Australian Centre for Astrobiology, Macquarie University, Sydney, and he holds a Visiting Professorship at Imperial College in London. His research interests are in the field of black holes, cosmology and quantum gravity. Professor Davies is the author of some twenty books, including, in Penguin, Superforce, Other Worlds, The Edge of Infinity, The Mind of God, The Cosmic Blueprint, Are We Alone?, About Time and The Fifth Miracle.

He is the recipient of a Glaxo Science Writers' Fellowship, an Advance Australia Award and a Eureka prize for his contributions to Australian science, and in 1995 he won the prestigious Templeton Prize for his work on the deeper meaning of science. The Mind of God won the 1992 Eureka book prize and was also shortlisted for the Rhône-Poulenc Science Book Prize, as was About Time in 1996.

Paul Davies

GOD AND THE NEW PHYSICS

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THE BEGINNING

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Acknowledgements

I should like to give special thanks to Dr. John Barrow of the University of Sussex, whose detailed comments have much improved the presentation of this book. The subject matter has also provoked some lively coffee-time discussions in my own department, and I have found conversation with Dr. Stephen Bedding, Mr. Kerry Hinton, Dr. J. Pfautsch, Dr. Stephen Unwin and Mr. William Walker very fruitful. I should also like to thank Mr Nicholas Denyer for drawing my attention to some factual errors in the original work.

The author and publishers wish to thank: Faber and Faber Ltd for permission to quote from ‘The Expanding Universe’ by Norman Nicholson in The Pot Geranium; Harvester Press Ltd for permission to quote from Gödel, Escher, Bach by D.R. Hofstadter and The Mind's I by D.R. Hofstadter and D.C. Dennett; Methuen London Ltd for permission to quote from Summa Theologiae, Vol I: Christian Theology by St Thomas Aquinas, edited by Thomas Gilby; Richard P. Feynman to quote from his book The Character of Physical Law; Pergamon Press Ltd for permission to quote from Sir Herman Bondi, ‘Religion is a good thing’ in Living Truths, edited by Ronald Duncan and Miranda Weston-Smith.

Preface

Over fifty years ago something strange happened in physical science. Bizarre and stunning new ideas about space and time, mind and matter, erupted among the scientific community. Only now are these ideas beginning to reach the general public. Concepts that have intrigued and inspired physicists themselves for two generations are at last gaining the attention of ordinary people, who never suspected that a major revolution in human thought had occurred. The new physics has come of age.

In the first quarter of this century two momentous theories were proposed: the theory of relativity and the quantum theory. From them sprang most of twentieth-century physics. But the new physics soon revealed more than simply a better model of the physical world. Physicists began to realize that their discoveries demanded a radical reformulation of the most fundamental aspects of reality. They learned to approach their subject in totally unexpected and novel ways that seemed to turn commonsense on its head and find closer accord with mysticism than materialism.

The fruits of this revolution are only now starting to be plucked by philosophers and theologians. Many ordinary people too, searching for a deeper meaning behind their lives, find their beliefs about the world very much in tune with the new physics. The physicist's outlook is even finding sympathy with psychologists and sociologists, especially those who advocate a holistic approach to their subjects.

In giving lectures and talks on modern physics I have discerned a growing feeling that fundamental physics is pointing the way to a new appreciation of man and his place in the universe. Deep questions of existence — How did the universe begin and how will it end? What is matter? What is life? What is mind? — are not new. What is new is that we may at last be on the verge of answering them. This astonishing prospect stems from some spectacular recent advances in physical science — not only the new physics, but its close relative, the new cosmology.

For the first time, a unified description of all creation could be within our grasp. No scientific problem is more fundamental or more daunting than the puzzle of how the universe came into being. Could this have happened without any supernatural input? Quantum physics seems to provide a loophole to the age-old assumption that ‘you can't get something for nothing’. Physicists are now talking about ‘the self-creating universe’: a cosmos that erupts into existence spontaneously, much as a subnuclear particle sometimes pops out of nowhere in certain high energy processes. The question of whether the details of this theory are right or wrong is not so very important. What matters is that it is now possible to conceive of a scientific explanation for all of creation. Has modern physics abolished God altogether?

This is not a book about religion. Rather, it is about the impact of the new physics on what were formerly religious issues. In particular, I make no attempt to discuss religious experiences or questions of morality. Nor is it a science book. It is a book about science and its wider implications. Inevitably, it is necessary here and there to explain some technicalities in careful detail, but I do not claim that the scientific discussions are either systematic or complete. The reader should not be deterred by the thought that he or she is in for some punishing mathematics or strings of specialist terminology. I have tried to avoid technical jargon as much as possible.

