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Science

Protons Aren't round 75

Posted by chrisd from the go-figure dept.
drox writes "USA Today reports that protons are ovoid rather than spherical, as most of us learned in school." In related news, thousands of high school science labs have thrown out a bunch of little plastic balls.
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Protons Aren't round More

Protons Aren't round

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  • As if (Score:2, Insightful)

    by leviramsey ( 248057 )

    ...USA Today, the newspaper that specializes in boiling down complex issues into six sentences, knows anything about physics. Yeah, um... right.

    • I think quarks are just compressions and expansions of space time curving around themselves, Do Not Disrespect the cheese, We could all be killed.
    • My favorite part is:

      "The proton is the simplest thing around, and it is not spherical," says physicist Charles Glashausser of the Rutgers University campus in Piscataway, N.J.

      Either USA Today took him completely out of context, or I just lost all of my respect for Rutgers campus in Piscataway. I don't think anyone who has studied physics for a few years, let alone a physics professor, would ever say that a proton is "simple."

      When will "reputable" news sources ever write articles that don't dumb down physics until it's just plain wrong?
  • ...can I still sprinkle them on my cheerios for my morning breakfast?
  • ...nobody cares. Uhm, seriously, I'm not trolling. But this is definitely not a hot news item that belongs on the front page.
  • They ain't teachin' you nothin' at that damn school. Pie are round! Cornbread are squared.
  • Does that mean I should start approximating cows as ovoids instead of spheres?

    The implications!!!

  • Not surprising (Score:3, Interesting)

    by andfarm ( 534655 ) on Wednesday September 25, 2002 @10:25PM (#4333334)
    As the protons are moving at such high speeds in the nucleus (disregarding for the moment the fact that their speed and location are rather hard to determine exactly), this is an expected result.

    Why? Relativity. Objects moving at high speeds appear contracted along the axis of their movement to observers in a "fixed" reference frame.

    No surprises here, move on, move on...
    • Ehh, now this is borderline oddness. I'm no quantum physicist, so bear with me here.

      It seems to me that light, moving at the speed of light, of course, shouldn't be subject to those effects.

      The reasoning is the asymptote in the equations: objects *approaching* the speed of light elongate. If an object were to actually reach that speed, you'd get a buttload of infinities. So....?

      Thoughts? My reasoning is probably full of holes, but it makes sense in my head!
      • you'd get a buttload of infinities. So....?

        There are two possibilities here. Either general relativity is a correct description of the effects of relative velocity on the interval (0, c), or general relativity is a correct description of the effects of relative velocity on the interval (0, c]. Nobody's quite sure which--both sides have their partisans, but there's an appalling lack of physical evidence all around. If the former, then yes, anything with mass which travels at c basically turns into a pumpkin. If the latter, then we don't know what happens, because at that point we're beyond relativity's ability to describe things.

        Even if the former is correct, there are still ways to get around the c barrier. For instance, treat c as a singularity in the complex-mathematical sense and integrate around it. This is a really cute mathematical solution to the lightspeed barrier; unfortunately, to implement it would require that we have some way of imparting imaginary velocity, which at the present time we have no idea how to do.

        Short version--nobody knows what happens if/when an object hits c. Makes for some real interesting theorizations, though. :)
        • unfortunately, to implement it would require that we have some way of imparting imaginary velocity, which at the present time we have no idea how to do.
          That's because you lack imagination.

        • Well, there is a good side to things, though --- to accelerate a massive object (one having mass) to c would require an infinite amount of energy. Not something you're likely to have around.

          On the other hand, I seem to remember that massless objects (like photons) are *always* travelling at c in some direction. This leads to some oddities, but none that can't be resolved in some way.

          • On the other hand, I seem to remember that massless objects (like photons) are *always* travelling at c in some direction. This leads to some oddities, but none that can't be resolved in some way.

            Massless objects which don't travel at c would have zero momentum-energy, and would not have many ways of interacting with massive stuff in an observable fashion. They may "exist" in some philosophical sense, but there's no reason for physicists to care.

