Forgot your password?
typodupeerror
Science

Purported Relativity Paradox Resolved 128

Posted by timothy
from the disappears-in-a-puff-of-logic dept.
sciencehabit writes "A purported conflict between the century-old theory of classical electrodynamics and Einstein's theory of special relativity doesn't exist, a chorus of physicists says. Last April, an electrical engineer claimed that the equation that determines the force exerted on an electrically charged particle by electric and magnetic fields — the Lorentz force law — clashes with relativity, the theory that centers on how observers moving at a constant speed relative to one another will view the same events. To prove it, he concocted a simple 'thought experiment' in which the Lorentz force law seemed to lead to a paradox. Now, four physicists independently say that they have resolved the paradox."
This discussion has been archived. No new comments can be posted.

Purported Relativity Paradox Resolved

Comments Filter:
  • Read original paper (Score:4, Informative)

    by Janek Kozicki (722688) on Saturday January 26, 2013 @07:46AM (#42699727) Journal
    http://prl.aps.org/toc/PRL/v108/i19 [aps.org]

    Scroll down to "Trouble with the Lorentz Law of Force: Incompatibility with Special Relativity and Momentum Conservation", there you can get the pdf, if you have university access. Whew, it took me more than 20 minutes to find it. Why those journalists do not include the cited source?!

    This paper is actually quite interesting, and I remember my ED teacher complaining about the Lorentz Law incompatibility during his lectures too. Whether "hidden moment" exists or not - maybe is a matter of performing the right experiments :)

    And what about the proton radius problem?
  • by forand (530402) on Saturday January 26, 2013 @08:36AM (#42699857) Homepage
    Glad to see that others are noticing that in Physics we are still willing to entertain questioning of the foundations of modern Physics by those outside the field. Another great thing about our field is that most every paper is openly available on one of the abstract services. The original article noting the apparent paradox can be found here [harvard.edu]. While the subsequent discussion can be seen by looking at the papers citing the original, found here [harvard.edu]. Some of the commentaries have yet to be released from their embargo and are thus not yet available but will likely be so soon.
  • Re:Dark matter (Score:5, Informative)

    by buchner.johannes (1139593) on Saturday January 26, 2013 @09:28AM (#42699981) Homepage Journal

    So, hidden momentum and dark matter... What other concept will we invent to explain we dont know anything?

    Dark matter is not an invented concept, it is a name for something we observe. Galaxies just rotate faster than from what is there in normal matter. So something is going on, and this something is called "dark matter", just because it does not produce/interact with light but behaves like a mass.

    Now in what way you explain this (new physical laws, new elementary particles) is still an open question. But it's there and needs to be addressed. Dark matter is just the name of the problem.

  • by maxwell demon (590494) on Saturday January 26, 2013 @10:14AM (#42700187) Journal

    All you have to do to access it is to give them the right amount of money (or to be at an institution which does so, as for example an university).

    However, these days many physics articles are also found on arXiv [arxiv.org] so it makes sense to search for the article there. And indeed, this article can be found there. [arxiv.org] The journal reference given there also makes it clear that it is really the same article.

    Note that everything on arXiv is Open Access.

  • by henryteighth (2488844) on Saturday January 26, 2013 @10:20AM (#42700221)
    http://arxiv.org/abs/1205.0096 [arxiv.org] Many physics papers are also uploaded to the arxiv where they are freely accessible.
  • by daaxix (218354) on Saturday January 26, 2013 @11:31AM (#42700567)

    Read his paper and his rebuttal. He is basically saying that if the Lorentz law of force is replaced with a more elegant equation (Einstein-Laub), then you naturally obtain the "hidden momentum" terms that are inserted under a covariant transformation. Furthermore, there is another candidate equation, Helmholtz force, which is different but takes care of the "hidden momentum" in a similar way. Predictions in differences in experiments can be made and Mansuripur is attempting to realize these experiments. These experiments will determine if Einstein-Laub is correct or if Helmholtz force is correct. Interestingly, the covariant transformation of the hidden momentum gives a term like the Helmholtz force I believe, so these experiments really should determine who is right.

    I really don't see why he is being attacked, his analysis doens't disagree with relativity, it just moves the mathematical terms for the hidden momentum to a different place. What I really find interesting is his claim about the experiments...

  • Re:Cognition (Score:5, Informative)

    by thegreatemu (1457577) on Saturday January 26, 2013 @01:01PM (#42700993)

    Not by any means. For probably the best example, look at the Einstein-Rosen-Podalsky paradox , a simple thought experiment used an attempt to disprove the so-called Copenhagen interpretation of quantum mechanics because it would require the instantaneous transmission of quantum states in such a way that would violate special relativity. People did try to think their way out of it, until Bell's theorem "thought" everyone back into the paradoxical corner - leading to the modern sciences of quantum entanglement.

    In fact if you look back, many of the advances in modern physics have come about specifically because of paradoxes arising from thought experiments. See also the ultraviolet catastrophe, or even Schrodinger's cat for that matter.

  • Re:Dark matter (Score:4, Informative)

    by Omnifarious (11933) * <eric-slash&omnifarious,org> on Saturday January 26, 2013 @01:30PM (#42701165) Homepage Journal

    Observations of the gravitational lensing caused by far away galaxies in the process of merging have distinctly shown concentrations of something that's lensing the light that's not in either of the two galaxies. There are also other observations that kill any possible 'alternate law of gravity' explanations.

    I thought these explanations were interesting myself and I've been paying attention to the topic. And there's been a lot of study of these ideas, because you're right, positing a brand new form of matter is a big step. And study leads to experiments. And the experiments have lead to the general consensus is that dark matter has to be something that has mass and doesn't otherwise interact with light (or normal matter) at all.

No amount of careful planning will ever replace dumb luck.

Working...