What is Theoretical: 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. rhotonsix

    I Pure mathematics problem solving and relevance to theoretical physics

    I am recreationally self studying physics and math with the ultimate goal of understanding theoretical/mathematical framework of classical mechanics, general relativity, and quantum mechanics (in addition to the actual physics). The question I have is how deep in the realm of pure math does one...
  2. T

    Programs PhD Theoretical Physics (study, application & all sorts of guidance)

    After graduating with 2-years Masters in TP, I wish to return to academia by undertaking a PhD in theoretical physics and I have A LOT of questions since I am aware that it is a, extremely competitive area especially when you were out of the game for a while, about 5 years for me… What are the...
  3. A

    A Green's function for tunneling electrons between quantum dots

    Good afternoon! I am writing with such a problem, I hope to find someone who could help me. I'm almost desperate! So, there is such a thing as the Braess paradox, this is a classic paradox for roads and power grids, and there is also such an article...
  4. fresh_42

    I Theoretical bounds on dark matter masses

    It looks as if ultra-light and super-heavy have become less likely. https://www.sciencedirect.com/science/article/pii/S0370269321000083
  5. W

    How to study Mathematics for Theoretical Physics

    I have a B.S in Mathematics, but wish to pursue Theoretical Physics. I still have a great deal of undergraduate Physics coursework to take before I can apply to graduate programs. My question has to do with the Mathematics that is crucial in order to do Theoretical Physics. Is the mathematics...
  6. Mayhem

    Theoretical Possibility of a N-methyl Polymer Structure

    Out of sheer curiosity, would a polymer of the following structure be theoretically possible? Imagine that the "N-methyl" groups are just the bounds of what is shown, and not actual carbon-containing substituents... It doesn't seem to break any elementary bonding rules. However, the C-C bond...
  7. TonyCross

    Calculating Theoretical Reaction Force of Ball Traveling in Semi-Circle

    Summary:: Theoretical reaction force due to ball traveling in a semi-circle circum Hi, Can anyone please help me with the following question: Setup... 1 x length of pipe bent 180 degrees with an inner diameter of 22mm, it's radius is 2mtrs, the mass of this object is 100kg. Total length of...
  8. M

    Theoretical question about the Sun

    I would like to understand, for a science fiction book idea, if there is a possibility to create a theoretical energy plant that would circle the sun and tap into it's core and drain energy from the core (to use for human needs) and in the process would "drain" the sun or "shorten" it's life...
  9. nomadreid

    I Ratio of a real value to the max theoretical value: what term to use?

    If the Summary is not clear, the following is an example translated from: https://telecombloger.ru/7335 '... air conditioning systems. For example, the efficiency of a compressor is about 85%. The remaining 15% is spent on friction, oil movement, overflows, heating, etc. The efficiency of the...
  10. M

    Calculating Time to Reach Highest Point in Theoretical Mechanics Problem

    A rough explanation of my attempts: I set the coordinate axis in a way that x is the horizontal base and y is perpendicular. But I guess it is a 3d problem, so I struggle finding the right position of the coordinate system. Then, my next step was applying 2nd NL for every axis. So far I have...
  11. andrew0310

    Physics What is it like to do theoretical physics research?

    Hello everybody, I am an undergraduate student studying computer science and I love it, especially Artificial Intelligence. I'm a curious person, so there are a lot of things that I find intriguing. But I sometimes wonder if a physics career would be more interesting, not because I don't like...
  12. S

    Highest theoretical temperature on Earth

    I had read somewhere that this value is 130 °F at sea level (and thus the 134 °F one at Death Valley back in 1913 is suspect). Is there some paper that explains how this figure was derived?
  13. Kiah Palmer

    Chemistry Calculate the theoretical yield percentage for this reaction

    Conversion: 1.0 t = 1.0x10^6 g impure Si Conversion: 2.33 t = 2.33x10^6 g SiCl4 Atomic Mass Si = 28.085 g/mol Atomic Mass Cl2 = (2 x 35.453) = 70.906 g/mol Mass SiCl4 = 28.085 + (4x35.453) = 169.897 g/molI got all this part down, however, I'm not quite sure where I am supposed to go from there...
  14. mahonskey

    B Quantum total eclipse of the sun?

