What is Theories: Definition and 481 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. Gullets

    A History of Particle Physics

    Books like Griffith, Martin, and Perkins are best if I consider them for the thorough history of particle physics.
  2. jmheer

    A Current theories on the lepton masses?

    Hi, all! I'm currently studying the 3 families of leptons. 1) Are there any accepted theories about why the lepton masses are what they are? 2) What are the best journals to read about this kind of thing? I'm aware of the Koide formula, but that seems to be an empirical formula, not a theory...
  3. J

    Where to discuss new theories.

    Hi, Fairly new to the forum, but trying to post some ideas on new ways to look at gravity, but not sure where the correct place is. Where is the best place to discuss new ideas please? John.
  4. DagmaarUlereich

    Unconventional wire illustration/diagram.

    I have my own thoughts and possible could provide sketch or instance use case, elaborate using evident setsettings. But I don't want to persuade, influence or lead other people who are actually educated and inadvertently guide and ultimately hinder the outcomes of their initial assessment. The...
  5. lektroon

    I Theories of Nicolas Gisin

    Hello, As a layman in physics, I wonder the ideas of people who have more knowledge in physics than I do about the theories of Swiss Physicist Nicolas Gisin and his arguments about the intuitionist mathematics. Is there a way to reconcile these ideas with more fundamental theories like SR and...
  6. Bertin

    Studying Comparing Candidate Theories of Quantum Gravity

    Hi, you all, I have been for a couple of semesters interested in quantum gravity as a problem, but truth is I never have been properly introduced to any of the candidate theories. Actually, there are multiple candidates and I would like to compare them. The question then is the following: do...
  7. Morbert

    I Events in Quantum Theories

    This thread picks up a discussion between myself and @A. Neumaier in another thread. In particular, this comment: Reference: https://www.physicsforums.com/threads/nobody-understands-quantum-physics.1049370/page-8 First some basic background. If we consider the usual presentation of a...
  8. Boy_saber

    A Please help solve the equation in black hole f(R) theories

    In the paper https://arxiv.org/abs/1210.4699. How to solve this equation? I've tried it, it's not same as in this paper. Even zero order still not the same. This is what I try to do at zero order. input $$E=E_0\left(r_0\right)$$ $$H=H_0\left(r_0\right)$$ $$b=b\left(r_0\right)$$...
  9. Astronuc

    How to Spot Pseudoscience in an Age of Conspiracy Theories

  10. A

    I Some classical models of particles and quantum gauge theories

    My article has been published in Quantum Reports. Expanded abstract: There is currently no consensus on the interpretation of quantum theory, so this article may be of interest as it contains a review and new results on some relevant mathematical models emulating well-known quantum theories...
  11. A

    A Why Statistical Theories of Mental Test Scores?

    In 1968, Lord and Novick published a book called Statistical Theories of Mental Test Scores. I wonder why they used the adjective 'statistical'. Does this suggest that the theories mentioned are not psychological theories and, if so, what could be the meaning of such theories? Should these...
  12. R

    Theories on how the food supply evolved along with life?

    Along with the endless complexities of life and the evolution of life, it occurs to me that at all points there had to be enough available nutrition for existent life forms - and that food supply itself had to go through a process of evolution. It seems self-evident that the environment of early...
  13. arivero

    I Does the property "equal charges repel" still work for non abelian theories?

    I recall that there was an argument from Born expansion showing that exchange of odd spin between equal sign charges generates a repulsive potential, and if the charges are different or the spin is even the potential is attractive. I wonder, how does it work for non abelian gauge theory...
  14. BillTre

    Parallel-ish Theories Terminology

    What is it called went to different theories (or kinds of theories, apparently) overlap in their explanations over major parts of their explanatory field and you want to talk about the area of overlap in the phenomena they explain? Classic examples: Newtonian physics vs. relativity, similar...
  15. malawi_glenn

    High Energy (free kindle) Gauge Theories in Particle Physics by Aitchison & Hey

    Free Kindle via Amazon, both part 1 and part 2 Part 1: https://www.amazon.com/dp/B00OD49Z96/?tag=pfamazon01-20 Part 2: https://www.amazon.com/dp/B00OD49Z00/?tag=pfamazon01-20 Enjoy
  16. Arman777

    Relativity Exploring Scalar/Tensor/Scalar-Tensor Theories - A Guide

    Is there a book or article that discusses the scalar/tensor/scalar-tensor (maybe others as well) theories ? (Look at this wiki page for a general overview of the theories that I am talking about) So, I am looking for a book that discusses these theories either in general or in detail. It does...
  17. Oldman too

    Medical Acute severe Hepatitis in Children, theories as to causation

    Summary: Recent world wide acute hepatitis outbreak in children and possible etiology. I've watched these cases with much interest lately, particularly since some of the possible vectors are being studied and identified. As the theories are being explored as to the cause, or causes of the...
  18. ErikZorkin

    I Simulating physics: the current status of lattice field theories

    I recently watched this video by David Tong on computer simulation of quantum fields on lattices, fermionic fields in particular. He said it was impossible to simulate a fermionic field on a lattice so that the action be local, Hermitian and translation-invariant unless extra fermions get...
  19. C

    B Are there more theories about the start of our Universe?

