Theory of everything

This article is about the hypothetical physical concept. For other uses, see Theory of everything (disambiguation).
Beyond the Standard Model
Simulated Large Hadron Collider CMS particle detector data depicting a Higgs boson produced by colliding protons decaying into hadron jets and electrons
Standard Model
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Supersymmetry
Quantum gravity
Experiments

A theory of everything (TOE), final theory, ultimate theory, unified field theory, or master theory is a hypothetical, singular, all-encompassing, coherent theoretical framework of physics that fully explains and links together all aspects of the universe.[1]: 6  Finding a theory of everything is one of the major unsolved problems in physics.[2][3]

Over the past few centuries, two theoretical frameworks have been developed that, together, most closely resemble a theory of everything. These two theories upon which all modern physics rests are general relativity and quantum mechanics. General relativity is a theoretical framework that only focuses on gravity for understanding the universe in regions of both large scale and high mass: planets, stars, galaxies, clusters of galaxies, etc. On the other hand, quantum mechanics is a theoretical framework that focuses primarily on three non-gravitational forces for understanding the universe in regions of both very small scale and low mass: subatomic particles, atoms, and molecules. Quantum mechanics successfully implemented the Standard Model that describes the three non-gravitational forces: strong nuclear, weak nuclear, and electromagnetic force – as well as all observed elementary particles.[4]: 122 

General relativity and quantum mechanics have been repeatedly validated in their separate fields of relevance. Since the usual domains of applicability of general relativity and quantum mechanics are so different, most situations require that only one of the two theories be used.[5][6][7]: 842–844  The two theories are considered incompatible in regions of extremely small scale – the Planck scale – such as those that exist within a black hole or during the beginning stages of the universe (i.e., the moment immediately following the Big Bang). To resolve the incompatibility, a theoretical framework revealing a deeper underlying reality, unifying gravity with the other three interactions, must be discovered to harmoniously integrate the realms of general relativity and quantum mechanics into a seamless whole: a theory of everything may be defined as a comprehensive theory that, in principle, would be capable of describing all physical phenomena in the universe.

In pursuit of this goal, quantum gravity has become one area of active research.[8][9] One example is string theory, which evolved into a candidate for the theory of everything, but not without drawbacks (most notably, its apparent lack of currently testable predictions) and controversy. String theory posits that at the beginning of the universe (up to 10−43 seconds after the Big Bang), the four fundamental forces were once a single fundamental force. According to string theory, every particle in the universe, at its most ultramicroscopic level (Planck length), consists of varying combinations of vibrating strings (or strands) with preferred patterns of vibration. String theory further claims that it is through these specific oscillatory patterns of strings that a particle of unique mass and force charge is created (that is to say, the electron is a type of string that vibrates one way, while the up quark is a type of string vibrating another way, and so forth). String theory/M-theory proposes six or seven dimensions of spacetime in addition to the four common dimensions for a ten- or eleven-dimensional spacetime.

  1. ^ Weinberg, Steven (2011-04-20). Dreams of a Final Theory: The Scientist's Search for the Ultimate Laws of Nature. Knopf Doubleday Publishing Group. ISBN 978-0-307-78786-6.
  2. ^ Cite error: The named reference NYT-20201123 was invoked but never defined (see the help page).
  3. ^ Overbye, Dennis (11 September 2023). "Don't Expect a 'Theory of Everything' to Explain It All – Not even the most advanced physics can reveal everything we want to know about the history and future of the cosmos, or about ourselves". The New York Times. Archived from the original on 11 September 2023. Retrieved 11 September 2023.
  4. ^ Hawking, Stephen W. (28 February 2006). The Theory of Everything: The Origin and Fate of the Universe. Phoenix Books; Special Anniversary. ISBN 978-1-59777-508-3.
  5. ^ SMOLIN, L. (2004). "An Invitation to Loop Quantum Gravity". Quantum Theory and Symmetries. []: 655–682. arXiv:hep-th/0408048. Bibcode:2004qts..conf..655S. doi:10.1142/9789812702340_0078. ISBN 978-981-256-068-1. S2CID 16195175.
  6. ^ Carlip, Steven (2001). "Quantum Gravity: a Progress Report". Reports on Progress in Physics. 64 (8): 885–942. arXiv:gr-qc/0108040. Bibcode:2001RPPh...64..885C. doi:10.1088/0034-4885/64/8/301. S2CID 118923209.
  7. ^ Priest, Susanna Hornig (14 July 2010). Encyclopedia of Science and Technology Communication. SAGE Publications. ISBN 978-1-4522-6578-0.
  8. ^ Overbye, Dennis (10 October 2022). "Black Holes May Hide a Mind-Bending Secret About Our Universe – Take gravity, add quantum mechanics, stir. What do you get? Just maybe, a holographic cosmos". The New York Times. Archived from the original on 16 November 2022. Retrieved 22 October 2022.
  9. ^ Starr, Michelle (16 November 2022). "Scientists Created a Black Hole in The Lab, And Then It Started to Glow". ScienceAlert. Archived from the original on 15 November 2022. Retrieved 16 November 2022.