What is Theories: Definition and 485 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. P

    Kinetic lagrangian for non-abelian gauge theories

    hello everyone! i've got a very special question on the gauge invariance (gauge group: SU(N), non-abelian) of the kinetic term in the lagrangian. is it invariant for any representation? i only know, that for the fundamental rep. this is true. to be more specific: the usual kinetic term...
  2. W

    Request for Book: "Gauge Theories of the Strong and Electroweak Interaction

    dear all, I am eager to read the "Gauge Theories of the Strong and Electroweak Interaction" wriiten by Manfred Böhm,Ansgar Denner,Hans Joos. But in my country, there's no the book. If you have the ebook or know the web sites to download it, please send it to my email(wuleihnu@yeah.net). Thank...
  3. J

    Toy Field Theories for Calculating Cross-Sections

    Hi all, Can you help me come up with toy field theories to practice calculating cross-sections? I'm not considering theories with derivative couplings like scalar electrodynamics. The interaction vertices I'm aware of are \bar{\psi} \gamma^\mu A_\mu \psi (QED), \bar{\psi}\psi\varphi...
  4. 8

    Exploring Non-Mainstream Theories in Cosmology: A Discussion with Experts

    Hi everyone. This is my first post so at this point I want to thank all of you for your terrific and interesting and informative forum on cosmology. I understand, and agree with, not getting into non-mainstream theories not published in peer-reviewed journals in this discussion group that...
  5. K

    Gauge Theories: Explained & Why They Matter

    What are gauge theories? Any simple explanations? Why are they so important? Whats renomalization?
  6. O

    Is a Gauge Theory of Gravity Possible in Flat Spacetime?

    I am an Italian physicist working in the field of condensed matter and non-relativistic quantum mechanics. Unfortunately my background in general relativity is very poor. In the last few monthes, as a hobby I am trying to learn a little bit of general relativity. Besides reading textbooks on...
  7. N

    Physicists and their pet theories

    In quantum mechanics there has been more different interpretations than religions trying to explain the "creation" it seems. I remember when Afshar Experiment was conducted John G Cramer immediately used the results to advocate his own pet theory while saying Copenhagen and MWI was falsified...
  8. M

    About the origen of the fundamental theories

    Hi , i have this question - it's not an idea , and it's not a theory indeed , it's merely a question - we all know that the theory of relativity is inspired by maxwell theory of electromagnetism , from which the constancy of speed of light in any frame of reference is derived . and we know that...
  9. M

    Why Do GUT Theories Only Use Left Spinors?

    Why in every single text about GUT theories only the left spinors are used? Why use the conjugate of the spinor instead of the spinor itself? Is it just a another historic definition? Thanks
  10. J

    Renormalizability of metric theories

    Are all metric theories non-renormalizable? As a hand-wavy argument, it seems like any theory where spacetime geometry itself is an "active" player would run into similar problems when trying to quantize the theory to give a quantum description of spacetime. So my question is. QED is...
  11. Fredrik

    Mathematica Mathematical theories and axioms

    Maybe this is a dumb question. I'm a bit tired right now. :smile: What is a "theory" in mathematics, and what kind of statements can we call "axioms"? To be more specific, is "group theory" a mathematical theory, and if yes, what are its axioms? Should I think of the definition of "group"...
  12. E

    What theories have sociologists proposed?

    I don't know much about sociology but I am somewhat curious about the discipline. I'd like to start a little discussion on sociology where I hope you all will inform me about the subject. What theories have sociologists proposed? What hypotheses have they came up with? What hypotheses have...
  13. S

    Nakanishi proves 2-d string theories inconsistent(?)

    From Peter Woit's http://www.math.columbia.edu/~woit/wordpress/?p=643#comments" some guy named Nakanishi claims to have proven that 2-d string theories are inconsistent: question: answer: Back to the drawing board?
  14. D

    Just how many different theories of gravity are there?

    Hello. I’m new to this forum and I’m unsure of the best way to start out. Can I just jump in and begin a new thread? I was just wondering about something and am interested to see if anyone might think this is at least worth note and have something to say. Just how many different theories...
  15. R

    Theories of Gravity: Explaining the Perihelion of Mercury's Orbit

    Do any theories of gravity exist other than general relativity that are capable of explaining the perihelion of mercury's orbit? In particular, I would like to know if a theory of gravity exists that does not impose the fact that nothing can exceed the speed of light in a vacuum. Newton's theory...
  16. A

    Alternative Theories to Particle Theory: Doubts & Debunking

    Does anyone know of / thought of or considered alternative theories to the present theory of particles forming the basis of all matter? On the other hand does anyone have any doubts as to the validity of the particle theory. I am aware that a lot of phenomena have been explained on the...
  17. Z

    What are some other theories about dark matter and dark energy?

