The Science Book

310 GABRIELE VENEZIANO

P

ut simply, string theory is
the remarkable—and still
controversial—idea that all
matter in the universe is made up
not of pointlike particles, but of tiny
“strings” of energy. The theory lays
out a structure that we cannot
detect, but that explains all the
phenomena that we see. Waves of
vibration within these strings give
rise to the quantized behaviors
(discrete properties such as electric
charge and spin) that are found in
nature, and mirror the harmonics
that can be produced, for example,
by plucking a violin string.

The development of string theory

has had a long and bumpy road,

and it is still not accepted by many

physicists. But work on the theory

continues—not least because it is

currently the only theory trying to

unite the “quantum gauge” theories

of the electromagnetic, weak,

and strong nuclear forces with

Einstein’s theory of gravity.

Explaining the strong force

String theory began life as a model

to explain the strong force that

binds together the particles in the

nuclei of atoms, and the behavior of

IN CONTEXT

BRANCH

Physics

BEFORE

1940s Richard Feynman

and other physicists develop

quantum electrodynamics

(QED), which describes

quantum-level interactions due

to the electromagnetic force.

1960s The standard model of

particle physics reveals the full

range of subatomic particles

known so far and the

interactions that affect them.

AFTER

1970s String theory falls out of

favor temporarily as quantum

chromodynamics appears to

offer a better explanation of

the strong nuclear force.

1980s Lee Smolin and Italian

Carlo Rovelli develop the

theory of loop quantum

gravity, which removes

the need to theorize hidden

extra dimensions.

The Big Bang may

be the result of two

branes colliding.

String theory treats particles

as vibrating strings of energy.

Adding hidden dimensions and

“supersymmetric” particles produces

superstring theory.

Superstring theory

may explain the interaction

of the four fundamental

forces in the universe.

Superstring theory

gives rise to

multidimensional

branes.

String theory is

a possible candidate

for a “Theory of

Everything.”

hadrons, the composite particles

that are subject to the influence of

the strong force.

In 1960, as part of an ongoing

study of the properties of hadrons,

American physicist Geoffrey

Chew proposed a radical new

approach—abandoning the

preconception that hadrons were

particles in the traditional sense,

and modeling their interactions

in terms of a mathematical object

called an S-matrix. When Italian

physicist Gabriele Veneziano

investigated the results of

Chew’s model, he found patterns