viii FOREWORD
neglect Einstein's personal side—and an interesting picture of Einstein the man
indeed comes through—the real strength of this work lies in its handling of the
physical ideas. As Einstein had earlier commented: "The essential of the being of
a man of my type lies precisely in what he thinks and how he thinks, not what he
does or suffers".
On the scientific side, there is, indeed, much to be said. For Einstein contributed
far more to the physics of the early 20th century than just relativity. Apart from
Max Planck, with his ground-breaking work of 1900 (on the spectrum of black-
body radiation), Einstein was the first to break away from the classical physics of
the time and to introduce the crucial quantum "wave/particle" idea—the idea that
despite light being an electromagnetic wave, it sometimes had to be treated as a
collection of particles (now called "photons"). Through this work Einstein
discovered the explanation of the photo-electric effect, this eventually winning him
a Nobel Prize. He provided (in his doctorate thesis) a novel method of determining
the sizes of molecules, at a time when their very existence was still controversial.
He was one of the first to understand the detailed nature of the tiny wiggling
"Brownian" motion of small particles in suspension and to provide a beginning
to the new statistical physics. He contributed key ideas that led to the development
of lasers. And all this is not to mention his revolutionary theories of special and
general relativity!
In describing each of these contributions, Pais first sets the stage, lucidly
describing the state of the relevant parts of physics at the time Einstein entered
the scene, often explaining in significant detail the work of Einstein's precursors.
Then we find Einstein's own fundamental contributions, introduced and discussed
in depth, the essential novelty of Einstein's viewpoint being all very clearly set out,
as is the profound influence that it had on subsequent work. This account indeed
provides a wonderful overview of the developments in physics of the early 20th
century, as there seems to be no major area of theoretical physics on which Einstein
did not have some impact. This book is not a "popular" work, in the sense of the
term that so often seems to involve distortions and oversimplifications in attempts
to explain technical concepts to the lay reader. Instead, it comes seriously to grips
with the physics involved in each major area that is treated and, where appropriate,
mathematical equations are presented without apology.
Yet this is by no means simply a cold scientific account in which personal
influences are deemed irrelevant. Pais illuminates many facets of Einstein's life,
some of which may at first seem almost paradoxical. Pais may not always provide
answers, but he expounds these issues in insightful ways. The common picture of
Einstein is as an unworldly almost saintly old man, with twinkling eyes,
moustache, wild white hair, and attired in a floppy sweater. But this was the
Einstein who spent the last twenty years of his life in Princeton on a certain
approach to a unified field theory that the majority of physicists would now judge
to be basically misconceived. How does this picture relate to that of the Einstein
of the "miraculous" year 1905, with an apparently dapper appearance, working at