Special Rel. Doubt

Discussion in 'Physics & Math' started by mathman, Oct 24, 2021.

  1. mathman Valued Senior Member

    Messages:
    1,921
    In the latest issue of American Scientist there is an article by Tony Rothman questioning E=mc^2. Are the assertions made in the article valid? Are there comments by other physicists available?
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. exchemist Valued Senior Member

    Messages:
    11,158
    So what does it say, then?
     
    DaveC426913 likes this.
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. DaveC426913 Valued Senior Member

    Messages:
    16,515
    Yeah, MM. I think I'd rather you provide the particular assertions that cause you doubt and why. Especially since SciAm is generally behind a SubscribeWall.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. exchemist Valued Senior Member

    Messages:
    11,158
    I tried to look this up and it's American Scientist not Scientific American (I didn't know there were two of them). But it, too, is behind a pay wall. All I could see was that Rothman's article contends that: E=mc2 only applies at low speeds (well we knew that: the complete form is E² = (mc²)² + p²c²); that Einstein came up with it as a conjecture rather than a formal derivation (which we also knew: that doesn't invalidate it, of course); and that apparently some situations have led to a derivation of E=3/4mc², the meaning of which is said to be still debated. I think I may have come across this once, when reading about the history of the mass/energy equivalence, but I had thought it was just a wrong answer obtained along the way by someone back around 1900. But I forget the details.

    It is only the last of these that seems to me to be of potential interest. For that, we shall have to wait for mathman to give us a synopsis.
     
  8. mathman Valued Senior Member

    Messages:
    1,921
    The 3/4mc^2 was the gist of the author's point. The article described pre 1905 papers developing this formula.
     
  9. exchemist Valued Senior Member

    Messages:
    11,158
    It might be interesting to look at some of those papers. But we would need to know which papers they were. Which only you can tell us from the article, which you have (supposedly) read and we have not. And it would also be useful to have a brief synopsis, from you, of what Rothman has to say about them.

    But since you evidently can't be bothered, I've looked this up myself. It may be Hasenöhrl's derivation of something called electromagnetic mass in 1905: https://en.wikipedia.org/wiki/Friedrich_Hasenöhrl

    Rothman is in fact quoted in this Wiki article as having explained why Hasenöhrl got the wrong answer:

    " more generally the reason he [Hasenöhrl] achieved an incorrect result on both occasions is that he wants to rigorously equate the work performed to kinetic energy, as the work-energy theorem demands. Unfortunately, he does not know how to properly compute the energy. In particular, Hasenöhrl does not conceive of the fact that if the radiators are losing energy, they must be losing mass, which contains an element of irony because it is precisely a mass-energy relation that he is trying to establish. [...]
    Let us end by saying that Fritz Hasenöhrl attempted a legitimate thought experiment and tackled it with the tools available at the time. He was working during a transition period and did not create the new theory necessary to allow him to solve the problem correctly and completely. Nevertheless, his basic conclusion remained valid and for that he should be given credit."

    So I'm not sure what the fuss is about. Rothman isn't casting any doubt on SR. He may just want to give due credit to the other workers in the field around that time.

    As ever with science, Einstein was not treading an entirely unknown path.

    So, now, you tell us whether or not what I have written accounts for what you have read, or whether you think Rothman is really casting doubt on E=mc².
     
    Last edited: Oct 26, 2021
  10. phyti Registered Senior Member

    Messages:
    612
    Max Abraham

    His picture is on the article, he having his own version of an electron theory, differing from that of Lorentz, and being anti-relativity.

    Max Abraham (1875 - 1922) - Biography - MacTutor History of Mathematics.mhtml

    https://mathshistory.st-andrews.ac.uk
     
  11. exchemist Valued Senior Member

    Messages:
    11,158
    Link doesn't seem to work.
     
  12. mathman Valued Senior Member

    Messages:
    1,921
    . I had a lot of trouble following the author. I posted the same question on Physics Forum https://www.physicsforums.com/ The responses there are more informative.
     
  13. exchemist Valued Senior Member

    Messages:
    11,158
    It seems to me those answers add nothing to what I have already posted. What further information do you glean from them?
     
  14. phyti Registered Senior Member

    Messages:
    612
    It doesn't work from this forum, but does if searched outside.
     
  15. phyti Registered Senior Member

    Messages:
    612
    There is this on Wiki,
    'On the Electromagnetic Mass of a Moving Electron'

    'Max Abraham', with 'works' listing available publications.
     
  16. exchemist Valued Senior Member

    Messages:
    11,158
    Yes. Thanks. Just another person from that era who turned out to be barking up the wrong tree. But my enthusiasm for chasing dead ends in physics is limited. I think we've dealt with the OP now.
     

Share This Page