The book is primarily intended for the general reader, both aetheist and believer, with no previous knowledge of science. However, I hope that it also contains some material of real scholarly value. In particular, I do not believe that some of the very recent work on cosmology has previously come to the attention of philosophers and theologians.

The central theme of the book concerns what I call the Big Four questions of existence:

Towards the end of the book, tentative answers to these questions begin to emerge – answers based on the physicist's conception of nature. The answers may be totally wrong, but I believe that physics is uniquely placed to provide them. It may seem bizarre, but in my opinion science offers a surer path to God than religion. Right or wrong, the fact that science has actually advanced to the point where what were formerly religious questions can be seriously tackled, itself indicates the far-reaching consequences of the new physics.

Although I have endeavoured to exclude my own religious opinions throughout, my presentation of physics is inevitably a personal one. No doubt many of my colleagues would strongly disagree with the conclusions I attempt to draw. I respect their opinions. This is simply one man's perception of the universe; there are many others. My motivation for writing the book is that I am convinced there is more to the world than meets the eye.

The word ‘billion’ is used to mean one thousand million. Occasionally it is convenient to use the shorthand ‘powers of ten’ notation for very large or small numbers. For example, 10⁶ denotes one million, 10⁹ one billion, 10^–6 one millionth, 10^–9 one billionth.

1. Science and religion in a changing world

‘The wise man regulates his conduct by the theories both of religion and science.’

.B.S. Haldane

‘But because I have been enjoined, by this Holy Office, altogether to abandon the false opinion which maintains that the Sun is the centre and immovable, and forbidden to hold, defend, or teach, the said false doctrine in any manner… I abjure, curse, and detest the said errors and heresies, and generally every other error and sect contrary to the said Holy Church…’

Galileo Galilei

Science and religion represent two great systems of human thought. For the majority of people on our planet, religion is the predominant influence over the conduct of their affairs. When science impinges on their lives, it does so not at the intellectual level, but practically, through technology.

In spite of the power of religious thought in the daily lives of the general public, most of our institutions are organized pragmatically, with religion, insomuch as it is included at all, relegated to a stylized role. Such is the constitutional position of the Church of England for example. There are exceptions: Ireland and Israel remain religious states in the legal sense, while the revival of militant Islam is, if anything, increasing the influence of religion in political and social decision making.

In the industrialized world, where the impact and success of science is most conspicuous, there has been a sharp decline in affiliation to the major traditional religious institutions. In Britain, only a tiny percentage of the population now attend church regularly. It would be a mistake, however, to conclude that declining church attendance can be directly attributed to the raised profile of science and technology. In their personal lives many people still hold deep beliefs about the world that could be classed as religious, even though they may have rejected, or at least ignored, the traditional Christian doctrines. And any scientist will verify that, if religion has been displaced from people's consciousness, it has certainly not been replaced by rational scientific thought. For science, despite its great impact on all our lives at the practical level, is as elusive and inaccessible to the general public as any exclusive religion.

More relevant to the decline of religion is the fact that science, through technology, has altered our lives so radically that the traditional religions may appear to lack the immediacy necessary to provide any real assistance in coping with contemporary personal and social problems. If the Church is largely ignored today it is not because science has finally won its age-old battle with religion, but because it has so radically reoriented our society that the biblical perspective of the world now seems largely irrelevant. As one television cynic recently remarked, few of our neighbours possess an ox or an ass for us to covet.

The world's major religions, founded on received wisdom and dogma, are rooted in the past and do not cope easily with changing times. Hastily discovered flexibility has enabled Christianity to incorporate some new features of modern thought, to the extent that today's Church leaders might well have appeared heretical to a Victorian; yet any comprehensive philosophy based on ancient concepts faces a hard task in adapting to the space age. As a result, many disillusioned believers have turned to ‘fringe’ religions that seem more in tune with the era of Star Wars and microchips. The huge rise in popularity of cults associated with UFOs, ESP, spirit contacts, scientology, transcendental meditation and other technology-based beliefs testifies to the continued persuasiveness of faith and dogma in a superficially rational and scientific society. For although these eccentric ideas have a scientific veneer, they are unashamedly irrational — ‘cults of unreason’, to use Christopher Evans's phrase from his book of the same title (Panther 1974). People turn to them not for intellectual enlightenment but for spiritual comfort in a harsh and uncertain world.

