Essays in Science Read online

  Essays in Science

  Albert Einstein

  Contents

  Preface to the New Edition

  Preface to Abridged Edition

  Publisher’s Note

  Translator’s Note

  Principles of Research

  Inaugural Address to the Prussian Academy of Sciences

  On Scientific Truth

  On the Method of Theoretical Physics

  Johannes Kepler

  The Mechanics of Newton and Their Influence on the Development of Theoretical Physics

  Clerk Maxwell’s Influence on the Evolution of the Idea of Physical Reality

  Niels Bohr

  On the Theory of Relativity

  What Is the Theory of Relativity?

  The Problem of Space, Ether, and the Field in Physics

  Notes on the Origin of the General Theory of Relativity

  The Cause of the Formation of Meanders in the Courses of Rivers and of the So-Called Beer’s Law

  The Flettner Ship

  Relativity and the Ether

  Address at Columbia University

  A Biography of Albert Einstein

  Preface to the New Edition

  ALBERT EINSTEIN WAS THE greatest physicist of the twentieth century. His image and name are recognizable to almost everyone, along with his equation E=mc2, which describes the relationship between energy and mass. His impact on science and intellectual thought during his lifetime was profound.

  This volume contains a collection of sixteen essays written before 1935, when Einstein was at the height of his scientific powers but not yet known as the sage of the atomic age. His stature in the world allowed him to express his views on philosophical issues relating to the field of physics. These essays established his early foray into this area.

  Why are we so interested in all aspects of Einstein’s philosophical positions and his thought processes? His theories of relativity and universal gravitation are generally regarded as inaccessible to the ordinary person. Yet we know that he was an original thinker who was able to see beyond the conventional scientific worldview of his age. What is remarkable is that Einstein’s greatest discoveries belong to him alone. It is perhaps fitting that this volume is being published one hundred years after Einstein settled the question of why the sky is blue. What we see is a giant intellect struggling as an ordinary person to make sense of the realities of life in the twentieth century.

  This volume concentrates on the essays on science that Albert Einstein included in the first authorized edition of Mein Weltbild. These essays had an amazing breadth and made many fundamental points about the nature of the universe. The central theme answered the question of how Einstein came to his theories. He believed that the only source of knowledge was experience, and that in the case of general relativity such experience did not always suggest the scientific truth of a theory. The development of a theory depended on “only intuition resting on a sympathetic understanding of experience.” It was the “object of all theory to make the irreducible elements as simple and few in number as possible.” He was “convinced that we can discover by purely mathematical constructions […] the key to the understanding of natural phenomena.” Experience suggests, the mind constructs (with the help of mathematics), and experience confirms.

  Einstein bolstered his argument by tracing the development of various universal theories of science and the advances that these theories brought to our ability to understand the world. Euclid’s geometry gave “the human intellect the confidence in itself for subsequent achievements.” “Purely logical thinking [such as Euclid] cannot yield us any knowledge of the empirical world.” Galileo and Kepler showed that “all knowledge of reality starts from experience and ends in it.” And Newton “still believed that the basic laws of his system could be derived from experience.”

  Further, in his essay On Scientific Truth, the idea of a superior mind as conceived in Spinoza’s “pantheistic” religion revealing itself in the world of experience represented Einstein’s conception of God.

  Spinoza’s metaphysics created a world view which was in conflict with the idea of an ever-expanding universe as predicted by an early version of the generalized relativity theory. By 1919, Einstein had amended his general theory of relativity to include a cosmological term so that the universe would be spatially self-enclosed as outlined in On the Theory of Relativity. In 1929, Edwin Hubble verified by astronomical observations that the universe was expanding and consequently there was at some time a “big bang.” Had Einstein not added the cosmological term and accepted his early version of the generalized relativity theory the expanding universe would perhaps have been his greatest predication.

  With the advent of Maxwell, Faraday, Hertz, and Lorentz there was a shift from description of material points to electro-magnetic fields, which became the ultimate entity. According to Einstein the development of field theory led directly to the special theory of relativity once he realized that field theory creates “reciprocal actions between bodies […] by processes which are propagated through space at a finite speed.” Such fields “ruled out the existence of forces acting at a distance, with the resulting destruction of the notion of absolute simultaneity.” Einstein felt that a final leap had to be made to develop the general theory of relativity. Such a theory can no longer be based on observation and reality. The theory must first be conceived through intuition by making the theory as simple as possible and then checked to see if it fits reality. It happens that generalized relativity depends heavily on mathematical constructions due to Riemann, Ricci, and Levi-Civita, which were already known. It is clear that Einstein felt that he would not have been able to complete his theory without their mathematical constructions.

  Where does quantum mechanics fit into all this? Can field theory find a way to include quantum mechanics? Can there be a “unified” field theory? In 1934, Einstein had hope of finding a solution but spent the remainder of his life looking unsuccessfully for it.

