Theory Definition and 1000 Threads

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.

View More On Wikipedia.org
  1. parshyaa

    I Is It Valid to Cancel Sets in Set Theory?

    We can prove that When A and B are two sets(A≠B) (A-B) = (A∩B') = (A-(A∩B)) {We can also confirm them using venn diagram} From first and third relation A-B = A - (A∩B) By cancelling A from both side I get B = (A∩B) Which is only possible when A and B are same set. What is wrong in my proof , is...
  2. K

    I Is there an alternative theory to dark matter?

    My physics teacher, who dislikes the idea of dark matter, told me that a physicist created an alternative explanation to the phenomena caused by dark matter. Is there something I missed on the news? What is the alternative theory to dark matter and how does it explain 'things' ?
  3. S

    A QCD as a classical field theory?

    Hi everyone, I have a question that, when came to me, sounded a bit silly to me as well, but then I realized, I myself maybe don't understand the logic behind this 100%, so why not discussing with you about it. So my question is the following. Usually we are used to do quantum field theory...
  4. H

    I Can Emission Theory Produce Doppler-Shift Formula?

    Emission theories propose that the velocity of light depends on the velocity of the light source. But the ordinary Doppler effect assumes the velocity of light remains as ##c## with respect to the ether medium, even when the light source is moving at speed ##v## with respect to the ether. They...
  5. mpolo

    B Einstein's Unified Field Theory - Details

    I saw a documentary the other day where Michio Kaku said something that really peaked my interest. He said that Einstein in his last days was working on something having to do with how small geometries of some sort being the cause of gravity. Does anyone know the details of Einstein's Unified...
  6. Aslet

    I How Does the Inclusion-Exclusion Principle Relate to Probability Theory?

    Hello everyone! I'm studying the physics of complex systems and I'm approaching probability theory. I understand that we need a ## \sigma-algebra ## and the Kolmogorov axioms in order to define a probability space but then I bumped into the following relation: $$ p(A_1 \cup A_2 ) = p( A_1 ) + p(...
  7. DaveC426913

    B Knot theory: closed loops in n dimensions

    I'm not a math machine, but I dabble in dimensional stuff. I think this falls under knot theory. I have built several prototypes of a tesseract. Each of them sits in a little case in my office. One of them is made from truncated cubes, held together with elastic cord: In theory, the...
  8. N

    A Gauge Theory: Principal G Bundles

    I've been studying TQFT and gauge theory. Dijkgraaf-Witten theory in particular. One learns that a topological field theory applied to a manifold outputs the number of principal G bundles of a manifold. My question is for the Physicists in the room, why do you want to know the number of...
  9. binbagsss

    QFT Klein Gordon Theory, momentum commutator computation

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] I think I understand part b) . The idea is to move the operator that annihilates to the RHS via the commutator relation. However I can't seem to get part a. I have: ## [ P^u, P^v]= \int \int \frac{1}{(2\pi)^6} d^3k d^3 k'...
  10. binbagsss

    Quantum Theory, propagator and causality, commutator

    Homework Statement Question: To find/ explain why there exists a continuous lorentz transformation that flips the sign for space-like separation but not time-like. Homework Equations Signature ## (-,+,+...) ## Definition of lorentz transformation: ##x^u=\lambda^u_v x^v ##...
  11. binbagsss

    Quantum Theory: derive EoM of action for a 'general' potential

    Homework Statement Action attached: To find the EoM of ##\phi ## / ##\phi^* ## Homework Equations The Attempt at a Solution [/B] Without deriving from first principles, using E-L equations I have: ## \partial_{u}\frac{\partial L}{\partial_u \phi} - \frac{\partial L}{\partial \phi} =0 ##...
  12. D

    Probability theory and statistics for Robotics and ME

    I study control theory and robotics. Recently I figured out that I have a much deeper understanding of probability and statistics compared to my colleagues. Is this 'talent' valuable in my field and if so, where? We used this theory to define white noise, but nothing more...as of now. Also I am...
  13. Urs Schreiber

