back to article Look, we know it feels like everything's going off the rails right now, but think positive: The proton has a new radius

The positively charged proton sitting inside the nuclei of atoms has a radius smaller than a trillionth of a millimeter, according to a paper published in Science on Thursday. Scientists have been scratching their heads over the size of the proton. Various methods used to measure the subatomic particle’s radius produced …

  1. Richard 12 Silver badge

    This proton is very small, that one is far away.

    I for one salute our tinier-than-previously-thought overlords and the boffins who measure them.

    That's some seriously hard experimenting.

    1. John G Imrie

      Difference in size explained

      The Proton's been on a diet after being fat shamed by the electron.

      1. LDS Silver badge

        Re: Difference in size explained

        I always knew electrons have a negative behaviour.

        1. Adam 1

          Re: Difference in size explained

          If it were up to me, I'd create a more positive environment by getting rid of some of them.

      2. el kabong

        The classical electron radius is roughly 3 times that of the proton

        ~2.8 femtometers for the classical electron radius

        ~0.8 femtometers for the proton radius

        Light fat vs heavy muscle.

        1. John G Imrie

          Re: The classical electron radius is roughly 3 times that of the proton

          This, article suggests that the classical electron radius may not be the correct way of measuring it.

          1. Cuddles Silver badge

            Re: The classical electron radius is roughly 3 times that of the proton

            "This, article suggests that the classical electron radius may not be the correct way of measuring it."

            It depends what you mean by "correct". Electrons, like all other fundamental particles, are thought to be point particles with zero physical size. Some theories suggest it might not be exactly zero, but instead something like the Planck length, but certainly far smaller than anything we can even dream of measuring in the foreseeable future. The classical radius of an electron isn't actually a measure of its physical size, but rather a sort of representative parameter that can be useful in some calculations. It gets its name from the fact that it shows up as the non-relativistic (ie. classical) limit of certain equations, such as calculating scattering cross-sections for low energy particles.

            The proton, on the other hand, is a composite particle with a real, finite, physical size. The quarks and gluons inside are also thought to be point particles, but since they're separated from each other we can measure how much space the whole ensemble actually takes up. It's a little more complicated since, like atoms, there are the usual quantum probability clouds involved rather than nice little solid balls orbiting each other in a sensible manner, but depending on exactly how you define what it is you want to measure, there is definitely a real size there somewhere.

            So it's not that the classical radius is not correct, it's just not measuring the same thing and so can't be sensibly compared. In the size talked about in this article, in the sense of what you'd get if you used a really, really small micrometer to measure them, protons are infinitely bigger than electrons because they actually have non-zero size. In terms of classical radius, the electron is much bigger since it scales with 1/m. However, since that means the classical proton radius is much smaller than its actual physical size, it's not a very useful parameter since other effects will always dominate.

        2. MyffyW Silver badge

          Re: The classical electron radius is roughly 3 times that of the proton

          Given the electron is a tiny fraction of the mass of a proton, the proton is orders of magnitude more dense.

          1. Tom 7 Silver badge

            Re: The classical electron radius is roughly 3 times that of the proton

            The proton is made of 3 quarks hugging together. The electron is all on its own and unloved so it reaches out.

    2. Roger Greenwood

      Hard to remain neutral on this one

  2. Anonymous Coward
    Anonymous Coward

    The lamb shift

    What happens after 10 pints and a dodgy kebab...

    1. jgard

      Re: The lamb shift

      I once provided a similar response to a question when on a C programming course many moons ago. In front of the class the instructor asked when I would use void main(), 'after 10 pints a dodgy curry' was my reply. I thought it was hilarious but only me and the instructor laughed!

      1. swm Silver badge

        Re: The lamb shift

        Should be int main()

        1. Anonymous Coward
          Anonymous Coward

          Re: The lamb shift

          i bet you return EXIT_SUCCESS instead of 0 too, you square. Live a little dangerous some time. :V

  3. defiler

    Can they not just use a micrometer?

    I can get some pretty accurate results with mine. I can even measure when somebody has used it and not cleaned the anvils.

    1. Alister

      Re: Can they not just use a micrometer?

      You have to hold it really, really still though, or you might end up measuring the wrong proton.

      1. Jimmy2Cows Silver badge

        Re: Can they not just use a micrometer?

        That's what the bench vice is for.

        1. illiad

          Re: Can they not just use a micrometer?

          well if the vice is not at absolute zero, it will be bouncing all over the place...

