The concept of mass is one of the most fundamental notions in physics, comparable in importance only to those of space and time. But in contrast to the latter, which are the subject of innumerable physical and philosophical studies, the concept of mass has been but rarely investigated. Here Max Jammer, a leading philosopher and historian of physics, provides a concise but comprehensive, coherent, and self-contained study of the concept of mass as it is defined, interpreted, and applied in contemporary physics and as it is critically examined in the modern philosophy of science. With its focus on theories proposed after the mid-1950s, the book is the first of its kind, covering the most recent experimental and theoretical investigations into the nature of mass and its role in modern physics, from the realm of elementary particles to the cosmology of galaxies.

The book begins with an analysis of the persistent difficulties of defining inertial mass in a noncircular manner and discusses the related question of whether mass is an observational or a theoretical concept. It then studies the notion of mass in special relativity and the delicate problem of whether the relativistic rest mass is the only legitimate notion of mass and whether it is identical with the classical (Newtonian) mass. This is followed by a critical analysis of the different derivations of the famous mass-energy relationship E = mc2 and its conflicting interpretations. Jammer then devotes a chapter to the distinction between inertial and gravitational mass and to the various versions of the so-called equivalence principle with which Newton initiated his Principia but which also became the starting point of Einstein's general relativity, which supersedes Newtonian physics. The book concludes with a presentation of recently proposed global and local dynamical theories of the origin and nature of mass.

Destined to become a much-consulted reference for philosophers and physicists, this book is also written for the nonprofessional general reader interested in the foundations of physics.

The philosophy of religion and the quest for spiritual truth preoccupied Albert Einstein--so much that it has been said "one might suspect he was a disguised theologian." Nevertheless, the literature on the life and work of Einstein, extensive as it is, does not provide an adequate account of his religious conception and sentiments. Only fragmentarily known, Einstein's ideas about religion have been often distorted both by atheists and by religious groups eager to claim him as one of their own. But what exactly was Einstein's religious credo? In this fascinating book, the distinguished physicist and philosopher Max Jammer offers an unbiased and well-documented answer to this question.

The book begins with a discussion of Einstein's childhood religious education and the religious atmosphere--or its absence--among his family and friends. It then reconstructs, step by step, the intellectual development that led Einstein to the conceptions of a cosmic religion and an impersonal God, akin to "the God of Spinoza." Jammer explores Einstein's writings and lectures on religion and its role in society, and how far they have been accepted by the general public and by professional theologians like Paul Tillich or Frederick Ferre. He also analyzes the precise meaning of Einstein's famous dictum "Science without religion is lame, religion without science is blind," and why this statement can serve as an epitome of Einstein's philosophy of religion.

The last chapter deals with the controversial question of whether Einstein's scientific work, and in particular his theory of relativity, has theologically significant implications, a problem important for those who are interested in the relation between science and religion. Both thought-provoking and engaging, this book aims to introduce readers, without proselytizing, to Einstein's religion."

Max Jammer's Concepts of Simultaneity presents a comprehensive, accessible account of the historical development of an important and controversial concept -- which played a critical role in initiating modern theoretical physics -- from the days of Egyptian hieroglyphs through to Einstein's work in 1905, and beyond. Beginning with the use of the concept of simultaneity in ancient Egypt and in the Bible, the study discusses its role in Greek and medieval philosophy as well as its significance in Newtonian physics and in the ideas of Leibniz, Kant, and other classical philosophers. The central theme of Jammer's presentation is a critical analysis of the use of this concept by philosophers of science, like PoincarA(c), and its significant role in inaugurating modern theoretical physics in Einstein's special theory of relativity. Particular attention is paid to the philosophical problem of whether the notion of distant simultaneity presents a factual reality or only a hypothetical convention. The study concludes with an analysis of simultaneity's importance in general relativity and quantum mechanics.