Purported Relativity Paradox Resolved

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."

Comments

Summary of Resolution Ceremony

[CodeBuster]

The four physicists waived their hands over the box containing Schrödinger's cat while repeating, "omine, omine, omine" before walking away without looking inside and thus the conjecture was false and the paradox is resolved.

Re:Summary of Resolution Ceremony

[Anonymous Coward]

So they refrained from using their hands?

Re:Summary of Resolution Ceremony

[alphatel]

So they refrained from using their hands?

They refrained from using thoughts.

It's good to see that .....

[thephydes]

Science is alive and well in at least the Physics community. Whilst I won't even pretend to understand General Relativity, the questioning of it and discussion about those questions is the true essence of science. facts ->theory->more facts->questions->revised theory. Beautiful!

Re:It's good to see that .....

[Anonymous Coward]

Science is alive and well in at least the Physics community. Whilst I won't even pretend to understand General Relativity, the questioning of it and discussion about those questions is the true essence of science.

Sigh. General Relativity was not even at question here. Perhaps commenting on Slashdot should require a minimum amount of knowing what one is talking about. AAAHAHAHAHAHAHAHAHHAHAHAHA. Sigh.

At any rate, electrical engineers tend to view parts of Special Relativity in isolation. That makes them easier to handle and "visualize" in some respects, but much harder to deal with interactions. Minkovsky vectors and tensors are what theoretical physicists use instead, grouping several codependent field parts into one entity that can then be transformed as a whole.

So the physicists will most likely just have employed a better mathematical toolbox for resolving the "paradox". I've not actually read the original Einstein papers, but I would not be much surprised if his equations were closer to what Electrical Engineers get to deal with than what Theoretical Physicists do. Shaking out all that tensor stuff is more or less elegant wrapup work.

That sort of approach was, however, at the core of General Relativity, and mastering it took quite a bit more time for Einstein. I seem to remember that he discussed the underpinnings with Hilbert, and Hilbert came up with the general equations independently within something like a week, but retracted his papers out of respect for Einstein doing all the visionary groundwork as well as shouldering the math (though being quite slower at it than well-versed mathematicians).

Re:It's good to see that .....

[maxwell demon]

I've not actually read the original Einstein papers, but I would not be much surprised if his equations were closer to what Electrical Engineers get to deal with than what Theoretical Physicists do.

Indeed. When Minkowski reformulated it with 4D tensors, Einstein complained that he didn't recognize his own theory any more.

However, for General Relativity, Einstein had to go that path as well, and learned to love the power of it.

Re:It's good to see that .....

[EzInKy]

You worry too much about silly shit. Some of the best and most insightful posts here are from "Anonymous Cowards".

Re:It's good to see that .....

[maxwell demon]

I don't like spending modpoints on anonymous cowards.

Why not? Moderation is done for the sake of the readers, so they can more easily spot posts which may be worth reading. This primary function of moderation is independent of someone posting as AC or not.

Moderation also has secondary effects on the posters, to encourage writing good posts. For logged-in users, it changes their Karma. For ACs, it affects the number of allowed posts that day (and probably also the time until the next post is possible) from the same IP. While the effect is not the same for logged-in posters and ACs (and in particular, for ACs it is no lasting effect), there is an effect on ACs as well. Thus even if you only care about the secondary effects, moderating ACs makes sense.

Re:It's good to see that .....

[rocket rancher]

Science is alive and well in at least the Physics community. Whilst I won't even pretend to understand General Relativity, the questioning of it and discussion about those questions is the true essence of science. facts ->theory->more facts->questions->revised theory. Beautiful!

Did you mean trueFacts, or goodFacts? Anything can be politicized, even physics. Humans, as a rule, don't care about "facts" when they conflict with personal beliefs. If the algorithm starts with "facts", you are setting up a conflict between trueFacts and goodFacts, which allows personal beliefs to corrupt the entire process. Let me propose a slightly different algorithm that takes personal belief out of the way of the pursuit for knowledge:

model -> hypothesis -> measurement -> failure of hypothesis -> revised model.

Start with a model, not some "fact." A model is just a model. As long as it is empirically adequate, it doesn't require truth with a capital "T" to be useful, so nobody has to get their knickers in a twist over those parts of the model that disgust or terrify them. That's how Galileo and Copernicus got their ideas past the Catholic Church. By insisting they were just models that were more useful to them than the Ptolemaic "truth" endorsed by Rome, they therefore posed no threat to the Church's "facts."

