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    The ABC of Relativity
    The ABC of Relativity
    The ABC of Relativity
    Ebook174 pages3 hours

    The ABC of Relativity

    By Bertrand Russell

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    About this ebook

    The Nobel Prize winner offers “an ideal introduction to the theories of special and general relativity” in clear, comprehensible language(Nature).
     
    A renowned mathematician and philosopher, and as well as recipient of the Nobel Prize in Literature, Bertrand Russell was acclaimed for his ability to address complex subjects in accessible ways. In this classic reference book, Russell delves into physics and relativity, helping everyday readers grasp the genius and implications of Albert Einstein’s theory. When originally published in 1925, The ABC of Relativity brought science to a more general audience—and it continues to do so in the twenty-first century.
     
    “A mind of dazzling brilliance.” —The New York Times
    LanguageEnglish
    PublisherOpen Road Media
    Release dateJan 5, 2021
    ISBN9781504000994
    The ABC of Relativity
    Author

    Bertrand Russell

    Bertrand Arthur William Russell, 3rd Earl Russell was a British philosopher, logician, mathematician, historian, social reformer, and pacifist. Although he spent the majority of his life in England, he was born in Wales, where he also died. Russell led the British “revolt against Idealism” in the early twentieth century and is one of the founders of analytic philosophy along with his protégé Wittgenstein and his elder Frege. He co-authored, with A. N. Whitehead, Principia Mathematica, an attempt to ground mathematics on logic. His philosophical essay “On Denoting” has been considered a “paradigm of philosophy.” Both works have had a considerable influence on logic, mathematics, set theory, linguistics and analytic philosophy. He was a prominent anti-war activist, championing free trade between nations and anti-imperialism. Russell was imprisoned for his pacifist activism during World War I, campaigned against Adolf Hitler, for nuclear disarmament. He criticized Soviet totalitarianism and the United States of America’s involvement in the Vietnam War. In 1950, Russell was awarded the Nobel Prize in Literature, “in recognition of his varied and significant writings in which he champions humanitarian ideals and freedom of thought.”

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    • 5/5
      This was the right book at the right time for me, and reading it in my teens triggered my own interest in physics and cosmology. A great layman's starter on some of the most important ideas of our time.
    • 4/5
      In this book, first published in 1925 (although the edition I have was revised in 1959), Bertrand Russell attempts to explicate both special and general relativity. With the exception of a couple of very short sections that he advises non-mathematical readers to skip, he uses little or no math. This means that reading this book will not, in fact, allow you to completely understand relativity, as you pretty much need a good grasp of the math for that. But he does give a decent accounting of the reasons, both experimental and theoretical, why we believe these theories to be sound ones, explains the important ideas involved, and gives the reader a sense of the often strange and counter-intuitive implications that result from them. The style is perhaps a little old-fashioned by today's standards, and the subject matter a bit difficult -- I majored in physics in college, and I don't even pretend to fully understand all of it -- but Russell uses a lot of examples and analogies that are helpful. In the last few chapters (and, to a certain extent throughout the book), he also delves into some philosophical and epistemological territory, which gets a little abstruse, even by the standards of a book on relativity. I'm not entirely sure what to make of some of that, but I did find all of it interesting.I'm not sure I'd recommend this as a first introduction to the subject; there are doubtless more recent books that do a better job of that. But for those who know just a little bit about relativity, are still trying to get a handle on what it all means in terms of our conception of space and time, and are interested in reading a few deep thoughts, I'd say it's still worth a look.
    • 4/5
      Presents several psychologically challenging implications of the theory of relativity. I most enjoyed the discussion on the distinctions between various sciences, especially the relationship between geometry and physics. The main downside for me was the increasingly confusing gap between the jargon and the mathematics the jargon is intended to represent. Probably unavoidable, but I fell behind on the discussion toward the end.

    Book preview

    The ABC of Relativity - Bertrand Russell

    The ABC of Relativity

    Bertrand Russell

    Edited by Felix Pirani

    Contents

    Preface to the Fourth Edition

    Touch and Sight: The Earth and the Heavens

    What Happens and What is Observed

    The Velocity of Light

    Clocks and Foot-rules

    Space-Time

    The Special Theory of Relativity

    Intervals in Space-Time

    Einstein’s Law of Gravitation

    Proofs of Einstein’s Law of Gravitation

    Mass, Momentum, Energy, and Action

    The Expanding Universe

    Conventions and Natural Laws

    The Abolition of ‘Force’

    What is Matter?

    Philosophical Consequences

    Preface to the Fourth Edition

    This book first appeared in 1925. The basic principles of relativity have not changed since then, but both the theory and its applications have been much extended, and some revision has been necessary for the second and subsequent editions. For the second and third editions I carried out these revisions with Bertrand Russell’s approval. The revisions for this fourth edition are entirely my responsibility. I have again altered a number of passages to agree with present knowledge or opinion, and I have attempted to eliminate the possessive case, as applied to laws or theories, where it seemed to me no longer appropriate.