    I have heard of and read about the big bang theory for the start of our universe. Are there other competing theories that I should look at. Thanks Chiefly
  20. T

    Looking for a book to understand physics theories

    Hi, I am looking for a book exploring the current theories of physics and their fundamental interactions. As we know, each fundamental theory is associated to a specific interaction. I wish to explore this tree of theories and see their links. Thank you
  21. nomadreid

    Serious critique of Erikson's psychological theories?

    This is asking for suggestions for freely-available serious on-line sources (with links) for criticism of the theories of Erik Erikson. Details: The neo-Freudian psychologist Erik Erikson https://en.wikipedia.org/wiki/Erik_Erikson was and remains quite popular. However, looking through his...
  22. T

    B Request for an up to date list of cosmological theories

    Is there an up to date list of all cosmological theories resource which provides some or preferably all of the following information: Which theories are considered speculative and even highly speculative? (degree 1 to 4) Which theories are still actively being worked on and roughly how many...
  23. T

    B A question about which Cosmology theories are mainstream and how?

    I was reading recently about string theory recently which postulates that there are 11 dimensions representing all possibilities for everything. This is an interesting theory, although very difficult to prove and therefore somewhat speculative in my opinion. [Ed.: personal speculation removed]...
  24. L

    Engineering Understanding Shear Stress Theories: Moors Circle & McGraw Hill

    Hello:) Our homework is done through mcgraw hill connect. I am able to see the solution to the problem and it contradicts what the book and powerpoint says. according to the powerpoint given by my professor, moors circle, sigma1 = Sy or yield strength. Powerpoint also states that sigma(x) is...
  25. S

    I Theories and Laws of Physics

    Hello All We have Newton's Laws of Motion, which have been superseded by Einstein's Theory of General Relativity. Who determines what's a Theory and what's a Law? best regards ... Stef
  26. S

    I Models and theories of laws of physics emerging from chaos?

    Some physicists (like John A Wheeler, Holger B Nielsen or Ilya Prigogine) have proposed that all the laws of physics (including the most fundamental ones) emerged from a primordial chaos (for example, in the case of Wheeler, he proposed that laws of physics emerged from an initial random and...
  27. T

    I Why are some theories in physics falsifiable?

    Hello. Do you know why some theories in physics are falsifiable?If we take for example Newtonian gravity and general relativity, we see that a more exact approximation or theory in physics can be proposed. Why does this happen? More phenomena can be described from the new approximation, but...
  28. A

    A Gravity Theories: GR vs Alternatives - Post 2018

    As per the summary I would like to find a review paper, monograph or book. Google is not find any recent reviews. Post 2018 would be ideal. Thanks for any pointers. Regards Andrew
  29. A

    A How useful are quantum-classical hybrid theories?

    I have seen several attempts at building a consistent quantum-classical theory, i.e., a theory where a quantum (sub) system interacts with a classical one somehow, and both affect each other (do note that this definition rules out things like just plugging an external classical EM field into the...
  30. B

    I Interpretation of quantum theories through the interpretation of classical ones

    Perhaps the reason is that the principle of least action is elevated to a divine principle that does not require materialistic interpretation. If so, then the solution to the "secrets" of quantum theories lies in the solution of the materialistic essence of the physical magnitude of action.
  31. DarkMattrHole

    B Question regarding 'beauty' in the theories that go beyond the standard model

    There has been a lot of talk about the value of beauty in theoretical physics. There seems to be a lot of little things that are beautiful because they make sense, according to what we already know, like the discovery of anti-particles, and recently the Higgs. The standard model was revealed...
  32. BWV

    Testing Scientific Theories Against Data

    [Moderator's Note: Thread spun off from previous thread in General Discussion since it is more specifically about particular scientific theories and how to test them against data.] So in your opinion, everything in the list below is quantitative, not qualitative...
  33. T

    A Alternative theories to General Relativity

    Hey there.Have you read about the alternative theories proposed by other scientists to General Relativity?So far General Relativity still stays the most accurate.But if we could generalise it?Perhaps try with some new maths like complex differentiable manifolds or Lie groups or another...
  34. A

    Studying Does math have tons of false theories like physics?

    it seems to me that in math don't exist false theorys,missconcepions or examples where after 200years some theory prove that was false like in physics do...etc do you know that in most high school aerodynamic books last 50 years lift is explain with "equal transit time" theory which is...
  35. DennisN

