volume II: Synopsis
Part III: Modern Physics
page 17: Albert Einstein
At the turn of the twentieth century even the existence of atoms was moot. Einstein not only produced a new way to look at space and time, but made great contributions to the new idea that the physical world is discrete or quantized. In particular he suggested that light, even though it has wave properties, is emitted and moves as a particle, the photon. He is best known, however, for the special and general theories of relativity. Photon - Wikipedia
Einstein announced his 'new kinematics', now known as the special theory of relativity, in 1905. He was motivated by the apparent asymmetry between the classical treatment of electric and magnetic fields even though Maxwell's equations. which describe these fields, see them as symmetrical. Albert Einstein
Maxwell's equations determine the velocity of light, and Einstein found that if we are to treat electric and magnetic fields symmetrically we must conclude that the velocity of light is independent of the velocity of the both the source of light and the observer of that light. Classical physicists like Maxwell imagined light waves travelling in a medium called the ether, like sound waves in air. Maxwell's equations - Wikipedia
This idea led to an attempt by the physicists Michelson and Morley to measure the velocity of the Earth through the ether by measuring the differences in the velocity of light coming from different directions. Despite the high precision of their measurements, they found that the velocity of light was the same in every direction. Einstein's conclusion was consistent with this result and suggested that the ether did not exist. Michelson and Morley
The special theory of relativity reveals that ordinary space appears to have a rather extraordinary structure. This structure arises from the fact that the finite velocity of any physical signal delays communication between different points in space. How an observer sees an event depends on the velocity of the event relative to the observer. Metric space - Wikipedia
Special relativity predicts that time appears to go more slowly, distances appear shorter and masses greater in a relatively moving event. Because of the great velocity of light, these phenomena are very small at the velocity differences we ordinarily experience but they become important at velocity differences typical of observations in astronomy and particle physics. Special relativity - Wikipedia
The special theory of relativity shown how to transform observations on a moving system to the rest frame of the observer. These 'Lorentz transformations' are based on the well verified assumption that all observers seen the same physical phenomena in their own rest frame. Lorentz transformation - Wikipedia
Another effect of the finite velocity of communication is the 'relativity of simultaneity'. Two events separated in space may appear to be simultaneous to one observer, but not to another, depending on the relative velocities between the observes and the events in question.
Particles at rest with respect to a given observer appear to have neither kinetic energy nor momentum. Particles in relative motion, however, are seen to have momentum which varies linearly with their relative velocity and kinetic energy that varies as the square of their relative velocity. These observations are verified if and when the observer comes into collision with the moving particles. Momentum - Wikipedia, Kinetic energy - Wikipedia
If we apply the Lorentz transformations to this situation, we find that mass and energy are related by the famous equation E = mc2. We will examine the consequences of this relationship when we come to deal with quantum field theory. Quantum field theory, Mass-energy equivalence - Wikipedia
Newtonian physics works in a space that comprises the three dimensions of ordinary space, plus the fourth time dimension. Newtonian space and time are independent because signals are considered to move with infinite velocity yielding zero travel time. Nevertheless, distinction between space remains real in both Newtonian and Einsteinian physics. We can move in any direction in physical space, but we are restricted to one direction in time which we usually see as a movement from past to future.
The metric imposed on physical space by the finite velocity of light has an analogue in all other situations where communications take a finite time to cover a finite distance. The evolution of email to replace snail mail, for instance, changes the spacetime metric of written communication in a manner analogous to increasing the velocity of light in physics.
From the special theory, which describes the phenomena observed by systems in uniform relative motion, Einstein extrapolated to accelerated motion to arrive at the general theory of relativity. The general theory which has the capacity to represent the whole of spacetime, and so have become one of the foundations of modern cosmology. General relativity - Wikipedia, Cosmology - Wikipedia
The structure of the Universe is constrained by the time delay in communication, so we will not be surprised to find that much of the structure of the Universe is constrained by the structure of communication. One hope for this work is to use the idea that the Universe is a transfinite communication network as a tool to develop the much sought after connection between general relativity and quantum mechanics. Unified field theory - Wikipedia, Equivalence principle - Wikipedia
[revised 23 May 2013]
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|Einstein, Albert, The Principle of Relativity, Dover 1924 Amazon.com reader review: 'This book is a collection of the most important lectures given by Einstein, Lorentz, Minkowski and Weyl that led to the formulation of the theory of relativity in its two parts. The first part is the special theory, which studies the inertial and moving reference frames without considering the effects of gravity. The second part, the general theory, explains the nature of gravity.' Reinaldo Olivares
|Feynman, Richard Phillips, and Gerry Neugebauer (Preface), Roger Penrose (Introduction), Six Not-So-Easy Pieces: Einstein's Relativity, Symmetry and Space-Time, Perseus Press 1998 'No single breakthrough in twentieth-century physics (with the possible exception of quantum mechanics) changed our view of the world more than that of Einstein's discovery of relativity. The notions that the flow of time is not a constant, that the mass of an object depends on its velocity, and that the speed of light is a constant no matter what the motion of the observer, at first seemed shocking to scientists and laymen alike. But, as Feynman shows so clearly and so entertainingly in the lectures chosen for this volume, these crazy notions are no mere dry principles of physics, but are things of beauty and elegance. No one - not even Einstein himself - explained these difficult, anti-intuitive concepts more clearly, or with more verve and gusto, than Richard Feynman.'
