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. C

    I If we had a TOE, would we be able to explain why there is something rather than nothing?

    If we could have one day theory of everything thing, would we be able to explain why there is something rather than nothing and would we be able to know why there are physical laws?
  2. Rick16

    B What ever happened to Classical Unified Field Theory?

    Are there currently professional physicists who work on Einstein’s quest to unify the gravitational field and the electromagnetic field (as classical fields), or has this idea been completely abandoned? Is it simply a hopeless endeavour?
  3. M

    A Towards a purely gravitational effective theory of dark matter

    "The Price of Abandoning Dark Matter Is Nonlocality" (Deffayet, Woodard) written in response to "What is the price of abandoning dark matter? Cosmological constraints on alternative gravity theories" (Pardo, Spergel) In a nutshell, as explained after equation 34, by adding a nonlocal...
  4. Rayan

    Time-dependent perturbation theory

    So I have the solution here and trying to understand what happened at the beginning of the second row! How did we get the exponential $$e^{i(\omega_m - \omega_0 ) t' }$$ ?
  5. Th_Kramer

    B Nuclear Fusion in the Singularity

    Would it be possible for Black Holes to undergo nuclear fusion of materials with very high atomic numbers (above 118 or the majority of known atoms) in their singularity, producing any signs, including photons across the spectrum? Furthermore, I was thinking aloud and wondering, what prevents...
  6. M

    Proof in number theory: the sum of all divisors of n

    let n be a positive integer show that if n is square then σ(n)( the sum of all divisors of n )is odd.
  7. Hill

    Quantum 'Quantum Field Theory for the Gifted Amateur' by Tom Lancaster and Stephen J. Blundell as a self-study textbook?

    I'd like to hear your professional opinion on and experience with using Quantum Field Theory for the Gifted Amateur by Tom Lancaster and Stephen J. Blundell as a self-study textbook. Thank you.
  8. H

    Is the Atomic Bomb a Hoax Perpetuated by Conspiracy Theorists?

    Someone wrote to me that the atomic bomb didn't exist and was probably a hoax. T They said that in World War II German scientists declared the bomb impossible. German scientists were the best in the world so the bomb must be fake.
  9. U

    I Can Superstring Theory Ever Be Refuted or Confirmed?

    I am reading a hebrew translation of the popular book by Michio Kaku on HyperSpace. It seems Superstring Theory will never be refuted since if it's a theory of everything then you need infinite energies since the universe is infinite, and we can never get a from finite machines infinite...
  10. J

    Extended Essay Research question help (first year IB student)

    Hi guys, I am a first year IB student and I need to give hand in my research question for the extended essay today, the only thing is that I don't really know what I could do it on. The extended essay is basically a 4000 word research project. I was going to do it on photoelasticity, but when I...
  11. WMDhamnekar

    Chemistry Valence Bond Theory: Energy of a system with H and Cl atoms

    Answer: The energy of a system with H and Cl atoms at varying distances can be represented by a curve that shows the potential energy of the system as a function of the distance between the two atoms. At very large distances, the potential energy is zero because there is no interaction between...
  12. Demystifier

    I Ontology is to quantum theory what hardware is to computation theory

    In interpretations of quantum mechanics there are two types of physicists: those who care about ontology and those who don't. The ontologists, or realists, want to know what is the world made of. The non-realists, on the other hand, think that this question is not relevant to physics. Usually...
  13. StenEdeback

    Classical Looking for book about relativistic classical field theory

    Hi, I am trying to learn relativistic classical field theory as a preparation for studying quantum field theory. I am currently reading chapter 13 i Herbert Goldstein's Classical Mechanics edition 3, but I think that this book is a bit too brief and does not fully derive and explain the...
  14. raminee

    A Mapping and Recovering Combinations: A Challenge in Combination Theory

    Hello All, Not sure if this belongs in general math but lets start here and see where it takes us. In mathematics, a combination is a way of selecting items from a collection where the order of selection does not matter. As an example , say we have digits 1 to 10. And we want to select 3...
  15. hagopbul

    What Caused the Sinking of the Titanic?

    Hello : I apologise for my last post about the titanic , I didn't think it will be considered conspiracy theory , although I see it as a good science post Best regards Hagop
  16. Sumeru

    Please express this theory of mine mathematically or through equations

    Can you please express this theory mathematically or through equations? Destiny is the automatically predestined chain or course of events spread throughout the universe that originated from the first cosmic event called the Big Bang. It automatically determined when, where and exactly what...
  17. Y

    Quantum Theory, particle in a ring

    hello i would to get some help with my homework. 1. true 2. i dont know 3. true 4. i dont know 5, false 6. i dont know about 2,4,6 i really have know idea what to think I really appreciate help
  18. chwala