  Another interesting thread throughout Essays in Science involved the use of mathematics in developing a theory of reality. Starting with Euclid, the mathematics was whole unto itself. This was followed by Kepler, who developed the motion of the planets using circles and ellipses, which exhibit “the simplest conceivable form of regularity.” According to Einstein, Kepler’s “achievement is a particularly fine example of the truth that knowledge cannot spring from experience alone but only from the comparison of inventions of the intellect with observed facts.” Kepler’s laws represented integrals of the motion. Newton’s mechanics required the development of the calculus, ordinary derivatives, and differential equations. Field theory required partial derivatives. And finally, general relativity required the Rici calculus and the concept of invariant derivatives, which were independent of the geometry of space.

  In the essay The Cause of the Formation of Meanders . . . Einstein used simple arguments to give the “elementary principles involved [and a] short qualitative exposition of them.” In the next pages he used thought experiments to prove his thesis. Together with the following essay, The Flettner Ship, they provide outstanding examples of Einstein’s mind at work.

  Einstein’s connection to all things German, and in particular the scientific community in Berlin, through his appointment to the Kaiser Wilhelm Institute for Physics, made it very painful for him to give up his German citizenship. Throughout his years in America he sought the friendship and association with German Jews. Through this connection he developed a deep friendship with Dr. Dagobert D. Runes, the founder of Philosophical Library, who had written his doctoral dissertation on Spinoza. Many of Einstein’s essays were subsequently published by Philosophical Library, which is now reissuing this volume.


  Neil Berger

  Associate Professor Emeritus of Mathematics

  University of Illinois at Chicago

  August 2010

  Preface to Abridged Edition

  The World as I See It in its original form includes essays by Einstein on Judaism, Germany, Politics and Pacifism and sundry other topics. These have been omitted in the present abridged edition. The object of this reprint is simply to give the general reader an opportunity to examine some of the distinguished scholar’s papers dealing with science.

  Publisher’s Note

  to the original edition, entitled “The World as I See It”

  ALBERT EINSTEIN IS ONE of the most modest people in the world. In the letters and papers in this book he constantly refers to his “accidental” fame and his “unearned popularity.” So deep-rooted is this feeling that he has merely tilled his own row, howbeit that row was an inconceivably fertile one, that for many years his friends and intimates were unable to prevail upon him to publish his letters, papers and speeches, although opportunities and requests were showered on him. Even his scientific articles he would release to none save academic journals that do not reach the general public. The imagination of the world is stirred by the name of Albert Einstein, and yet hitherto it has had only the scantiest material to feed upon. Occasional, all-too-brief interviews; a few instances where Einstein suppressed his modesty for the sake of some great humanitarian cause; and the famous four-page pamphlet on the special theory of relativity.

  The publishers do not know what good fortune at last prompted Albert Einstein to relax his attitude a little. Perhaps he felt that in times like these each man must sacrifice himself if he can help but a little to alleviate the horrible conditions which have fallen upon the world. If anything could break Einstein’s silence, it was the threat of war in Europe. Perhaps, too, it was the persecution of his people, the Jews. Perhaps it was, in some small degree, a further extension of his modesty in a desire to show how much his scientific work has been prepared for, supported, and amplified by less heralded collaborators, as he explains in his articles and speeches on Kepler, Newton, Maxwell, Planck, Niels Bohr and others. Whatever the cause, he at last gave permission to one of his intimates, who prefers to conceal his identity beneath the initials J.H., because his was a labor of love, to collect and publish certain of his writings.

  These papers were originally published by the Querido Verlag in Amsterdam. In fairness to Professor Einstein, his American publishers would like to make it clear that although they have his full authorization to translate the German text as published in Holland, and although the documents from which the original publication was made have his authentication, there has been no further collaboration by him. Because of this, the publishers have taken extra and unusual care to check every detail of the translation. An expert has gone over the work to make sure that it represents the exact meaning of Professor Einstein. Thus, the responsibility for the accuracy of the translation, though every attempt has been made to insure it, must not be placed with Professor Einstein.

  There is a saying that only twelve people in the world can understand Einstein’s theory of relativity. The difficulties of reaching such an understanding have heretofore been heightened by lack in print of anything but the abstract mathematical formulation of the theory. The papers and speeches published for the first time in this volume will be comprehensible to any well-educated person. They deal only in part with the central core of the theory; but the very fact that they carry its elaborations somewhat afield to particular applications and examples will help the scientific-minded layman to achieve a more complete comprehension of the theory itself. This book presents to the world at large for the first time what Einstein has really accomplished in the field of abstract physics. We cannot help but feel that its publication is an event of historical importance.

  Translators’ Note

  I have had the benefit of the expert supervision of Dr. H. Stafford Hatfield,

  to whom my thanks are due.

  A.H.

