What is Theory: Definition and 1000 Discussions

A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may either be scientific or other than scientific (or scientific to less extent). Depending on the context, the results might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings.
In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that scientific tests should be able to provide empirical support for it, or empirical contradiction ("falsify") of it. Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge, in contrast to more common uses of the word "theory" that imply that something is unproven or speculative (which in formal terms is better characterized by the word hypothesis). Scientific theories are distinguished from hypotheses, which are individual empirically testable conjectures, and from scientific laws, which are descriptive accounts of the way nature behaves under certain conditions.
Theories guide the enterprise of finding facts rather than of reaching goals, and are neutral concerning alternatives among values. A theory can be a body of knowledge, which may or may not be associated with particular explanatory models. To theorize is to develop this body of knowledge.The word theory or "in theory" is sometimes used erroneously by people to explain something which they individually did not experience or test before. In those instances, semantically, it is being substituted for another concept, a hypothesis. Instead of using the word "hypothetically", it is replaced by a phrase: "in theory". In some instances the theory's credibility could be contested by calling it "just a theory" (implying that the idea has not even been tested). Hence, that word "theory" is very often contrasted to "practice" (from Greek praxis, πρᾶξις) a Greek term for doing, which is opposed to theory. A "classical example" of the distinction between "theoretical" and "practical" uses the discipline of medicine: medical theory involves trying to understand the causes and nature of health and sickness, while the practical side of medicine is trying to make people healthy. These two things are related but can be independent, because it is possible to research health and sickness without curing specific patients, and it is possible to cure a patient without knowing how the cure worked.

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  1. S

    What makes a good physics theory

    Hello! What makes a theoretical model stand out compared to others. I was thinking about the Higgs mechanism and the fact that there were quite a lot of other models (proposed in the 60's-70's) to explain symmetry breaking, which (I assume based on the fact that they got published) were...
  2. amjad-sh

    Joule Heating and the Thomson effect in Drude theory

    Homework Statement ##\mathbf A##.Joules heating Consider a metal in a uniform temperature in a static uniform electric field E.An electron experiences a collision, and then after a time t, a second collision. In the drude model , Energy is not conserved for collisions, for the mean speed of an...
  3. Demystifier

    A Quantum field theory, spacetime, and coordinates

    [Moderator's note: This thread is spun off from another thread since it was dealing with a more technical point that is out of scope for the previous thread. The quote that starts this post is from the previous thread.] I feel the same about transformations of Dirac matrices and Dirac field...
  4. J

    I What is the best theory why our vacuum may be in the edge of metastability?

    What is the best theory why our vacuum may be in the edge of metastability? Is it possible there are many false vacuum separated by energy barriers and the reason why our vacuum may be metastable is so that it is easier to cross the different false vacua (not necessarily to the true vacuum)?
  5. Demystifier

    B Quantum theory for high-school students

    I believe this could be interesting to many people here who are interested in quantum theory but are not (yet) professional physicists: http://lanl.arxiv.org/abs/1803.07098
  6. J

    I Thermal field theory of an isolated electroweak plasma

    The theory of electroweak temperature says that when you have a plasma of particles at energy above the electroweak phase transition (100 GeV). The Higgs field would turn from nonzero vev to zero and the electroweak forces would unite and the electroweak bosons would become massless. What...
  7. S

    I Representation Theory clarification

    Hello! I am reading some things about representation theory for SU(n) and I want to make sure I understand it properly. I will put an example here and explain what I understand out of it and I would really appreciate if someone can tell me if it is right or not. So for SU(2) we have ##2 \otimes...
  8. ertagon2

    MHB Set Theory Questions (check if right)

    Could someone please check if these are right?
  9. M

    A How to construct a spin-3/2 theory from the ground up

    I'll start by saying I'm posting this in Beyond the SM just because we have no elementary spin-3/2 particles in the SM as far as we know, though I was also considering posting it elsewhere. If you feel it's more appropriate in another area just let me know. As for the question itself, I'd like...
  10. S

    I Is there a frequency cutoff for Debye theory of capillary waves?

    I calculated the energy density of capillary waves with Debye method (pretty much Debye model in 2D), and I assumed there is a frequency cutoff for capillary waves as well. However, when I checked my work with solution I was quite surprised that the solution suggests there is no such a cuttoff...
  11. R

    Does r=mv/Bq hold true considering Maxwell's E.M wave theory?

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  12. Wrichik Basu

    I Explanation of optical phenomena in light of Feynman's Theory

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  13. B

    B Constrains in E8xE8 heterotic superstring theory

    Can someone at least gives a summary of the constrains in the E8xE8 heterotic superstring theory? Many sources are mostly outdated that was written decades ago when not much research were done yet in superstring theory. So is E8xE8 already refuted? Or to what degrees and what constrains? I need...
  14. S

    B Is cosmopsychism theory just babble copied from The Force?