        • For instance, treat c as a singularity in the complex-mathematical sense and integrate around it.

          Perhaps you are referring to analytic continuation. Unfortunately, whatever extended function you produce is only guaranteed to be single-valued in special cases, like rational functions. As it happens, if you somehow got your velocity to move around c in a loop, your mass and length would become negative, because the Lorentz contraction formula contains a square root. You'd have to make a second loop to get back to normal.

    • Hmm...well, physicists have been studying the spin properties of protons for decades, and the specialists were surprised. But I guess you're smarter than they are.

      Your argument doesn't make sense, because quarks are pointlike particles.

  • How can it have shape? (Score:4, Interesting)

    by therealmoose ( 558253 ) on Wednesday September 25, 2002 @10:25PM (#4333336)
    How can a proton have definate (or semi definate) shape? Shape can only be observed by sight (and protons are much smaller than the wavelength of light and don't just bounce high energy electo-magentic radiation), or by collision. Protons do not collide in the normal way, they either repulse like-charged particles by the electroweak force or attract them. So, how can the shape have any meaning?

    • Re:How can it have shape? (Score:5, Insightful)

      by rjh ( 40933 ) <rjh@sixdemonbag.org> on Wednesday September 25, 2002 @11:01PM (#4333625)
      A related question: a proton doesn't even have a distinct location, so how can it have a shape? The answer is to change what you think "shape" means. When quantum physicists talk about the shape of a proton or an electron or what-have-you, they're actually talking about a probability distribution.

      Let's take a very simple probability distribution. (Real physicists will take great umbrage at how I'm simplifying things--so just let me defend myself by saying this is a gross simplification.) Let's say that the proton has a 95% chance of existing within X distance of a given point in space (i.e., within X along all three direction axis). That probability distribution is spherical; the region of 95% probability is spherical in area.

      Let's say the proton has a 95% chance of existing within X distance along the x axis, Y distance along the y axis and Z distance along the z axis. Suddenly, you no longer have a spherical probability distribution; the probability distribution is longer along one axis than another.

      In the case of the proton, the "shape" of the proton is ovoidal.

      Remember, pretty much all of your observations about the macro universe are totally inapplicable at the quantum level. Even the Second Law of Thermodynamics doesn't apply at the micro level like it does on the macro. So before you say "it can't have a shape"... make sure that you're not trying to apply your macro concept of "shape" to the micro.
      • OK... the probability distribution is longer on the z axis than it is on the x or y axes. What are the axes relative to? If z is the direction of motion, then we have something which seems to be explainable by relativity. If z is perpendicular to the direction of motion, relativity is screwed...

        Anybody have a link to a more scientific article?

        • If z is the direction of motion, then we have something which seems to be explainable by relativity. If z is perpendicular to the direction of motion, relativity is screwed...

          Methinks the proton is not moving near the speed of light but the quarks which compose the proton. -- drinks a glass of water and quotes from the article -- "'The new thing we've figured out is that quarks are moving around inside the proton at relativistic (near speed of light) speeds,' says physicist Gerald Miller of the University of Washington-Seattle. Quarks moving at those speeds simply elongate the particle's electromagnetic shape, Miller says. In a paper in the journal Physical Review C, he outlines how quarks moving at high speeds, about 90% of the speed of light, stretch out protons."

          GR remains intact and the posters return to their normal lives. If you want, you could look up the paper referred to in Physical Review C. I need to get back to work and I'm too lazy to do it for you ;)
    • How can a proton have definate (or semi definate) shape? Shape can only be observed by sight (and protons are much smaller than the wavelength of light and don't just bounce high energy electo-magentic radiation), or by collision.

      So... if you can't observe it, it's not there?

      Doug

    • What about touch? I mean when you pick up a proton ... oh wait.

