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. M

    Exploring ABJM-like Theories and M-theory on dS4 x X7

    The ABJM model is a super-Chern-Simons theory in 2+1 dimensions which is dual to M-theory on AdS4 x S7/Z_k. Other ABJM-like theories are being explored which are dual to M-theory on other AdS4 x X7 backgrounds. One difficulty of dS/CFT is that you can't match up supersymmetries as you do in...
  2. S

    Who's the Top Expert in Black Hole & Time Travel Theories?

    Hello Friends, I need to find out who is currently THE TOP expert in the US in black hole, worm hole and time travel theories. When I last checked, it might have been Kip Thorne or Stephen Hawking, but perhaps there are others who are also prominent. I would love to hear your opinions...
  3. S

    Are there theories for the different sound in different volume of beaker?

    This question just pop out from my mind when my brother played with the glass cups with different volume of water in it to produce some kind of music When I tried to do some research on net I found not much informations So just want to know that are there any theories that proved the volume...
  4. A

    Calculating Maximum Distributed Load on Beam Using Failure Theories

    Having a hard time with failure theories. Beam length 20 feet, 6"h x 4"w. sigma yield is 40 ksi. How to calculate the maximum distributed load the beam could carry using von Mises and Tresca failure theories. I have my shear and moment diagrams drawn and know they are right. I found that...
  5. F

    Some theories concerning potential difference

    Homework Statement In my book, it says the following http://img849.imageshack.us/img849/388/unledpx.th.png Uploaded with ImageShack.us If you go from a to b, you gain potential. Now here is my question: I thought the E-field points from + to - in that cell, so if the current is...
  6. ShayanJ

    Physical Laws vs Physical Theories

    What's the difference between a physical Law and a physical theory? thanks
  7. A. Neumaier

    Time evolution in quantum field theories

    It requires more than that: a well-defined, selfadjoint Hamiltonian. See http://arxiv.org/pdf/quant-ph/9907069 for a gentle introduction and counterexamples. An in depth discussion is given in Vol. 1 of the math physics treatise by Reed and Simon, or Vol.3 of the math physics treatise by...
  8. StevieTNZ

    Difference between 'Quantum theories'

    Hey there This may sound a bit silly to a lot of 'experts' but, what are the differences between standard qunatum mechanics, quantum field theory, and quantum electrodynamics? Are they all predicting different aspects of natures workings, or has one superseded another? I get confused...
  9. C

    Where Can I Post Speculative Personal Theories?

    As per the subject. Where on the net can I post a personal hypothesis for feedback from people who are qualified to comment?
  10. P

    Do Mathematical Truths Depend on the Existence of Mathematical Objects?

    Hey guys, I have been thinking about the problem of mathematical truths. We simply do not know if the things that mathematics deals with really exist or not, yet people still believe that its statements are true and indubitable. Unfortunately, the only truly well-respected theory of truth in the...
  11. V

    Large VEVs in SUSY gauge theories

    Hi N=1 supersymmetric gauge theories usually have moduli spaces of vacua that are parametrized by vacuum expectation values of the scalar components of chiral superfieds. Often these are lifted quantum mechanically due to non-perturbative effects. For example in the lectures hep-th/9509066...
  12. P

    Lattice Gauge Theory: Active Physics Research or Passe?

    Are Lattice Gauge Theories still considered an area of active physics research? (i.e., are people still producing PhDs in this subject?) Or has this research area become passe?
  13. F

    An Exploration of Unified Theories

    I am starting this thread with an observation and three questions. I post this only as a starting point. I would appreciate any comment on the search for a unified theory. I am an amateur physicist at best, yet it often seems as though the scientific world over complicates the search for...
  14. A

    Photon Red Shift Energy losses in expanding universe theories

    The evidence points to an expanding universe, we tell this by looking at the redshift/distance relationship, objects further away are receding faster, with their redshift and distance at an almost linear relation. My question is, the photons emitted by those objects that we are just now...
  15. J

    Acid-base theory for DNA and RNA

    I'm not a science student - quite a layman. So, please keep your replies simple and straightforward. Thanks. Why are there more than one theory on acid-base? Why isn't one theory enough? Are these theories inter-compatible? Does one theory try to counter the limitations of earlier...
  16. M

    In principle limitations of hidden variable theories

    "In principle" limitations of hidden variable theories Does this mean that the "hidden variable" is the factor the knowledge of which is limited in principle? What I am wondering about is to what extent such factor can be said to exist if they cannot be know in principle. I'm sorry if...
  17. H

    Einstein & Hawking: Delivering Theories Without Experiments?

