| ABC of Relativity by B.Russell |
| 1 | Ask a dozen people to name a genius and the odds are that 'Einstein' will spring to their lips. Ask them the meaning of 'relativity' and few of them will be able to tell you what it is. The ABC of Relativity is Bertrand Russell's most brilliant work of scientific popularisation. With marvellous lucidity he steers the reader who has no knowledge of maths or physics through the subtleties of Einstein's thinking; in easily assimilable steps he explains the theories of special and general relativity and describes their practical application (among much else to discoveries about gravitation and the invention of the hydrogen bomb). |
| 2 | 'Einstein', wrote Russell, 'revolutionised our conception of the physical world, but the innumerable popular accounts of his theory generally cease to be intelligible at the point where they begin to say something important.' The basic principles of relativity have not changed since Russell first published his lucid guide for the general reader. This new edition takes account of the extension of our knowledge about the theory and its applications. |
| 3 | 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. |
| 4 | 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 pre-human, 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. |
| 5 | 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. |
| 6 | 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. |
| 7 | 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. |
| 8 | 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. |
| 9 | 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. |
| 10 | 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. |
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