string theory

Introduction
Relativity and quantum mechanics
Predictions and theoretical difficulties
Dimensions and vibrations
M-theory and AdS/CFT correspondence
Supersymmetry and cosmological signature

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Hear about the speculation and different types of multiverse models

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string theory summary

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Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950.

Physics and Natural Law

Nicolaus Copernicus. Nicolas Copernicus (1473-1543) Polish astronomer. In 1543 he published, forward proof of a Heliocentric (sun centered) universe. Coloured stipple engraving published London 1802. De revolutionibus orbium coelestium libri vi.

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Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920.

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Related Questions

How are electrons and quarks represented by different vibrational patterns in string theory?
How could gravitational waves provide indirect evidence for string theory?
How could the shape of extra dimensions affect the masses and charges of particles?
How did Gabriele Veneziano’s use of the Euler beta function contribute to the beginnings of string theory?
How did Leonard Susskind, Holger Nielsen, and Yoichiro Nambu connect string vibrations to particle physics?
How did the electroweak theory partially unify two fundamental forces?
How do vibrating strings represent different elementary particles in string theory?
How does M-theory connect different versions of superstring theory?
How does general relativity describe gravity differently from quantum theory?
How does string theory differ from the point-particle model used in conventional particle physics?
How does string theory try to unite quantum mechanics with general relativity?
How does superstring theory include a possible quantum particle of gravity called the graviton?
How does the garden-hose analogy explain hidden dimensions in string theory?
How many dimensions does M-theory propose?
How might branes help explain cosmic inflation in the early universe?
How small are the strings proposed by string theory?
What role does the massless particle predicted by string theory play in describing gravity?
What superpartners are predicted for electrons and quarks by supersymmetry?
Which four fundamental forces does string theory aim to include in one framework?
Why are particle accelerators unable to observe strings directly?
Why did John Schwarz, Joel Scherk, and Tamiaki Yoneya reinterpret string theory in 1974?
Why did early versions of string theory fail as explanations of the strong force?
Why do many possible shapes for extra dimensions make string theory difficult to test?
Why have the extra dimensions proposed by string theory not been observed?
Why is a graviton expected to have a spin of 2?
Why is gravity especially difficult to combine with quantum mechanics?
Why would finding superpartner particles not prove that string theory is correct?
Why does physics work in SI units?
Is mathematics a physical science?
When did science begin?
Where was science invented?

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External Websites

Physics Libretexts - String theory
Carnegie Center University - Computing Services - String Theory
Stanford Institute for Theoretical Physics - Formal Quantum Field and String Theory
IOPscience - IOP Conference Series: Earth and Environmental Science - The String Theory: Past and Present
OpenStax - College Physics 2e - Superstrings
University of Cambridge - Department of Applied Mathematics and Theoretical Physics - String Theory (PDF)
ABC News - What is string theory? An astrophysicist explains one way the universe might work at the fundamental level
Space.com - String Theory: A Brief Overview
LiveScience - What is String Theory?
Annenberg Learner - String theory and extra dimensions

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Articles from Britannica Encyclopedias for elementary and high school students.

Superstring theory - Student Encyclopedia (Ages 11 and up)

string theory

physics

Also known as: superstring theory, superunification theory

Written by

Brian Greene

Brian Greene is a professor of physics and mathematics at Columbia University; a popular author, lecturer, and TV commentator on science-related topics; and host and narrator of the award-winning PBS series...

Brian Greene

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Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

Last updated

Oct. 26, 2026 •History

string theory, in particle physics, a theory that attempts to merge quantum mechanics with Albert Einstein’s general theory of relativity. The name string theory comes from the modeling of subatomic particles as tiny one-dimensional “stringlike” entities rather than the more conventional approach in which they are modeled as zero-dimensional point particles. The theory envisions that a string undergoing a particular mode of vibration corresponds to a particle with definite properties such as mass and charge....

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