Albert Einstein

I

Introduction

Albert Einstein (1879-1955), German-born American physicist and Nobel laureate, best known as the creator of the special and general theories of relativity and for his bold hypothesis concerning the particle nature of light. He is perhaps the best-known scientist of the 20th century.

Einstein was born in Ulm on March 14, 1879, and spent his youth in Munich, where his family owned a small shop that manufactured electric machinery. He did not talk until the age of three, but even as a youth he showed a brilliant curiosity about nature and an ability to understand difficult mathematical concepts. At the age of 12 he taught himself Euclidean geometry.

Einstein hated the dull regimentation and unimaginative spirit of school in Munich. When repeated business failure led the family to leave Germany for Milan, in Italy, Einstein, who was then 15 years old, used the opportunity to withdraw from the school. He spent a year with his parents in Milan, and, when it became clear that he would have to make his own way in the world, he finished secondary school in Arrau, Switzerland, and entered the Swiss National Polytechnic in Zurich. Einstein did not enjoy the methods of instruction there. He often missed classes, using the time to study physics on his own or to play his beloved violin. He passed his examinations and graduated in 1900 by studying the notes of a classmate. His professors did not think highly of him and would not recommend him for a university position.

For two years Einstein worked as a tutor and substitute teacher. In 1902 he secured a position as an examiner in the Swiss Patent Office in Bern. In 1903 he married Mileva Marić, who had been his classmate at the polytechnic. They had two sons but eventually divorced. Einstein later remarried.

II

Early Scientific Publications

In 1905 Einstein received his doctorate from the University of Zurich for a theoretical dissertation on the dimensions of molecules, and he also published three theoretical papers of central importance to the development of 20th-century physics. In the first of these papers, on Brownian motion, he made significant predictions about the motion of particles that are randomly distributed in a fluid. These predictions were later confirmed by experiment.

The second paper, on the photoelectric effect, contained a revolutionary hypothesis concerning the nature of light. Einstein not only proposed that under certain circumstances light can be considered as consisting of particles, but he also hypothesized that the energy carried by any light particle, called a photon, is proportional to the frequency of the radiation. The formula for this is E = hu, where E is the energy of the radiation, h is a universal constant known as Planck's constant, and u is the frequency of the radiation. This proposal—that the energy contained within a light beam is transferred in individual units, or quanta—contradicted a 100-year-old tradition of considering light energy to be a manifestation of continuous processes. Virtually no one accepted Einstein's proposal. In fact, when the American physicist Robert Andrews Millikan experimentally confirmed the theory almost a decade later, he was surprised and somewhat disquieted by the outcome.

Einstein, whose prime concern was to understand the nature of electromagnetic radiation, subsequently urged the development of a theory that would be a fusion of the wave and particle models for light. Again, very few physicists understood or were sympathetic to these ideas.

III

Einstein's Special Theory of Relativity

Einstein's third major paper of 1905, “On the Electrodynamics of Moving Bodies”, contained what became known as the special theory of relativity. Since the time of the English mathematician and physicist Sir Isaac Newton, natural philosophers (as physicists and chemists were known) had been trying to understand the nature of matter and radiation, and how they interacted in some unified world picture. The position that mechanical laws are fundamental has become known as the mechanical world view, and the position that electrical laws are fundamental has become known as the electromagnetic world view. Neither approach, however, is capable of providing a consistent explanation for the way radiation (light, for example) and matter interact when viewed from different inertial frames of reference, that is, an interaction viewed simultaneously by an observer at rest and an observer moving at uniform speed.

In the spring of 1905, after considering these problems for ten years, Einstein realized that the crux of the problem lay not in a theory of matter but in a theory of measurement. At the heart of his special theory of relativity was the realization that all measurements of time and space depend on judgements as to whether two distant events occur simultaneously. This led him to develop a theory based on two postulates: the principle of relativity, that physical laws are the same in all inertial reference systems, and the principle of the invariance of the speed of light, that the speed of light in a vacuum is a universal constant. He was thus able to provide a consistent and correct description of physical events in different inertial frames of reference without making special assumptions about the nature of matter or radiation, or how they interact. Virtually no one understood Einstein's argument.

IV

Early Reactions to Einstein

The difficulty that others had with Einstein's work was not because it was mathematically complex or technically obscure; the problem resulted, rather, from Einstein's beliefs about the nature of good theories and the relationship between experiment and theory. Although he maintained that the only source of knowledge is experience, he also believed that scientific theories are the free creations of a finely tuned physical intuition and that the premises on which theories are based cannot be connected logically to experiment. A good theory, therefore, is one in which a minimum number of postulates is required to account for the physical evidence. This sparseness of postulates, a feature of all Einstein's work, was what made his work so difficult for colleagues to comprehend, let alone support.

Einstein did have important supporters, however. His chief early patron was the German physicist Max Planck. Einstein remained at the Patent Office for four years after his star began to rise within the physics community. Then he moved rapidly upwards in the German-speaking academic world. His first academic appointment was in 1909 at the University of Zurich. In 1911 he moved to the German-speaking university at Prague, and in 1912 he returned to the Swiss National Polytechnic in Zurich. Finally, in 1913, he was appointed director of the Kaiser Wilhelm Institute for Physics in Berlin.