Science, then, has invaded our lives, our language and our religions, but not at the intellectual level. The vast majority of people do not understand scientific principles, nor are they interested. Science remains a sort of witchcraft, its practitioners regarded with a mixture of awe and suspicion. Browse through any bookshop. Books on science are usually catalogued under ‘The Occult’, and modern astronomy textbooks jostle The Bermuda Triangle and Chariots of the Gods for space on the shelves. Lip service may be paid to the importance of science and rational thought for ordering our society, but at the personal level most people still find religious doctrine more persuasive than scientific arguments.

We live in a world that, in spite of appearances, is still fundamentally religious. Ranging from countries like Iran and Saudi Arabia, where Islam remains the dominant social force, to the industrialized West, where religion has fragmented and diversified, occasionally into vague pseudo-scientific superstition, the search for a deeper meaning to life continues. Nor should that search be derided. Scientists also are searching for a meaning: by finding out more about the way the universe is put together and how it works, about the nature of life and consciousness, they can supply the raw material from which religious beliefs may be fashioned. To argue whether the date of the Creation was 4004 B.C. or 10,000 B.C. is irrelevant if scientific measurements reveal a 4½ billion-year-old Earth. No religion that bases its beliefs on demonstrably incorrect assumptions can expect to survive very long.

In this book we shall be looking at some of the very latest discoveries in fundamental science, and exploring their implications for religion. In many cases the old religious ideas are not so much disproved as transcended by modern science. By looking at the world from a different angle, scientists can provide fresh insights and new perspectives of Man and his place in the universe.

Both science and religion have two faces: the intellectual and the social. In both cases the social effects leave a lot to be desired. Science may have alleviated the miseries of disease and drudgery and provided an array of gadgetry for our entertainment and convenience, but it has also spawned horrific weapons of mass destruction and seriously degraded the quality of life. The impact of science on industrial society has been a mixed blessing.

On the other hand, organized religion comes off, if anything, even worse. Nobody denies the many individual cases of selfless devotion by religious community workers all over the world, but religion long ago became institutionalized, often concerning itself more with power and politics than with good and evil. Religious zeal has all too frequently been channelled into violent conflict, perverting man's normal tolerance and unleashing barbaric cruelty. Christian genocide of the South American native populations in the Middle Ages is one of the more dreadful examples, but the history of Europe generally is littered with the corpses of those slain because of minor doctrinal differences. Even in this so-called enlightened age, religious hatred and conflict fester all over the world. It is ironical that although most religions extol the virtues of love, peace and humility, it is all too often hatred, war and arrogance that characterize the history of the world's great religious organizations.

Many scientists are critical of organized religions, not because of their personal spiritual content, but for their perverting influence on otherwise decent human behaviour, especially when they involve themselves in power politics. The physicist Hermann Bondi is a harsh critic of religion, which he regards as a ‘serious and habit-forming evil’. He cites as an example the excesses of the European witch-craze:

In much of Christian Europe the godfearing used to burn old women suspected of being witches, an arduous duty they felt had been clearly put upon them by the Bible. The facts on witch burning are clear enough: First, faith made otherwise decent people commit acts of unspeakable horror, showing how ordinary and everyday feelings of human kindness and revulsion at cruelty can be and have been overruled by religious belief. Secondly, it exposes as utterly hollow the claim that religion sets an absolute and unchanging foundation for morality.¹

Bondi claims that the ruthless power wielded by the Church and other religious institutions over the centuries leaves these organizations morally bankrupt.

Few would deny that religion remains, for all its pretentions, one of the most divisive forces in society. Whatever the good intentions of the faithful, the bloodstained history of religious conflict provides little evidence for universal standards of human morality among the major organized religions. Nor is there any reason to believe that love and consideration are lacking in those who do not belong to such organizations, or are even committed aetheists.

Of course, not all religious people are fanatical zealots. The vast majority of Christians today share a revulsion of religious conflict and deplore the Church's past involvement with torture, murder and suppression. But the outbreaks of spectacular violence and brutality in the name of God which still plague society today are not the only manifestations of the antisocial face of religion. Segregation in education and even habitation continues in supposedly civilized countries like Northern Ireland and Cyprus. Even within their own ranks, religious organizations often sanction prejudice, whether against women, racial minorities, homosexuals or whoever their leaders decree to be inferior. The status of women in Catholicism and Islam, or blacks in the South African Church, I find particularly offensive. Although many people would be appalled that their own religion might be described as vicious or intolerant, they will readily agree that the world's other religions have a lot to answer for.

