Albert Einstein and His Theories
Einstein, Albert (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 most well-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. ...view middle of the document...
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 hundred-year-old tradition of considering light energy 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.
Einstein's Special Theory of Relativity
Einstein's third major paper in 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 judgments 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...