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Space, Time and Einstein: An Introduction

J. B. Kennedy
Copyright Date: 2003
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    Space, Time and Einstein
    Book Description:

    In Space, Time and Einstein J.B. Kennedy offers an introduction to one of the liveliest and most popular fields in philosophy - time and space - aimed specifically at a beginning readership with no background in philosophy or science. He goes to the philosophical heart of the issues without recourse to jargon, mathematics, or logical formulas and introduces Einstein's revolutionary ideas in a clear and simple way, as well as concepts and arguments of other relevant philosophers, both ancient and modern. Current debates in philosophy and physics are also handled with exemplary clarity and Kennedy is able to provide readers with a real sense of where we have come from and where we are going. The writing is engaging, lively, and entertaining and serves to introduce the subject for beginning students as well as providing a clear statement of the "state of the debate" for a popular science readership. Kennedy covers such topics as Einstein's special and general relativity, how to build an atom bomb, the four-dimensional universe, the possibility of time travel, the impossibility of motion, whether space curves, the big bang, black holes, and the idea of inflationary and accelerating universes.

    eISBN: 978-0-7735-8276-7
    Subjects: Philosophy

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-viii)
  3. Preface and acknowledgements
    (pp. ix-x)
    J. B. Kennedy
  4. Part I: Einstein’s revolution
    • CHAPTER 1 From Aristotle to Hiroshima
      (pp. 3-6)

      Cup your hands together and peer down between your palms.

      What is between them?

      One answer is “air”. But we think of air as composed of separate molecules, like isolated islands. What lies between the molecules?


      The distances between the molecules differ. Could there be more “nothing” between some, and less “nothing” between others? Could nothing really exist?

      The empty space does seem to be nothing. It is tasteless, colourless and weightless. It does not move, and the gentlest breeze can pass through it without resistance.

      This is our first question. What is between your cupped palms? Is it...

    • CHAPTER 2 Einstein in a nutshell
      (pp. 7-30)

      There are two Einsteins. For most of the world, Einstein (1879–1955) is a cult figure: the pre-eminent icon of genius. With his wispy, wild grey hair, missing socks and other-worldly idealism, he has replaced the wizards of earlier times in the popular mind. This Einstein is dangerous, a stereotype with a life of its own that distorts both the man behind it and the nature of the science that so shapes our world.

      Among physicists, Einstein is at times remembered as a grumpy, cutting and arrogant fellow with little patience for family or colleagues. He so annoyed his teachers...

    • CHAPTER 3 The twin paradox
      (pp. 31-39)

      Among physicists, the word “symmetry” means “sameness across difference”. The prefixes “sym” and “syn” mean “same”, so “symphony” means “many musicians making the same sound” and “synchrony” means “same time”. “Metry” comes from the Greek word for “measure”(as in “metric”) and here means “size” or “shape”. Thus a face has a symmetry when it has the same shape on different sides, but the charm of a human face often lies in its slight asymmetries.

      One of the most outrageous aspects of Einstein’s theories is their unexpected symmetries. Suppose that two identical spaceships, A and B, are approaching each other and...

    • CHAPTER 4 How to build an atomic bomb
      (pp. 40-49)

      A few months after Einstein published his first paper on relativity in 1905, he sent in a sort of extended footnote to the same journal. His theory had an odd little consequence. It seemed so strange that he phrased the note’s title as a question: “Does Mass Depend on Energy?” To leaf through the next four flimsy pieces of paper and contemplate all that followed is to feel the power of ideas. For better or worse, Einstein had unlocked the secret of the atom. Here was the destruction of Hiroshima and Nagasaki. Here were 40 years of fear and tension...

    • CHAPTER 5 The four-dimensional universe
      (pp. 50-65)

      Three years after Einstein published his paper on special relativity, his former teacher Hermann Minkovski forever transformed our view of the universe. Einstein had predicted length contraction and time dilation, but Minkovski drew out their radical implications. As the famous quotation above suggests, Minkovski (pronounced Min-koffski) showed that space and time were mixed together in a sort of “union”. We do not live in a three-dimensional universe with time flowing through. Instead, we live in afour-dimensional spacetime. Time is the fourth dimension.

      These are strange claims. To assess them, the next two sections lay out some important philosophical issues...

    • CHAPTER 6 Time travel is possible
      (pp. 66-70)

      The iron chains of causality link events together into a definite order: a cause always precedes its effect. If, however, there are distant events that do not influence each other, what decides their order?

      As noted above, time dilation implies that different sets of rulers and clocks moving relative to each other will assign different orders to distant events. Consider, for example, three events: event A, which causes event B, and a distant event, X. Since A and B are connected by some causal process, their order is fixed. But if event X is distant enough from both, then different...

    • CHAPTER 7 Can the mind understand the world?
      (pp. 71-74)

      We have studied the elements of Einstein’s special theory of relativity, and can now put them together into a more panoramic view. He began by assuming the truth of two principles, both drawn from experience and experiments: the principle of relativity; and the constant speed of light. From these two central principles, Einstein and his followersdeduceda series of stunning consequences, of which we have met several in turn during the previous chapters:

      time dilation

      relativity of simultaneity

      length contraction

      symmetry of effects

      relativistic mass increase

      energy-mass conversion

      celestial speed limit

      invariance of the spacetime interval.

