Nicosia, James F.Reading Mark Strand: His Collected
Works, Career, and the Poetics of the Privative. New
York: Palgrave Macmillan, 2007.
Kris Bigalk
See also Angelou, Maya; Komunyakaa, Yusef; Lit-
erature in the United States; Poetry.
String theory
Definition A theory that replaces the
dimensionless point particles of the Standard
Model with vibrating strings and/or membranes
Date Second string revolution, 1995-1998
Despite a great deal of excitement generated by a wave of
discoveries in the previous decade, string theorists faced a
serious dilemma in the early 1990’s: The equations that de-
fined the theor y were either impossibly difficult or nonexis-
tent. To get around this, approximations of the needed
equations were produced. However, when faced with spend-
ing their careers finding approximate solutions to approxi-
mate equations with no real proposals for improving the sit-
uation, many physicists turned to other lines of research. If
the potential “theor y of ever ything” was to avoid the back-
waters of science, new methods of attacking the equations
would be required.
In addition to its difficult mathematics, string the-
ory had evolved into five separate theories by the
beginning of the 1990’s. All five variations were
similar in many ways. For instance, each required
the existence of ten dimensions, the familiar four-
dimensional space-time plus six other spatial dimen-
sions. However, there were also some significant
differences, and having so many different varia-
tions hurt the credibility of the theory with many ob-
servers.
Then, in the mid-1990’s, a breakthrough occurred
that was christened the “second string revolution.” It
was proposed that the five separate variants of the the-
ory were actually parts of an overarching, eleven-
dimensional theory given the name M-theory. Even
more important for theorists, it was also discovered
that the equations for the five different variants ex-
hibited a property physicists refer to as duality.
Duality occurs when two theoretical models ap-
pear to be different when in fact they describe iden-
tical physics. An example of linguistic duality would
be a sentence in English and one in French that are
very different in appearance but in fact make the
same statement. It was found that any of the variants’
more obscure equations had more manageable
counterparts in the other variants.
Another promising proposal for string theory,
sometimes called superstring theory because of its
supersymmetry, was that supersymmetry itself was a
tool that could be used to improve the equations. It
was shown that the constraints necessarily added by
supersymmetry could make the equations more pre-
cise.
Impact Even with these major advances, opinions
were mixed about the value of string theory as the
decade ended. Critics still felt that the theorists were
promising too much with too little to back them up.
Adherents believed more than ever that the theory
was bringing them nearer to the grand unification
theory, an elusive goal of science since the days of Al-
bert Einstein. In either case, the theory caught the
imagination of a group of physicists and mathemati-
cians who have used their new perspective along
with the new tools developed by and for the theory
to provide a better understanding of the universe.
Further Reading
Adams, Steve.Frontiers: Twentieth Centur y Physics. New
York: Taylor & Francis, 2000.
Greene, Brian.The Elegant Universe: Superstrings, Hid-
den Dimensions, and the Quest for the Ultimate Theor y.
New York: W. W. Norton, 1999.
_______.The Fabric of the Cosmos: Space, Time, and the
Texture of Reality. New York: Alfred A. Knopf, 2004.
Salmon, Wesley C.Causality and Explanation. New
York: Oxford University Press, 1998.
Wayne ShireySee also Science and technology. Strug, Kerri
Identification American gymnast
Born November 19, 1977; Tucson, Arizona
Strug is best known for her performance in the 1996 Olym-
pic Games that clinched the first-ever gold medal for the U.S.
women’s gymnastics team, landing her vault despite a se-
vere ankle injur y.
Although Kerri Strug became well known as a result
of her performance in the 1996 Olympic Games in818 String theory The Nineties in America