About Time: Einstein's Unfinished Revolution
Davies (Paul C.W.)
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Back Cover Blurb

  1. What is time? Did it have a beginning? What makes it appear to flow? Why is there a directionality, or 'arrow', of time, and can it ever be reversed? Is time travel1 possible? And might the universe be older than we thought?
  2. The puzzles and paradoxes of time have dazzled the world's finest thinkers and throughout the ages philosophers have wrestled with the tensions between time and eternity, linear time and cyclicity, being and becoming. When Einstein formulated his theory of relativity early this century, it brought about a revolution in our understanding of time, yet also presented a new set of mysteries. Einstein's time can be warped, leading to bizarre possibilities such as black holes and time travel2, while making nonsense of our perception of a 'now' and a division of time into past, present and future. In relation to quantum physics, time takes on even stranger aspects.
  3. In this, his latest book, acclaimed physicist and writer Paul Davies confronts the tough questions about time, including the weird relationship between physical time and our psychological perception of it. He gives straightforward descriptions of topics such as the theory of relativity, time dilation and Hawking's 'imaginary time'. Davies concludes that despite decades of progress in unravelling the mysteries of time, the revolution begun by Einstein remains tantalizingly incomplete.

Author’s Preface
  1. This is the second book I have written on the subject of time. The first, published in 19743, was intended for professional physicists. I always intended to write another book on this subject, for the wider public, but somehow I never found the time. At last I have accomplished it. Fascination with the riddle of time is as old as human thought. The earliest written records betray confusion and anxiety over the nature of time. Much of Greek philosophy was concerned with making sense of the concepts of eternity versus transience. The subject of time is central to all the world's religions, and has for centuries been the source of much doctrinal conflict.
  2. Although time entered science as a measurable quantity with the work of Galileo and Newton, it is only in the present century that it has developed into a subject in its own right. Albert Einstein, more than anyone else, is responsible for this advance. The story of time in the twentieth century is overwhelmingly the story of Einstein's time. Although I have sketched biographical details where appropriate, this book is not a biography of Einstein, because several such have appeared since his centenary in 1979. Nor did I set out to write a systematic and comprehensive study of time. Instead, I have chosen a selection of topics that I personally find particularly intriguing or mysterious, and used them to illustrate the general principles of time as we have come to understand them.
  3. Although Einstein's theory of relativity is nearly a century old, its bizarre predictions are still not widely known. Invariably people learn of them with delight, fear and perplexity. Much of the book is devoted to covering the more straightforward consequences of the theory; the broad conclusion I reach, however, is that we are far from having a good grasp of the concept of time. Einstein's work triggered a revolution in our understanding of the subject, but the consequences have yet to be fully worked out. Much of the theory of relativity remains uncharted territory, and crucial topics, like the possibility of time travel4, have only very recently received attention. There are also major problems which hint at deep-seated limitations of the theory; discrepancies concerning the age of the universe and obstacles to unifying Einstein's time with quantum physics are two of the more persistent difficulties. Perhaps more worryingly, Einstein's time is seriously at odds with time as we human beings experience it. All this leads me to believe that we must embrace Einstein's ideas, but move on. The orthodox account of time frequently leaves us stranded, surrounded by a welter of puzzles and paradoxes. In my view, Einstein's time is inadequate to explain fully the physical universe and our perception of it.
  4. The scientific study of time has proved to be disturbing, disorienting and startling. It is also befuddling. I have written this book for the reader with no specialist scientific or mathematical knowledge. Technical jargon is kept to a minimum, and numerical values are avoided except where absolutely necessary. However, I cannot deny that the subject is complex and intellectually challenging. To try and ease the pain a bit, I have resorted to the device of introducing a tame imaginary skeptic, who may from time to time voice the reader's own objections or queries. Nevertheless, you may well be even more confused about time after reading this book than you were before. That's all right; I was more confused myself after writing.it.
  5. Many people have helped me shape my ideas of time over the years. I have especially benefited from discussions and debate with John Barrow, George Efstathiou, Murray Gell-Mann, Ian Moss, James Hartle, Stephen Hawking, Don Page, Roger Penrose, Frank Tipler, William Unruh and John Wheeler…

