About Time: Einstein's Unfinished Revolution

Front Cover
Simon and Schuster, Apr 9, 1996 - Science - 316 pages
The traditional association between time and creation is at the heart of science, cosmology, and religion. When scientists began to explore the implications of Einstein's time for the universe as a whole, they discovered that time is elastic, and can be warped by rapid motion or gravitation, that time cannot be meaningfully divided into past, present, and future, nor does time flow in the popular sense. And they made one of the most important discoveries in the history of human thought: that time, and hence all of physical reality, must have had a definite origin in the past. There can be both a beginning and an end to time. But important though Einstein's theory of time turned out to be, it still did not solve "the riddle of time, " and the search for a deeper understanding of time and its relationship with the rest of the physical universe remains at the top of the scientific agenda. From black holes, where time stands still, to the bizarre world of quantum physics, where time vanishes completely, Professor Davies finds evidence that our current theories of time simply don't add up. Why, for instance, does the universe appear younger than some of the objects within it? And how does the concept of time emerge from the timeless chaos of the big bang? Is the passage of time merely an illusion? Can time run backwards? Is time travel possible?
 

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ABOUT TIME: Einstein's Unfinished Revolution

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A prolific popularizer of science, Davies (Physics/Univ. of Adelaide, Australia; The Matter Myth, 1992, etc.) gives a broad survey of concepts of time, a subject he has become intimately acquainted ... Read full review

About time: Einstein's unfinished revolution

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Ever since the huge commercial success of Stephen Hawking's A Brief History of Time (LJ 4/15/88), publishers have brought forth dozens of books examining the physical and theoretical foundations of ... Read full review

Contents

Preface
11
Profogue
21
Time for a Change
44
Timewarps
78
Black Holes Gateways to the EntcI of Time
104
The Beginning of Time When Exacrly Was It?
126
Einsteins Greatest Triumph?
146
Quantum Time
163
The Arrow of Time
196
Backwards in Time
219
Time Travel Fact or Fantasy?
233
But What Time Is It Now?
252
Experimenting with Time
265
The Unfinished Revolution
279
Notes
287
Bibliography
293

Imaginary Time
183

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About the author (1996)

CHAPTER 1

A VERY BRIEF HISTORY OF TIME

Time is at the heart of all that is important to human beings.

Bernard d''Espagnat

WHOSE TIME IS IT ANYWAY?

Time must never be thought of as pre-existing in any sense; it is a manufactured quantity.

Hermann Bondi

In a dingy laboratory in Bonn lies a submarine-shaped metal cylinder. It is about three meters long, and rests comfortably in a steel frame surrounded by wires, pipes and dials. At first glance, the entire contraption looks like the inside of a giant car engine. In fact, it is a clock -- or, rather, the clock. The Bonn device, and a network of similar instruments across the world, together constitute "the standard clock." The individual instruments, of which the German model is currently the most accurate, are cesium-beam atomic clocks. They are continually monitored, compared, tweaked and refined via radio signals from satellites and television stations, to cajole them into near-perfect step. At the International Bureau of Weights and Measures at Sèvres, not far from Paris, the data are collected, analyzed and broadcast to a time-obsessed world. Thus originates the famous pips, the radio time signals by which we set our watches.

So, as we go about our daily toil, the Bonn cesium-beam clock keeps the time. It is, so to speak, a custodian of Earth time. The trouble is, the Earth itself doesn''t always keep good time. Occasionally our clocks, all supposedly linked to the master system in France like a retinue of obedient slaves, must be adjusted by a second to track changes in the Earth''s rotation rate. The last such "leap second" was added on 30 June 1994. The planet''s spin, accurate enough to serve as a perfectly suitable clock for a thousand generations, is now defunct as a reliable chronometer. In this age of high-precision timekeeping, poor old Earth doesn''t make the grade. Only an atomic clock, man-made and mysterious, serves to deliver those all-important tick-tocks with the precision demanded by navigators, astronomers and airline pilots. One second is no longer defined to be 1/86,400 of a day: it is 9,192,631,770 beats of a cesium atom.

But whose time is the Bonn clock telling anyway? Your time? My time? God''s time? Are the scientists in that cluttered laboratory monitoring the pulse of the universe, fastidiously tracking some abstract cosmic time with atomic fidelity? Might there be another clock, perhaps on another planet somewhere, faithfully ticking out another time altogether, to the joy of its makers?

We know clocks need not agree: the Earth clock gets out of sync with the Bonn clock. So which one is right? Well, presumably the Bonn clock, because it''s more accurate. But accurate relative to what? To us? After all, clocks were invented to tell the time for entirely human purposes. Are all humans "on" the same time, however? The patient in the dentist''s chair and the audience listening to a Beethoven symphony experience the same atomically tagged duration in quite different ways.