    This might be total nonsense, but the thought popped into my head while I was trying to get to sleep, so I thought I see if I could find any advanced help with the following hypothetical: If light were instantaneous, how far from Earth would the sun have to be to cause a quark orbiting in place...
  15. K

    A Differential Forms or Tensors for Theoretical Physics Today

    There are a few different textbooks out there on differential geometry geared towards physics applications and also theoretical physics books which use a geometric approach. Yet they use different approaches sometimes. For example kip thrones book “modern classical physics” uses a tensor...
  16. P

    I Difficult Series Battery Problem

    Modern batteries use double-sided anode and cathodes for greater energy density. Series wiring of batteries is typically accomplished by connecting the anode of one cell to the cathode of another. However, can series be accomplished by stacking double-sided anode and cathode alternatingly with...
  17. R

    Ladder-like bandpass filter theoretical analysis problem

    I consider the band-pass filter of the following configuration (the ##u_m## is a voltage controlled voltage source): The transfer function is $$K_1(p)=\hat{U}_o(p) = \frac{p}{RC(p+1/RC)^2} = \frac{\omega_c p}{(p+\omega_c)^2}, \quad \omega_c=\frac{1}{RC}.\qquad (1)$$ Now I connect ##n## such...
  18. w4y021

    Courses Changing my life from Engineering to Theoretical Physics

    Long times have been that I've decided changing my job from engineering to theoretical physics. Because I don't want to learn the rules that have been discovered by any scientists and make a situation about getting it real :]. I want to learn how the rules of nature is being discovered and what...
  19. T

    Nolting Theoretical Physics 1, Jacobian Notation Question

    On Page 406 of Nolting Theoretical Physics 1 he has the following notation for the Jacobian determinant $$\frac{\partial( x_{1}, x_{2})}{\partial (y_{1}, y_{2})} = \begin{vmatrix} \left (\frac{\partial x_{1}}{\partial y_{1}} \right )_{y_{2}}& \left ( \frac{\partial x_{1}}{\partial y_{2}}...
  20. E

    Programs Masters then PhD in theoretical physics: Cambridge vs EU?

    Hello, this is my first post. So sorry for the long read in advance. I will graduate from Part II mathematical tripos this year, and I'm currently having a hard time deciding where to go for my Master: For now, I'm definite that I want to do theoretical physics PhD (gravity, cosmology, or...
  21. N

    Math Switching from Electrical Engineering to Theoretical Physics

    Hi all, I'm going to graduate this May with a degree in Electrical Engineering. While I've done pretty well, my passion was never in EE and I'd like to aim for graduate school in Computational Neuroscience. When I look at the background and methodology employed by many favorite (current)...
  22. nikoladjal

    Other Topic for a Master's Degree in theoretical Astrophysics final project

    Hello all, I'm doing a Master's Degree in Theoretical Astrophysics and now I need to decide in which topic I will do my final project and I wanted to ask you what would be the best option. I would like to do something that would make me have some future in the investigational path I choose...
  23. Q

    What's the timeline for theoretical physics PhD admissions in the UK?

    If I haven't heard back as of yet, does that mean that I haven't been shortlisted? When are interviews usually held and when do people usually find out? My feeling is that if I haven't heard back from the universities as of yet, I haven't been shortlisted but I'm hoping someone more...
  24. TechieDork

    Are theoretical physicists and pure mathematicians just like priests?

    I was often told that If you want to pursue something pure and abstract like theoretical physics and pure maths you have to give up the materialism , say good bye to your dream of living a big house , swimming pool and a yatch. there is no weath in these fields. And people who work in these...
  25. J

    Schools Help to find best high school in the US to become a theoretical phyicist

    Dear everyone, My younger brother who is 15 years old and me, both live in the UK. He is determined to become a theoretical physicist like Zeldovich or Ginzburg. We have an opportunity to send him to a US high school because it is the best place to become and be a physicist. Could you please...
  26. I

    Career advise: theoretical physics PhD?