    Problem involving irreducible element -Ring theory

    Hey guys, i need insight on the highlighted part...the steps before this are quite clear: where is the ##\dfrac{3}{4}M ## coming from? and how to show the argument does not work for ##n=-3##? i should be able to check on this ...later. and why is the Norm of say; ##ϒ =a+c\sqrt b## taken...
  19. C

    Discover the Real Gem: Neoclassical Theory of Electromagnetic Interactions

    TL;DR Summary: Book: Neoclassical Theory of Electromagnetic Interactions - A Single Theory for Macroscopic and Microscopic Scales I've found the book of Babin & Figotin: Neoclassical Theory of Electromagnetic Interactions - A Single Theory for Macroscopic and Microscopic Scales. I like their...
  20. haziq

    Problem 2 in "Quantum Theory for Mathematicians", Solving for the travel time of a particle in a potential

    I’ve been trying to solve this for ages. Would really appreciate some hints. Thanks
  21. Mustafa Bayram

    I Diffraction of Matter: Examining Bohr's Theory

    Does matter (like electrons) diffract at the single slit and create an interference pattern on the screen? If it's not why? Isn't that violation of Bohr's Theory?
  22. A

    A Schrodinger equation in quantum field theory

    What is the Schrodinger equation in QFT? is it the nonrelativistic approximation of a Klein-Gordon scalar field? or Is there more? I have read that the Schrodinger equation describes a QFT in 0 dimensions. I accept every answer
  23. S

    I Explore Spacetimes, Metrics & Symmetries in Relativity Theory

    I was discussing this paper with a couple of physicists colleagues of mine (https://arxiv.org/abs/2011.12970) In the paper, the authors describe "spacetimes without symmetries". When I mentioned that, one of my friends said that no spacetime predicted or included in the theory of relativity...
  24. GreenLemon

    I Exploring the Possibility of Dark Matter as Stray Exoplanets or Collapsed Stars

    I was thinking about how the dark matter theory was proposed due to inconsistencies with observed mass vs the calculated required mass for a galaxy to exist. Just wondering how we know its not just stray exoplanets or possibly even smaller collapsed stars, really any kind of mass that wouldn't...
  25. V

    B Conflicting definition of degree of freedom in Kinetic Theory of Gases

    I am seeing conflicting definitions of degree of freedom in my textbook. If I look at the definition given as per screenshot below then it is the number of independent terms/variables/coordinates used to define the energy of a molecule. But, if I look at the statement of Equipartition of energy...
  26. C

    Can you please explain Bernoulli's equation?

    Can you please explain why is there work done by F2(on photo of textbook explanation of Bernoully equation (photo below)). I can understand that W2 is caused by F2 which is gravitational force(screenshot photo from YT). But for the explanation in textbook pipe is straight, no height...
  27. John Bernier

    Towards a new theory of information kinematics

    The physical world is highly parallel; many things are happening side by side simultaneously. This is true not only at the macroscopic scales that we can see but as far as we know down to the subatomic scales. This is referred to as the principle of locality [1], which states that an object is...
  28. jedishrfu

    Recent Article on the Evolution of a Theory of Covid Origins

  29. M

    A Maxwell theory invariant under dual field strength tensor application

    Hello everybody! I know in classical field theory adding in the Lagrangian density a term of the form Fαβ (*F)αβ (where by * we denote the dual of the field strength tensor) does not change the EOM, since this corresponds to adding a total derivative term to the action. However when computing...
  30. Conn_coord

    B Long String Theory: Unveiling the Universe's Secrets

    In theories of particle physics based on string theory, the characteristic length scale of strings is assumed to be on the order of the Planck length, or 10−35 meters. I am sure few people have heard about the long strings theory. If there is information on the topic big request to share it...
  31. Spinnor

    I De Broglie–Bohm theory scattering from point charge, paths

    I think I read somewhere that the trajectories of particles in the De Broglie–Bohm theory do not cross, is that true? If true, then in the case of Rutherford scattering the trajectories below can't be those of the De Broglie-Bohm theory? Thanks.
  32. L

    B Quantum field theory and wave particle duality

    I recently watched this lecture "Quantum Fields: The Real Building Blocks of the Universe" by David Tong where the professor provides a succinct explanation of QFT in about 6 minutes around the midway mark. The main point being that there are fields for particles and fields for forces and the...
  33. C

    Comp Sci Regular Expression in Theory of Automata and Computation

    In first part,since every block of 4 consecutive symbol contain at least 2 a's The answer in notes is given (aa(a+b)(a+b)+a(a+b)a(a+b)+a(a+b)(a+b)a+(a+b)aa(a+b)+(a+b)a(a+b)a+(a+b)(a+b)aa)+ But this wont be true since if we choose aabbbbaa which is possible according to the above regular...
  34. R

    "New" theory of human movement as described by Tesla. Right?

    Nikola Tesla, the prominent 20th century inventor, stated in his book "My Inventions" that all human movements appear to come from the will but are are actually generated from the outside. He goes on to say that this phenomenon is of incalculable vale to the human race and he urged further study...
  35. H

    Is AI a Portal to Another Dimension?

