Sheldon Lee Glashow is a Jewish American theoretical physicist and winner of the 1979 Nobel Prize in Physics.
Glashow (born December 5, 1932) was born in
Manhattan, New York.
He received a Bachelor of Arts degree from Cornell University
in 1954 and received a Ph. D. degree in physics from
Harvard University in 1959. From 1958 to 1960, Glashow
worked at the Niels Bohr Institute in Copenhagen. It
was here that he discovered the structure of the electroweak
theory. Between 1960 and 1966, Glashow became an assistant
professor at Stanford University, and then taught at
the University of California, Berkley. In 1966, he returned
to Harvard University.
The following press release from the Royal Swedish
Academy of Sciences describes Glashow's work:
other sciences, aspires to find common
causes for apparently unrelated natural
or experimental observations. A classical
example is the force of gravitation introduced
by Newton to explain such disparate phenomena
as the apple falling to the ground and
the moon moving around the earth.
Another example occurred in the 19th century when
it was realized, mainly through the work of Oersted
in Denmark and Faraday in England, that electricity
and magnetism are closely related, and are really different
aspects of the electromagnetic force or interaction
between charges. The final synthesis was presented in
the 1860's by Maxwell in England. His work predicted
the existence of electromagnetic waves and interpreted
light as an electromagnetic wave phenomenon.
The discovery of the radioactivity of certain heavy
elements towards the end of last century, and the ensuing
development of the physics of the atomic nucleus, led
to the introduction of two new forces or interactions:
the strong and the weak nuclear forces. Unlike gravitation
and electromagnetism these forces act only at very short
distances, of the order of nuclear diameters or less.
While the strong interaction keeps protons and neutrons
together in the nucleus, the weak interaction causes
the so-called radioactive beta-decay. The typical process
is the decay of the neutron: the neutron, with charge
zero, is transformed into a positively charged proton,
with the emission of a negatively charged electron and
a neutral, massless particle, the neutrino.
Although the weak interaction is much weaker than
both the strong and the electromagnetic interactions,
it is of great importance in many connections. The actual
strength of the weak interaction is also of significance.
The energy of the sun, all-important for life on earth,
is produced when hydrogen fuses or burns into helium
in a chain of nuclear reactions occurring in the interior
of the sun. The first reaction in this chain, the transformation
of hydrogen into heavy hydrogen (deuterium), is caused
by the weak force. Without this force solar energy production
would not be possible. Again, had the weak force been
much stronger, the life span of the sun would have been
too short for life to have had time to evolve on any
planet. The weak interaction finds practical application
in the radioactive elements used in medicine and technology,
which are in general beta-radioactive, and in the beta-decay
of a carbon isotope into nitrogen, which is the basis
for the carbon-14 method for dating of organic archaeological
Theories of weak interaction
A first theory or weak interaction was put forward
already in 1934 by the Italian physicist Fermi. However,
a satisfactory description of the weak interaction between
particles at low energy could be given only after the
discovery in 1956 that the weak force differs from the
other forces in not being reflection symmetric; in other
words, the weak force makes a distinction between left
and right. Although this theory was valid only for low
energies and thus had a restricted domain of validity,
it suggested a certain kinship between the week and
the electromagnetic interactions.
In a series of separate works in the 1960's this year's
Nobel Prize winners, Glashow, Salam and Weinberg developed
a theory which is applicable also at higher energies,
and which at the same time unifies the weak and electromagnetic
interactions in a common formalism. Glashow. Salam and
Weinberg started ,from earlier contributions by other.
scientists. Of special importance was a generalization
of the so-called gauge principle for the description
of the electromagnetic interaction. This generalization
was worked out around the middle of the 1950's by Yang
and Mills in USA. After the fundamental work in the
1960's the theory has been further developed. An important
contribution was made in 1971 by the young Dutch physicist
The theory predicts among other things the existence
of a new type of weak interaction, in which the reacting
particles do not change their charges. This behaviour
is similar to what happens in the electromagnetic interaction,
and one says that the interaction proceeds via a neutral
current. One should contrast this with the beta-decay
of the neutron, where the charge is altered when the
neutron is changed into a proton.
First observation of the weak neutral current
The first observation of an effect of the new type
of weak interaction was made in 1973 at the European
nuclear research laboratory, CERN, in Geneva in an experiment
where nuclei were bombarded with a beam of neutrinos.
Since then a series of neutrino experiments at CERN
and at the Fermi Laboratory near Chicago have given
results in good agreement with theory. Other laboratories
have also made successful tests of effects of the weak
neutral current interaction. Of special interest is
a result, published in the summer of 1978, of an experiment
at the electron accelerator at SLAC in Stanford, USA.
In this experiment the scattering of high energy electrons
on deuterium nuclei was studied and an effect due to
a direct interplay between the electronmagnetic and
weak parts of the unified interaction could be observed.
Interaction carried by particles
An important consequence of the theory is that the
weak interaction is carried by particles having some
properties in common - with the photon, which carries
the electromagnetic interaction between charged particles.
These so-called weak vector bosons differ from the massless
photon primarily by having a large mass; this corresponds
to the short range of the weak interaction. The theory
predicts masses of the order of one hundred proton masses,
but today's particle accelerators are not powerful enough
to be able to produce these particles.
The contributions awarded
this year's Nobel Prize in physics have
been of great importance for the intense
development of particle physics in this