    When I was studying the bachelor in physics, I was happy and got good marks (not the best, but good). I always liked the more theoretical and mathematical subjects. Then I did a masters in Theoretical Physics in Spain. At the beginning I was happy: all subjects were hard but interesting. I spent...
  27. S

    Expositions of why theoretical attempts failed

    Are there expositions of why various theoretical attempts by prominent physicists failed? - or is it mostly the case that they told people they were making such attempts and never published anything? For example in the thread...
  28. Pispi Choudhury

    Courses Pursuing Theoretical Physics Research: What Courses to Take

    I just finished my sophomore year of a 4-year undergrad in Physics, what relevant courses should I take to pursue my career in theoretical physics research? Advanced grad courses are to be recommended too, thanks.
  29. parazit

    I Comparing theoretical calculations with experimental data

    Dear users, The situation I have encountered is a simple statistical comparison of the experimental data, which accepted as correct, with the results obtained via six theoretical models. In the experimental data, there exist y values corresponding to x values and also the measurement errors of...
  30. Stephen Miller

    Engineering Initially evacuated chamber and maximum theoretical work

    Given: V_1 = 10 L, V_2 = 22 L Not sure what I need to do here. We are told to ignore heat transfer, and the problem suggests that this is not a steady-state problem. The gage pressure is given, so I think that means we need to calculate for the absolute pressure, which would be 997 kPa. Cp and...
  31. warhammer

    I Is Theoretical Physics Progressing Slower Than Experimental Physics?

    In respect to the above question, I also have a follow up question. Is progress in Theoretical Physics somewhat slow currently as compared to Experimental Physics?
  32. E

    A Validity of theoretical arguments for Unruh and Hawking radiation

    [Moderator's note: New thread spun off from previous discussion due to more advanced subject matter being discussed.] There is, in fact, a quite good argument that Hawking radiation cannot be derived by semiclassical theory. It is the comparison with the scenario where the collapse stops some...
  33. Dingleberry

    Courses Don't enjoy studying theoretical physics

    I'd like to start by saying I don't know if this is the right place to post this, but I feel this community will be able to help me more than any other regarding my issue. I'm an Irish student currently studying undergrad theoretical physics in Trinity College Dublin. Growing up, I was somewhat...
  34. K

    Physics How to do research in theoretical physics or math?

    Hello! All of my undergraduate research so far was in experimental fields, mainly because most of my professors are doing that at the university. The few ones who are doing something more theoretical are mainly working on numerical simulations. I have always been fascinated about theoretical...
  35. PeterDonis

    A Theoretical status of hypothesized Generic Objects of Dark Energy

    I have come across some online references to Generic Objects of Dark Energy (GEODEs). They are briefly described in this Wikipedia article: https://en.wikipedia.org/wiki/Generic_object_of_dark_energy The only reference from that article that I have been able to find online is this paper...
  36. P

    A Theoretical status of the Landauer Principle

    I am interested to understand the current theoretical status of Landauer's Principle and related ideas. I am looking for key papers and results in the subject. I will highlight one key paper. An improved Landauer principle with finite-size corrections Abstract: Landauerʼs principle relates...
  37. W

    Theoretical Physics: Learning to make simple mathematical statements

    Hi all, I am currently involved in a theoretical physics project and would like some advice. One of the main takeaways I hope to (well,) take away is the capacity to make simple physical/mathematical statements that are valid, which seems to be an important part of theoretical physics. How do...
  38. P

    Physics How risky is doing a PhD in theoretical Physics?