      These are predictions...

  5. Part II: Philosophical progress
    • [Part II: Introduction]
      (pp. 75-76)

      The relativity revolution has left in its wake a topsy-turvy world of immense power and immense insecurity, and a sense of both progress and perplexity. We have learned the most profound secrets about space and time, only to be confronted by renewed mystery. Is matter a form of motion? Do the past and future exist now? Is there change? Why is the speed of light constant? Does the very length of a body depend on how it is measured? Do the past and future exist now? Is time travel possible?

      From the eclipse expedition in 1919 through to today, this...

    • CHAPTER 8 Who invented space?
      (pp. 77-91)

      Some 5,000 or 6,000 years ago, early societies living in Turkey and Armenia spoke Indo-European: the language from which modern European languages have descended. Their vocabulary for concrete objects and simple actions paints a vivid picture of prehistoric life: “bear”, “wolf”, “monkey”, “wheat”, “apple”, “wheel”, “axle", “tree", “father", “carry", “see", “know", and so on. Words for less concrete aspects of the world were a long time coming. The adjective for “big” in Indo-European, for example, was “mega”: the root of our “megabyte”. This is an abstract word because it can apply to many different kinds of concrete objects; both bears...

    • CHAPTER 9 Zeno’s paradoxes: is motion impossible?
      (pp. 92-103)

      Counting things was the beginning of mathematics. The integers came first: 1,2,3,…. Later the need to measure straight lines and flat areas led to the study of geometry in ancient Egypt and India. But mathematics stumbled when it came to curves, spheres, continuous quantities and smooth changes. Early mathematics could not grasp our more fluid world, could not bring its changes and subtleties to life. Mathematics had to learn about change and infinity. It had to enter the labyrinth of the continuum.

      Zeno’s famous paradoxes may seem to be merely teasing riddles or bewildering games, but they are much, much...

    • CHAPTER 10 Philosophers at war: Newton vs. Leibniz
      (pp. 104-125)

      The Englishman Sir Isaac Newton, one of the greatest physicists of all time, has been reinvented. During the past 30 or so years, historians like Betty Jo Dobbs began to uncover the human behind the scientist and made discoveries that have surprised the world of science.

      Newton has often been idolized, but at such a distance that he seemed a cold, remote and austere figure, like the marble statues that depict him. He was famous for basing his science strictly on what he could observe and measure. He mocked other philosophers whose premises and hypotheses were spun out of their...

    • CHAPTER 11 The philosophy of left and right
      (pp. 126-132)

      Some boys and girls find it very difficult to learn which is their right and which their left hand. Likewise, when they begin writing, some confuse their p’s and q’s, or their b’s and d’s. Kant had the brilliant insight that children are right to be confused. Something deeply puzzling is involved. In a famous argument published in a four-page essay in 1768, Kant diagnosed the children’s problem and found in it a beautiful justification for Newton’s absolute space.

      If two objects have the same size and shape, they are called “congruent”. If an object is removed from a place...

    • CHAPTER 12 The unreality of time
      (pp. 133-138)

      British philosophy is sometimes celebrated and sometimes satirized as sturdy common sense. It tends to be grounded in facts and logic, and prefers science to mysticism. But for a generation or two during the late 1800s and early 1900s, a loose movement called British Idealism came to dominate philosophy in the universities. The major figures—Bradley, McTaggart, Green and Alexander—often disagreed among themselves, but they typically denied the reality of space and time, claiming that the world of science and appearance was contradictory. They believed instead in some sort of higher, spiritual reality. They were rational mystics.

      James McTaggart...

    • CHAPTER 13 General relativity: is space curved?
      (pp. 139-148)

      The 1905 special theory of relativity was limited to measurements made by equipment moving without acceleration. The general theory of relativity eliminates this special restriction. To achieve this, however, Einstein had to even more deeply revolutionize our concepts of space and time. Building on the insights of the earlier theory, he now argued that space can be bent by matter.

      Thus we have reached a third stage in the philosophy of space and time. The atomists first proclaimed that space or “nothing” existed in order to solve the problem of change. Newton revived this doctrine when, despite the criticisms of...

    • CHAPTER 14 The fall of geometry: is mathematics certain?
      (pp. 149-158)

      Some seek truth and some doubt it. Some are dedicated to seeking progress in our knowledge of reality, and some find it all too absurd. In the European tradition, the battles between these two warring tribes took place in the shadow of a great fortress. Defenders of truth could raise their fingers over the heads of the sceptics and point upwards to mathematics: a shining crystal palace of certainty surrounded by thick walls of deductions and demonstrations. But the revolution in theories of space and time during the twentieth century finally levelled this fortress. Sceptics have overrun even mathematics. Much...

