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Where Physics currently stands

  1. Apr 9, 2014 #1
    I am fairly new to Physics and it seems to me that there are a lot of things we know to be true.

    I'm interested to know the sort of concepts that are still being debated nowadays. If you as a physicist held a conversation with another physicist, would there be anything at which where you might respond, "Hang on, that doesn't sound right"? Are there any huge concepts left that we have not yet reached a consensus on? For example I have heard that we still do not know what causes gravity - we only know from observation that it is related to mass. (Is this even true?)

    I want to get an idea of the sort of things physicists even discuss. I am only still learning the basics that are already considered 'truths' and have no idea what sort of things researchers at the highest levels even research.

    Thanks for reading, please blow my mind.

    -RT
     
  2. jcsd
  3. Apr 9, 2014 #2

    Simon Bridge

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    Welcome to PF;
    I'm afraid your question is too general - what sort of thing are you interested in?

    ... it is, at best, an oversimplification of what physicists do.

    "gravitation" is a label being given to a phenomena which is still under investigation.
    The best we can make out so far, gravitation does not have a "cause" in the usual every-day sense ... consider: sphere's are round ... roundness is part of what a sphere is, it does not have a cause it's geometry. Similarly gravity is part of what the Universe is. Going further than that would be philosophy.

    The best model we have for gravitation right now is called "General Relativity" and it works for everything from stones on the ground to galactic clusters ... it sort-of works well for the Universe as a whole. In this model, the amount of gravity is related to the energy density.

    The more advanced you get the less esoteric things become. I shared an office with a guy researching rainfall (when he wasn't chasing clouds with a radar) and across the road was a guy working on a pendulum (quantum kicked rotor). I was attaching wires to a rock (making a I vs V graph - but it was a special rock).
    We tended to talk about that sort of thing a lot.

    Really simple things can turn out to be very complicated and subtle, and being a physicists usually means taking an interest in pretty much everything that goes on around you.

    So what do we talk about? Everything.
    It's how we talk that counts - part of this website's purpose is to teach that.
     
    Last edited: Apr 9, 2014
  4. Apr 9, 2014 #3

    Matterwave

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    If you are talking about just "what are the frontiers of physics?", then the answers are really too broad to answer here. There are a LOT of unanswered questions, even in "known physics". For example, even in classical mechanics, a branch of physics that has been in development since the time of Newton, the motion of fluids is still under research. The Navier-Stokes equation, which governs general fluidic motion, has not been solved in a great many cases. Thermodynamics, another similarly old branch of physics, also has many unanswered questions. Namely, the modeling of liquids (again, this ties back to the fluidic motion point) using thermodynamics is quite poorly understood. The modeling of thermodynamic particles which interact non-trivially with each other, is also notoriously difficult. Even in the theory of solids, the most well studied and most successful branch of the phases studied by thermodynamics (solid state physics) has unanswered questions (which is why we have so many condensed matter physicists around!).

    Now, these are all examples of unsolved problems in what are so-called "known" and "developed" theories (classical mechanics, fluid dynamics, thermodynamics). What that means is, we know basically the laws which govern these objects and things, but we can't solve the mathematical equations for them because they are too complicated.

    On the other hand, there are still many BASIC physics problems which are unanswered, and many phenomena we have NO explanation for. These are the problems which perhaps require us to modify our current THEORIES of the physical laws of the universe. In other words, we don't even know what equations to use when working with these problems, because they may require equations that we don't have yet. These problems include the inability of gravity to be included into the standard model (in physics lingo, the fact that general relativity is not a re normalizable (as far as we know) theory), the dark matter problem, the dark energy problem, the black-hole information paradox, etc. There are many of these as well.
     
  5. Apr 10, 2014 #4
    Ask a physicist about inertia. You'll get a formula. Then ask for inertia's place in General Relativity. Then you will be hearing physicist talking philosophy unavoidably having to admit the difference between ontology and epistemology. What "is" versus what we know. If you're lucky you'll find pragmatism resolving the matter of the following: "The Copenhagen interpretation of quantum theory uncritically slides from ’we cannot know, simultaneously, the precise velocity and location of a lepton’ to ’a lepton has no precise simultaneous location and velocity.’ The founding principle of modern physics seems to be: if you can't in principle know something, then it doesn't exist." ~ Mark Rowland
     
  6. Apr 10, 2014 #5
    How about string theory which attempts to reconcile quantum mechanics and relativity. To date there is no experimental evidence for it but many leading physicists think it has the best chance to successfully do this.
     
