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The Proton Just Got Smaller

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?"

30 of 289 comments (clear)

  1. Ummm... by Monkeedude1212 · · Score: 5, Insightful

    "'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?

    1. Re:Ummm... by Securityemo · · Score: 4, Insightful

      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?

      --
      Emotions! In your brain!
    2. Re:Ummm... by Anonymous Coward · · Score: 5, Insightful

      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.

    3. Re:Ummm... by Bakkster · · Score: 4, Insightful

      And thus, the reason why the % exists. It allows us to determine if a 1kg change is significant (weight of a bowling ball), insignificant (weight of the earth), of wildly significant (weight of a swallow) by giving a single digit which compares the magnitude of change to the initial value.

      In other words, 4% of a value is not an 'infinitesimal' change, even if the values of concern are generally considered to be infinitesimally small. As far as relative change, it is significant enough to care (1/25th).

      --
      Write your representatives! Repeal the 2nd Law of Thermodynamics!
    4. Re:Ummm... by prgrmr · · Score: 4, Insightful

      It's the author's way of saying he doesn't understand physics, and that he doesn't get why anyone else would.

    5. Re:Ummm... by wurp · · Score: 5, Insightful

      Size is a somewhat ambiguous concept. I *think* what's been discovered to be off by 4% is the radius of the charge distribution. If that's true, then the volume is off by more than 12%.

      If the results of this experiment are accurate, it's a Big Deal.

    6. Re:Ummm... by smackenzie · · Score: 4, Interesting

      "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."

    7. Re:Ummm... by blair1q · · Score: 5, Interesting

      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).

    8. Re:Ummm... by mea37 · · Score: 4, Insightful

      If your lamp is emitting protons, I recommend staying away from it.

  2. Poor Protons by BobMcD · · Score: 5, Funny

    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.

  3. Re:Negative by nadaou · · Score: 5, Funny

    two hydrogen pals are sitting on the curb, sipping from their 40s. One says to the other "I think I've lost an electron". The other says "Are you sure"? To which the first replies, "Yeah, I'm positive".

    --
    ~.~
    I'm a peripheral visionary.
  4. Previous measurement error? by RobertB-DC · · Score: 4, Interesting

    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.

    --
    Stressed? Me? Of course not. Stress is what a rubber band feels before it breaks, silly.
    1. Re:Previous measurement error? by thue · · Score: 5, Insightful

      > 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.

    2. Re:Previous measurement error? by meringuoid · · Score: 5, Interesting
      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 :-)

      --
      Real Daleks don't climb stairs - they level the building.
    3. Re:Previous measurement error? by MozeeToby · · Score: 4, Insightful

      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

    4. Re:Previous measurement error? by radtea · · Score: 5, Interesting

      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.

      --
      Blasphemy is a human right. Blasphemophobia kills.
    5. Re:Previous measurement error? by radtea · · Score: 4, Insightful

      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.

      --
      Blasphemy is a human right. Blasphemophobia kills.
  5. Re:Ingo Sick by camnrd · · Score: 5, Funny

    That's actually the writing on paper bags on Algerian Airways.

  6. see... by gandhi_2 · · Score: 5, Funny

    this is why i never listen to scientist.

    they're always lying, and making me pissed.

    fucking protons, how do they work?

    1. Re:see... by Red+Flayer · · Score: 4, Funny

      Well, first, a daddy proton and a mommy proton get married...

      Homogeneous marriages are not legal in most states. Besides, it's just plain repulsive.

      A daddy proton and a mommy electron get married...

      --
      "Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
  7. Honey... by vilemike · · Score: 5, Funny

    I shrunk the proton. The kids are fine, though.

  8. Re:Ridiculous notion. by Remus+Shepherd · · Score: 5, Informative

    Physicist here.

    What's the diameter of the earth's magnetosphere?

    About 10 Earth radii, defined as the point where the Earth's magnetic field is stronger than the solar wind and thus becomes the dominant force on electrical particles.

    Similarly, we define the proton's radius in terms of its charge distribution. See how easy that is? It only takes a simple definition to make a word like 'size' meaningful.