      It's funny how little bits of misinformation become "common knowledge". The solar system model of atomic structure was shot down almost a century ago, but the picture of a bunch of electrons orbiting a clump of protons and neutrons is still the picture most people conjur up when you say "atom". Other examples: "Columbus proved the earth was round" (astronomers did this centuries before, and even measured the diameter of the planet, of which data Columbus was quite ignorant); "Lindbergh was the first pilot to fly solo accross the Atlantic" (technically true, but it's sad that people think an aviation pioneer is famous simply for going without sleep for 36 hours). Etc., etc.

      • "Columbus proved the earth was round" (astronomers did this centuries before, and even measured the diameter of the planet, of which data Columbus was quite ignorant)

        Make that about 2200 years ago. Erastothenes of Samos, [istos.com.au] also credited with the sieve for Prime numbers, measured the diameter of the Earth using trigonometry.

    • Comment removed based on user account deletion
    • A body like a football, consisting of ~10^23 particles, has a very well defined shape.

      A body like a uranium nucleus, with 238 particles, has a little more fuzziness in the definition of its shape, but you can still say that it has a shape. Due to quantum fluctuations, the shape is not perfectly well defined. Roughly speaking, the ellipticity has a fuzziness on the order of 1 part in 238. In fact, a uranium nucleus is elliptical by something like 20% (plus or minus those small fluctuations). It's prolate, like an American football.

      A proton consists of three quarks, so we expect the shape fluctuations to be on the order of 1 part in 3.

      Shape can only be observed by sight
      No, there are lots of other techniques. With nuclei, a couple of standard techniques are (1) measure its electric quadrupole moment, and (2) measure the spacing of its rotational bands. Unfortunately USA Today didn't give us the info on the exact technique :-)

  • how do 3 small objects (quarks) that are presumably the same shape (or at least 2, up up down...) make up a larger object thats ovoid? i realy don't think subatomic particles can ever be given a definite shape, heisenberg anyone, can we actually observe the shape or orbit(do they orbit?) of quarks?

    • I think a more accurate statement is the probability density of the location of the proton has an ovoid appearance. Just as only the s orbitals of electrons have a spherical distribution and the others take on some rather remarkable shapes [orbitals.com].

      An additional caveat is the electrons scattering was used to probe the proton. So the primary interaction was electromagnetic with a very small weak component. Protons may have a different "shape" when viewed by a neutrino since neutrinos do not couple with the electromagnetic field. This is a guess though and I am not qualified to make that statement more precise.

      Finally, the obvious question is how do we define a "top" for a proton, ie, how do we know which direction the ovoid is oriented in? The answer is since a proton has a nonzero spin it assumes one of two diametrically opposed orientations in a magnetic field and we can use the axis formed by those directions to define "up". Finally, thinking about it that way, since quarks also couple to the electromagnetic field as well as interacting with each other through the strong force, it's not that surprising that a proton has a shape, it may be a result of the complicated interactions between the quarks. Then again, no one has done the calculation (which is fiendishly difficult and impossible to do analytically since it's a pretty general 3 body problem) so maybe it's a little unjust to call the result unsurprising.

  • Protons are made up of only three quarks. Of course they'd be a little misshapen. Find me a subnuclear particle with four or six quarks, then I'll surprised to find out it's not a perfect sphere.
    • Four or six quark particles just won't form. It is energeticly much better to have two mesons (2 quark particles) or 2 baryons (3 quark particles).

      On the side, there may be a MUCH MUCH MUCH larger quark particle that may have been recently discovered. It is several kilometers accross. A "Quark star" is like a neutron star, but has by some process collapesed one stage farther into being not made of neutrons, but a vast number of quarks bound together. It is theorized to be made of approximently equal parts of up, down, and stragge
    • Um, ignore that last, incomplete, comment.

      Four or six quark particles just won't form. It is energeticly much better to have two mesons (2 quark particles) or 2 baryons (3 quark particles).

