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Science

The Proton Just Got Smaller 289

Posted by samzenpus
from the size-does-matter dept.
inflame writes "A new paper published in Nature has said that the proton may be smaller than we previously thought. The article states 'The difference is so infinitesimal that it might defy belief that anyone, even physicists, would care. But the new measurements could mean that there is a gap in existing theories of quantum mechanics. "It's a very serious discrepancy," says Ingo Sick, a physicist at the University of Basel in Switzerland, who has tried to reconcile the finding with four decades of previous measurements. "There is really something seriously wrong someplace."' Would this indicate new physics if proven?"
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The Proton Just Got Smaller

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  • by drewhk (1744562) on Thursday July 08, 2010 @11:03AM (#32840984)

    ... and now this! These scientists have no shame!

    • Re: (Score:3, Funny)

      by KUHurdler (584689)
      Not to worry, just look up. It's right there next to Uranus. You can't miss it.
    • by thewiz (24994) * on Thursday July 08, 2010 @01:55PM (#32843324)

      Does this mean we'll have to start referring to the proton as a "dwarf particle"?

  • Negative (Score:4, Funny)

    by Rockoon (1252108) on Thursday July 08, 2010 @11:04AM (#32841006)
    are they saying that the consequences of this information are, dare I say it, negative?
  • Ummm... (Score:5, Insightful)

    by Monkeedude1212 (1560403) on Thursday July 08, 2010 @11:06AM (#32841024) Journal

    "'The difference is so infinitesimal that it might defy belief that anyone, even physicists, would care"

    Does this sentence bother any one else? Just me?

    • Re:Ummm... (Score:5, Insightful)

      by Securityemo (1407943) on Thursday July 08, 2010 @11:11AM (#32841108) Journal
      Most people live in the world of senses, not the gulfs between the stars or in the mathematical models we've scrounged together to explain the eldritch abomination we call "reality". Rewrite it as "The difference is so infinitesmal that it's amazing we've come so far as to care about it." Happy?
    • Re:Ummm... (Score:5, Insightful)

      by Anonymous Coward on Thursday July 08, 2010 @11:16AM (#32841188)
      According to the article the difference is 4%. How is that small? I'm not even a physicist and that seems like a pretty huge difference to me.
      • by Pojut (1027544)

        "...I believe the Star Wars episode doubled that audience."

        "Well, yeah, but double ten people is, like, twenty people, so..."

      • Re: (Score:3, Informative)

        by painandgreed (692585)

        According to the article the difference is 4%. How is that small? I'm not even a physicist and that seems like a pretty huge difference to me.

        It is a significant difference, however, this is Nature magazine and does not usually deal with data or presenting it to scientists but rather the common person. This can be seen by their writing out "0.00000000000003 millimetres" rather than the more usually useful "3*10^-16 m". The people reading their article are not actually intended to make sense out of that numb

      • Re:Ummm... (Score:5, Interesting)

        by smackenzie (912024) on Thursday July 08, 2010 @12:27PM (#32842240)
        "Oh, welcome back to Citibank, Mr. Smith. Your portfolio indicates that all of your investments are 4% down, but we think the difference is so infinitesimal small that it might defy belief that you cared."

        "Hi Ms. Smith. Your cancer cell growth has increased 4%, but we think the difference is so infinitesimal that it might defy belief that you cared."

        "Little Timmy scored an 86.6 (grade B) instead of 90 (grade A), but we think the difference is so infinitesimal small that it might defy belief that he cared."
        • Re: (Score:3, Funny)

          by ArsonSmith (13997)

          Your Mom's so fat that she lost 4% of her weight and nobody cared.

      • Re:Ummm... (Score:5, Interesting)

        by blair1q (305137) on Thursday July 08, 2010 @12:44PM (#32842488) Journal

        If it were grains of sand packed under the foundation of your house, it might be important.

        But protons only aggregate in small groups that don't get close to each other very often. In fact, they emit a force-field that prevents it, so the size of the proton rarely if ever comes into play even in interatomic interactions.

        Which brings up a rather glaring point: SLAC, Fermilab, CERN, et al have been colliding protons together for decades. You'd think they would have noted something funny in the statistics by now to indicate that their colliding objects were consistenly not colliding with the predicted probabilities. If "size" means anything, it means the most when you try to make objects bash each other head-on.

        I'll be rightly surprised if the re-review of past data confirms that the 4% discrepancy was there and they simply ignored it.

        And maybe I missed this yesterday when I read the story (linked from Twitter; /. is about as timely as the Wall Street Journal any more), but is the 4% volume, cross-sectional area, or radius? A 4% volume difference would be trivially easy to miss; a 4% radius error would be one hell of an oversight.