|Hawking, Steven W, and G F R Ellis, The Large Scale Structure of Space-Time , Cambridge UP 1975 Preface: Einstein's General Theory of Relativity ... leads to two remarkable predictions about the universe: first that the final fate of massive stars is to collapse behind an event horizon to form a 'black hole' which will contain a singularity; and secondly that there is a singularity in our past which constitutes, in some sense, a beginning to our universe. Our discussion is principally aimed at developing these two results.'
|Misner, Charles W, and Kip S Thorne, John Archibald Wheeler, Gravitation, Freeman 1973 Jacket: 'Einstein's description of gravitation as curvature of spacetime led directly to that greatest of all predictions of his theory, that the universe itself is dynamic. Physics still has far to go to come to terms with this amazing fact and what it means for man and his relation to the universe. John Archibald Wheeler. . . . this is a book on Einstein's theory of gravity. . . . '
|Nathan, Otto, and Heinz Norden (eds), Einstein on Peace, Avenel 1981 Bertrand Russell, Preface: "It is a very good thing that Einstein's letters and writings on other than scientific subjects are being collected and printed. Einstein was not only the ablest man of science of his generation, he was also a wise man, which is something different. If statesmen had listened to him, the course of human events would have been less disastrous than it has been.'
|Pais, Abraham, 'Subtle is the Lord...': The Science and Life of Albert Einstein, Oxford UP 1982 Jacket: In this ... major work Abraham Pais, himself an eminent physicist who worked alongside Einstein in the post-war years, traces the development of Einstein's entire ouvre. ... Running through the book is a completely non-scientific biography ... including many letters which appear in English for the first time, as well as other information not published before.'
|Einstein, Albert, "Zur Elektrodynamik bewegter Körper (On the electrodynamics of moving bodies)", Annalen de Physik, 17, , 1905, page 891. Introduction: 'It is known that Maxwell's electrodynamics - as understood at the present time - when applied to moving bodies, leads to asymmetries which do not appear to be inherent in the phenomena. Take, for example, the reciprocal electrodynamic action of a magnet and a conductor. The observable phenomenon here depends only on the relative motion of the conductor and the magnet, whereas the customary view draws a sharp distinction between the two cases in which either the one or the other of these bodies is in motion. For if the magnet is in motion and the conductor at rest, there arises in the neighbourhood of the magnet an electric field of a certain definite energy, producing a current at the places where parts of the conductor are situated. But if the magnet is stationary and the conductor is in motion, no electric field arises in the neighbourhood of the magnet. In the conductor, however, we find an electromotive force, to which in itself there is no corresponding energy, but which gives rise - assuming equality of relative motion in the two cases discussed - to electric currents of the same path and intensity as those produced by the electric forces in the former case.
