What Is Relativity?

What Is Relativity?: An Intuitive Introduction to Einstein's Ideas, and Why They Matter

JEFFREY BENNETT
Copyright Date: 2014
Pages: 208
https://www.jstor.org/stable/10.7312/benn16726
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  • Book Info
    What Is Relativity?
    Book Description:

    It is common knowledge that if the Sun suddenly turned into a black hole, it would suck Earth and the rest of the planets into oblivion. Yet as bestselling author and astrophysicist Jeffrey Bennett points out, black holes don't suck. With that simple idea in hand, Bennett begins an entertaining introduction to Einstein's theories, describing the amazing phenomena readers would actually experience if they took a trip through a black hole.

    The theory of relativity also gives us the cosmic speed limit of the speed of light, the mind-bending ideas of time dilation and curvature of spacetime, and what may be the most famous equation in history: e = mc2. Indeed, the theory of relativity shapes much of our modern understanding of the universe, and it is not "just a theory:" every major prediction of relativity has been tested to exquisite precision and its practical applications include the Global Positioning System (GPS). Bennett proves anyone can understand the basics of Einstein's ideas. His intuitive, nonmathematical approach gives a wide audience its first real taste of how relativity works and why it is so important not only to science but also to the way we view ourselves as human beings.

    eISBN: 978-0-231-53703-2
    Subjects: Physics, Astronomy

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-v)
  3. PREFACE
    (pp. vii-x)
    Jeffrey Bennett
  4. Part 1 GETTING STARTED
    • 1 VOYAGE TO A BLACK HOLE
      (pp. 3-24)

      IMAGINE THAT the Sun magically collapsed, retaining the same mass but shrinking in size so much that it became a black hole. What would happen to Earth and the other planets? Ask almost anyone, including elementary school kids, and they’ll tell you confidently that the planets “would be sucked in.”

      Now imagine that you’re a future interstellar traveler. Suddenly, you discover that a black hole lurks off to your left. What should you do? Again, ask around, and you’ll probably be told to fire up your engines to try to get away, and that you’ll be lucky to avoid being...

  5. Part 2 EINSTEIN’S SPECIAL THEORY OF RELATIVITY
    • 2 RACING LIGHT
      (pp. 27-44)

      ALTHOUGH WE usually speak ofthetheory of relativity, Einstein actually published the theory in two distinct parts. The first part, known as thespecial theory of relativity, was published in 1905. This is the theory that explains the slowing of time that made you age less than those who stayed home on Earth during your voyage to the black hole. It’s also the theory that tells us that nothing can travel faster than light, and from which Einstein discovered his famous equationE=mc². You may be thinking, “Well, thatispretty special, but isn’t it odd to...

    • 3 REDEFINING SPACE AND TIME
      (pp. 45-66)

      THE FORESHORTENED race course that Ben experiences while running comes about for the same reason that you found the distance to the black hole shorter during your imaginary journey in chapter I. It is also closely related to the reason why less time passed for you than for people on Earth during your trip, as well as to other effects described by Einstein’s special theory of relativity. These include the idea that observers in different reference frames may disagree about whether two events are simultaneous, and the famous equivalence of mass and energy embodied in the equationE=mc²....

    • 4 A NEW COMMON SENSE
      (pp. 67-84)

      IN CHAPTERS 2 and 3, we saw how all the major consequences of Einstein’s special theory of relativity flow from two simple absolutes: that the laws of nature are the same for everyone and that everyone always measures the same speed of light. We found that you can’t outrace your own light. We found that observers in different reference frames, by which we mean frames that are moving relative to each other, will come up with differing measurements for time, space, and mass. We found that different observers won’t necessarily agree on the order or simultaneity of two events that...

  6. Part 3 EINSTEIN’S GENERAL THEORY OF RELATIVITY
    • 5 NEWTON’S ABSURDITY
      (pp. 87-106)

      IN ADDITION to making many aspects of the universe make more sense than they did before, the special theory of relativity also solved several important and well–known problems in physics, including the apparent problem with the equations of electromagnetism that we discussed earlier. Many physicists had been working on these problems at the time, and several besides Einstein were closing in on the correct solution.

      The general theory of relativity is a different story, as most historians of science suspect that without Einstein, it would not have been discovered for many more years. Part of the reason for Einstein’s...

    • 6 REDEFINING GRAVITY
      (pp. 107-132)

      THE IDEA of gravity arising from curvature of spacetime takes some getting used to, especially since the only visualizations we can do are somewhat inadequate two–dimensional analogies, such as bent pieces of paper or orbital paths in salad bowls. Nevertheless, the appeal of this new idea should be clear. Just as special relativity made the universe make more sense than it did before, so does general relativity. As we saw in chapter 5, general relativity eliminates Newton’s absurdity, it allows us to treat all motion as relative (or, more precisely, to get the same answers no matter what reference...

  7. Part 4 IMPLICATIONS OF RELATIVITY
    • 7 BLACK HOLES
      (pp. 135-162)

      OVER THE past several chapters, we have discussed the reasons behind many of the phenomena you experienced during your voyage to a black hole. We have seen why less time passed for you during the journey than passed for people back home on Earth. We’ve learned that the structure of spacetime at a distance from any mass depends only on the amount of mass, which is why you can orbit a black hole at a distance just as you can orbit a star, without fear of being sucked in. We’ve found that the slowing of time and the gravitational redshift...

    • 8 THE EXPANDING UNIVERSE
      (pp. 163-180)

      EINSTEIN’S THEORIES sound so revolutionary and modern that it’s easy to forget that he discovered them at a time when much of the rest of our understanding of the universe was still quite limited. For example, as we discussed in chapter 7, while general relativity made allowance for black holes, few people thought they might really exist until many decades later. Similarly, althoughE=mc² suggested that stars could in principle be shining by converting a small fraction of their mass into energy, the mechanism of nuclear fusion wasn’t discovered until more than 30 years after Einstein first came...

    • EPILOGUE: YOUR INDELIBLE MARK ON THE UNIVERSE
      (pp. 181-184)

      I BEGAN this book with the claim (in the preface) that relativity isimportantto understanding how we as humans fit into the overall scheme of the universe. Now that we have completed our introduction to Einstein’s theories, it seems a good time to look back and think more deeply about that claim. Of course, different people may come to different conclusions about exactly what makes relativity important, and I encourage you to come up with your own ideas. For myself, however, I find relativity to be important on at least four different levels.

      The first level is that of...

  8. ACKNOWLEDGMENTS
    (pp. 185-186)
  9. INDEX
    (pp. 187-192)