    And in the case of the proton is *is* meaningful, because you are incorrect about the proton being a singularity. The proton is composed of three quarks, each with their own charges and charge fields.

    The quarks inside a proton are held together by strong force interactions. So any change in the measurable size of a proton is a change in what we know about the strong force. This is significant. Either the strong force is 4% stronger than our calculations predict, or there is another mechanism that is squeezing that proton's charge field down. Another force? Another particle? It'll be exciting to find out, now that we know there's something there to find.

    The journalists who write about science often use bad, confusing, or just plain nonsensical terms. But it's almost always the journalists, and you can't really fault them for dumbing down their story to appeal to the largest group of readers. Whatever you do, don't blame the scientists. They are doing good work. It's not their fault if journalists relate it improperly, nor is it the scientists' fault if you don't understand the explanations.

    --
    Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
  9. Re:Misleading use of absolute numbers by Anonymous Coward · · Score: 4, Insightful

    (0.8768-0.84184)/0.8768 = 0.03987

    Why didn't you say "about 4%"?

  10. Re:Ridiculous notion. by Remus+Shepherd · · Score: 4, Insightful

    No, such a size is not defined. But it could be, if it were a useful measurement. It would have to be defined in relation to the gravitational fields in the neighborhood, which would make it around the same radius as the L1 Lagrange point. Voila, we have defined a gravitational 'size', and it can even be represented graphically.

    Nothing exists unless someone has defined it; by the same token, anything can be defined in some way.

    --
    Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
  11. Missed opportunity: by S77IM · · Score: 4, Funny

    "For my ally is the Strong Nuclear Force, and a powerful ally it is."

    --
    Student: Is it true that the foundation of the universe is paradox?
    Master: Well, yes and no.
  12. Re:does a muon have "internal structure"? by mbkennel · · Score: 4, Interesting

    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.

  13. Re:Ridiculous notion. by Ungrounded+Lightning · · Score: 5, Insightful

    The journalists who write about science often use bad, confusing, or just plain nonsensical terms. But it's almost always the journalists, and you can't really fault them for dumbing down their story to appeal to the largest group of readers.

    Sure I can. Because it breaks the story, making it false. This confuses the readers further and makes the story have less value than not running the story at all. Yes I know the REAL job of newsies is to attract eyeballs to sell to advertisers. But they pay for the eyeballs by offering information, so "dumbing down" the story until it's worse-than-useless is outright fraud. (And it's a big part of why the old news media are dying.)

    English is a very expressive language. It's usually possible to come up with wording that can get the meaning across just as clearly and just about as tersely. For instance, in this case the proton didn't just "get smaller" i.e. suddenly change size. "New measurement technique finds protons unexpectedly smaller." is my first attempt - and I'm NOT an expert in such composition. News writers are SUPPOSED to be experts in this, so there's no excuse for them.

    Slashdot had an article and discussion on this - and science popularization - a few days ago.

    --
    Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
  14. Re:No it didn't. by UnknownSoldier · · Score: 5, Interesting

    > oh well, i'm figuring that he's probably right seeing as science is just a bunch of atheistic dogma anyway...

    Considering that Max Plank said:
      "Eine neue wissenschaftliche Wahrheit pflegt sich nicht in der Weise durchzusetzen, daß ihre Gegner überzeugt werden und sich als belehrt erklären, sondern vielmehr dadurch, daß ihre Gegner allmählich aussterben und daß die heranwachsende Generation von vornherein mit der Wahrheit vertraut gemacht ist."
    which is translated as
      "A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it."
    or paraphrased as the common English phrase:
      "Truth never triumphs -- its opponents just die out."
      "Science advances one funeral at a time."

    You might be right on the dogma bit.

    http://en.wikiquote.org/wiki/Max_Planck

  15. Hello! by jamrock · · Score: 5, Funny

    My name is Ingo Sick. You cast doubt on the Standard Model. Prepare to die!

  16. Re:Pluto is not a planet anymore... by thewiz · · Score: 4, Funny

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

    --
    If "disco" means "I learn" in Latin, does "discothèque" mean "I learn technology"?