    Hello everyone. I've been interested in Dark Matter ever since I read "His Dark Materials" trilogy which they are making a movie about... I was wondering, what are some other theories out there about what dark matter & dark energy is?
  18. M

    Is it helpful in formulating theories to assume the opposite of what we see?

    Maybe this can lead to some absurd things that make no sense, but sometimes it may be enlightening. For instance, we think that gravity is an attractive force. Maybe we can ask "What if it's really repulsive instead"? What would it take to make gravity be repulsive and still see the results...
  19. S

    Problem with the theories about the Sun and the planets

    I am not an astronomer or astrophysicist but lately, I have been reading a lot of books to upgrade my knowledge in cosmology. I have encountered two issues that I am baffled about and wonder if anyone can help me throw some light on them (1) If the planets are parts of the sun or came from...
  20. A

    Study topological field theories

    hello, I have just started to study topological field theories but my problem is that I do not find of books really specialized in the subject, can somebody inform me what I must do?
  21. wolram

    Can LQC explain the bounce of black holes?

    If theories of cosmology produce a (bounce) what happens to Black holes, it is hard to imagine that these posited things being riped apart.
  22. A

    Are there any theories about why causality appears?

    I have a question, but I am not sure how to express it. I have been thinking about the idea of the universe as a four-dimensional object, with time as just another dimension. I have also been thinking about David Deutsch's idea of the universe as a sequence of quantized slices or slides...
  23. H

    Exploring Three Acid-Base Theories: Arrhenius, Brønsted-Lowry, and Lewis

    I need a little help. In my on-line class they want me to find Acid-Base Theories for Arrhenius, Brønsted-Lowry, and Lewis and to list chemical reactions that demonstrate the action of each acid or base. I only found one chemical reactions that demonstrate the action of each acid or base...
  24. Jim Kata

    Covariant quantum field theories

    I am not as well read as most of the people in here so I thought I would ask you guys first. What work has been done in the way of developing a covariant field theory? I'm going to ramble for just a little bit so try to follow. It seems to me that QFT is built on two principles Poincare...
  25. H

    What theories appose a multiverse?

    Recently I saw a magazine which published an article on multiverse, where our universe is just one of the many possible universes resulted from inflation. That article claimed that the notion of a multiverse is gaining momentum. I am wondering if the view is shared by the majority of the...
  26. B

    Path Integrals and Non-Abelian Gauge Theories

    Ok, I have a question about this Fade'ev Popov procedure of teasing out the ghosts when one quantizes a non-Abelian gauge theory with path integrals. The factor of 1 that people insert, for some gauge fixing function f, and some non-Abelian symmetry \mathcal{G} is: 1=\int \mathcal{D}U...
  27. DrChinese

    Non-local Realistic theories disproved

    In an exciting and important development, a team of respected scientists has just announced the results of a direct test of non-locality using Leggett's Inequality. An experimental test of non-local realism, by Simon Groblacher, Tomasz Paterek, Rainer Kaltenbaek, Caslav Brukner, Marek...
  28. E

    How similar is Wen's spin lattice model to LQG's 4D spin foam theories?

    Is there a way to get a local bosonic theory out of spin foam formalism? Xiao-Gang Wen's suggestion, first published 6 Jul 2004 http://arxiv.org/abs/cond-mat/0407140v2 Page 8 "Remarkably, it appears that the theory of loop quantum gravity can be reformulated in terms of a particular kind of...
  29. wolram

    Exploring Theories of Spiral Galaxy Formation

    So far i have found two theorise of how they form, the SSPSF shock wave model ,and the Density wave model, or they may form by a combination of the two. As i am not sure how old these theories are, i wonder if there are any new insights on the subject?
  30. P

    Special Relativity at HighSchool, theories against.

    Hi all, i am 17 and researching Special Relativity for my coursework. It is due in next friday so i have left it late. I have researched some basics. I was wondering if anybody could help me out with any bright ideas, and tellme anything about the theories against light speed being constant. Id...
  31. K

    Falsification for scientific theories

    I am interest how one might falsify a scientific theory when we consider the objection from the quine-duham thesis. We can always blame one of the hypothesis that goes to making a perdiction, when the prediction does not correspond to reality.
  32. DrChinese

    Review of Local Hidden Variable Theories

    Marco Genovese has put out a review that fairly well summarizes where things are at in tests of Bell's Theorem. He has done similar papers previously, and the references are quite comprehensive (there are 505, and they cover the spectrum). Research on Hidden Variable Theories: a review of...
  33. N

    Theories and the begining of universe

    could anyone tell me about the various theories about the universe and the most accepted ones i want to know just kinda like a summary of it so that when i go for this interview and they ask me to talk about these diff theories i can give them a jist of it/them Thank you
  34. M