        My money is on the possibility that the guys doing this new research bollixed the theory that predicts the frequency to use in their experiment. And then on the possibility that the theory they're using has never been confirmed very well. QED seems to be more concerned with photons and electrons and other less-massive particles (in fact, it doesn't say anything about mass, and if this 4% is real maybe it's a way to link gravity and GUT (the Grand Unified Theory of electromagnetism, the weak force, and the strong force...) to make the GUTE (Grand Unified Theory of Everything).

    • Re:Ummm... (Score:5, Insightful)

      by prgrmr (568806) on Thursday July 08, 2010 @11:42AM (#32841580) Journal
      It's the author's way of saying he doesn't understand physics, and that he doesn't get why anyone else would.
    • by blair1q (305137)

      Other than the fact that it's sensationalist blather masquerading as insight?

      QED's worked pretty well so far. The size of the proton doesn't seem to affect much else. And defining what "size" means for objects made of sub-objects of unknown size and shape is somewhat iffy in itself.

    • "'The difference is so infinitesimal that it might defy belief that anyone, even physicists, would care"
      Does this sentence bother any one else? Just me?

      As physicists, they already suspended disbelief when they studied/accepted the Standard Model.

    • by Anonymous Coward

      There is another sentence that doesn't make sense either,

      "Would this indicate new physics if proven?"

      Physics doesn't get "proven", mathematics gets proven. It's akin to proving reality - it doesn't make sense. AFAIK, the cornerstone of physics is the experiment. If the experiment shows something, then that's it. There is no debate except maybe about the procedure employed. There is never argument if something is "real" - it's right there.

      If the proton is shown to be smaller than what QM predicts, then the u

  • by BobMcD (601576) on Thursday July 08, 2010 @11:08AM (#32841074)

    Just remember, dear protons:

    Size matters not. Look at me. Judge me by my size, do you? Hmm? Hmm. And well you should not. For my ally is Physics, and a powerful ally it is.

  • by tverbeek (457094) on Thursday July 08, 2010 @11:08AM (#32841076) Homepage

    Have they tried re-doing the math in Base 13?

    • well, then they'd have to cut off an !odd appendage
  • by RobertB-DC (622190) * on Thursday July 08, 2010 @11:10AM (#32841098) Homepage Journal

    This paragraph from TFA has the most salient information:

    Pohl and his team have a come up with a smaller number by using a cousin of the electron, known as the muon. Muons are about 200 times heavier than electrons, making them more sensitive to the proton's size. To measure the proton radius using the muon, Pohl and his colleagues fired muons from a particle accelerator at a cloud of hydrogen. Hydrogen nuclei each consist of a single proton, orbited by an electron. Sometimes a muon replaces an electron and orbits around a proton. Using lasers, the team measured relevant muonic energy levels with extremely high accuracy and found that the proton was around 4% smaller than previously thought.

    4% sure does seem significant. But more interesting is that the measurement is thought to be much more precise because of the method of measurement. Doesn't it seem more likely that it's just not possible to get an accurate measurement with the electron -- like measuring a grape with a yardstick instead of a micrometer?

    And of course, there's that stupid cat-in-a-box thing... you can't measure something without affecting it, so maybe muons interact in some strange (lol) way with protons that doesn't happen (or happens differently) with electrons. But as a non-physicist, even throwing those terms out there puts me far outside my league.

    Of course, these more prosaic explanations don't lead to nearly as many cool sci-fi plot threads. FTL drive powered by a process that squeezes protons to black hole density, perhaps? That would be awesome. Or, perhaps the expansion of the universe is actually reducing the size of subatomic particles -- so in a few billion years, all matter will simply wink out of existence. Or, there's a time dilation effect as well, so that time drags longer and longer, especially on Mondays.

    • by thue (121682) on Thursday July 08, 2010 @11:25AM (#32841314) Homepage

      > 4% sure does seem significant. But more interesting is that the measurement is thought to be much more precise because of the method of measurement.

      No. The interesting thing is that the proton size is now shown to be different than expected from theory. Which means that the theory is wrong. Which is the first step in exciting new physics.

      • by MozeeToby (1163751) on Thursday July 08, 2010 @11:43AM (#32841596)

        In other words, it's a "that's funny..." kind of moment.

        "The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I found it!) but 'That's funny...'"
            -Asimov

      • by radtea (464814) on Thursday July 08, 2010 @11:55AM (#32841766)

        Which means that the theory is wrong

        At best it means either the theory or the experiment is wrong, and the "wrong" can vary from mundane to really interesting, with the vast weight of probability on the side of mundane.