    I have also done my best to renounce the convention that the masculine includes the feminine. Sixty years ago this may have been acceptable, or at least tolerated; now it is no longer so,’and I have little doubt that Russell, who was a pro-feminist ahead of his time, would have approved of the renunciation. I have not presumed to meddle with the substance of the last two chapters, which are largely philosophical, rather than physical, in character, although there is much in them which I disagree with.

    F.P.

    Chapter 1

    Touch and Sight: The Earth and the Heavens

    Everybody knows that Einstein did something astonishing, but very few people know exactly what it was. It is generally recognised that he revolutionised our conception of the physical world, but the new conceptions are wrapped up in mathematical technicalities. It is true that there are innumerable popular accounts of the theory of relativity, but they generally cease to be intelligible just at the point where they begin to say something important. The authors are hardly to blame for this. Many of the new ideas can be expressed in non-mathematical language, but they are none the less difficult on that account. What is demanded is a change in our imaginative picture of the world—a picture which has been handed down from remote, perhaps prehuman, ancestors, and has been learned by each one of us in early childhood. A change in our imagination is always difficult, especially when we are no longer young. The same sort of change was demanded by Copernicus, who taught that the earth is not stationary and the heavens do not revolve about it once a day. To us now there is no difficulty in this idea, because we learned it before our mental habits had become fixed. Einstein’s ideas, similarly, will seem easier to generations which grow up with them; but for us a certain effort of imaginative reconstruction is unavoidable.

    In exploring the surface of the earth, we make use of all our senses, more particularly of the senses of touch and sight. In measuring lengths, parts of the human body are employed in pre-scientific ages: a ‘foot’, a ‘cubit’, a ‘span’ are defined in this way. For longer distances, we think of the time it takes to walk from one place to another. We gradually learn to judge distance roughly by the eye, but we rely upon touch for accuracy. Moreover it is touch that gives us our sense of ‘reality’. Some things cannot be touched: rainbows, reflections in looking-glasses, and so on. These things puzzle children, whose metaphysical speculations are arrested by the information that what is in the looking-glass is not ‘real’. Macbeth’s dagger was unreal because it was not ‘sensible to feeling as to sight’. Not only our geometry and physics, but our whole conception of what exists outside us, is based upon the sense of touch. We carry this even into our metaphors: a good speech is ‘solid’, a bad speech is ‘gas’, because we feel that a gas is not quite ‘real’.

    In studying the heavens, we are debarred from all senses except sight. We cannot touch the sun, or apply a foot-rule to the Pleiades. Nevertheless, astronomers have unhesitatingly applied the geometry and physics which they found serviceable on the surface of the earth, and which they had based upon touch and travel. In doing so, they brought down trouble on their heads, which was not cleared up until relativity was discovered. It turned out that much of what had been learned from the sense of touch was unscientific prejudice, which must be rejected if we are to have a true picture of the world.

    An illustration may help us to understand how much is impossible to the astronomer as compared with someone who is interested in things on the surface of the earth. Let us suppose that a drug is administered to you which makes you temporarily unconscious, and that when you wake you have lost your memory but not your reasoning powers. Let us suppose further that while you were unconscious you were carried into a balloon, which, when you come to, is sailing with the wind on a dark night—the night of the fifth of November if you are in England, or of the fourth of July if you are in America. You can see fireworks which are being sent off from the ground, from trains, and from aeroplanes travelling in all directions, but you cannot see the ground or the trains or the aeroplanes because of the darkness. What sort of picture of the world will you form? You will think that nothing is permanent: there are only brief flashes of light, which, during their short existence, travel through the void in the most various and bizarre curves. You cannot touch these flashes of light, you can only see them. Obviously your geometry and your physics and your metaphysics will be quite different from those of ordinary mortals. If an ordinary mortal were with you in the balloon, you would find his speech unintelligible. But if Einstein were with you, you would understand him more easily than the ordinary mortal would, because you would be free from a host of preconceptions which prevent most people from understanding him.