This sad history of bigotry seems inevitably to result once religious organizations become institutionalized and constitutionalized, and has prompted a huge disaffection with established religion in the Western world. Many are turning instead to the so-called ‘fringe’ religions, in an attempt to find a less strident and more gentle route to spiritual fulfilment. There are, of course, a wide variety of new movements, some of which are still more intolerant and sinister than the traditional religions. But many emphasize the importance of mysticism and quiet inner exploration, as opposed to evangelical fervour, and so attract those people who are critical of the social and political impact of the established religions.

For the greater part of human history, men and women have turned to religion not only for moral guidance, but also for answers to the fundamental questions of existence. How was the universe created and how will it end? What is the origin of life and mankind? Only in the last few centuries has science begun to make its own contributions to such issues. The resulting clashes are well documented. From its origin with Galileo, Copernicus and Newton, through Darwin and Einstein, to the age of computers and high technology, modern science has cast a cold and sometimes threatening light on many deep-rooted religious beliefs. Accordingly, there has grown the feeling that science and religion are inherently incompatible and antagonistic. It is a belief encouraged by history. The early attempts by the Church to hold back the flood-gates of scientific advance have left a deep suspicion of religion among the scientific community. For their part, scientists have demolished a lot of cherished religious beliefs and have come to be regarded by many as faith-wreckers.

There is no doubt, however, about the success of the scientific method. Physics, the queen of sciences, has opened up vistas of human understanding that were unsuspected a few centuries ago. From the inner workings of the atom to the weird surrealism of the black hole, physics has enabled us to comprehend some of nature's darkest secrets and to gain control over many physical systems in our environment. The tremendous power of scientific reasoning is demonstrated daily in the many marvels of modern technology. It seems reasonable then, to have some confidence in the scientist's world-view also.

The scientist and the theologian approach the deep questions of existence from utterly different starting points. Science is based on careful observation and experiment enabling theories to be constructed which connect different experiences. Regularities in the workings of nature are sought which hopefully reveal the fundamental laws that govern the behaviour of matter and forces. Central to this approach is the willingness of the scientist to abandon a theory if evidence is produced against it. Although individual scientists may cling tenaciously to some cherished idea, the scientific community as a group is always ready to adopt a new approach. There are no shooting wars over scientific principles.

In contrast, religion is founded on revelation and received wisdom. Religious dogma that claims to contain an unalterable Truth can hardly be modified to fit changing ideas. The true believer must stand by his faith whatever the apparent evidence against it. This ‘Truth’ is said to be communicated directly to the believer, rather than through the filtering and refining process of collective investigation. The trouble about revealed ‘Truth’ is that it is liable to be wrong, and even if it is right other people require a good reason to share the recipients' belief.

Many scientists are derisory about revealed truth. Indeed, some maintain it is a positive evil:

Generally the state of mind of a believer in a revelation is the awful arrogance of saying ‘I know, and those who do not agree with my belief are wrong’. In no other field is such arrogance so widespread, in no other field do people feel so utterly certain of their ‘knowledge’. It is to me quite disgusting that anybody should feel so superior, so selected and chosen against all the many who differ in their beliefs or unbeliefs. This would be bad enough, but so many believers do their best to propagate their faith, at the very least to their children but often also to others (and historically there are of course plenty of examples of doing this by force and ruthless brutality). The fact that stares one in the face is that people of the greatest sincerity and of all levels of intelligence differ and have always differed in their religious beliefs. Since at most one faith can be true, it follows that human beings are extremely liable to believe firmly and honestly in something untrue in the field of revealed religion. One would have expected this obvious fact to lead to some humility, to some thought that however deep one's faith, one may conceivably be mistaken. Nothing is further from the believer, any believer, than this elementary humility. All in his power (which nowadays in a developed country tends to be confined to his children) must have his faith rammed down their throats. In many cases children are indeed indoctrinated with the disgraceful thought that they belong to the one group with superior knowledge who alone have a private wire to the office of the Almighty, all others being less fortunate than they themselves.²

Nevertheless, those who have had religious experiences invariably regard their own personal revelation as a sounder basis for belief than any number of scientific experiments. Indeed, many professional scientists are also deeply religious and apparently have little intellectual difficulty in allowing the two sides of their philosophy to peacefully coexist. The problem is how to translate many disparate religious experiences into a coherent religious world-view. Christian cosmology, for example, has differed radically from Oriental cosmology. At least one must be wrong.