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  15. Demystifier

    A Is there a decidable set theory?

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  16. Urs Schreiber

    Mathematical Quantum Field Theory - Renormalization - Comments

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  17. JTC

    Best way to learn control theory for mechanical engineers

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  18. Spinnor

    I Can String Theory Explain the Energy Density of Empty Space?

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  19. A

    Quantum Field Theory, Momentum Space Commutation Relations

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  20. Joppy

    MHB Reference request - Measure theory

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  21. H

    What is the Best Way to Prove a Reincarnation Claim?

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  22. E

    MHB Math Problem: Find # of Elements in 2nd/3rd Subsets

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  23. Urs Schreiber

    Mathematical Quantum Field Theory - Interacting Quantum Fields - Comments

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  24. bhobba

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  25. slow

    B Is it time to rebuild quantum theory?

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  26. J

    B Quantum Theory and its Precision

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  27. PHstud

    No drag thin airfoil theory / Pressure drag

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  28. M

    A "UV completion of a theory of Superfluid Dark Matter"

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  29. stickman76

    I Graphic Anim of Special Theory of Relativity: Exploring Interrelationships

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  30. Urs Schreiber

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  31. I

    Schools String theory school recommendation: UC Davis, UIUC or other

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  32. Q

    B Does this connect Quantum Theory and Special Relativity?

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  33. Spinnor

    B String theory, Calabi–Yau manifolds, complex dimensions

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  34. Urs Schreiber

    Mathematical Quantum Field Theory - Quantization - Comments

    Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Quantization Continue reading the Original PF Insights Post.
  35. J

    A Path Integral of a Spontaneously Broken Theory

    A scalar field theory with potential $$V(\phi)=-\mu^2\phi^2+\lambda \phi^4$$ is spontaneously broken and as a consequence, for the ground state, $$\langle \phi(x) \rangle \neq 0$$. However, the path integral, which should give ground state expectation values, looks to be zero by oddness of the...
  36. K

    I Wavefunctions in first order degenerate pertubation theory

    Suppose we want to solve the Hamiltonian ##H=H_0+\lambda V## pertubatively. Let ##E_1,...,E_n## be the eigenvalues of ##H_0## and ##S_1,...,S_n## the eigenspaces that belong to them. In order to do that, one usually choses an orthonormal Basis ##|\psi_{i,j}>## of each ##S_i## with the property...
  37. John1945

    Mathematical Quantum Field Theory -- Equations? So what?

    << Mentor note -- posts broken off from an Insights comment thread >> Ok, this is where I show my ignorance, but all this is theoretical and why I get lost with these academia discussions. Time is just a mathmatical construct to measure the motion of two or more objects relative to each other...
  38. N

    I Exploring Einstein's theory about the curvature of space

    Einstein's theory states that curvature of space (created by a celestial body around itself) determines the orbital path of other celestial bodies around it within that curved space by a constant lateral force acting towards the centre upon that revolving body. Then why is that a similar force...
  39. rocdoc

    Dirac's Generalized Hamiltonian Dynamics Theory?

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  40. N

    I Einstein's Pursuit of Unified Theory: Motivation and Observations

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  41. S

    MHB Proving Rationality of Squares of 9th Day 2 ARO 2004/2005 Numbers

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  42. A

    I Density Functional Theory and pseudopotentials

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  43. B

    Exploring String Theory: Recommended Books and Critiques

    What are the books that speak about string theory you would suggest me? And the book against this theory? (I'm an undergraduate physics student) Thanks!
  44. Urs Schreiber

    Mathematical Quantum Field Theory - Gauge Fixing - Comments

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  45. binbagsss

    Polyakov action, reparameterisation q, string theory

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  46. J

    B M Theory: What's the Consensus?

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  47. Ranku

    I Grand Unified Theory and proton decay

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  48. S

    B Why does the multiverse theory have only 4 levels?

    Why does max tegmark's and brian greene's levels of multiverses consider as the highest level the mathematical multiverse hypothesis if other authors like David Lewis consider that there could be also universes non described by maths? Why does it stop at level iv (mathematical universes...
  49. Spinnor

    B New theory, our solar system formation, "space bubble"

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  50. Pouyan

    Probability theory and statistics

    Homework Statement The time (minute) that it takes for a terrain runner to get around a runway is a random variable X with the tightness function fX = (125-x)/450 , 95≤x≤125 How big is the probability of eight different runners, whose times are independent after 100 minutes: a) Everyone has...
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