    Suppose I am simple man, who studies in home and read some scientific journals . Could I be able to deliver some theories(and would it be possibly correct ?. Would I have to be engaged in big laboratories consiting super computers, advance telescopes etc? How was eeinstein became able to...
  18. Z

    Describing Massive Theories by Dimensional Reduction

    Hi, I know that massive field theories are not conformally invariant. However one can incorporate mass by adding an extra dimension, and setting its corresponding momentum to be equal to mass and thereby modifying the constraint equation for spin. The next step as I understand is to perform...
  19. bcrowell

    Well-motivated theories with nonzero PPN ζ?

    Does anyone know of any well-motivated theories of gravity -- preferably viable ones -- that have nonzero values of the PPN ζ parameters, which describe momentum nonconservation? In http://relativity.livingreviews.org/Articles/lrr-2006-3/articlesu6.html#x12-200003.3 , table 3 shows some...
  20. inflector

    What Do UV and IR Mean in the Context of Quantum Gravity Theories?

    I keep seeing references to UV and IR in references to string theory and quantum gravity. This seems to come up in discussions of renormalization especially. Can someone please explicitly explain the term? Google doesn't seem to help here. There are way too many references. I have tried...
  21. S.Daedalus

    Are dualities not just an expression of equivalence in physical theories?

    By 'equivalence', I mean of the computational kind -- i.e. in the same way any universal computer can emulate any other. First of all, hi there, I'm not sure I put this question in exactly the right forum, but it seems to me that most dualities currently being discussed fall under the...
  22. haushofer

    SUSY gauge theories and representations

    Hi, I'm currently reading "Supersymmetry demystifed" by Patrick Labelle, chapter 10, about SUSY non-Abelian gauge theories. We have a Lagrangian with SU(N)-gauge fields, and gaugino's. What puzzles me are the following claims of Labelle about the representations. In the...
  23. PrincePhoenix

    Why are theories of QM and relativity not possible to combine?

    Why are theories of Quantum Mechanics and Relativity not possible to combine? I read this on wikipedia and heard this on a documentary on TV.
  24. tom.stoer

    Gribov ambiguities in gauge theories

    Two decades ago, Gribov copies arising in the Lorentz- or Coulomb gauge were considered problematic in non-perturbative calculations, e.g. due to potential failure of cluster decomposition (are there other reasons?) In the meantime this bug turned into a feature, as IR properties, especially...
  25. W

    The main obstacle in learning relativity related theories

    i really cannot understand what contravariant and covariant mean why do we need the machinery of raising and lowering the indices? i think at least in pure mathematics, we do not need this type of trashes i cannot see how this notation will not cause any inconsistency it is really...
  26. T

    Theories based on intuition: calculus telling us and us telling calculus

    Greetings. For your information, I am an undergraduate college student studying electrical engineering and also intend to get a degree in particle physics. At this point in time I am only beginning to learn calculus. For the past several years I’ve been watching television documentaries...
  27. tom.stoer

    Quantization = construction of quantum theories based on the classical limit?

    I have a question regarding quantization. In most cases one never starts with a quantum theory, but always writes down a classical expression, goes through quantization, implementation of constraints (Dirac, BRST, ...), construction of Hilbert space, inner product, measure of an path integral...
  28. M

    Has anyone ever programmed a computer system to evolve theories?

    You would feed it experimental data and it would generate theories or mathematical structures which fit the data. The theories would then be run against related experimental data to see if the theory also predicted them as well. Slight mutations, mating successful ones ---> evolved theory...
  29. L

    Higher order derivatives in field theories

    It is common lore to write lagrangians in field theories in the form L(t)=\int d^{3}x\mathcal{L}(\phi_{a},\partial_{\mu}\phi_{a}). Nonetheless, is there any particular reason for doing that? Why do we neglect higher order derivatives? Does it mess around with Lorentz invariance or something...
  30. E

    Do infinite probabilities hurt multiverse theories?

    Do "infinite probabilities" hurt multiverse theories? I got some good responses to my last thread on here I thought I'd try one more. I'm wondering about the multiverse theories where whenever a quantum 'decision' is made, the universe branches out into versions of itself in which each of the...
  31. P

    Fermi Gamma Ray Telescope: Ruling Out Lorentz-Violating Theories

    The almost simultaneous detection of low energy and high energy photons puts tight constraints on models predicting linear dependence of c on E. But it's very far from ruling out quadratic dependence. My question is, why do Lorentz-violating theories commonly predict linear rather than quadratic...
  32. F

    Astro-Physics: New Theories & Layman's Book Recs

    can anyone give me a good book recommendation for the newest theories in astro-physics? in reletively layman's terms
  33. R

    Inception [SPOILER ALERT]- What are your theories?

    Anybody watch Inception yet? What are your theories? What is the answer?
  34. haushofer

    Gauge theories and constraints

    Hi, I have a short question about gauge theories and constraints. Imagine I have a symmetry algebra, and I gauge it. With N generators in the algebra I get N gauge fields and N gauge curvatures. In realizing the algebra on the gauge fields I assume the gauge parameters are independent and...
  35. I

    Can Internal Vibrations Affect Temperature and Specific Heat?