It is a great mistake, however, to infer from the scientist’s suspicion of revealed truth that he is necessarily a cold, hard, calculating soulless individual, interested only in facts and figures. Indeed, the rise of the new physics has been accompanied by a tremendous growth of interest concerning the deeper philosophical implications of science. It is a lesser-known side of scientific endeavour, and it frequently comes as a complete surprise. The pathologist, writer and television producer Kit Pedlar describes his astonishment, while planning a television series on mind and the paranormal, at coming across the concern that modern physicists have for broader issues:

For almost twenty years I occupied my research time as a happy biological reductionist believing that my painstaking research would eventually reveal ultimate truths. Then I began to read the new physics. The experience was shattering.

As a biologist I had imagined the physicists to be cool, clear, unemotional men and women who looked down on nature from a clinical, detached viewpoint — people who reduced a sunset to wavelengths and frequencies, and observers who shredded the complex of the universe into rigid and formal elements.

My error was enormous. I began to study the works of people with legendary names: Einstein, Bohr, Schrödinger and Dirac. I found that here were not clinical and detached men, but poetic and religious ones who imagined such unfamiliar immensities as to make what I have referred to as the ‘paranormal' almost pedestrian by comparison.³

It is ironical that physics, which has led the way for all other sciences, is now moving towards a more accommodating view of mind, while the life sciences, following the path of last century's physics, are trying to abolish mind altogether. The psychologist Harold Morowitz has remarked on this curious reversal:

What has happened is that biologists, who once postulated a privileged role for the human mind in nature's hierarchy, have been moving relentlessly toward the hard-core materialism that characterized nineteenth-century physics. At the same time, physicists, faced with compelling experimental evidence, have been moving away from strictly mechanical models of the universe to a view that sees the mind as playing an integral role in all physical events. It is as if the two disciplines were on fast-moving trains, going in opposite directions and not noticing what is happening across the tracks.⁴

In the coming chapters we shall see how the new physics has given ‘the observer’ a central role in the nature of physical reality. A growing number of people believe that recent advances in fundamental science are more likely to reveal the deeper meaning of existence than appeal to traditional religion. In any case, religion cannot afford to ignore these advances.

2. Genesis

‘In the beginning God created the heaven and the earth.’

Genesis 1: 1

‘But no one was there to see it.’

Steven Weinberg in The First Three Minutes

Was there a creation? If so, when did it occur and what caused it? Nothing is more profound or more baffling than the riddle of exis-tence. Most religions have something to say about how things got started; so does modern science. In this book I shall address the enigma of genesis in the light of recent cosmological discoveries. This chapter deals with the origin of the universe as a whole. Some people have used the word ‘universe’ to mean the solar system or the Milky Way galaxy. I shall use it in the more conventional sense of ‘every physical thing that exists’, by which I mean all matter distributed among and between all the galaxies, all forms of energy, all non-material things such as black holes and gravity waves, and all of space as well, stretching (if indeed it does) right out to infinity. Sometimes I shall use ‘world’ to mean the same thing.

Any system of thought that claims to provide an understanding of the physical world must make some statement about the origin of the world. At its most basic, the choice is stark. Either the universe has always existed (in one form or another) or it began, more or less abruptly, at some particular moment in the past. Both alternatives have long been a source of perplexity to theologians, philosophers and scientists, and both present obvious difficulties for the layman.

If the universe had no origin in time — if it has always existed — then it is of infinite age. The concept of infinity leaves many people reeling. If there has been an infinite number of events already, why do we find ourselves living now? Did the universe remain quiescent for all of eternity only to spring into action relatively recently, or has there been some activity going on for ever and ever? On the other hand, if the universe began, that means accepting it appeared suddenly out of nothing. This seems to imply that there was a first event. If so, what caused it? Is such a question even meaningful?

Many thinkers baulk at these issues, and turn instead to the scientific evidence. What can science tell us about the origin of the universe?

These days most cosmologists and astronomers back the theory that there was indeed a creation, about eighteen billion years ago, when the physical universe burst into existence in an awesome explosion popularly known as the ‘big bang’. There are many strands of evidence to support this astonishing theory. Whether one accepts all the details or not, the essential hypothesis – that there was some sort of creation – seems, from the scientific point of view, compelling. The reason stems directly from a large body of scientific evidence that is encompassed by the most universal law of physics known – the second law of thermodynamics. In its widest sense this law states that every day the universe becomes more and more disordered. There is a sort of gradual but inexorable descent into chaos. Examples of the second law are found everywhere: buildings fall down, people grow old, mountains and shorelines are eroded, natural resources are depleted.