  4. Tessier-Ashpool

    Pinch of proton salt

    Just be aware that a proton is a composite particle comprising three quarks. A given charge radius is its most probable value at any given instant. The quarks themselves are jiggling around incessantly and there is no real boundary as such.

    1. Paul Shirley

      Re: Pinch of proton salt

      Also shouldn't be a total surprise if a composite particles apparent size depended on its environment.

    2. Mage

      Re: Pinch of proton salt

      Electrons are worse, behaving as waves, particles or probability clouds in different situations. I remember in 1970s my Materials Science Lecturer saying it was all really good fairy tales. I later had doubts about his expertise as he "proved" no material had the bandgap needed for blue LEDs.

      I suspect most atomic, quantum and semiconductor physics is Alchemy/Magic dressed up as science. Newton and Kepler were Alchemists. Not sure about Copernicus and Galileo, but they and Kepler also had Astrology as a sideline.

      1. Nick Ryan Silver badge

        Re: Pinch of proton salt

        To be fair to your lecturer, no single element had the enargy/bandgap require for blue LEDs. However a rather smart scientist managed to work out how to use a combination of elements to produce the required gap and his research also contributed to much brighter LEDs than were previously thought possible.

        Science is full of people claiming limits, later scientists merrily break these "limits"... because they can. The statement a couple of hundred years that there was nothing left to discover was probably the lowest point of such claims.

    3. Anonymous Coward
      Anonymous Coward

      Re: Pinch of proton salt

      stupid squishy protons I bet that gets really important when thinking about how neutron stars squish up together :O hey I bet theres different types of crystal structure in them too, like how iron forms different packing patterns :V bet you get a massive cosmic ding when one collapses from one packing structure to another cos it just had enough mass added or something that'd be pretty awesome they'd be like really stiff spherical bells hah that's like a perfect assumption already ;D

  5. Chris G Silver badge

    Shifting a lamb

    From experience, I can tell you the energy in a lamb shift is variable.

    A lot depends on whether it is a breach birth or if the ewe is in the barn or under a bloody hedge.

    Regarding size I need something give wn idea of scale, aniseed balls are small and I know what they look like, so how do they compare with a proton?

    1. Michael

      Re: Shifting a lamb

      Well, as aniseed balls are about 1cm in diameter, 0.5cm in radius. So the aniseed ball is around 600,240,096,038,415.4 times bigger than the proton. .

      Or to look at it another way, if you imagine that the aniseed ball is the proton, you'd need to compare it to something with a radius of around 20 Astronomical units.

      1. Avatar of They

        Re: Shifting a lamb

        So an AU being the distance from Earth to the Sun (avge). I think you just put it into a measurement of range I can understand.

      2. caffeine addict

        Re: Shifting a lamb

        So... an aniseed ball that is the size of Uranus's orbit and a proton the size of an aniseed ball?

        My head hurts.

    2. caffeine addict

      Re: Shifting a lamb

      if the ewe is in the barn or under a bloody hedge

      The answer is always "under a bloody hedge".

      For such stupendously stupid animals, they have a real knack for knowing how to make life difficult for people trying to help them.

      1. Grinning Bandicoot

        Re: Shifting a lamb

        Coyotes have no problem with that

  6. Conscious and verbal


    So is it 0.833 or .876?

    1. 9Rune5

      Re: Huh?

      They are saying that it is shrinking.

      Possibly due to shrinkage; i.e. what happens when small objects are immersed in cold water (there's a documentary here:

      1. caffeine addict

        Re: Huh?

        You probably have to get it really cold to stop it moving around too much.

        ( I've just realised my 'joke' may actually be true. In which case that's what I meant. )

    2. Wize

      Re: Huh?

      Both might be true. Who says it has to be round? Measure a rugby ball orientated in different ways and you'll get different numbers.

    3. Roj Blake

      Re: Huh?

      So is it 0.833 or .876?


    4. Mark 85 Silver badge

      Re: Huh?

      Does it really matter unless your income is based on a research grant? I'm not sure, other than curiosity all the ruckus is about.

      Icon: curious minds doing what they do.

  7. Blockchain commentard

    "smaller than a trillionth of a millimeter" - that's also the value of the pound after Brexit !!!!

    1. caffeine addict

      You're so desperate to make everything a Brexit joke you're even willing to mix your units? Do you have no standards?