    • CHAPTER 15 The resurrection of absolutes
      (pp. 159-171)

      Philosophy does make progress. The achievement of philosophers of space and time over the past 30 years has been extraordinarily important and far-reaching. The dramatic claims made by Einstein and many other physicists about the death of Newton’s absolute space have been rebutted. The nature of spacetime has been substantially clarified in ways that would have astonished the pioneers.

      This success is all the more significant because it has taken place in the face of hostility from many physicists. Even today, many or most physicists cling to some of the naive early claims made about relativity theory, which survive as...

    • CHAPTER 16 The resilience of space
      (pp. 172-174)

      The concept of space was born in paradox and seemed to have the flimsiest claim to existence. Although nothing but mere empty extendedness, it helped make motion and change understandable. Aristotle’s rugged common sense rejected “space” out of hand, and made do with his plenum of concrete objects. We have now seen that this ancient debate was preparation for the grander controversies over Newton and Einstein’s concepts of space. Like the ancient atomists, Newton embraced space to make sense of motion. His law of inertia demanded a world of geometric lines, and the sloshing water in his bucket seemed to...

  6. Part III: Frontiers
    • CHAPTER 17 Faster than light: was Einstein wrong?
      (pp. 177-184)

      For a hundred years, physicists trumpeted the celestial speed limit. Einstein has shown, they said, that nothing travels faster than light. But for a generation now, there has been stunning experimental evidence that hints that some mysterious influences are travelling faster than light.

      Contemporary physics rests on two great pillars. Einstein’s theories describe the large-scale structure of space and time. Quantum theory describes the small-scale behaviour of matter within space and time: the behaviour of molecules, atoms and other particles. Roughly, one describes the container, and the other the contents. Although research continues, the two traditions are so much at...

    • CHAPTER 18 The Big Bang: how did the universe begin?
      (pp. 185-187)

      One philosophical question is so exquisitely compact, so breathtakingly deep, that it can only be regarded as a miniature masterpiece. It seems that Leibniz was the first to express it in the haunting words “Why is there something rather than nothing?” It is clear that not even “God” could be the answer here, for even if God created all things and even the universe itself, we could still ask why God existed. If the divine existence is pronounced “necessary”, we could ask in turn “Why this necessity?”

      Some philosophers find Leibniz’s question so frustrating and unanswerable that they declare it...

    • CHAPTER 19 Black holes: trapdoors to nowhere
      (pp. 188-192)

      Anyone hauling a boulder to the top of a skyscraper and dropping it on to the street below would expect a catastrophic impact: flying shards of rock and road, streaks of sparks and smoke, the clap and crack of the reverberating bang. Similarly, when a planet, comet or any other material falls into a star, the resulting explosion is often dramatic. It can produce blinding flashes, bursts of high-energy X-rays and gigantic glowing flares of fiery gases.

      But, in early 2001, astronomers observing a strange object 6,000 light-years from Earth with the orbiting Hubble Telescope reported that they had seen...

    • CHAPTER 20 Why haven’t aliens come visiting?
      (pp. 193-196)

      Where does life come from? Thetheory of evolutiondescribes how one species slowly develops out of another, how humans evolved from apes, but does not explain the ultimate origin of life. Charles Darwin, who first published his theory of evolution in 1859, was always baffled by this mystery. At one point, even though he was an atheist, he even desperately suggested that God must have “breathed” life into the earliest organisms.

      For most scientists, this mystery was solved by the famous experiments of the chemists Stanley Miller and Harold Urey, performed in 1953 at the University of Chicago. In...

    • CHAPTER 21 The inflationary and accelerating universe
      (pp. 197-201)

      The most exciting and profound new physics, the first glimpses of twenty-first-century physics, are now coming from astronomy. Stunning new, supersensitive instruments and dazzling theoretical models have combined to squeeze revolutionary data from the faintest observations. From satellites in outer space and camps 800 metres from the South Pole, astronomers are mapping the shape of space and reaching back to the birth of time.

      Despite its many successes, the Big Bang model led to some new, deeply perplexing puzzles. Suppose our telescopes look at very distant objects in opposite directions. They might be so remote that nothing could travel from...

    • CHAPTER 22 Should we believe the physicists?
      (pp. 202-206)

      There is an old debate in philosophy about whether the world outside our minds exists at all. In the early-seventeenth century, Descartes pioneered the new mechanical and geometrical view of material reality in which every event was determined. But he also believed that we each had a soul and that our will was free. Thus he had to insist that matter and the soul were entirely different: the mind–body split was born. Descartes’s critics soon pointed out that a soul confined within the “veil of perception” had no direct evidence that its perceptions were true. Perhaps they were mere...

  7. APPENDIX A: Spacetime diagrams
    (pp. 207-221)
  8. APPENDIX B: Symmetry and Lorentz’s minority interpretation
    (pp. 222-224)
  9. APPENDIX C: Simple formulas for special relativity
    (pp. 225-226)
  10. APPENDIX D: Websites
    (pp. 227-228)
  11. APPENDIX E: Guide to further reading
    (pp. 229-238)
  12. Index
    (pp. 239-246)