  Principles of Research

  IN THE TEMPLE OF Science are many mansions, and various indeed are they that dwell therein and the motives that have led them thither. Many take to science out of a joyful sense of superior intellectual power; science is their own special sport to which they look for vivid experience and the satisfaction of ambition; many others are to be found in the temple who have offered the products of their brains on this altar for purely utilitarian purposes. Were an angel of the Lord to come and drive all the people belonging to these two categories out of the temple, it would be noticeably emptier, but there would still be some men, of both present and past times, left inside. Our Planck is one of them, and that is why we love him.

  I am quite aware that we have just now light-heartedly expelled in imagination many excellent men who are largely, perhaps chiefly, responsible for the building of the temple of Science; and in many cases our angel would find it a pretty ticklish job to decide. But of one thing I feel sure: if the types we have just expelled were the only types there were, the temple would never have existed, any more than one can have a wood consisting of nothing but creepers. For these people any sphere of human activity will do, if it comes to a point; whether they become officers, tradesmen or scientists depends on circumstances. Now let us have another look at those who have found favor with the angel. Most of them are somewhat odd, uncommunicative, solitary fellows, really less like each other, in spite of these common characteristics, than the hosts of the rejected. What has brought them to the temple? That is a difficult question and no single answer will cover it. To begin with I believe with Schopenhauer that one of the strongest motives that lead men to art and science is escape from everyday life with its painful crudity and hopeless dreariness, from the fetters of one’s own ever shifting desires. A finely tempered nature longs to escape from personal life into the world of objective perception and thought; this desire may be compared with the townsman’s irresistible longing to escape from his noisy, cramped surroundings into the silence of high mountains, where the eye ranges freely through the still, pure air and fondly traces out the restful contours apparently built for eternity. With this negative motive there goes a personal one. Man tries to make for himself in the fashion that suits him best a simplified and intelligible picture of the world; he then tries to some extent to substitute this cosmos of his for the world of experience, and thus to overcome it. This is what the painter, the poet, the speculative philosopher and the natural scientist do, each in his own fashion. He makes this cosmos and its construction the pivot of his emotional life, in order to find in this way the peace and security which he cannot find in the narrow whirlpool of personal experience.

  What place does the theoretical physicist’s picture of the world occupy among all these possible pictures? It demands the highest possible standard of rigorous precision in the description of relations, such as only the use of mathematical language can give. In regard to his subject matter, on the other hand, the physicist has to limit himself very severely: he must content himself with describing the most simple events which can be brought within the domain of our experience; all events of a more complex order are beyond the power of the human intellect to reconstruct with the subtle accuracy and logical perfection which the theoretical physicist demands. Supreme purity, clarity and certainty at the cost of completeness. But what can be the attraction of getting to know such a tiny section of nature thoroughly, while one leaves everything subtler and more complex shyly and timidly alone? Does the product of such a modest effort deserve to be called by the proud name of a theory of the Universe?

  In my belief the name is justified; for the general laws on which the structure of theoretical physics is based claim to be valid for any natural phenomenon whatsoever. With them, it ought to be possible to arrive at the description, that is to say, the theory, of every natural process, including life, by means of pure deduction, if that process of deduction were not far beyond
the capacity of the human intellect. The physicist’s renunciation of completeness for his cosmos is therefore not a matter of fundamental principle.

  The supreme task of the physicist is to arrive at those universal elementary laws from which the cosmos can be built up by pure deduction. There is no logical path to these laws; only intuition, resting on sympathetic understanding of experience, can reach them. In this methodological uncertainty, one might suppose that there were any number of possible systems of theoretical physics all with an equal amount to be said for them; and this opinion is no doubt correct, theoretically. But evolution has shown that at any given moment, out of all conceivable constructions, a single one has always proved itself absolutely superior to all the rest. Nobody who has really gone deeply into the matter will deny that in practice the world of phenomena uniquely determines the theoretical system, in spite of the fact that there is no logical bridge between phenomena and their theoretical principles; this is what Leibnitz described so happily as a “pre-established harmony.” Physicists often accuse epistemologists of not paying sufficient attention to this fact. Here, it seems to me, lie the roots of the controversy carried on some years ago between Mach and Planck.

  The longing to behold this pre-established harmony is the source of the inexhaustible patience and endurance with which Planck has devoted himself, as we see, to the most general problems of our science, refusing to let himself be diverted to more grateful and more easily attained ends. I have often heard colleagues try to attribute this attitude of his to extraordinary will-power and discipline—wrongly, in my opinion. The state of mind which enables a man to do work of this kind is akin to that of the religious worshiper or the lover; the daily effort comes from no deliberate intention or program, but straight from the heart. There he sits, our beloved Planck, and smiles inside himself at my childish playing-about with the lantern of Diogenes. Our affection for him needs no threadbare explanation. May the love of science continue to illumine his path in the future and lead him to the solution of the most important problem in present-day physics, which he has himself posed and done so much to solve. May he succeed in uniting the quantum theory and electrodynamics in a single logical system.