      Mind, if the Daily Mail has it's way I guess we won't have any standards either. We'll end up using those Imperial things like the Americans...

  8. Sgt_Oddball Silver badge

    I for one am disappointed at the journalism here...

    This is the register. We have standards. Like a Proton being 0.0059 femtolinguine...

  9. KittenHuffer Silver badge

    Perhaps they should have run the experiment in Wales!

    Then they'd have been surrounded by experts in shafting sheep!




    Oh! It was shifting!!!

    1. Alister

      Re: Perhaps they should have run the experiment in Wales!

      The Welsh are quite good at lamb shifting, as well, often in the dead of night...

      1. A.P. Veening Silver badge

        Re: Perhaps they should have run the experiment in Wales!

        The Welsh are quite good at lamb shifting, as well, often in the dead of night...

        For true sheep shifting, I recommend Feegles ;)

        1. Kane Silver badge
          Thumb Up

          Re: Perhaps they should have run the experiment in Wales!

          "We are a famously stealin' folk. Aren't we, lads? Whut's it we're famous for?"

          "Stealin'!" shouted the blue men.

          "And what else, lads?"


          "And what else?"


          "And what else?"

          There was a certain amount of thought about this, but they all reached the same conclusion.

          "Drinkin' and fightin'!"

          "And there was summat else," muttered the twiddler. "Ach, yes. Tell the hag, lads!"

          "Stealin' an' drinkin' an' fightin'!" shouted the blue men cheerfully.

        2. Chris G Silver badge

          Re: Perhaps they should have run the experiment in Wales!

          Wasn't that Odo bloke in Star Trek some kind of sheep shifter?

          1. The Bobster

            Re: Perhaps they should have run the experiment in Wales!

            He doesn't use // The bucket anymore

      2. Fruit and Nutcase Silver badge

        Re: Perhaps they should have run the experiment in Wales!

        And the Welsh plod could have helped to identify individual sheep using their facial recognition kit

  10. 0laf

    I opened that story and saw words on a page. Individual words made perfect sense to me but as a whole this article served to inform me that there are some things in the universe I will never understand in the slightest. I am now comfortable with this.

    Boffins please continue.

    If any of this quantum doofery will affect the price or taste of my ale please let me know.

    1. Jellied Eel Silver badge

      If any of this quantum doofery will affect the price or taste of my ale please let me know.

      The research was sponsored by property developers and realtors. Luxury 6-proton apartment nearing completion. Only $599,995!

  11. Anonymous Coward
    Anonymous Coward

    Standard units please

    In an uncharacteristic oversight for El Reg the article fails to give new proton diameter in linguine.

    1. Anonymous Coward
      Anonymous Coward

      Re: Standard units please

      I thought the standards for comparing the size of things were London buses, football pitches and Wales

      1. Alister

        Re: Standard units please

        London buses, football pitches and Wales

        Those are macro measurements, linguine are micro...

  12. Christopher Lane

    So it's not only Wagon Wheels...

    ...getting smaller as I get older! (for non-UK readers -->

    1. Doctor Syntax Silver badge

      Re: So it's not only Wagon Wheels...

      These days I call them Wheelbarrow Wheels. The main difference is that with a wheelbarrow one is sufficient.

  13. JimmyPage

    (whispers) perhaps it doesn't have a fixed size ?

    Who knows, it's only a cloud of energy at the end of the day. Who's to say it doesn't vary with respect to another cloud of energy. Or indeed time itself ?

    And just to muddy the waters further, are we sure all protons are the same ? I appreciate there's no reason to think otherwise, but are we assuming or is there some sort of proof in the equations of the boffins or has someone actually tried to experimentally demonstrate it.

    The great thing about science, is that for every question you can think of to try and answer, there's 10 more waiting to be asked.

    1. Tom 7 Silver badge

      Re: (whispers) perhaps it doesn't have a fixed size ?

      I wonder if string theory comes up with a good 'reason' for this? When I was doing nuclear physics it was noticeable that atomic nuclei were different sizes to different things, Nearly invisible to neutrinos and energetic neutrons and yet some will just swallow neutrons of the right energy as if they were a near solid wall!

    2. swm Silver badge

      Re: (whispers) perhaps it doesn't have a fixed size ?

      You can do interference experiments with protons so they must be identical according to quantum mechanics.

      1. Anonymous Coward
        Anonymous Coward

        Re: (whispers) perhaps it doesn't have a fixed size ?