        The structure function of the proton is not simple, and calculating it depends on QCD approximations that are even less simple. The notion that it can be characterized by a single parameter is questionable.

        Muons probe a very different part of the proton structure function than electrons. Muon orbitals are much smaller than electron orbitals, so protons look even less like a point mass to them. As such it is not surprising that they would result in a significantly different value for a single parameter in a particular model of the proton, even if the experiment is not in error somehow. By far the hardest part of the structure function of nucleons to model in QCD are the tails, and that is exactly what muons will be most sensitive too.

        This is how experimentalists react to anomalous results: the most probable explanation, always, is that the people doing the work screwed up. We then set out to prove how they screwed up. If we can't, we start to think about other corrections seriously.

        Theorists will of course have no difficulty explaining this result, even if it later turns out to be incorrect. But even if the results are correct, they will almost certainly be accounted for by relatively insignificant tweaking of QCD estimates of the proton structure function, which is good solid science, but not the kind of great big deal that TFA seems to want to make of it.

      • by blair1q (305137)

        Unless the theory is wrong in a way that doesn't affect any other measurable phenomena but adds arcane terms and virgules over virgules to the equations. Then it's the sort of fiddly physics that takes the elegance out of the current theory.

    • by meringuoid (568297) on Thursday July 08, 2010 @11:28AM (#32841348)
      4% sure does seem significant. But more interesting is that the measurement is thought to be much more precise because of the method of measurement. Doesn't it seem more likely that it's just not possible to get an accurate measurement with the electron -- like measuring a grape with a yardstick instead of a micrometer?

      Maybe, but this is still surprising. Measure a grape with a metre rule, you should still be able to say 'it's between a centimetre and a centimetre and a half.' Measure it with a micrometer, and you'd expect to see a result like 'It's 1.2144 centimetres.' If the micrometer instead measured the grape at 0.7218 centimetres, well, you'd be puzzled. First of all, of course, you'd check you were doing it right. You'd examine your micrometer and make sure you were operating it correctly. You'd recheck how you measured it with the metre rule - is it zero from where the number is printed, or from the edge of the ruler, is the ruler maybe worn down at the edge?

      But if all that checked out and you still had this discrepancy, you'd start to wonder if your ruler and your micrometer were really measuring the same units.

      Hence the suggestion of new physics. Theoretically the muon should act like a heavy electron - interacting with the proton in just the same way, so that it can be used as a more precise probe on the size of the proton. It would be the micrometer to the electron's metre rule. If it doesn't - if the muon interacts with the proton in some unexpected way so as to throw the measure off - then we've discovered something beyond the standard model.

      There are quite a few indications that there is physics beyond the standard model - heavy neutrinos, the abundance of matter over antimatter, the dark matter - and so if we can add this to the list then maybe it can help pin down just what sort of a new theory we're looking for. We've got to have something to do once the good people of Geneva finally hammer us out a Higgs, after all :-)

      • by radtea (464814) on Thursday July 08, 2010 @12:06PM (#32841932)

        But if all that checked out and you still had this discrepancy, you'd start to wonder if your ruler and your micrometer were really measuring the same units.

        The grape analogy is not a particularly good one. Consider instead a peach analogy. With an electron you're looking at it from 20 m away. With a muon from 10 cm away.

        At 10 cm you're going to be vastly more sensitive to the detailed structure of the peach. What at 20 m looked like it could be characterized adequately by a single radial parameter is now clearly a copmlex shape that doesn't even have a very sharp boundary, being covered with fuzz and all.

        By far the most likely explanation of this result is something slightly wrong with our understanding of the tails of the proton's structure function, not anything as deep as physics beyond the standard model.

        Massive neutrinos aside--as they require only the most minor tweak in the form of off-diagonal elements in the KM matrix--physics beyond the standard model is a bit like fusion power: we've been a few years away from detecting it for the past thirty years... It's gotta be out there somewhere, granted, but I'll be shocked if this experiment is the smoking gun.

      • Thanks for correctly using metre and meter. That's incredibly rare here on Slashdot and sincerely appreciated.

    • by jfengel (409917) on Thursday July 08, 2010 @11:31AM (#32841414) Homepage Journal

      And of course, there's that stupid cat-in-a-box thing...

      Not relevant in this case. The uncertainty is between two different measurements, say, mass and momentum. You don't care about the momentum in this case, so the uncertainty in the momentum can be as high as you like. (In this case they're measuring radius rather than mass, but the uncertainty principle governs many different pairs of measurements.)

      Doesn't it seem more likely that it's just not possible to get an accurate measurement with the electron -- like measuring a grape with a yardstick instead of a micrometer?

