[...]... distinguish various kinds of theories in physics Most of them are constructive They attempt to build up a picture of the more complex phenomena out of the materials of a relatively simple formal scheme from which they start out Thus the kinetic theory of gases seeks to reduce mechanical, thermal and diffusional processes to movements of molecules—i.e., to build them up out of the hypothesis of molecular motion... principle of the conservation of heat We might say that the principle of the conservation of energy, having previously swallowed up that of the conservation of heat now proceeded to swallow that of the conservation of mass—and holds the field alone It is customary to express the equivalence of mass and energy (though somewhat inexactly) by the formula E=mc2, in which c represents the velocity of light about... provide the possibility of this kind of freedom if the problem of a reasonable division of labor were solved The development of science and of the creative activities of the spirit in general requires still another kind of freedom, which may be characterized as inward freedom It is this freedom of the spirit which consists in the independence of thought from the restrictions of authoritarian and social... implications of a theory which was perfected and published during the War in the land of your enemies Even though the investigation of the influence of the gravitational field of the sun on light rays is a purely objective matter, I cannot forbear to express my personal thanks to my English colleagues for their work; for without it I could hardly have lived to see the most important implication of my theory... the second goal, that is, the possibility of the spiritual development of all individuals, is to be secured, a second kind of outward freedom is necessary Man should not have to work for the achievement of the necessities of life to such an extent that he has neither time nor strength for personal activities Without this second kind of outward liberty, freedom of expression is useless for him Advances... their state of motion? If it is necessary for the purpose of describing nature, to make use of a co-ordinate system arbitrarily introduced by us, then the choice of its state of motion ought to be subject to no restriction; the laws ought to be entirely independent of this choice (general principle of relativity) The establishment of this general principle of relativity is made easier by a fact of experience... principle of relativity It turns out, however, that this contradiction is only an apparent one which is based essentially on the prejudice about the absolute character of time or rather of the simultaneity of distant events We just saw that x, y, z and t of an event can, for the moment, be defined only with respect to a certain chosen system of coordinates (inertial system) The transformation of the x,... the help of a Lorentztransformation on x, y, z, t) The special theory of relativity has led to a clear understanding of the physical concepts of space and time and in connection with this to a recognition of the behavior of moving measuring rods and clocks It has in principle removed the concept of absolute simultaneity and thereby also that of instantaneous action at a distance in the sense of Newton... shown how the law of motion must be modified in dealing with motions that are not negligibly small as compared with the velocity of light It has led to a formal clarification of Maxwell’s equations of the electromagnetic field; in particular it has led to an understanding of the essential oneness of the electric and the magnetic field It has unified the laws of conservation of momentum and of energy into... (general principle of relativity) Now it is not difficult to understand why the general principle of relativity (on the basis of the equivalence principle) has led to a theory of gravitation There is a special kind of space whose physical structure (field) we can presume as precisely known on the basis of the special theory of relativity This is empty space without electromagnetic field and without matter . Israel (1949) A Biography of Albert Einstein Acknowledgments 1 Publisher’s Preface THIS SECOND VOLUME of collected essays by Albert Einstein covers a period of about fifteen years 1934 to 1950; the. h1" alt="" Out of My Later Years The Scientist, Philosopher and Man Portrayed Through His Own Words Albert Einstein Contents 1. Publisher’s Preface Convictions and Beliefs 2. Self-Portrait (1936) 3 political and individual freedom of man. Awareness of this state of affairs overshadows every hour of my present existence, while ten years ago it did not yet occupy my thoughts. It is this that