Difference between revisions of "String theory"

From Conservapedia
Jump to: navigation, search
(string theory is a failure)
(removed inaccurate statements in intro, but retained important point that string theory is uncertain)
Line 1: Line 1:
 
'''String theory''', (or super-string theory when coupled with [[Supersymmetry]]), is a class of models in [[theoretical physics]] which replace zero-dimensional points (particles) in four-dimensional spacetime with one-dimensional strings in an eleven-dimensional spacetime as the fundamental building block of the universe.  The elusive goal is to develop a set of equations that unify all known natural forces (gravitational, electromagnetic, weak, and strong), according to some preconceived philosophical beliefs about how they ought to be unified.  Leading proponents of string theory have been Edward Witten of the [[Institute for Advanced Study]] and [[Brian Greene]], the renowned author of ''The Elegant Universe''.
 
'''String theory''', (or super-string theory when coupled with [[Supersymmetry]]), is a class of models in [[theoretical physics]] which replace zero-dimensional points (particles) in four-dimensional spacetime with one-dimensional strings in an eleven-dimensional spacetime as the fundamental building block of the universe.  The elusive goal is to develop a set of equations that unify all known natural forces (gravitational, electromagnetic, weak, and strong), according to some preconceived philosophical beliefs about how they ought to be unified.  Leading proponents of string theory have been Edward Witten of the [[Institute for Advanced Study]] and [[Brian Greene]], the renowned author of ''The Elegant Universe''.
  
Some physicists argue that string theory (and its alter ego M-theory) is currently the most viable candidate for a unified theory of physics which describes all forces of nature, encompassing the physics of gravity as well as quantum field theory. Major research centers include, for example, MIT, with five faculty members and numerous postdocs and graduate students working in this area.<ref> see [http://ctp.lns.mit.edu/research-strings.html MIT Center for Theoretical Physics]</ref> However, string theory has proved to be unrelated to any of the known forces of nature.
+
Some physicists argue that string theory (and its alter ego M-theory) is currently the most viable candidate for a unified theory of physics which describes all forces of nature, encompassing the physics of gravity as well as quantum field theory. Major research centers include, for example, MIT, with five faculty members and numerous postdocs and graduate students working in this area.<ref> see [http://ctp.lns.mit.edu/research-strings.html MIT Center for Theoretical Physics]</ref> At present, however, the potential status of string theory as a genuine "theory of everything" remains uncertain.
  
Princeton University researchers have found new mathematical evidence that some aspects of string theory may be related to a well-respected body of physics called "gauge theory," which has been demonstrated to underlie the interactions among quarks and gluons, the vanishingly small objects that combine to form protons, neutrons and other, more exotic subatomic particles. The discovery, say the physicists, could open up a host of uses for string theory in attacking practical physics problems.<ref>See [http://www.princeton.edu/main/news/archive/S17/80/32S21/index.xml?section=newsreleases "Princeton physicists connect string theory with established physics," May 1, 2007] </ref> However, string theory does not have any way of describing quarks, gluons, protons, or anything else in the real world.
+
Princeton University researchers have found new mathematical evidence that some aspects of string theory may be related to a well-respected body of physics called "gauge theory," which has been demonstrated to underlie the interactions among quarks and gluons, the vanishingly small objects that combine to form protons, neutrons and other, more exotic subatomic particles. The discovery, say the physicists, could open up a host of uses for string theory in attacking practical physics problems.<ref>See [http://www.princeton.edu/main/news/archive/S17/80/32S21/index.xml?section=newsreleases "Princeton physicists connect string theory with established physics," May 1, 2007] </ref>
  
 
==History==
 
==History==

Revision as of 16:53, June 16, 2009

String theory, (or super-string theory when coupled with Supersymmetry), is a class of models in theoretical physics which replace zero-dimensional points (particles) in four-dimensional spacetime with one-dimensional strings in an eleven-dimensional spacetime as the fundamental building block of the universe. The elusive goal is to develop a set of equations that unify all known natural forces (gravitational, electromagnetic, weak, and strong), according to some preconceived philosophical beliefs about how they ought to be unified. Leading proponents of string theory have been Edward Witten of the Institute for Advanced Study and Brian Greene, the renowned author of The Elegant Universe.

Some physicists argue that string theory (and its alter ego M-theory) is currently the most viable candidate for a unified theory of physics which describes all forces of nature, encompassing the physics of gravity as well as quantum field theory. Major research centers include, for example, MIT, with five faculty members and numerous postdocs and graduate students working in this area.[1] At present, however, the potential status of string theory as a genuine "theory of everything" remains uncertain.

Princeton University researchers have found new mathematical evidence that some aspects of string theory may be related to a well-respected body of physics called "gauge theory," which has been demonstrated to underlie the interactions among quarks and gluons, the vanishingly small objects that combine to form protons, neutrons and other, more exotic subatomic particles. The discovery, say the physicists, could open up a host of uses for string theory in attacking practical physics problems.[2]

History

String theory originated in 1970 when particle theorists realized that the theories developed in 1968 to describe the particle spectrum also describe the quantum mechanics of oscillating strings. Supersymmetry was introduced in 1971. The watershed year was 1984, when string theory became accepted by the mainstream physics community as an actual candidate theory that could unite quantum mechanics, particle physics, and gravity. Around 2000, many physics conceded that string theory was a failure, and that it had no hope of realizing any of its goals.

Falsifiability

There is much debate on whether string theory is truly scientific. Under the positivist philosophy, models must be falsifiable (i.e. it must be possible to define an experiment which could contradict the theory) for them to qualify as science, and then they must survive these tests. In more general terms, a model should be able to make predictions about the world we observe. String theory has yet to yield a particular definitive test, or to produce any models that resemble any known particles or forces.

The discovery of dark energy in 1998 was a particularly damaging blow to string theory. It was just the sort of thing that string theorists hoped to explain, and yet string theory cannot explain it. As of today, string theory has attracted strong interest among theorists but has not suggested any critical experiments.

Some string theorists, such as Leonard Susskind, say that string theory may not be testable but may still provide insights on multiple universes. His recent book is The Cosmic Landscape: String Theory and the Illusion of Intelligent Design.

Mathematical Predictions

Although string theory has so far failed to make viable experimental predictions, it has proved remarkably successful at predicting new theorems in mathematics. For example, from string-theoretic considerations, Candelas, de la Ossa, Green, and Parks conjectured the correct formula for the number of degree d rational curves in a Calabi-Yau quintic. Their formula was later rigorously proved correct by Givental and Lian, Liu, and Yau, establishing that the string-theoretic prediction was accurate. More generally, string theory has predicted a deep relationship in mathematics called "mirror symmetry" which connects seemingly unrelated topics in symplectic and complex geometry. Mirror symmetry remains an active area of mathematical research, and many highly non-trivial examples of mirror symmetry have been mathematically verified.

Further reading

  • Smolin, Lee. The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next (2007)part 2 online

External links

See also

references

  1. see MIT Center for Theoretical Physics
  2. See "Princeton physicists connect string theory with established physics," May 1, 2007