FUNDAMENTAL BUILDING BLOCKS 311
Gabriele Veneziano
Born in Florence, Italy, in 1942,
Gabriele Veneziano studied
in his home city before obtaining
his PhD from Israel’s Weizmann
Institute of Science, where he
returned in 1972 as professor
of physics following some time
at the European particle physics
laboratory CERN. While at the
Massachusetts Institute of
Technology (MIT) in 1968, he
hit upon string theory as a
model for describing the strong
nuclear force, and began to
pioneer research into the topic.From 1976 onward, Veneziano
worked mainly at CERN’s
Theory Division in Geneva,
rising to become its director
between 1994 and 1997.
Since 1991, he has focused on
investigating how string theory
and QCD can help to describe
the hot, dense conditions just
after the Big Bang.Key work1968 Construction of a
Cross-Symmetric, Regge-
behaved Amplitude for
Linearly Rising Trajectoriessuggesting that particles would
appear at points along straight
one-dimensional lines—the first
hint of what we now call strings.
In the 1970s, physicists continued
to map these strings and their
behavior, but their work began
to bring up annoyingly complex
and counterintuitive results. For
example, particles have a property
called spin (analogous to angular
momentum), which can only take
certain values. The initial drafts
of string theory could produce
bosons (particles with zero or
whole-number spins, typically
the “messenger” particles in
models of quantum forces), but
not fermions (particles with half-
integer spins, including all matter
particles). The theory also predicted
the existence of particles that move
faster than the speed of light, thus
traveling backward in time.See also: Albert Einstein 214–21 ■ Erwin Schrödinger 226–33 ■ Georges Lemaître 242–45 ■ Paul Dirac 246–47 ■
Richard Feynman 272–73 ■ Hugh Everett III 284–85 ■ Sheldon Glashow 292–93 ■ Murray Gell-Mann 302–07One final complication was that
the theory could not properly work
without assuming the existence
of no fewer than 26 separate
dimensions (instead of the usual
four—three dimensions of space,
plus time). The concept of extra
dimensions had been around for a
long time: German mathematician
Theodor Kaluza had attempted
to unify electromagnetism and
gravity through the use of an extra
(fifth) dimension. This was not a
problem mathematically, but did
pose the question as to why we
do not experience all dimensions.
In 1926, Swedish physicist Oscar
Klein explained how such extra
dimensions might remain invisible
on everyday macroscopic scales
by suggesting they might “roll up”
into quantum-scale loops.
String theory suffered a fall from
grace in the mid-1970s. The theory
of quantum chromodynamics
(QCD), which introduced the
concept of “color charge” for quarks
to explain their interaction via the
strong nuclear force, offered a
much better description. But ❯❯According to
string theory,
the quantized
properties we
observe arise
when a string
takes on different
vibrational
states, similar
to the harmonic
notes played on
a violin.String theory is an attempt
at a deeper description of
nature by thinking of an
elementary particle not as
a little point but as a little
loop of vibrating string.
Edward Witten