So much of what we believe about time is a result of cultural conditioning. I once met a mystic in Bombay who claimed he could alter his state of consciousness through meditation and so suspend the flow of time altogether; he was unimpressed with talk of atomic clocks. In a lecture in London some years ago, I found myself sharing the platform improbably with the Dalai Lama. Our task was to compare and contrast time as it enters into Western scientific thinking and Eastern philosophy. The Lama spoke with quiet assurance, but unfortunately in Tibetan. Though I tried to follow the translation for enlightenment, I didn''t receive much, regrettably. Culture clash, I suppose.

After my lecture, we had a tea break, and the Dalai Lama took my hand as we walked out of the building into the sunshine. Someone dropped to his knees and presented His Holiness with a daffodil, which he graciously accepted. I had the overwhelming impression of a gentle and intelligent man with insights of value to us all, but prevented by the trappings of his office from effectively communicating them to the assembled Western scientists. I came away from the occasion with a deep sense of missed opportunity.

THE QUEST FOR ETERNITY

Eternity? thou pleasing, dreadful thought?

Joseph Addison

In the madcap world of modern Western society, where time is money, railways, airline schedules, television programs, even cooking are subject to the tyranny of the clock. Our hectic lives are firmly bolted to the treadmill of time. We are slaves of our past and hostages to the future. But was it always thus? Running like a common thread through the history of human thought, East and West, North and South, is a belief that the entire paradigm of human temporality is rooted in some sort of monstrous illusion; it is but an elaborate product of the human mind:

And likewise time cannot itself exist,

But from the flight of things we get a sense of time....

No man, we must confess, feels time itself,

But only knows of time from flight or rest of things.


Thus wrote the Roman poet-philosopher Lucretius in his first-century epic De Rerum Natura. From such unsettling ideas it is but a small step to believe that the passage of time can be controlled or even suspended by mental power, as we discover in the following haunting words of the sixteenth-century mystical poet Angelus Silesius:

Time is of your own making,

its clock ticks in your head.

The moment you stop thought

time too stops dead.


For such temporal relativists, true reality is vested in a realm that transcends time: the Land Beyond Time. Europeans call it "eternity," Hindus refer to it as "moksha" and Buddhists as "nirvana." For the Australian aborigines it is the Dream Time. Angelus Silesius again:

Do not compute eternity
as light-year after year
One step across
that line called Time
Eternity is here.


In our struggle to come to terms with mental and physical reality, nothing vexes us more than the nature of time. The paradoxical conjunction of temporality and eternity has troubled Man through the ages. Plato concluded that the fleeting world of daily experience is only half real, an ephemeral reflection of a timeless domain of pure and perfect Forms, which occupy the realm of eternity. Time itself is but an imperfect "moving image of Eternity which remains forever at one," but which we human beings incorrigibly reify: "The past and future are created species of time, which we unconsciously but wrongly transfer to the eternal essence.

The abiding tension between the temporal and the eternal pervades the world''s great religions, and has led to generations of heated and sometimes violent theological debate. Is God inside or outside of time? Temporal or eternal? Process or Being? According to Plotinus, a third-century pagan, to exist in time is to exist imperfectly. Pure Being (i.e., God) must therefore be characterized by the utter absence of any relation to time. For Plotinus, time represents a prison for human beings, separating us from the divine realm -- the true and absolute reality.

Belief that God lies outside of time altogether also became the established doctrine among many early Christian thinkers, such as Augustine, Boethius and Anselm, starting a tradition that continues to the present day. Like Plato and Plotinus before him, Augustine places God in the realm of eternity, "supreme above time because it is a never-ending present." In this existence, time does not pass; rather, God perceives all times at once:

Your years are completely present to you all at one because they are at a permanent standstill. They do not move on, forced to give way before the advance of others, because they never pass at all...Your today is eternity.

Thus, the God of classical Christianity not only exists outside of time, but also knows the future as well as the past and present. These farreaching ideas have been subjected to detailed analysis and received some sharp criticism by the medieval church, as well as by modern theologians and philosophers. The core of the debate is the daunting problem of how to build a bridge between God''s presumed eternity on the one hand and the manifest temporality of the physical universe on the other. Can a god who is completely atemporal logically relate in any way at all to a changing world, to human time? Surely it is impossible for God to exist both within and outside of time? After centuries of bitter debate, there is still no consensus among theologians about the solution to this profound conundrum. These tangled issues are reviewed in greater depth in my book The Mind of God, for those readers who are interested.

ESCAPE FROM TIME

The great thing about time is that it goes on.

Arthur Eddington

Although theologians and philosophers wrangle over the technicalities of the logical relationship between time and eternity, many religious people believe that the most powerful insights into the subject are provided, not by academic debate, but by direct revelation:

I remember that I was going to bathe from a stretch of shingle to which the few people who stayed in the village seldom went. Suddenly the noise of the insects was hushed. Time seemed to stop. A sense of infinite power and peace came upon me. I can best liken the combination of timelessness with amazing fullness of existence to the feeling one gets in watching the

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