    The theory of relativity depends, to a considerable extent, upon getting rid of notions which are useful in ordinary life but not to our drugged balloonist. Circumstances on the surface of the earth, for various more or less accidental reasons, suggest conceptions which turn out to be inaccurate, although they have come to seem like necessities of thought. The most important of these circumstances is that most objects on the earth’s surface are fairly persistent and nearly stationary from a terrestrial point of view. If this were not the case, the idea of going on a journey would not seem so definite as it does. If you want to travel from King’s Cross to Edinburgh, you know that you will find King’s Cross where it has always been, that the railway line will take the course that it did when you last made the journey, and that Waverley Station in Edinburgh will not have walked up to the Castle. You therefore say and think that you have travelled to Edinburgh, not that Edinburgh has travelled to you, though the latter statement would be just as accurate. The success of this common-sense point of view depends upon a number of things which are really of the nature of luck. Suppose all the houses in London were perpetually moving about, like a swarm of bees; suppose railways moved and changed their shapes like avalanches; and finally suppose that material objects were perpetually being formed and dissolved like clouds. There is nothing impossible in these suppositions. But obviously what we call a journey to Edinburgh would have no meaning in such a world. You would begin, no doubt, by asking the taxi-driver: ‘Where is King’s Cross this morning?’ At the station you would have to ask a similar s question about Edinburgh, but the booking-office clerk would reply: ‘What part of Edinburgh do you mean? Prince’s Street has gone to Glasgow, the Castle has moved up into the Highlands, and Waverley Station is under water in the middle of the Firth of Forth.’ And on the journey the stations would not be staying quiet, but some would be travelling north, some south, some east or west, perhaps much faster than the train. Under these conditions you could not say where you were at any moment. Indeed the whole notion that one is always in some definite ‘place’ is due to the fortunate immobility of most of the large objects on the earth’s surface. The idea of ‘place’ is only a rough practical approximation: there is nothing logically necessary about it, and it cannot be made precise.

    If we were not much larger than an electron, we should not have this impression of stability, which is only due to the grossness of our senses. King’s Cross, which to us looks solid, would be too vast to be conceived except by a few eccentric mathematicians. The bits of it that we could see would consist of little tiny points of matter, never coming into contact with each other, but perpetually whizzing round each other in an inconceivably rapid ballet-dance. The world of our experience would be quite as mad as the one in which the different parts of Edinburgh go for walks in different directions. If—to take the opposite extreme—you were as large as the sun and lived as long, with a corresponding slowness of perception, you would again find a higgledypiggledy universe without permanence—stars and planets would come and go like morning mists, and nothing would remain in a fixed position relatively to anything else. The notion of comparative stability which forms part of our ordinary outlook is thus due to the fact that we are about the size we are, and live on a planet of which the surface is not very hot. If this were not the case, we should not find pre-relativity physics intellectually satisfying. Indeed we should never have invented such theories. We should have had to arrive at relativity physics at one bound, or remain ignorant of scientific laws. It is fortunate for us that we were not faced with this alternative, since it is almost inconceivable that one person could have done the work of Euclid, Galileo, Newton and Einstein. Yet without such an incredible genius physics could hardly have been discovered in a world where the universal flux was obvious to non-scientific observation.

    In astronomy, although the sun, moon and stars continue to exist year after year, yet in other respects the world we have to deal with is very different from that of everyday life. As already observed, we depend exclusively on sight: the heavenly bodies cannot be touched, heard, smelt or tasted. Everything in the heavens is moving relatively to everything else. The earth is going round the sun, the sun is moving, very much faster than an express train, towards a point in the constellation Hercules, the ‘fixed’ stars are scurrying hither and thither. There are no well-marked places in the sky, like King’s Cross and Edinburgh. When you travel from place to place on the earth, you say the train moves and not the stations, because the stations preserve their topographical relations to each other and the surrounding country. But in astronomy it is arbitrary which you call the train and which the station: the question is to be decided purely by convenience and as a matter of convention.

    In this respect, it is interesting to contrast Einstein and Copernicus. Before Copernicus, people thought that the earth stood still and the heavens revolved about it once a day. Copernicus taught that ‘really’ the earth rotates once a day, and the daily revolution of sun and stars is only ‘apparent’. Galileo and Newton endorsed this view, and many things were thought to prove it—for example, the flattening of the earth at the poles, and the fact that bodies are heavier there than at the equator. But in the modern theory the question between Copernicus and earlier astronomers is merely one of convenience; all motion is relative, and there is no difference between the two statements: ‘the earth rotates once a day’ and ‘the heavens revolve about the earth once a day’. The two mean exactly the same thing, just as it means the same thing if I say that a certain length is six feet or two yards. Astronomy is easier if we take the sun as fixed than if we take the earth, just as accounts are easier in decimal coinage. But to say more for Copernicus is to assume absolute motion, which is a fiction. All motion is relative, and it is a mere convention to take one body as at rest. All such conventions are equally legitimate, though not all are equally convenient.

    There is another matter of great importance, in which astronomy differs from terrestrial physics because of its exclusive dependence upon sight. Both popular thought and old-fashioned physics used the notion offeree’, which seemed intelligible because it was associated with familiar sensations. When we are walking, we have sensations connected with our muscles which we do not have when we are sitting still. In the days before mechanical traction, although people could travel by sitting in their carriages, they could see the horses exerting themselves, and evidently putting out ‘force’ in the same way as human beings do. Everybody knew from experience what it is to push or pull, or to be pushed or pulled. These very familiar facts made ‘force’ seem a natural basis for dynamics. But the Newtonian law of gravitation introduced a difficulty. The force between two billiard balls appeared intelligible because we know what it feels like to bump into another person; but the force between the earth and

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