For what it is worth, as a mathematician, I've always chuckled at physicists who think that reality is going to be accessible via mathematics, which is a purely abstract tool. :)

Re:It's good to see that .....

[bill_mcgonigle]

And it's a healthy sign that some random guy can say, "look Special Relativity seems to be broken," and nobody starts screaming about golden idols or anything, but rather four smart guys kindly consider what he has to say and show him where he went wrong. Everybody learns something, egos remain intact, and nobody starts swinging guns. Science FTW.

Re:It's good to see that .....

[semi-extrinsic]

Bullshit. If you have a Ph.D., you've published original research papers, so you know your field as well as anyone. Sounds like someone never got theirs, but still thinks they should be considered to be in the same league as someone who did?

Re:how strange

[Anonymous Coward]

Well, "hunt the paradox" is a standard exercise in Theoretical Physics 101, special relativity. There are quite a number of them, and not too few involve understandings of "orthogonal" and "simultaneous" and other conceptual geometric invariants that are not actually invariant.

Electrical engineers don't go through that enfuriating and embarrassing spectacle of "ok, what did I take for granted now again" of relativity initiation.

Read original paper

[Janek Kozicki]

http://prl.aps.org/toc/PRL/v108/i19

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?

Re:Read original paper

[henryteighth]

http://arxiv.org/abs/1205.0096 Many physics papers are also uploaded to the arxiv where they are freely accessible.

Has nothing to do with physics

[Anonymous Coward]

Since a paradox is not a feature of the Universe; it is a feature of a limited mind trying to understand the Universe.

Open access links to actual papers

[forand]

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. While the subsequent discussion can be seen by looking at the papers citing the original, found here. 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

[buchner.johannes]

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.

It's not a paradox

[mocm]

if you forget part of the energy-momentum tensor when you transform your coordinates from a stationary into a moving frame of reference.
Special relativity really cannot "clash" with the Lorentz force law, because it is based on the Lorentz invariance of Maxwell's equations. I think a "paradox" like this keeps coming up ever so often in discussions of special relativity, form people who don't understand it. I just don't see how PRL can accept such a paper.
I admit it would make a nice problem for a physics test, but not much more.

Re:It's not a paradox

[daaxix]

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:Back to middle ages

[maxwell demon]

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 so it makes sense to search for the article there. And indeed, this article can be found there. The journal reference given there also makes it clear that it is really the same article.

Note that everything on arXiv is Open Access.

What is it with physics?

[exploder]

First of all, this post is aimed not at the engineer from the article, but at some of the posters to this story and others like it. What is it about physics in particular that attracts so many uneducated crackpots? It seems to be the sweet spot for cranks on the XKCD spectrum--they don't go all the way over to math, and try to promote their pet tensor analysis theory ("this is how we really should compute the induced map on the cotangent bundle!"), and even less often are we treated to their "revolutionary" theories of hydrocarbon structure or ribosomal protein synthesis.

Nope, they gravitate straight to physics. Is it that concepts are (relatively) familiar, like light, gravity, time, particles, etc? Is it Star Trek? Must drive physicists nuts.

Re:Back to middle ages

[Zontar The Mindless]

You could, you know, pay to play. Like all other aspects of life.

I hate being the one to break this to you, but... If your girlfriend is billing you for services rendered, she's not really your girlfriend.

Re:Cognition

[thegreatemu]

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

[Omnifarious]

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.

Re:Dark matter

[lgw]

You're about 5 years behind the facts on dark matter. The cosmic microwave background radiation studies comfirmed the dark matter hypothesis for galaxy/cluster rotation rates several years ago now.

Dark matter was proposed in the 1930s. At the time it was one of several hypotheses for why rotation rates weren't as expected. But a few years ago the CMBR studies also "observed" dark matter, and the matter/dark matter ratio matched the predictions to a couple of significant digits (which for cosmology is amazing).

The existance of dark matter is now confirmed as much as anything can be in cosmology - the evidence is as strong or srtonger than, say, black holes existing.

Re:Dark matter

[lgw]

Sorry, you're just wrong on this one. In the 1930s, then the hypothesis was new, you would have been correct, but in the past decade measurements of the early universe (via the CMBR) have directly confirmed predictions made by the dark matter hypothesis.

Dark matter is as confirmed as anything else in science that there's not actual engineering built around. Everything in science is a theoretical concept: that's not a useful statement.