Einstein's Principle Research Articles

Certain Matters in Relation to the Restricted Theory of Relativity, with Special Reference to the Clock Paradox and the Paradox of the Identical Twins. I. Fundamentals

The paper first discusses the significance of the meaning of space-time coordinates as attached to “events” in the Lorentzian transformation. Restricted relativity involves two distinct parts: A—the invariance of the forms of the laws under the transformation: B—the hypothesis that similar experiments performed in relatively moving frames S and S′ give identical results. The test of A is a matter of pen and paper. B involves the hypothesis that the instruments are such that the actual measurements of space-time coordinates of events shall be related, for the two systems, by the transformation. Only by the postulation of a theory such as the quantum theory, but one relativistically invariant in sense A, can one understand the relationship between the instruments, whether the said instruments be constructed by independent observers in S and S′ from the material around them, or whether the observer in S′ acquires his instruments from S by setting them in motion. The second method of acquiring the instruments will not, in all cases, yield measurements related by the transformation. Thus, if we start with a system of isolated clocks which have been synchronized in S according to Einstein's principle, and if we transfer them to S′, their “rates” (in a suitably defined manner) may be expected to alter in accordance with the transformation. However, it will remain for the observer in S′ to synchronize the clocks in that new frame, having adjusted the time origin of one of them.

The Physical Basis of Gravitation

It is shown that Einstein's principle of equivalence permits the gravitational field to be interpreted as an ether flow, and the experimentally verifiable results of the relativistic gravitational theory are deduced directly from elementary physical principles by the use of this interpretation.

Cosmic Rays

THE twenty-fourth Guthrie Lecture of the Physical Society was delivered by Prof. P. M. S. Blackett on February 26. He took as his subject “Cosmic Rays: Recent Developments”. He said that the most important discovery of recent years in the field of cosmic rays was the realization that the hard or penetrating component of the rays consists of particles of a new type, called mesotrons. This new particle has a mass intermediate between that of the electron and the proton and possesses the peculiar property of being spontaneously unstable. Its average life when at rest is about one millionth of a second, but when moving fast it lives longer—thus giving a nice verification of Einstein's principle of relativity.

Introduction

SINCE 1905, when Prof. A. Einstein published his Principle of Relativity in its special form, much attention has been devoted to the subject in scientific circles, and during the last two or three years keen interest has been shown in it by many general readers of intellectual type. Nearly a thousand books, pamphlets, and papers have appeared in which the principle as a whole is described, or some of its aspects are discussed, and among these are a few which aim at making its character and consequences clear without the mathematical expressions which give it precise significance. A praiseworthy essay of this kind is that by Mr. L. Bolton, a senior examiner in the Patent Office, published in the Westminster Gazette on Monday by arrangement with the Scientific American, which awarded it a prize of five thousand dollars as the clearest explanation of Einstein's principle for general readers.

Einstein's principle of relativity and its bearing upon physics

Einstein's principle of relativity and its bearing upon physics