If all natural activity produces more disorder (measured in some appropriate way) then the world must change irreversibly, for to restore the universe to yesterday's condition would mean somehow reducing the disorder to its previous level, which contradicts the second law. Yet at first sight there seem to be many counter-examples of this law. New buildings are erected. New structures grow. Isn't every new-born baby an example of order arising out of disorder?

In these cases you have to be sure you are looking at the total system, not merely the subject of interest. The concentration of order in one region of the universe is always paid for by increasing disorder somewhere else. Take the construction of a new building, for example. The materials used inevitably deplete the world's resources, while the energy expended in the building process is also lost irretrievably. When a full balance sheet is drawn up, disorder always wins.

Physicists have invented a mathematical quantity called entropy to quantify disorder, and many careful experiments verify that the total entropy in a system never decreases. If the system is isolated from its surroundings, any changes that occur within it will remorselessly drive up the entropy until it can go no higher. After that there will be no further change: the system will have reached a condition of thermodynamic equilibrium. A box containing a mixture of chemicals provides a good example. The chemicals will react, some heat may be produced, the constituent substances will alter their molecular form and so on. All these changes increase the entropy inside the box. Eventually, the contents settle down at a uniform temperature in their final chemical form and nothing further happens. To return the contents to their former state is not impossible, but it would mean opening the box and expending energy and materials to reverse the changes that had occurred. This manipulation would produce more than enough entropy to offset the entropy reduction within the box.

If the universe has a finite stock of order, and is changing irreversibly towards disorder — ultimately to thermodynamic equilibrium — two very deep inferences follow immediately. The first is that the universe will eventually die, wallowing, as it were, in its own entropy. This is known among physicists as the ‘heat death’ of the universe. The second is that the universe cannot have existed for ever, otherwise it would have reached its equilibrium end state an infinite time ago. Conclusion: the universe did not always exist.

We see the second law of thermodynamics at work in all the familiar systems around us. The Earth, for example, cannot have existed for ever, or its core would have cooled down. From radioactivity studies the Earth can be dated to about 4½ billion years, which is similar to the age of the moon and of various meteorites.

As far as the sun is concerned, it clearly cannot continue burning away merrily ad infinitum. Year by year its fuel reserves decline, so that eventually it will cool and dim. By the same token its fires must have been ignited only a finite time ago: it does not have unlimited sources of energy. Estimates place the age of the sun at a little greater than that of the Earth, which accords well with current astronomical theories that the solar system formed together as a single unit. Nevertheless, the solar system is only a minute component of the universe, and it would be rash to draw sweeping conclusions from considerations of the Earth and sun alone. The sun, however, is a typical star, and our galaxy alone contains many billions of other stars whose life cycles can be studied by astronomers. Stars exist that have reached various stages in their evolution, enabling us to build up a detailed picture of stellar birth, life and death.

Stars form, along with planets, as a result of the gradual contraction and fragmentation of huge, tenuous clouds of inter-stellar gas which consist mainly of hydrogen. Today it is easy to find regions of the galaxy where starbirth is taking place. One of these, the Great Nebula in Orion, is visible to the naked eye. The stars were not simply made once and for all. Our sun, for example, at about five billion years old, is at most only half the age of the oldest stars in the galaxy. The formation of the solar system would have been just one further product of a continuing process that has occurred hundreds of billions of times in the Milky Way alone, and will continue in the future. Thus, as far as the formation of stars and planets are concerned, there was no real creation as such at all, merely a sort of cosmic assembly line steadily turning the raw material — hydrogen, helium, and a minute fraction of heavier elements — into stars and planets.

Given that stars are continually burning out while others are being formed to replace them, might this cycle of birth and death have continued endlessly? Alas, no, as the second law of thermodynamics assures us. The material of burnt-out stars can never be fully recycled. The energy needed dissipates away into space in the form of starlight radiated over the aeons. Some of the star stuff is lost irretrievably down black holes.

There is, however, a more direct reason for believing that the entire cosmic system has not been recycling away for all eternity. Isaac Newton, one of the founders of modern science, established that gravity is a universal force, acting between all material bodies in the cosmos: every star, every galaxy, pulls on every other with a gravitational force. Because astronomical bodies float freely in space there seems to be no reason why they do not fall together as a result of this ubiquitous gravitational attraction. In the solar system, gravitational collapse of the planets on to the sun is avoided by centrifugal effects: the planets are revolving around the sun. Likewise the galaxy is rotating. But there is no evidence that the universe as a whole is rotating. Clearly the galaxies can't just hang there for ever. So the universe cannot always have enjoyed its present arrangement.