    Insights Super p-Brane Theory Emerging from Super Homotopy Theory - Comments

    Urs Schreiber submitted a new PF Insights post Super p-Brane Theory Emerging from Super Homotopy Theory Continue reading the Original PF Insights Post.
  14. Amaterasu21

    Kinetic theory of gases: rebound speed and force questions

    Hi everyone, I remember years ago at school memorising the derivation of the formula for pressure in the kinetic theory of gases, as explained in this Youtube video: Thinking a little more deeply about this derivation there are two things I don't get: 1) At 0:53, the video says the molecule...
  15. davidge

    I General Relativity as a Theory of Gravity Explained

    Suppose there is a charged particle far enough of any mass so that there is no gravitational interaction between the particle and any other body. The trajectory of the particle in space-time would appear to us like this (we are at the origin of our coordinate system). Consider that at...
  16. M

    Numerical Nonlinear Lifting Line Theory in MA

    1. Homework Statement Hello all. It is not a homework actually. I just didn't know at which forum I should post. I am working on a MATLAB code solving the finite wing properties iteratively by using the Anderson's Numerical Lifting Line Method. However, I got some wrong results. The...
  17. Telemachus

    I Sturm-Liouville theory in multiple dimensions

    Hi there. It is well known from the theory of differential equation the Sturm-Liouville theory, concerning with the eigenvalue problem: ##\displaystyle \frac{d}{dx} \left ( p(x) \frac{dy_n}{dx} \right ) - q(x) y_n(x)=\lambda_n w(x) y_n(x)## with prescribed boundary condtitions for ##a\leq x...
  18. Mary curie

    Want to learn about string theory

    Hello ! I have just graduated from high school but I have a big interest in the strings theory. I am trying to understand its roots aka from where/ how did it come! To that I Need some references for my research, references to make me understand the bases only ! Thank you!
  19. Fips

    Atomic Textbook about Perturbation Theory

    Hi I was hoping someone could advise me on a textbook/platform where I can learn more about the perturbation theory applied to helium and the perturbation theory time depedant. Thanks
  20. N

    My dilema in proving a theory (bending a steel tube)

    Hey everyone ! I am trying to learn how to mathematically prove that a steel tube (with wall thickness of ~ 1mm and external diameter of ~ 15 mm) will have ... At any point along its length, the shaft must : 1) bend in such a way that the deflection is the same regardless of how the shaft is...
  21. daniele1234

    Number Theory Undergraduate Number Theory Book Recommendations

    Hi , everyone! This is my first post/thread/anything on this forum so first I apologise if I slip up or make any mistakes. Anyway, my question is about recommendations for textbooks for Undergraduate Number Theory. So far, I have studied Calculus 1-3 (including things like line integrals...
  22. ShayanJ

    Insights Entanglement Entropy – Part 2: Quantum Field Theory - Comments

    ShayanJ submitted a new PF Insights post Entanglement Entropy – Part 2: Quantum Field Theory Continue reading the Original PF Insights Post.
  23. F

    Does Rotating a Gas Container Increase Its Temperature?

    If I place an insulated container of gas on the edge of a turntable and then rotate the container as a constant angular velocity, what happens to the gas? Does the temperature of the gas increase? If so, how was work done on the gas?
  24. M

    I Exploring the Identity Matrix in Multivariable Control Theory

    Hello everyone. Iam working on a course in multivariable control theory and I stumbled over the Identity Matrix. I understand what the identity matrix is, though the use of it is a mistery... I was reading about going from state space to transfer functions and I found this expressions...
  25. Jin khajama

    Other Which Books Are Best for Studying Electromagnetic Theory from Scratch?

    I want to study Electromagnetic theory from Zero.Although i have basic knowledge of electrostatics and magnets but i do not feel confident about EM theory.I am undergraduate with Instrumentation and Control Engineering.I am preparing for National level exam in which question related to Emt...
  26. Math Amateur

    MHB Galois Theory - Fixed Field of F and Definition of Aut(K/F) ....