    What we can learn from conspiracy theories

    I just read an article I found very interesting, about the psychology of and possible reasons for conspiracy theories: What we can learn from conspiracy theories (BBC, 25th May 2020) http://www.bbc.com/future/article/20200522-what-we-can-learn-from-conspiracy-theories "From political upheavals...
  36. S

    History The What-Ifs of history - vs personal theories and speculations

    What distinguishes discussions of the what-ifs of history from forum-prohibited discussions of personal theories and speculations? My thoughts: 1. Academic historians do discuss the what-ifs of history. 2. Speculations about things that might have happened can clarify the significance of...
  37. M

    History of the theories of electromagnetism

    I have lately been reading, with interest, the history leading up to Einstein's work as well as some of the debate that ensued after his theories were published. In particular, I was reading some of the ideas Ritz proposed and the disproof of his theories by de Sitter. A question occurred to me...
  38. P

    The key to unifying the theories of the very large and the very small

    Summary: The key to unifying the theories of the very large and the very small is asking if the object in question is physical Uncollapsed(stateless | unphysical) Quantum Waves + State(Matter Field or wave collapse) = Physical Matter Is a Matter Field state change the same thing as wave...
  39. K

    I Field theories in 4 dimensions

    Hello! I know this is a very general question (and I am really a very beginner in the field) so I am sorry if it is dumb, but here it goes. In Schwarz book on QFT, at the end of Section 14.4 (path integrals chapter) he says: "We do not know if QED exists, or if scalar ##\phi^4## exists, or even...
  40. Logic Cloud

    I 'Formulations' of Physical Theories: Overview?

    I'm trying to understand the various different ways in which we can 'formulate' theories in physics and I am finding it somewhat hard to obtain a bird's-eye view. I hope someone here can help clear up some ambiguities. I apologize in advance for the 'sketchy' ways I put matters in my...
  41. R

    A Were there any valid classical unified field theories ?

    1/ Amongst what seems like the plethora of classical Unified Field Theories; that seemed to exist in the first half of the 20th century; see for example https://link.springer.com/article/10.12942/lrr-2014-5 [caution 50MB download] were they all abandoned just because of failure to account for...
  42. hyksos

    I Theories and their domains of applicability?

    Modern physics is comprised of a quartet of theory specializations. I. Classical Physics + Special Relativity S.R. II. Quantum Mechanics. QM III. Quantum Field Theory QFT IV. General Relativity GR Under what practical conditions do the predictions of each of these theories become...
  43. A

    MHB Are there practical applications for Axiomatized Formal Theories?

    The study of these theories is interesting in itself,if only to understand Godel's work. My question concerns their practical applicability to the solution of problems in different disciplines like mathematics, engineering, physics and the like. Are there reasons for studying them beyond the...
  44. S

    Review of modern non-equilibrium thermodynamics theories

    Looking for thorough serious comparative review of modern generalisations of classical non-equilibrium thermodynamics of continua. I have heard about several such generalisations: 1) rational mechanics by Truesdell, Coleman, Noll. 2) extended thermodynamics by Müller (and Ruggeri). 3) the...
  45. G

    A The Standard Model's application to competing Covalent Bond theories?

    In the quantum mechanics of covalent bonding, there are two competing theories: https://en.wikipedia.org/wiki/Covalent_bond#Comparison_of_VB_and_MO_theories Both are complementary, but they don't overlap fully, they still leave some gaps.What I want to ask is, can all the literature of the...
  46. S

    I Is spacetime emergent - and in which theories?

    Some physicists, like Nima, Ed. Witten, Gross, and others have said/suggested that space-time is doomed, or emergent from something more fundamental. What ideas would replace space-time? Something similar to a perfect material? A fluid? Geometry? Quantum field theory of some sort? Entanglement...
  47. U

    Theories without a stress tensor

    Can someone tell me a theory in which the lowest twist operators are not the stress tensor and its derivatives? My aim is to work out the lightcone OPE for the theory and derive bounds like the averaged null energy condition. (as worked out in https://arxiv.org/pdf/1610.05308.pdf)
  48. J

    I What is the basic scheme of quantum field theories?

    In classical mechanics I would say: a particle can have any initial position and velocities, Newton laws give you the evolution of the particle: F=ma , is the basic equation, if you know the forces acting on the particle by solving this equation you get the future values for velocity and...
  49. phinds

    India scientists dismiss Einstein theories

    I am confident that there are scientific nut cases in every country (there certainly are in the US) but usually they are fringe people or just crackpots. It has long amazed me the extent to which seemingly responsible people in India subscribe to ridiculous theories. I've had a couple of direct...
  50. Auto-Didact

    A Taxonomy of Theories in Theoretical Physics

    It goes without saying that theoretical physics has over the years become overrun with countless distinct - yet sometimes curiously very similar - theories, in some cases even dozens of directly competing theories. Within the foundations things can get far worse once we start to run into...