Although this cosmic conundrum had been appreciated since the time of Newton, it was not until the 1920s that the resolution was discovered. The American astronomer Edwin Hubble found that the galaxies are not falling together because they are rushing apart instead. Hubble noticed that galactic light is slightly distorted in colour (‘red shifted’ to use the jargon), a circumstance that suggests rapid recession. The reason is that light consists of waves, so a moving light source can stretch or shrink the waves, just as a moving vehicle stretches or shrinks the sound waves it emits. The tone of a car engine, or the whistle of a train, drops dramatically in pitch as it rushes by. In the case of light, read ‘colour’ for ‘pitch’ and you have the Hubble red shift. The speeds involved, however, are vastly greater. Distant galaxies recede at many thousands of miles per second.

Hubble's discovery is sometimes misinterpreted to mean that our galaxy is at the centre of this headlong rush, with all the other galaxies flying directly away from us. That is quite wrong. Because the distant galaxies recede faster than the nearby ones, the gaps between the galaxies also expand, so in fact every galaxy is moving away from every other one. This is the famous ‘expanding universe’. The pattern of galactic dispersal would appear very much the same from wherever in the cosmos you looked.

The expanding universe accords very well with modern thinking on the nature of space, time and motion. Albert Einstein, who carries the same status in the scientific community as St. Paul does among Christians, revolutionized our conception of these matters with his mind-bending theory of relativity. Although it has taken sixty years for Einstein's spacewarps and timewarps to impinge on the popular imagination, physicists have long accepted his ideas of curved space-time as an explanation of gravity.

The force of gravity powers all large-scale cosmic phenomena. In objects of astronomical size, gravity far outweighs all other forces such as magnetism or electricity. It shapes the galaxies and controls the intergalactic motions. When it comes to explaining the expanding universe, gravity is the key.

Einstein argued convincingly that gravity stretches or distorts space and time, and the idea can be checked directly by watching the sun's gravity bend starbeams that graze its surface. The sky behind the sun appears from Earth to be slightly, but distinctly, bent. The elasticity of time can also be demonstrated, most directly by flying clocks in space. Time runs faster in the gravity-free environment up there than it does on the Earth's surface.

If the sun can stretch space so can the galaxy, which is made of many suns. So rather than thinking of the galaxies as moving apart through space, astronomers prefer to think of the space between the galaxies as stretching. If intergalactic space is being ‘inflated’, then each day every galaxy will find itself with more and more elbow room. In that way the universe expands, without having to expand into some external void.

Setting aside for now the concepts of elastic space and time, which many people find hard to understand, it is plainly obvious that a universe which is growing bigger must have been smaller in the past. If the present expansion rate had been maintained throughout history, then twenty or thirty billion years ago the whole observable universe would have been shrivelled up into an unrecognizable blob with no identifiable astronomical bodies at all. In fact, astronomers have discovered that the expansion rate is decellerating somewhat, so this highly compressed condition in fact occurred rather more recently, perhaps fifteen or twenty billion years ago. (Compare the sun's age of five billion years.) Because the expansion rate was much higher then, the early stages of the galactic dispersal resembled an outburst rather than a slow expansion.

It is sometimes said that the universe as we now know it was created by the explosion of a sort of primeval ‘egg’, the galaxies being fragments of the explosion that are still hurtling through space. It is a picture that captures some correct features but it can also be misleading. The thing that exploded was shrunken because space was shrunken. It is wrong to think in terms of an ‘egg’ surrounded by a void. An egg has a surface and a middle. Astronomers believe, however, that there is no edge or surface to the universe, and no privileged centre.

We are tangling here with the delicate subject of infinity. It is a topic full of pitfalls for the unwary. In view of its importance not only for the expanding universe, but for the broader issues of science and religion, it is worth a short digression at this stage.

Scientists have long recognized the need to base all their considerations of infinity on precisely formulated mathematical steps, for measuring the infinite can produce all sorts of paradoxes. Consider, for example the famous ‘hare and tortoise’ paradox due to Zeno of Elea (fifth century B.C.) In a race, the tortoise has a head start, but the hare, running faster, soon overtakes him. Clearly, at every moment of the race the hare is at a place and the tortoise is at a place. As both have been running for the same length of time — for an equal number of moments — then presumably they have passed through an equal number of places. But for the hare to overtake the tortoise he must cover a greater distance in the same time, and so pass through a greater number of places than the tortoise. How then can the hare ever overtake the tortoise?