    Exploring Theories of the Unifying Force Beyond the Standard Model

    Have there been any theories in recent decades that suggest one? Or more? I know it may seem unnecessary or even frivolous, but theories beyond the standard model are, after all, grappling with issues like how the entire universe and its four forces came to exist. Has anyone postulated a fifth...
  35. S

    Phenomenological theories: thermodynamics

    "Phenomenological" theories: thermodynamics Hello, I was reading A. O. Barut's Electrodynamics and Classical Theory of Fields and Particles and was interested by a phrase he used, "'atomistic' physical theories - in contrast to phenomenological theories like thermodynamics - ...". What could be...
  36. A

    Hubble Findings: What Does It Mean for Theories of Everything?

    http://physicsweb.org/articles/news/10/11/16/1 Latest data from Hubble indicates that: What are the ramifications of this finding for the various TOEs we have?
  37. K

    Untrained Physicist Seeking Feedback on Written Theory - Tips and Advice"

    Hello everyone. How does one get a theory "out"? Let's say I have theory, but I'm not a trained physicist. I can't write out my theory as a mathematical equation. I can simply put it in words. How can I get someone trained in physics to look at it and tell me whether I'm smoking crack...
  38. T

    What are Stephen Hawking's Theories?

    I've been trying to mine the web and Wikipedia but all I can find is his personal life, former students and some scanty information about his theories. Can someone explain to me some of his theories at least? I'd like to know what made this guy in a wheelchair so famous
  39. T

    Exploring Quasar Energy Theories

    What are the available theories to explain the amount of energy concentrated in quasars? And what are possible problems in those theories? I don't have any background in this, I'm just trying to ascertain whether the philosophy of technology book I'm reading is still up to date. Thanks.
  40. S

    What is/is not science? Which science disciplines have testable theories?

    Hello all - While discussing Darwin's Origin of Species with a friend, I was asked, "Do you really consider that 'science' "? My response was, "Yes." But upon reflection, the conversation made me realize I do not have a good definition of what science is and is not. Even after...
  41. T

    Proving Vector Theories & Equilibrium: Exploring Questions on Zero Vectors

    hello, i have a few theories questions to ask. (i don't know where to start for question such as these...) Question: By considering the angles between the vectors, show that vector A + vector B and vector A - vector B are perpendicular when |A| = |B|. Question: Prove for any vectors A and B...
  42. MathematicalPhysicist

    Theories in maths which do not use the axiom of choice.

    i read that there are some logicians who do not use the axiom of choice in their axioms systems. i wonder what is the math that isn't using the axiom of choice, or what theories do not use it?
  43. M

    Who have wone nobel prizes or discovered many theories

    Many well regarded physicist, who have wone nobel prizes or discovered many theories, never got their BS/SB/or Bsc in physics. Is it any easier to get a phd in physics without getting a undergraduate physics degree? (time wise) Math degree (2 years) Masters (1 to 2 years) phd (3+ years)...
  44. MathematicalPhysicist

    Theories without the use of cosmological principle.

    are there theories in cosmology which do not incorporate/use the cosmological principle?
  45. Amith2006

    Foucault's Experiment: Light Theories Supported

    # Foucault’s experiment to measure the velocity of light supported: 1)Corpuscular theory 2)Wave theory 3)Photon theory 4)Electromagnetic wave theory It cannot be Corpuscular theory because it said that the velocity of light in a denser medium is greater than that in a rarer medium. It...
  46. T

    Tensor Vector scaler theories.

    Hello I have recently read an article about tensor vector scaler theories (Te VeS), including John Moffats STVG and Philip Mannheim's "conformal gravity", available at http://physicsweb.org/articles/world/19/6/5/1 I understand that Newtonian-Einstein gravity works very well across a...
  47. I

    Calculating Time Travel & Wormhole Theories

    does anyone have any equations for calculating time travel without an accelration close, equal or greater than the speed of light or equations or theories that would help me understand traversable wormhole theories and how to calculate them
  48. G

    What is the evidence against hidden variable theories?

    "Hidden variables theories", what is the main arguments that these probably isn't theories of our universe? What kind of observations in a "hidden variable theory" would be diffrent from what we observe? And why are they different? Can someone please give some basic answears and maybe point...
  49. marcus

    Generic predictions of quantum theories of gravity

    this just out http://arxiv.org/abs/hep-th/0605052 Generic predictions of quantum theories of gravity Lee Smolin For inclusion in "Approaches to Quantum Gravity - toward a new understanding of space, time, and matter", edited by D. Oriti, to be published by Cambridge University Press "I...
  50. P

    Alternative theories about the origin of the universe

    Lately the number of scientists against the big bang theory is increasing for lots of reasons espacially the growing number of hypothetical entities like dark matter, dark energy and inflation which scientists were not able to observe but only to predict by the analysis of backround...
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