  7. Apr 10, 2014 #6
    "There is nothing new to be discovered in physics now, All that remains is more and more precise measurement."
    Lord Kelvin just before the most significant advances in physics.

    "Physics never captures truth, it is statements about our universe that are yet to be disproved."
    Me
     
  8. Apr 10, 2014 #7

    UltrafastPED

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    When I talk with my fellow physicists - we usually talk about instrumentation and problems with equipment. We work in the field of lasers, vacuum systems, electron beams, x-rays: applications of technology to solving problems.

    We never talk about airy-fairy philosophical issues ... because they never go anywhere.
     
  9. Apr 10, 2014 #8
    As long as you are happy I guess.

    Applied versus theoretical. Working within the known versus exploring the unknown.

    The world requires both types to advance, the dreamers and the doers have their place.
     
  10. Apr 10, 2014 #9

    UltrafastPED

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    Just goes to show how bad we are at making predictions. Certainly this is not a scientific statement - rather it is a mere prediction, or even an off-the-cuff remark.
     
  11. Apr 10, 2014 #10

    Simon Bridge

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    "There is nothing new to be discovered in physics now, All that remains is more and more precise measurement."
    ... anyone got a contemporary reference for this quote?

    Although reportedly from an address to the British Association for the Advancement of Science (1900), the quote is only duplicated without citation to any primary source in various books, including Superstring : A theory of everything? (1988) by Paul Davies and Julian Brown; also in Rebuilding the Matrix : Science and Faith in the 21st Century (2003) by Denis Alexander. To be more credible, a source prior to the 1980s and close to 1900 is needed.
    Confusion may be due to Michelson who made a similar quote whilst mentioning Lord Kelvin: In 1894, Albert A. Michelson remarked that in physics there were no more fundamental discoveries to be made. Quoting Lord Kelvin, he continued, “An eminent physicist remarked that the future truths of physical science are to be looked for in the sixth place of decimals." ​
    http://en.wikiquote.org/wiki/William_Thomson

    Derail aside ... I'm with Ultrafast here - actual conversations between working physicists tend to be quite down to earth and practical.
     
  12. Apr 10, 2014 #11

    Chronos

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    Oh, where to start. All we have is best guesses. Some are very good and have survived the test of time, others - not so much. Nothing of what we think we know is considered certain in science. But, science has never been about certainty, it's about predictive models. Our modern models, while generally very good at predictions, are widely recognized as imperfect - and will always be that way. That's what makes it fun and why we keep looking for better models. If science were perfect we could land a gnat's gonad on a gnat's bun - on mars. For now, we have to settle for getting a lander within a dozen or so miles of the target.
     
  13. Apr 10, 2014 #12
    Hi Simon, Accept point re Lord Kelvin. By some accounts, it was taken out of context too. Press was just as bad in those days. :-) Concur with Michelson as genuine - this can be traced to actual source text.
     
  14. Apr 10, 2014 #13
    Thanks for all the replies! Sorry if the thread was too general - I was trying to get a bit of an idea of where studying physics might lead me, although I guess asking about 'physics' in general wasn't very helpful considering all the different branches of physics out there. Nevertheless your replies have been insightful and interesting to read through!

    -RT
     
  15. Apr 10, 2014 #14
  16. Apr 10, 2014 #15
    Airy-fairy philosophical issues? Indeed I don't doubt your discussions would go nowhere considering you've not expressed but a straw man argument against philosophy of science.

    Theoretical, experimental, and technical (engineering) branches of science proceed best when funded. A heady topic of discussion and not without appreciation for the drama of human personalities in play.
     
  17. Apr 10, 2014 #16

    UltrafastPED

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    Every philosopher I've ever met can argue rings around anything I say; however I think that most of the useful discoveries have been made be scientists and engineers. Certainly the "philosophically derived" theories of Aristotle (an early example), and of Immanuel Kant (a more recent example) are examples of anti-physics.

    OTOH I am in favor of well-conducted thought experiments - pushing the details with rigor.
     
  18. Apr 10, 2014 #17

    ZapperZ

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    This thread has very little, if any, actual physics content to be on the physics subforums.

    Thread is closed.

    Zz.
     
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