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I How are physics theories discovered?

  1. Jan 22, 2017 #1
    I often read about how famous theoretical physicists have made ground-breaking contributions to physics, but I always end up wondering how they are able to "discover" something that they have never seen or experienced. I believe that it has to do with the application of mathematical theories to a physical context, but I fail to imagine how that could be done. Do they just "fiddle around" with different types of math until they find one that works? And if so, how do they go about discovering the exact equations using that math and also proving that the resulting theory and equations are right? Please go in as much detail as possible.
  2. jcsd
  3. Jan 23, 2017 #2


    Staff: Mentor

    Yes, a new physical theory is an educated guess.

    After the educated guess there is a bunch of mathematical work in figuring out the logical consequences of the guess. Then there is a bunch of work figuring out the experimental predictions for existing experiments. Then there is a bunch of work figuring out the predictions in new experiments.
    Last edited: Jan 23, 2017
  4. Jan 23, 2017 #3
    Usually, sometimes, it starts with an "epiphany", a breaking scientific revealation or idea ... that makes the difference! ...
    But before [...] and after that ... {details later, due to "time zones" ...}
    Last edited: Jan 23, 2017
  5. Jan 23, 2017 #4


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    It should be mentioned though that the epiphany or the educated guess, happens to the discoverer because s\he was immersed in the problem for a considerable amount of time and has tried many different things and has looked at the problem from many different angles. Its not like thinking about it for some hours and bang!
  6. Jan 23, 2017 #5
    That would be included and covered in my
    above, later in detail.

    But in some cases (how rare?) there can be a flash! (bang!) ...
  7. Jan 23, 2017 #6


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  8. Jan 23, 2017 #7


    Staff: Mentor

    We should point out that one-size-fits-all does not fully answer your question.

    @Dale told you of the case where problem comes first, then theory, then experimentation. There are other cases where things happen in the opposite order.

    Quantum Mechanics is a very good example. Science had a wealth of experimental data that did not fit existing theories. Scientists cleverly guessed at a mathematical model that proved to explain past experiments and which allowed further predictions to be verified by later experiments.

    Astronomy is another such case. In history, astronomers were surprised many times by unexpected things seen in space. They had to invent theories to match the observations.

    So I think that the broad answer to the OP question is that theories come about every which way.
  9. Jan 23, 2017 #8


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    It should also be mentioned that a lot of theories (in fact, I will go out on the limb and claim that the MAJORITY of new theories) came out of experimental observations or discoveries. This is especially true for the "Who Ordered That?"-type of discoveries.

    There were no hints of the existence of superconductivity prior to its discovery. Fractional quantum Hall effect and fractional charges came out of nowhere. Rutherford's experiments were all "Who Ordered That?" results. anorlunda mentioned the discoveries from astronomy/astrophysics, many of which fall under this category as well.

    So there are definitely evidence that the impetus for many theories came out of experimental observations and discoveries. And certainly such empirical measurements continue to be necessary in the development of theoretical ideas. The Standard Model, for example, continues to evolve with each new experiment and result that we acquire.

    Last edited: Jan 23, 2017
  10. Jan 23, 2017 #9


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    Usually discoveries start with an observation or question... Why do apples fall from trees or how did the sun bend the path of a comet? ...Then you (or Newton) think up possible explanations and apply or test them by performing experiments or making predictions. Astronomers observed irregularities in the paths of Mercury and Uranus that could not be explained using Newton's laws. So they formed a new theory... either Newton was wrong or there were other planets out there. They predicted the existence of Neptune before it was discovered. However no such planet was discovered to explain the orbit of Mercury. It wasn't until Einstein came along that we were able to prove Newton's laws weren't the whole story.
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