FUNDAMENTAL BUILDING BLOCKS 293
So what kind of boson might be
involved? Glashow guessed that
the bosons associated with the
weak force had to be relatively
massive because the force operates
over miniscule ranges and heavy
particles do not travel far. He
proposed two charged bosons,
W+ and W–, and a third neutral
Z boson. The W and Z force-carriers
were detected by CERN’s particle
accelerator in 1983.
Unification
In the 1960s, two physicists,
American Steven Weinberg and
Pakistani Abdus Salam, working
independently, incorporated the
Higgs field (pp.298–99) into
Glashow’s theory. The resultant
Weinberg–Salam model, or unified
electroweak theory, brought weak
interaction and electromagnetic
force together as a single force.
This was an astounding result,
since the weak and electromagnetic
forces operate in entirely different
spheres. The electromagnetic force
extends to the very edge of the
visible universe (the force is carried
by massless photons of light), while
the weak force barely reaches
across an atomic nucleus and is
some 10 million times weaker.
Their unification opens up the
tantalizing possibility that, under
certain high-energy conditions
such as those just after the Big
Bang, all four fundamental forces
may coalesce into one “superforce.”
The search continues for evidence
of such a Theory of Everything. ■At a temperature of about 10^32 K, gravity
separated from the other forces.At about 10^27 K, the strong nuclear force separated.A “Theory of Everything” suggests
an explanation of the unity of the
fundamental forces.At about 10^15 K, the electromagnetic and weak forces separated.See also: Marie Curie 190–95 ■ Ernest Rutherford 206–13 ■
Peter Higgs 298–99 ■ Murray Gell-Mann 302–07
Sheldon Glashow
Sheldon Lee Glashow was
born in New York in 1932,
the son of Russian Jewish
immigrants. He attended high
school with his friend Steven
Weinberg and upon graduating
in 1950, they both studied
physics at Cornell University.
Glashow earned his PhD from
Harvard, where he came up
with a description of the W
and Z bosons. After Harvard,
he went to the University of
California at Berkeley in 1961,
and later returned to join
the faculty at Harvard as a
professor of physics in 1967.
In the 1960s, Glashow
extended Murray Gell-Mann’s
quark model, adding a
property known as “charm”
and predicting a fourth quark,
which was discovered in- In recent years, he has
been heavily critical of string
theory, disputing its place
in physics due to its lack of
testable predictions, and
describing it as a “tumor.”
Key works1961 Partial Symmetries of
Weak Interactions
1988 Interactions: A Journey
Through the Mind of a
Particle Physicist
1991 The Charm of PhysicsIt is proposed that, at stupendously high temperatures just after
the Big Bang, all four forces were united as one “superforce.”