    I am reading Dummit and Foote, Chapter 14 - Galois Theory. I am currently studying Section 14.2 : The Fundamental Theorem of Galois Theory ... ... I need some help with Corollary 10 of Section 14.2 ... ... and the definition of \text{Aut}(K/F) ... ... Corollary 10 reads as follows: Now...
  27. Math Amateur

    I Galois Theory - Fixed Field of F and Definition of Aut(K/F)

    I am reading Dummit and Foote, Chapter 14 - Galois Theory. I am currently studying Section 14.2 : The Fundamental Theorem of Galois Theory ... ... I need some help with Corollary 10 of Section 14.2 ... ... and the definition of ##\text{Aut}(K/F)## ... ... Corollary 10 reads as follows: Now...
  28. T

    Discrete Graph Theory book or literature that dives into these concepts

    I need recommendations on literature to read. Basically i do not understand these section of Frank Harary's book on graph theory since the definition of what a boundary and a cycle vector is not clearly defined. I have googled literature on it but I am having a tough time finding the right...
  29. binbagsss

    String theory reparameterisation/ transformation law metric

    Homework Statement Attached Homework EquationsThe Attempt at a Solution [/B] where ##\tau## and ##\sigma## are world-sheet parameters. where ##h_{ab}## is the world-sheet metric. To be honest, I am trying to do analogous to general relativity transformations, since this is new to me, so in...
  30. Math Amateur

    MHB Galois Theory - Fixed Subfield of K by H ....

    I am reading "Abstract Algebra: Structures and Applications" by Stephen Lovett ... I am currently focused on Chapter 8: Galois Theory, Section 1: Automorphisms of Field Extensions ... ... I need help with Proposition 11.1.11 on page 560 ... ...Proposition 11.1.11 reads as follows...
  31. Math Amateur

    I Galois Theory - Fixed Subfield of K by H ....

    I am reading "Abstract Algebra: Structures and Applications" by Stephen Lovett ... I am currently focused on Chapter 8: Galois Theory, Section 1: Automorphisms of Field Extensions ... ... I need help with Proposition 11.1.11 on page 560 ... ...Proposition 11.1.11 reads as follows: In the...
  32. T

    Understanding the Variability of EMF in Real-Life Batteries

    Hey, My question isn't exactly a problem,it's just a doubt which occurred in my mind,while studying current electricity.The potential difference across the emf of an ideal battery is considered to be constant,whereas if the battery has an internal resistance (the case for all real life...
  33. Math Amateur

    MHB Galois Theory - Structure Within Aut(K/Q) .... Lovett, Example 11.1.10 .... ....

    I am reading "Abstract Algebra: Structures and Applications" by Stephen Lovett ... I am currently focused on Chapter 8: Galois Theory, Section 1: Automorphisms of Field Extensions ... ... I need help with Example 11.1.10 on page 560 ... ...Example 11.1.10 reads as follows: My questions...
  34. Math Amateur

    I Galois Theory - Structure Within Aut(K/Q) ....

    I am reading "Abstract Algebra: Structures and Applications" by Stephen Lovett ... I am currently focused on Chapter 8: Galois Theory, Section 1: Automorphisms of Field Extensions ... ... I need help with Example 11.1.10 on page 560 ... ...Example 11.1.10 reads as follows: My questions...
  35. G

    A Does Magnetic Braking Theory hold up?

    Magnetic braking is a theory explains the loss of stellar angular momentum and is used extensively to describe the given rotation stars. However, on a smaller and more directly observable level, when we consider Jupiter's rapid rotation rate of less than ten hours and its accompanying powerful...
  36. bhobba

    A State Space and Probability Theory

    Hi All This is in relation to the folllowing paper: https://arxiv.org/pdf/1402.6562.pdf See section 3 on examples where standard probability theory is discussed. Is it valid? To me its rather obvious but I had had a retired professor of probability say probability theory doesn't have a state...
  37. Chatterton

    Guide to Inferring Colors on Alien Worlds: Star Class, Luminosity, Atmosphere

    Is there a guide, based on existing evidence, that I could use to infer realistically how color would be affected on alien worlds due to factors like star class, luminosity, atmospheric composition, etc? I'm planning to develop a not-too-too-distant future scenario where all the stars in...
  38. Demystifier

    A Double field theory: Where is the extra space?