Examples of this sort together with the unsuccessful attempts to discover any motion of the earth relatively to the "light medium" suggest that the phenomena of electrodynamics as well as of mechanics prossess no properties corresponding to the idea of absolute rest.'. back |
|Albert Einstein On the Electrodynamics of Moving Bodies An english translation of the paper that founded Special relativity. 'Examples of this sort, [in the contemporary application of Maxwell's electrodynamics to moving bodies] together with the unsuccessful attempts to discover any motion of the earth relatively to the ``light medium,'' suggest that the phenomena of electrodynamics as well as of mechanics possess no properties corresponding to the idea of absolute rest. They suggest rather that, as has already been shown to the first order of small quantities, the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good.' back |
|Cosmology - Wikipedia Cosmology - Wikipedia, the free encyclopedia 'Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order. Modern cosmology is dominated by the Big Bang theory, which brings together observational astronomy and particle physics.' back |
|Equivalence principle - Wikipedia Equivalence principle - Wikipedia, the free encyclopedia 'In the physics of general relativity, the equivalence principle is any of several related concepts dealing with the equivalence of gravitational and inertial mass, and to Albert Einstein's assertion that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is actually the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.' back |
|General relativity - Wikipedia General relativity - Wikipedia, the free encyclopedia 'General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics. General relativity generalises special relativity and Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the four-momentum (mass-energy and linear momentum) of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of partial differential equations.' back |
|Kinetic energy - Wikipedia Kinetic energy - Wikipedia, the free encyclopedia 'The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body in decelerating from its current speed to a state of rest.' back |
|Lorentz transformation - Wikipedia Lorentz transformation - Wikipedia, the free encyclopedia 'In physics, the Lorentz transformation or Lorentz-Fitzgerald transformation describes how, according to the theory of special relativity, two observers' varying measurements of space and time can be converted into each other's frames of reference. It is named after the Dutch physicist Hendrik Lorentz. It reflects the surprising fact that observers moving at different velocities may measure different distances, elapsed times, and even different orderings of events.' back |
|Mass-energy equivalence - Wikipedia Mass-energy equivalence - Wikipedia, the free encyclopedia In physics, mass–energy equivalence is the concept that any mass has an associated energy and vice versa. In special relativity this relationship is expressed using the mass–energy equivalence formula E = mc2 where E = energy, m = mass, and c = the speed of light in a vacuum (celeritas). Two definitions of mass in special relativity may be validly used with this formula. If the mass in the formula is the rest mass, the energy in the formula is called the rest energy. If the mass is the relativistic mass, then the energy is the total energy.' back |
|Maxwell's equations - Wikipedia Maxwell's equations - Wikipedia, the free encyclopedia 'In classical electromagnetism, Maxwell's equations are a set of four equations that describe the properties of the electric and magnetic fields and relate them to their sources, charge density and current density. Maxwell used the equations to show that light is an electromagnetic wave.' back |
|Metric space - Wikipedia Metric space - Wikipedia, the free encyclopedia 'In mathematics, a metric space is a set where a notion of distance (called a metric) between elements of the set is defined.
The metric space which most closely corresponds to our intuitive understanding of space is the 3-dimensional Euclidean space. In fact, the notion of "metric" is a generalization of the Euclidean metric arising from the four long known properties of the Euclidean distance. The Euclidean metric defines the distance between two points as the length of the straight line connecting them.
The geometric properties of the space depends on the metric chosen, and by using a different metric we can construct interesting non-Euclidean geometries such as those used in the theory of general relativity.
A metric space also induces topological properties like open and closed sets which leads to the study of even more abstract topological spaces.' back |
|Michelson and Morley On the relative motion of the earth and the lumeniferous ether. The classic paper back |
|Momentum - Wikipedia Momentum - Wikipedia, the free encyclopedia 'In classical mechanics, momentum (pl. momenta; SI unit kg·m/s, or, equivalently, N·s) is the product of the mass and velocity of an object (p=mv). For more accurate measures of momentum, see the section "modern definitions of momentum" on this page.' back |
|Photon - Wikipedia Photon - Wikipedia, the free encyclopedia 'In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force. ' back |
|Special relativity - Wikipedia Special relativity - Wikipedia, the free encyclopedia 'Special relativity . . . is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein (after the considerable and independent contributions of Hendrik Lorentz, Henri Poincaré and others) in the paper "On the Electrodynamics of Moving Bodies".
It generalizes Galileo's principle of relativity—that all uniform motion is relative, and that there is no absolute and well-defined state of rest (no privileged reference frames)—from mechanics to all the laws of physics, including both the laws of mechanics and of electrodynamics, whatever they may be. Special relativity incorporates the principle that the speed of light is the same for all inertial observers regardless of the state of motion of the source.' back |
|Unified field theory - Wikipedia Unified field theory - Wikipedia, the fre encyclopedia 'In physics, a unified field theory is a type of field theory that allows all of the fundamental forces between elementary particles to be written in terms of a single field. There is no accepted unified field theory yet, and this remains an open line of research. The term was coined by Albert Einstein who attempted to unify the general theory of relativity with electromagnetism. A Theory of Everything is closely related to unified field theory, but differs by not requiring the basis of nature to be fields, and also attempts to explain all physical constants of nature . . . ' back |