The resolution of this paradox (one of several due to Zeno) involves a proper formulation of the concept of infinity. If time and space are infinitely divisible then both the hare and the tortoise run for an infinity of moments through an infinity of places. The essential feature of infinity here is that a part of infinity is as big as the whole. Although the tortoise's journey is shorter in distance than the hare's, he still covers as many places as the hare (i.e. infinity) — even though we know the hare passes through all the same places as the tortoise, and more!

Many surprises of this sort emerge from a study of the infinite, and it has taken mathematicians centuries of logical construction to fully comprehend the rules for the proper manipulation of infinity. An odd feature is that there exists more than one sort of infinity. There is the infinity of things that can be labelled by whole numbers (1, 2, 3… without end) and a bigger infinity for which even the whole numbers in their entirety are inadequate.

1 The irregular perimeter in this figure is constructed by raising equilateral triangles on the sides of larger triangles in a sequence of steps. The third step is shown in the figure. As the number of steps increases, so the perimeter becomes longer and more ‘spikey’. The length of the perimeter grows without limit as the number of steps is increased indefinitely, but the perimeter never protrudes outside the enclosing circle. The area enclosed by the irregular perimeter is therefore finite, even though the length of the perimeter approaches infinity in the limit of an infinite number of steps.

When it comes to geometry, intuition can lead you badly astray. Consider for example the length of a fence that surrounds a field of given area. It is easy to see that a long thin field requires more fence for a given area than a square field. A round field uses the minimum length offence. But just how long can the perimeter of a field become? Figure 1 shows a rather eccentrically shaped perimeter consisting of triangles built upon triangles in a sequence of steps. With each step the perimeter fence gets longer, and the area enclosed increases a bit. But the perimeter will never protrude beyond the enclosing circle, so the area will always remain finite, yet the perimeter can grow without limit as the number of additional triangular wedges is increased. It is thus possible to conceive of an infinitely long fence enclosing a finite area of field (see Fig. 1).

What has all this got to do with the creation of the universe? First, it illustrates that ideas like ‘infinity’ should not be used sloppily or they are likely to produce nonsense. Secondly, it demonstrates that the results obtained often run counter to common sense and intuition. This is one of the great lessons of science. It is often necessary to resort to the abstract — to formal mathematical manipulations — to make sense of the world. Ordinary experience alone can be an unreliable guide.

Is the universe infinite in size? If space has an infinite volume we can envisage an infinity of galaxies populating it with roughly uniform density. Many people then worry about how something that is infinite can expand. What is there for it to expand into? There is no problem: infinity can be boosted in magnitude and still remain the same size. (Remember what the ‘tortoise taught us’.) But visualization problems set in when we wind this model backwards to the ‘cosmic egg’ phase. If the galaxies are everywhere, there could never have been a finite egg, with a surface beyond which there was no matter. So eggs are out.

Imagine, in such an infinite universe, a huge sphere enclosing an enormous volume of space containing many galaxies. Now picture space everywhere rapidly shrinking, like Alice in Wonderland after eating the magic cake. The sphere contracts to a smaller and smaller radius; but however shrunken it becomes there is still unending space and an infinity of galaxies outside it. If the sphere shrinks to literally nothing, then we have the mathematically delicate problem of an infinite universe which is infinitely shrunken. There is still no centre or edge, but the contents of any sphere, however large it started out, would be crushed together into a single point. Astronomers believe that it was from such an infinitely shrunken, yet unbounded, state that the universe exploded.

There is, in fact, another possible model for the universe that avoids the competition of infinities; it was proposed by Einstein himself in 1917. Based on the fact that space can bend, Einstein argued that space can connect up to itself in a variety of unexpected ways. The curved surface of the Earth can be used as an analogy. The Earth's surface is finite in area, but unbounded: nowhere does a traveller meet an edge or boundary. Similarly space could be finite in volume, but without any edge or boundary. Few people can really envisage such a monstrosity, but mathematics can take care of the details for us. The shape is called a hypersphere. If the universe is a hypersphere an astronaut could, in principle, circumnavigate it like a cosmic Magellan by always pointing his rocket in the same direction until he returned to his starting point.

Although it is finite, Einstein's hyperspherical cosmos still has no centre or edge (just as the surface of the Earth has no centre or edge), so when shrunken it does not resemble a cosmic egg either. One can imagine the hypersphere shrivelling away to nothing, its volume vanishing, analogous to the surface of a sphere being shrunk to zero radius (see Fig. 2).