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Theoretical physics?

  1. Feb 22, 2013 #1
    Is theoretical physics a real thing? What's the point of doing something that is relatively unknowable? How are such things researched, quantified, and calculated? And why is it accurate? Isn't it unknown until its actually applied?
  2. jcsd
  3. Feb 22, 2013 #2


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    You seem to be asserting that ideas do not exist. That's a strange idea!
  4. Feb 22, 2013 #3
    Re: Re: Theoretical physics?

    Are you just trolling or what? I don't understand.
  5. Feb 22, 2013 #4


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    "Theoretical" doesn't have to mean "relatively unknowable". Theories can make predictions that can be tested by experiments, or successfully explain previously unexplained experimental results, or most often both. If a theory doesn't do this it generally don't get a lot of attention/interest, for basically the reason that you gave: What's the point?

    For example, Einstein's General Relativity was (and still is) pure theoretical physics. But it neatly explained the previously observed but inexplicable precession of Mercury's orbit; and it predicted that light would be deflected in a particular way by gravity, and (after a few false starts) exactly that deflection was observed.
  6. Feb 22, 2013 #5


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    Its a model and is used to predict things out there in reality - how good it is at that is a matter for experiment.

    If you count a model as a real thing and issues of that type belong to philosophy where reaching a consensus on anything is well known to be pretty close to impossible.

    Think back to good old Euclidean Geometry. Its relation to the real world and issues like you raise is the paradigm for all modern physical theories.

    Last edited: Feb 22, 2013
  7. Feb 22, 2013 #6


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    Yes, it is a real activity.
    Theoretical physics is not about 'unknowable'. Theoretical physics is about developing conceptions or models about Nature and various observed physical phenomena. Theoretical physics goes hand-in-hand with experimental and applied physics. Theories (and models) are developed based on observation (experiment), and then we make predictions about further/future observations, or behaviors in new experiments based on different inputs.
    It either explains the observables or it makes measurable predictions, or it doesn't.

    Conceptions/predictions start before new observations/experiments.
  8. Feb 23, 2013 #7
    I always think of theoretical physics as a model. We're finding simpler model to explain the universe, and some uses existing model to expect behaviour of certain system.
  9. Feb 23, 2013 #8


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    Newton's Laws is one example of "theoretical physics".

    The OP is probably confusing the word "theory" used in science with the pedestrian use of the same word. In the latter, it often means an substantiated guesswork. In science, a theory is often a mathematical description of a principle or a phenomenon, and it if often based on verified experimental observations. We often use the description "theoretical physics" to differentiate it from "experimental physics". It has nothing to do with theoretical physics being "unknowable", which is utterly a silly description.

  10. Feb 23, 2013 #9
    I think the OP may mean, that some modern topics in theoretical physics are unknowable/untestable, and therefore not really "hard" science.
  11. Feb 23, 2013 #10
    Some theories or more precisely their "spin-off consequences" predate experimental verification, like time dilation, the existence of a slew of elementary particles or the CMB.

    Other theories are born out of experimental facts, like some of the first ideas in quantum mechanics, or Newton's laws of motion.

    Sometimes theories require corrections or augmentations so they work in broader scenarios, like electron scattering in non-relativistic and relativistic regimes; ie: motivations behind the Klein-Nishina cross section for Compton scattering, when the classical electron cross section was failing to produce the observed experimental results. The KN formula provides a more general expression that works for both scenarios.
  12. Feb 25, 2013 #11


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    An example of theory turned into practice.


    Three-Dimensional Single-Sided Marchenko Inverse Scattering, Data-Driven Focusing, Green’s Function Retrieval, and their Mutual Relations
  13. Feb 25, 2013 #12
  14. Feb 25, 2013 #13
    Newton's "laws" are a good approximation.
  15. Feb 26, 2013 #14
    I dont think so. Two ways I like to reconcile the "law" in Newton's Laws... One: The term came about when modern science was less developed and the notion that all conclusions are tentative with respect to evidence was not in the forefront of the philosophy of science. Two: The mathematical equation or theorem is the "law". The mathematical equation or theorem is always true with respect to it's axioms, hence its a law. But when we want to claim that this equation models observations then that is a theory. Its a scientific theory that Newton's Laws model our observations and provide predictive power.

    Nothing really explains "why" in physics. "Why" questions necessarily appeal to a lower level, more fundamental layer of science. If you are talking about the lowest level or more fundamental science then any question of "why" becomes irrelevant and you really should be asking "what".
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