      It's more like trying to measure an watermelon with a yardstick rather than a grape. The muon is heavier by a factor of 200, so the energy levels are higher, making them easier to detect with precision. The energy levels of the electron are very small and fine, making them hard to measure with precision.

      • It's more like trying to measure an watermelon with a yardstick rather than a grape.

        Why would you want to measure a watermelon with a grape?

  • by l2718 (514756) on Thursday July 08, 2010 @11:13AM (#32841132)

    In fact, the correction is about 2% (from 0.8768(69) fm to 0.84184(67)fm; one femtometer is 10^{-15} metres). Yes, the absolute magnitude of the difference is small compared to everyday things, but that's meaningless. More importantly, this difference is more than 5 standard deviations, so this is unlikely to have happened by chance.

  • A hellaphysicist will be pretty mad is the proton is a hellometer smaller.

  • >> The Proton Just Got Smaller

    The price is the same, the box is the same, but now there's less proton.

    • Hey, I've been working on a new Proton Filter. Everything was going fine. Now I have to contact my Chinese factory engineers and retool for a smaller seive. Damn it all to hell. No one wants a proton filter that will let proton through. What am I going to do with 45k faulty proton filters?
  • see... (Score:5, Funny)

    by gandhi_2 (1108023) on Thursday July 08, 2010 @11:15AM (#32841176) Homepage

    this is why i never listen to scientist.

    they're always lying, and making me pissed.

    fucking protons, how do they work?

  • Honey... (Score:5, Funny)

    by vilemike (1820670) on Thursday July 08, 2010 @11:33AM (#32841438)
    I shrunk the proton. The kids are fine, though.
  • It's more likely that our ability to measure has improved.

    You're conclusions are only going to be as accurate as your ability to weigh, or measure.

    - Dan.
  • Since a low energy muon usually decays into an electron and couple of neutrinos, it may not be a point particle like an electron. The calculation may not have accounted for this.
    • by mbkennel (97636) on Thursday July 08, 2010 @12:24PM (#32842202)

      As far as our particle accelerators & theory can tell, electrons, muons and quarks are all elementary particles with no internal structure. Internal structure is not necessary for particle decay---particle decay isn't really inside-parts spewing out, it is energy in one form of matter being allowed by laws of physics & quantum mechanics to transform into another state.

      It would be extremely unlikely if muons had internal structure and electrons didn't.

      The most likely scenario is (unfortunately) that there are some effects which actually are part of Standard Model physics, but they weren't included in the theoretical calculations. The theoretical calculations can get quite hairy and complex; perhaps something was approximated in a way that isn't actually as valid as originally believed or some other interaction which is hard to compute was ignored.

  • Well seeing is believing, calculations can always be wrong ;) Show a real picture of a proton and I am convinced (please no photoshopping on that picture grrr).
    • by Chapter80 (926879)

      Well seeing is believing, calculations can always be wrong ;) Show a real picture of a proton and I am convinced (please no photoshopping on that picture grrr).

      Here ya go: [ . ]

      Actually, that is not only a "picture" of a proton, that is an actual proton. Simply eliminate everything that is not the proton in question, and you're left with a proton.

      See?

  • There's never a theoretical particle physicist when you need one. (Never thought I'd say that phrase)
    • Re: (Score:3, Funny)

      There's never a theoretical particle physicist when you need one. (Never thought I'd say that phrase)

      Theoretical physicist? I'd prefer the question be answered by an ACTUAL physicist. B-)

      (And if I weren't on a slow dialup link right now I'd hunt up the issue of "nukees" - a web comic written and drawn by an actual nuclear engineering PhD - where the new berkeley student opens the door to the "Theoretical physics conference room" and finds it opens into thin air about three stories up.)

    • by blair1q (305137)

      Seriously?

      You can't swing a dead theory of heat without hitting one.

      They even have their own sitcom [cbs.com] now.

      Bazinga.

  • they give the size of the proton in two or three diff units, and the diff in two or three units, but never have a simple explanation,old x femtometers, new y femtometers stupid mba journalists who don't know science
  • So what does size actually mean for a proton. For macro scale objects we measure with some physical item that has an electrostatic interaction with the item being measured. Previously all the measurements were being made using an electron. The new measurement is using a muon. Seems like they just redefined what "size" means, i.e. muon based vs electron based. What am I missing?

  • Upgrades (Score:3, Funny)

    by undecim (1237470) on Thursday July 08, 2010 @10:30PM (#32847366)

    God here. I just upgraded the universe server to PhysicsOS 1.1. Some users may notice a change in proton size due to the new quantum mechanics engine, but unless your working with the OS directly, this shouldn't be a problem for you.

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