    The Threat Of A.I. Is Already Here: “…Bill: So what is it? Can you give an example? How will it be different from these rudimentary forms of A.I.? Gideon: “The public is now getting a glimpse of it. You would want to reference the project known as OpenAI and ChatGPT. Also, Midjourney is very...
  36. K

    Exploring "The Mathematical Theory of Black Holes" by S. Chandrasekhar

    In page 67 of book "The mathematical theory of black holes" by S. Chandrasekhar in chapter 2 "Space-Time of sufficient generality" there is a theorem that metric of a 2-dimensional space $$ds^2 = g_{11} (dx^1)^2 + 2g_{12} dx^1 dx^2 + g_{22} (dx^2)^2$$ can be brought to a diagonal form. I would...
  37. H

    A Gauge theory on a lattice: intertwiners, gauge potentials...

    Hi Pfs i am interested in spin networks (a pecular lattices) and i found two ways to define them. they both take G = SU(2) as the Lie group. in the both ways the L oriented edges are colored with G representations (elements of G^L the difference is about the N nodes. 1) in the first way the...
  38. P

    I Is QBism simply a subjective interpretation of science?

    Quantum Bayesianism takes the view that the there are no quantum states in the objective sense and that the probabilities should only be interpreted as what information an agent has about the system. Isn't this the same as claiming that there are hidden variables, and that probabilities arises...
  39. J

    B How helpful is probability theory?

    I am interested in stomach acid and heat expansion, for instance the stomach will become heated due to an athelete competing. The heat causes atheletes to live shorter than people who don't have their body heated so often. I do a lot of differential equations and number theory, but I was...
  40. caffeinemachine

    I Full Course in Group Theory (and More) on YouTube

    I created a YouTube channel (here's the link) a few months ago in which I post detailed lectures in higher mathematics. I just finished my Group Theory Course. Here is a sample video. Apart from that, so far I have uploaded A first course on Linear Algebra (which I am currently renovating). A...
  41. B

    A Time dependent perturbation theory applied to energy levels

    Hello! I am reading this paper and in deriving equations 6/7 and 11/12 they claim to use second oder time dependent perturbation theory (TDPT) in order to get the correction to the energy levels. Can someone point me towards some reading about that? In the QM textbooks I used, for TDPT they just...
  42. V9999

    I May I use set theory to define the number of solutions of polynomials?

    Let ##Q_{n}(x)## be the inverse of an nth-degree polynomial. Precisely, $$Q_{n}(x)=\displaystyle\frac{1}{P_{n}(x)}$$, It is of my interest to use the set notation to formally define a number, ##J_{n}## that provides the maximum number of solutions of ##Q_{n}(x)^{-1}=0##. Despite not knowing...
  43. J

    Does a wing really "feel" the effective airflow or it is just theory to fits numbers with experimental results?

    Question is indeed very short and clear, but answer will eliminate many doubts and misleading conclusions. Theory predict downwash that will cause reduction in airflow angle,this we call effective airflow(airflow with lower angle compare at geometric AoA). Does wing of aircraft during flight...
  44. A

    A Solving this non-holonomic system using Dirac-Bergmann theory

    I have read in some books and articles that the Dirac-Bergmann procedure to deal with constraints in phase space does not care about holonomic and Non-holonomic constraints, but I've been unable to find a single example. So, I wanted to test that assertion by solving a simple non-holonomic...
  45. A. Neumaier

    A Ensembles in quantum field theory

    Then please explain how the transition in conceptual language from a single quantum field (extending all over spacetime, or at least over the lab during a day) to an ensemble of particles can be justified from the QFT formalism.
  46. J

    Does induced drag theory include the Lift = Weight condition?

    This is usual induced drag diagram. I have 2 questions: From Kutta–Joukowski theorem Fr is always perpendicular to effective airflow. 1. Does it mean for case without effective airflow(zero induced downward velocity), Fr is perpendicular to freestream airflow,so drag is zero? When effective...
  47. J

    The use of Riccati equations in optimal control theory

    I know that linear control theory, in the form ##\dot{x}=Ax+Bu##, ##\dot{u}=Cx+Du##, can be put in the form of a matrix Riccati equation. But is there really an advantage to doing so?
  48. fluidistic

    A Neumann's principle (group theory applied to crystals), Seebeck tensor

    I am reading about symmetries in crystals, and my knowledge in the field of group theory is almost nill. I am reading that, in the worst case, the electrical and thermal conductivity tensors can possess, at maximum, 6 different entries rather than 9, thanks to Neumann's principle which states...
  49. anm_ol

    Relativity Free Books & Lectures on Special Theory of Relativity

    I recently viewed some online free lecture series on Special theory of Relativity. I think I have an understanding of the basics so far, but would like some books for problems on special relativity. (Preferably solutions or at least answer keys included). It would be a great help if they...