    Double field theory [1] is an attempt to realize T-duality of string theory at the level of field theory. For instance, if a field in ordinary field theory lives in 4 non-compact spacetime dimensions, then a field in double field theory lives in 8 non-compact spacetime dimensions. I don't...
  39. A

    I String theory and Lorentz invariance - 10D vs. 4D....

    Hi all, Clarification question: I've read that string theory is manifestly Lorentz invariant - however, I'm confused about this being true in 4D spacetime or in the full 10D setting of the theory (well, one version anyway). At some point I'd also read in a paper that 4D Lorentz invariance...
  40. Pushoam

    Explaining transverse theory of light using EM theory

    just below eqn 3.25, it is said: At any given time, Ex is constant for all values of x, but of course, this possibility cannot therefore correspond to a traveling wave advancing in the positive x-direction. Why can't Ex be a constant?
  41. M

    LeSage gravitational theory: Can it be made to work?

    I'm sure you are familiar with Le Sages physics and how it predicts gravitational drag. But what if no velocity vector matters except the direct line between the two gravitational objects? Does this fix Le Sages theory?
  42. P

    I Color Theory Equations: Additive Color Mixing & Analytical Luminosity

    Hey guys I figured out something new about color theory in additive color mixing. So, the primary colors in additive color mixing are R, G, and B (Red, Green, and Blue). The secondary colors are C, M, Y (Cyan, Magenta, Yellow). Using basic knowledge we know that R + G = Y R + B = M G + B = C...
  43. I

    B Big Bang theory and the known universe

    I just want to verify from physicists whether what I have read in this article is true: http://www.astro.ucla.edu/~wright/infpoint.html It says: The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point
  44. O

    Alternative to Mie Theory for Analysis of Homogenous Sphere

    I know that mie theory is used to analyze the absorption/scattering/extinction of a homogeneous sphere within a homogeneous dielectric medium. However, if I wanted to perform the same analysis on a sphere enclosed by two different media, is there an analytic solution to this?
  45. A

    A Einstein manifolds as asymptotic background spacetimes in Type IIB string theory

    On page 30 of the notes (https://arxiv.org/abs/1501.00007) by Veronika Hubeny on The AdS/CFT correspondence, we find the following: So far, we have been describing just one particular case of the AdS/CFT duality, namely (3.3). There are however many ways in which the correspondence can be...
  46. The_Inventor

    A David Bohm's Paper on Hidden Variables Theory

    So I've been reading David Bohm's original paper on the alternative interpretation of quantum mechanics in terms of hidden variables, just out of interest. In the 4th section he presents a complex function ψ in terms of R and S, and then (using the time dependent schrodinger equation, TISE)...
  47. T

    What are the possible values of m in the equation 3m + 3n - 8m - 4n! = 680?

    Homework Statement this problem came out in the math olympiad i took today and i got completely wrecked by this consider the following equation where m and n are positive integers: 3m + 3n - 8m - 4n! = 680 determine the sum all possible values of m: Homework Equations not sure which The...
  48. charlesmartin14

    B In Fermi V-A theory, where does the Weak Interaction occur

    Where is the electron-nucleon interaction? On the surface of the nucleus, or at the origin (R-0) ?
  49. C

    A Best way to learn string theory?

    I am a cosmologist/theoretical astrophysicist, and so far my research (all 2 years of it) has focused on quantum cosmology. However, I have become interested in string cosmology recently, and wish to do some work in that field. Obviously though, there is a minor problem with that idea. Learning...
  50. M

    Nuclear Quantum Theory: Neutrons as Waves in Diffusion & Transport

    Hi , in the classical course " nuclear reactor theory we treated neutrons as particles. can we treat neutrons as waves when it comes to diffusion or transport equation ? neutrons flux/ cross-sections ? I googled it and I didn't find enough info. Like there a lot of common terms between quantum...
Back
Top