    Preface – 9
    Prologue – 13
  1. A Very Brief History of Time – 21
    • Whose time is it anyway? – 21
    • The quest for eternity – 23
    • Escape from time – 25
    • Cyclic worlds and the eternal return – 28
    • Newton's time and the clockwork universe – 29
    • Einstein's time – 32
    • Is the universe dying? – 33
    • The return of the eternal return – 36
    • The start of it all – 38
    • It happens when it happens – 40
  2. Time for a Change – 44
    • A gift from heaven – 44
    • Goodbye to the ether – 48
    • A timely solution – 51
    • Interlude – 54
    • Stretching time – 55
    • The puzzle of the twins – 59
    • Goodbye to the present – 65
    • Time is money – 67
    • Timescape – 70
  3. Timewarps – 78
    • The light barrier – 78
    • Perpetual motion and the uphill struggle – 84
    • Why time runs faster in space – 87
    • The clock in the box – 90
    • The best clock in the universe – 96
    • The echo that arrived late – 99
    • Going up in the world – 100
  4. Black Holes; Gateways to the End of Time – 104
    • Warp factor infinity – 104
    • A dark mystery – 108
    • Penetrating the magic circle – 111
    • A singular problem – 113
    • Beyond the end of time – 120
    • Are they really out there? – 122
  5. The Beginning of Time; When Exactly Was It? – 126
    • The great clock in the sky – 126
    • The big bang, and what happened before it – 129
    • Older than the universe? – 132
    • Einstein's greatest mistake – 135
    • Two-timing the cosmos – 140
  6. Einstein's Greatest Triumph? – 146
    • The handwriting of God – 146
    • Did the big bang ever happen? – 149
    • What's a few billion years among friends? – 152
    • A repulsive problem – 157
    • The loitering universe – 159
  7. Quantum Time – 163
    • Time to tunnel – 163
    • Watched kettles – 166
    • Erasing the past – 168
    • Spooky signals and psychic particles – 173
    • Faster than light? – 177
    • The time vanishes! – 178
  8. Imaginary Time – 183
    • The two cultures revisited – 183
    • How time got started – 185
    • The Hartle-Hawking theory – 188
    • Imaginary clocks – 192
  9. The Arrow of Time – 196
    • Catching the wave – 196
    • Signals from the future – 201
    • A matter of time reversal – 204
    • The particle that can tell the time – 208
    • The lopsided universe – 213
  10. Backwards in Time – 219
    • Into reverse – 219
    • Thinking backwards – 222
    • Antiworlds – 224
    • Winding the clock back – 226
    • Hawking's greatest mistake – 230
    • A time for everybody – 231
  11. Time Travel5; Fact or Fantasy? – 233
    • Signaling the past – 233
    • Visiting the past – 236
    • Black-hole time machines6 – 243
    • Wormholes and strings – 245
    • Paradox – 249
  12. But What Time Is It Now? – 252
    • Can time really flow? – 252
    • The myth of passage – 255
    • Does the arrow of time fly? – 256
    • Why now? – 258
  13. Experimenting with Time – 265
    • How long does the present last? – 265
    • Now you see it, now you don't – 267
    • Filling in time – 269
    • Subjective time – 272
    • The back door to our minds – 275
  14. The Unfinished Revolution – 279
  15. Epilogue – 284
    Notes – 287
    Bibliography – 293
    Index – 295

In-Page Footnotes ("Davies (Paul C.W.) - About Time: Einstein's Unfinished Revolution")

Footnote 3: The Physics of Time Asymmetry.


Penguin; New edition (25 April 1996)

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