      Besides, the quarks inside the proton don't really have an exact location. The exist in a cloudy state of uncertain position and velocity. Also, because of uncertainty, there are a number of "virtual" quark-antiquark pairs popping in and out of existance everywhere, but especialy inside hadrons (particles made of quarks). In addition, there are gluons and "virtual" gluons boucing around inside these particles, moderating the strong nuclear force that holds the whole thing together. This "shape" they are talking about probably refers to the boundry of probable positions of the individual quarks. i.e, there is a 99.9999999999999999% chance that the quark will be found inside this ovoid if you were to look at it.

      As a side note, there may be a MUCH MUCH MUCH larger quark particle that may have been recently discovered. It is several kilometers accross. A "Quark star" is like a neutron star, but has by some process collapesed one stage farther into being not made of neutrons, but a vast number of quarks bound together in a single hadron-like particle. It is theorized to be made of approximently equal parts of "up", "down", and "strange" quarks. Up and down make most of the mass you know of, as two ups and a down make a proton, and two downs and an up make a neutron. A strange is like a down, but more massive, and previously only seen in high energy particle collisions for a tiny fraction of a second.

  • Hey, that's nothing... (Score:5, Funny)

    by kawika ( 87069 ) on Wednesday September 25, 2002 @10:44PM (#4333453)
    I have a paper from Hendrik Schon here that says they're shaped like tiny little cheddar cheese goldfish. Who would you believe, USA Today or Bell Labs?

  • "The new thing we've figured out is that quarks are moving around inside the proton at relativistic (near speed of light) speeds,"

    They are saying that an object with mass is moving around inside the proton at near light speed.

    That would mean the proton's mass is near infinite, which is clearly not the case.

    As you can see from the comma after the quote, this was a quote taken out of context which distorted any meaning this story might have had.

    USA today has always had crap science reporting.

    • Junk Post (Score:3, Informative)

      by rjh ( 40933 )
      In the article it said quarks travel at around ninety percent of the speed of light. So, tell you what, let's compute just how much more massive those quarks are. Fire up your LISP interpreter. We're taking a trip into Mathemagicland.

      In LISP notation...

      (defun relativistic-mass (m v) (/ m (sqrt (- 1 (/ (* v v) 1)))))

      (relativistic-mass 1 .9)
      2.294157


      ... So as you can tell, relativity tells us that at ninety percent of c, an object is only going to have two and a quarter times its normal mass. I don't see how you come up with the notion that "if the quarks are traveling relativistically, then the proton's mass must be near-infinite, thus quarks aren't traveling relativistically". If anything, your science is just as much junk as the USA Today article you're blasting.
  • In recent studies, 65% of all protons are obese. 10% of the obese protons are so overweight that they are spherical in shape this leaves the majority of protons in a oblong shape.

    Studies have found that the cause of obesity in protons is caused by the loss of electrons. The loss of these elctrons makes the protons not need to work as hard leave them time to sit with other friends like their neighbor the neutron. ;-)
  • "Neutrons contain three quarks, like protons, but they're organized in a different fashion." .. this is an sentance from the script.. im not aruging against protons being slightly mishapen..

    im just here to ask the question how the hell do they know a proton/neuron contains 3 quarks? How could they could the number of something that we have not yet proven to exist? Someone please explain
    • Physicists have directly observed quarks countless times. You smash a couple protons together, and their quarks fly away.

      But besides that, even if no one had directly observed them, given what we do know about the actual behaviour of protons and other subatomic particles, the theoretical framework designed to explain those behaviours predicts certain numbers of quarks, as well as the charges, spins, and a dozen other types of particles.

      So, what exactly are you asking?
      • Quarks have yet to be directly observed - the strong forces involved in quark coupling will actually creat new quarks inbetween the two before they are seperated. While tons of physicists have tons of projects attempting to directly observe quarks, none is accepted as having succeeded yet.
        That being said, when we smash protons together to get other hadrons, we observe that integral properties are conserved, and the patterns of these conservations are very well documented in hundreds of labs for decades. Quarks are not 'theoretical' in the popular sense or being a cocamamy idea someone came up with - they are theoretical because while everyone gets the same results since the '50s, and can predict their behavior reliably. Hell, despite directly observing evolution everyday, its still called a 'theory'.
        • Observing evolution everyday? The underlying explanation of the evolutionary processes at work has been in a state of flux for the past 200 years.