    In thinking about specific heat, I have been unable to resolve a particular issue. If molecules in a substance are bumped and move faster, then they will measue to be at a temperature proportional to the speed they are moving which is a consequence of how hard on average they were hit(heat...
  36. H

    Weakly nonlinear theories in electrohydrodynamics

    I derived an equation describing the free surface of an electrified fluid. I am currently seeking traveling wave solutions for this problem, the equation I am looking at is (1-F) f+\frac{1}{90}h^{4}f^{(4)}+\frac{3}{4h}f^{2}-\frac{1}{2}\Bigg( B-\frac{1}{3}\Bigg)...
  37. H

    Weakly nonlinear theories in electrohydrodynamics

    I have been working on the problem of electrified fluid flow down a channel with a moving pressure distribution. I have derived an equation which describes the free surface of said fluid flow which is a Benjamin-Ono like equation. I have a numerical solution for this equation and it gives the...
  38. Planck and Einstein's theories.

    Hi all, I've just started reading upon quantum physics and came across Max Planck. I believe he was the one to state that the oscillating atoms or molecules that emit radiation could only occupy quantum states, whereby photons with energy according to E=hf are emitted when an atom changes...
  39. J

    A book on Einstein's theories of relativity

    Hi I'm not a science student neither of mathematics. I have a understanding of mathematics and physics topics up to high school - calculus etc. I was thinking of learning about relativity which is quite contrary to common sense, for fellows like me. I was look at this...
  40. M

    Weinberg, non-renormalizable theories and asym safety

    Until recently, I thought that any theory that contains non-renormalizable interactions in the power-counting sense (i.e. those whose couplings have negative mass dimension) must be an 'effective' theory that necessarily breaks down at some energy. However, I've been looking at Weinberg's QFT...
  41. L

    Besides the bigbang, are there other published theories about cosmic microwave

    That explain cosmic microwave background ? Cosmic microwave background (referring to the hiss that was detected by Wilson and Penzias, using microwave wavelength satellites, and it is found everywhere) and it is evidence of the big bang, but is it evidence of anything else? Are there other...
  42. M

    Survey on Theories of Everything

    Hey all, I'm a senior in high school doing a research report on all the various Theories of Everything in physics. I'm familiar with most of them and have a basic understanding of the concepts behind them. I'm starting this thread to get a better understanding on people's general opinions on...
  43. P

    Are effective field theories mathematically well-defined?

    The field theories in the standard model haven't been shown to be mathematically consistent. Do "effective field theories" bypass this difficulty? Are they completely mathematically well-defined as an approximation? Of course, if the deeper underlying theory is another QFT or string theory, you...
  44. marcus

    Connes Rovelli paper on time in gen. cov. quantum theories

    This paper was a "sleeper" for much of the past 16 years. But in the past 12 months, since March 2009, it has received 8 citations. Just random fluctuation or can we point to something that stirred up interest? http://arxiv.org/abs/gr-qc/9406019 Von Neumann Algebra Automorphisms and...
  45. rhody

    New Scientist: Knowing the mind of God: Seven theories of everything

    From a very very brief http://www.newscientist.com/article/dn18612-knowing-the-mind-of-god-seven-theories-of-everything.html?page=1"of seven competing theories for a Theory of Everything: from New Scientist: 15:33 04 March 2010 by Michael Marshall 1. String theory 2. Loop quantum gravity...
  46. N

    Exploring Quantum Gravity Theories and Gravitons

    Are quantum gravity theories trying to progress on the assumption that there are such things as gravitons?
  47. S

    Need a good book on the theories of Calculus

    Okay, so I've gone through calc I - III with Stewart's Calculus... I'm happy with the book for the most part, but I want a bit more theory now. I don't care what type of book, it could be like a pop-sci book for all I care, I just want to read about the theories behind the calculus without going...
  48. W

    Hypotheses, theories, laws and principles?

    I had this discussion about the differences between hypotheses, theories, and laws in my physical science class today, and I suddenly remembered the principles I had learned about in physics (e.g. Bernoulli's principle, Pauli exclusion principle). I was curious how principles fit into this whole...
  49. S

    First reactions to Einstein's theories? (support or refute)

    I'm just curious, what was the first reactions to Einstein's theories (it was 1905, right?) ... were they refuted or supported? was it like "Oh! these are nonsense..these are pseudoscience .. we shall burn you"?! or were they garnered respectable amount of debate?... were they supported by...
  50. B

    Exploring the Facts and Theories of Science

    I was just curious as to when science goes from fact to theory? What do we know to be absolute? Are balck holes for example still theory? Is GR and SR still only theory? Where is our line of absolute fact?
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