    Hello everyone! Apologies if this question has been asked and answered before, please feel free to direct me to that post and delete this one, if needed and if it has been asked before and this post is, hence, redundant. I looked up some of the earlier posts such as...
  39. M

    Programs Module Choice advice for a theoretical physics degree (Durham)

    I'm starting at Durham on the 29th of September and I need to get my module choices sorted. I have the choice between 40 credits of maths modules designed for scientists, and 40 credits of maths modules done by regular maths students. They say that you should only do the regular maths modules if...
  40. B

    MHB Find the Angle of Parable Tangent from Human Running Step

    I am a masters student studying motion analysis in human running. I need to find the angle of the parable tangent derived from the theoretical arc traced by a foot during a step and the ground (see attached). The arc comprises of a persons step height and step length and I need to find the...
  41. W

    Theoretical question about an electromagnet in an AC circuit

    This may be a stupid question, but here is what I am asking. Using a very simple circuit, say 120v AC water heating element rated at 1000 watts meaning 120v AC hot leg on 1 terminal and a neutral on the other terminal. That would give 8.3 amps of current, meaning the resistance would be 14.4...
  42. H

    I Theoretical Torricelli Vacuum Test: Impurity Impact on Pressure

    Does the real vacuum pressure/underpressure depends only on the amount of impurities? In the case of theoretical Torricelli vacuum test, when no purities left in the vacuum: Is the vacuum 0Pa at 1m height (with 760mm of Hg) and also the same at 10m height (also with 760mm of Hg) of the test...
  43. STasnim12357

    Schools How good is the Theoretical Physics MSc course at Queen Mary?

    Hello am currently an undergraduate student. My major is CSE. But I am very much interested to do my masters and then PhD in theoretical physics/mathematical physics. Is there any university that admits CS graduates for these courses? I have looked up some universities that offer these courses...
  44. Cerenkov

    B Examples of theoretical proofs overturned by evidence?

    Hello. https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1970.0021 The Singularities of Gravitational Collapse and Cosmology The above paper by Hawking and Penrose is presented in the form of a mathematical proof. To my knowledge the predictions it makes about the initial cosmological...
  45. M

    What avenue of physics can a scientist in the Star Wars galaxy study?

    What I’m looking for is some new avenue of physics for a scientist in the Star Wars galaxy to be studying. They probably know what dark matter and dark energy are since Starkiller Base is powered by it. I’m sure they know about how the universe began, why it’s expanding and what it’s fate is...
  46. P

    Testing Physics GRE or Math GRE for theoretical physics?

    I'm a student from the UK, completing a degree in theoretical physics. I'm interested in pursuing graduate opportunities in both the UK and the US. Of course, I am much more familiar with the 'UK standard' for graduate studies, in that the areas I want to pursue can fall into either the maths...
  47. G

    B Is the case for a Universal Speed Limit experimental or theoretical?

    ...Or even based on logic? I understand that it is expected that there might be a Universal Speed Limit and that this seems with extremely high probability to coincide with the speed of em transmission in a vacuum. This is borne out by experimentation and observation. Are there any other...
  48. SamRoss

    I Missing exponent in "Theoretical Minimum"?

    In "The Theoretical Minimum" (the one on classical mechanics), on page 218, the authors write a Lagrangian $$L=\frac m 2 (\dot r^2 +r^2\dot \theta ^2)+\frac {GMm} r$$ They then apply the Euler-Lagrange equation ##\frac d {dt}\frac {dL} {d\dot r}=\frac {dL} {dr}## (I know there should be...
  49. FourEyedRaven

    Other Errata for Greiner's Series on Theoretical Physics

    Hi. The #1 complaint about the Greiner series are the typos. It's a shame how it undermines the potential of this series which is, otherwise, highly acclaimed. Do you know where errata for any of these volumes can be found? Or perhaps those who have read some of the books could share their own...
  50. G

    Schools From theoretical physics master to 2nd year grad school

    I would like to ask if anyone has been admitted to a graduate school(US) straight to 2nd year after a theoretical masters MSc degree in the UK. I am asking because I would really like to study in the US, preferably on top universities but I don't want to waste another year taking essentially...
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