          (1) Evolution happens over a long period of time with small evolutionary changes over 100s of millions of years.

          (2) Evolution happens over a long period of time, but instead of small evolutionary changes, rapid change occurs for several thousands of years every several million year or so.

          Number (1) is being slowly displaced due to a lack of sufficient fossil evidence for all of the necessary intermediate forms required by the small change model.

          Number (2) is currently the more widely embraced theory. So if the definition of what is happening keeps changing, how can you see it everyday?

          Evolution is a theory for a reason. Facts don't change, theories change.

  • Only one radially symmetry (Score:4, Insightful)

    by bagsc ( 254194 ) on Thursday September 26, 2002 @08:43AM (#4335335) Journal
    The implication that the proton doesnt have three radial symmetries is pretty sweet - we now _know_ that the proton can support two axes of rotation, meaning that they can store rotational energy, that we could only assume if protons were perfectly radially symmetric (and therefore completely indistinguishable from their non-rotating kin). This has thermodynamic implications, the degrees of freedom are increased if the proton can store rotational quanta, and possibly increasing our understanding of plasmas. How can any right-thinking geek find this banal?
  • I'm not a physicist or anything but I thought that protons were of a smll enough scale where they existed as probablistic waves. you know, send a proton towards a double slit and who knows where it will go? does it make sense to assign a shape to something like that any more than it does to say that a photon is round?

    hell, it might. i don't know, that's why I'm asking.

  • This [aps.org] appears to be the abstract for the announced results. Note the lack of words like "round" in the abstract and article. You may need a subscription to Physical Review Letters to reach it and download the paper.

    This [aps.org] appears to be the abstract of the paper of Miller and Frank attempting to explain the phenomena. You will have to accept cookies to get any sort of information out of the APS site.

    This [jlab.org] seems to be the experimental project page. It doesn't appear to be an informative resource for the uninitiated.

    I'd never read a nuclear physics paper before, so I wasn't sure what to expect. It looks like straight pQFT calculation with the Feynman diagrams, etc. would be computationally intractible for these problems, so people are always looking for reasonable approximation schemes. I guess the ones that had been used in the past didn't factor in relativistic effects as much as they should have, and the recent models corrected this.

  • A number of comments posted here are mistaken about the nature of shape in the quantum world. It has nothing to do with the probability distribution of the proton's location; it has to do with the probability distributions of the quarks within the proton.

    Only entities that are extended in space have shape. Electrons, for example, are to the best of our knowledge pointlike, and therefore we say they do not have shape. Atoms, on the other hand, are extended in space and therefore do have shape. Their shape is given to them by the probability distributions for the locations of the electrons that surround them, not by the probability distribution of their own location.

    Shape is described in nuclear physics using the mathematical device of the "structure function", which is just a function of the three spatial co-ordinates that describes the size and (a)symmetries of the nucleus relative to some interaction. Structure functions are ususally expressed as linearly weighted sums of spherical harmonics or Legendre polynomials, which capture physically interesting processes in different terms.

    Protons are believed to have a spherically symmetric structure function. On a number of both theoretical and experimental grounds I'd be extremely doubtful that the dynamical structure function of the proton is asymmetric, and the article in fact suggests that the result is a purely kinematic one due to relativistic effects, which is suprising but in the final analysis not the kind of earth-shattering news dynamical asymmetry would be.

    In particular, a dynamical asymmetry of the proton would imply naively a comparable asymmetry of the neutron, and this is known not to exist experimentally at very high precision (and whose existence at a very small level is predicted by electro-weak theory.)

    --Tom

  • This is good. It means they won't roll off the glass slide when they study them under microscopes.

    Physicists hate it when that happens.

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