RELATIVITY The Special and the General Theory, (C)1961 by the Estate of Albert Einstein
Authorized translation by Robert W. Lawson, University of Sheffield
RELATIVITY is a classic of scientific literature. I now appreciate Albert Einstein much more than before after reading his own writings. I was amazed to find the most easy to understand, basic explanation of his theories on the Special and General Theories of Relativity and classical physics that I have ever come across. How I wish they could clone another Einstein (I understand his brain was removed and preserved, temporarily lost and then rediscovered).
Einstein is a physicist, not an abstract theoretician, who builds his Relativity theory on the foundation of the work of the great scientists who preceded him, referring often to supporting physical experiments. As he explains his theories, he gives attributes to the men upon whose work he has based his own discoveries. A modest man, he has a great admiration for Galileo Galilei, Newton, Kepler and Descartes, and refers often to the investigations of H. A. Lorentz into electromagnetic phenomena (“In contrast to classical mechanics, the Lorentz transformation explained all the electromagnetic and optical processes within ponderable bodies known at that time, on the assumption that the influence of ponderable matter on the electric field-and conversely-is due solely to the fact that the constituent particles of matter carry electrical charges, which share the motion of the particles”…A.E.). As his explanations of relativity evolve from chapter to chapter, he names the physicists whose work he has called upon: the Faraday-Maxwell interpretation of electromagnetic action at a distance; Fizeau, FitzGerald, Minkowski and his four dimensional “world” (described by four numbers- three space coordinates x,y,z and a time coordinate t); E. Mach, Gauss (combining the analytical and geometrical mode handling a system of arbitrary curves); Riemann, Helmholtz and Poincare on the question of the finiteness of space.
I have read so many complicated, incorrect explanations of his theory that I will not do what others have done-say what he said. I will only directly quote from him. And now, Professor Einstein has the floor:
“The Theory of Relativity arose out of efforts to improve, with reference to logical economy, the foundation of physics as it existed at the turn of the century. The so-called special or restricted relativity theory is based on the fact that Maxwell’s equations are converted into equations of the same form when they undergo Lorentz transformation. The content of the restricted relativity theory can accordingly be summarized in one sentence: all natural laws must be so conditioned that they are covariant with respect to Lorentz transformations. From this it follows that the simultaneity of two distant events is not an invariant concept and that the dimensions of rigid bodies and the speed of clocks depend upon their state of motion.”
What is the Theory of Relativity? The Theory of Relativity resembles a building consisting of two separate stories, the Special Theory and the General Theory. The Special Theory, on which the General Theory rests, applies to all physical phenomena with the exception of gravitation; the General Theory provides the law of gravitation and its relations to the other forces of nature.
By the “special principle of relativity” is meant the generalization of this definition to include any natural event whatever: thus, every universal law of nature which is valid in relation to a coordinate system C, must also be valid, as it stands, in relation to a coordinate system C’ which is in uniform translatory motion relatively to C.
The second principle, on which the Special Theory of Relativity rests, is the “principle of the constant velocity of light in vacuo.” This principle asserts that light in vacuo always has a definite velocity of propagation (independent of the state of motion of the observer or of the source of the light).
The most important upshot of the Special Theory of Relativity concerned the inert mass of corporeal systems. It turned out that the inertia of a system necessarily depends on its energy-content, and this led straight to the notion that inert mass is simply latent energy. The principle of the conservation of mass lost its independence and became fused with that of the conservation of energy: E=Mc2
In the General Theory of Relativity the doctrine of space and time, or kinematics, no longer figures as a fundamental independent of the rest of physics. The geometrical behavior of bodies and the motion of clocks rather depend on gravitational fields, which in their turn are produced by matter. An atom absorbs or emits light of a frequency which is dependent on the potential of the gravitational field in which it is situated.”
Right there he says that it is material, whereas I have read so many writers attempting to explain that in reality there is no such thing as gravitational attraction, somehow having gotten the idea that Newton is obsolete.
On the shape and structure of space, Einstein states that he believes there to be no such thing as “empty space” referring to Descartes who felt uneasy with the concept of nothingness, and the Universe to be finite, yet unbounded and expanding. He refers to Hubble’s investigation of extra-galactic nebulae and the Doppler theory and the Michelson-Morley experiment as some of the experiments which prove his theory.
“The possibility of a finite and yet unbounded universe…at first, the straight lines which radiate from the starting point diverge farther and farther from one another, but later they approach each other, and finally they run together again at a “counter point” to the starting point (Gaussian coordinates)…. elliptical space can be regarded as a curved space in which the two “counter-points” are identical (indistinguishable from each other). An elliptical universe can thus be considered to some extent as a curved universe possessing central symmetry.
It follows from what has been said that closed spaces without limits are conceivable. From amongst these, the spherical space (and the elliptical) excels in its simplicity, since all points on it are equivalent….Since in reality the detailed distribution of matter is not uniform, the real universe will deviate in individual parts from the spherical, i.e. the universe will be quasi-spherical. But it will be necessarily finite.”….Albert Einstein
So we’re all gold fish in a bowl. Who’s watching us? We can’t get out, I guess we’ll just have to learn to live with the Universe the way it is.