        So you're stating/assuming that the environment matters not at all? For example, might is not be that a proton is a little bigger if it's in a cloud of electrons? Sure, protons under identical conditions would show identical results....

        Is physical radius the same as charge radius?

        I think stating some things as certainties just now might be unwise.

  14. ratfox

    What is even the meaning of "proton size"? It's not as if the proton is a spherical object as depicted on diagrams. At that scale, it's not even clear that we're talking about something physical, or a property of a magnetic wave, or a messy equation with side effects...

  15. IanTP

    Size matters?

    It's shrunk, as the actress said to the bishop....

    Sorry, it's Friday and I'm off to Skegvegas,

    Have one on me -------->

    1. Tom Paine

      Re: Size matters?

      Better than Skagvegas, I guess

      1. Rich 11 Silver badge

        Re: Size matters?

        Skagvegas? That must be Blackpool.

        1. Rich 10

          Re: Size matters?

          Hi Rich11, I must have registered my account about one femtosecond before you did

  16. Alan Sharkey


    What enhancement in our everyday life willbe affected by knowing this? I can't say it has affected anything I intend to do this week (although, now I know, I may just have to bring it up in conversation).

    I feel a pub quiz question is probably the most useful outcome.


    1. Pascal Monett Silver badge

      Re: Why?

      Science is about understanding our Universe. The better we understand it, the better we can model it and the sooner we'll get warp drives.

      And that, my friend, will have an effect on your everyday life.

      In the mean time, I'll gladly partake in a pub quiz.

    2. Jimmy2Cows Silver badge

      Re: Why?

      If everyone thought like that we'd still be in the dark ages.

    3. I ain't Spartacus Gold badge

      Re: Why?

      How's your gran going to knit that woolly bobble hat for the winter to keep the proton warm, if she doesn't know the size to make it?

      That's why so much science is gran-funded.

      1. This post has been deleted by its author

  17. Anonymous Coward
    Anonymous Coward

    ... and in which dimensions ?

    Just to further muddy the waters :)

    1. John G Imrie

      Re: ... and in which dimensions ?

      All 3 Physical and both time dimensions. Oh dam it's only 2019 I'll be back in 10 years when you've discovered the second one.

      1. not.known@this.address

        Re: ... and in which dimensions ?

        Hello again John,

        Actually there are as many Time dimensions as Physical ones - but since you've only discovered Forwards/Backwards for Time and Forwards/Backwards, Left/Right, Up/Down and Spinward/Widdershins for Physical, I'll let you get on with it for a few fenovarr...

        1. A.P. Veening Silver badge

          Re: ... and in which dimensions ?

          Actually there are as many Time dimensions as Physical ones

          You are correct in the basics, but any given dimension has two directions, forward and backward, thus we have three dimensions of space and three of time. This gives us a total of six dimensions to move through and 666 permutations of those for those limited creaturs experiencing only three spatial dimensions and one for time. For those that really payed attention to the above, note that the number found is the true and exact Number of the Beast.

      2. Steve K Silver badge

        Re: ... and in which dimensions ?

        You mean that TimeCube will be discovered as real???

  18. Roj Blake

    Was this the same Proton...

    That walked into a pub that time?

    It asked for a pint, and the landlord asked if it was sure.

    "I'm positive" was the reply

  19. Not also known as SC

    Empty space

    So if a proton is 0.8e-16m and a hydrogen atom is 5e-11m that means that the proton only takes up about 4e-13 % of the volume of the atom. That's a lot of empty space.

    1. I ain't Spartacus Gold badge

      Re: Empty space

      That space is where all the explodium fits.

  20. TheRealRoland

    I know i have to deal with a Lamb shift, on my grill, to prevent it from overcooking... Hmmm... Lamb.

  21. DJ

    Would that be

    an African proton or a European proton?

    1. swm Silver badge

      Re: Would that be

      Correctly asked.

  22. Anonymous Coward
    Anonymous Coward

    The proton has ZERO size, there is no proton in the nucleus.

    Electrons connects magnetic and electric forces. If it had size it would have internal sheer and other forces. Those internal forces do not exist, so it has no size. Proton can also connect magnet and electric and its the same, ZERO sized.

    What you see as size is the movement in the oscillating electric field. When you measure it at any point in time, its position is whatever its nearest resonance point on the field at that point in the oscillation pattern.

    See that twirling motion in the cloud chamber as you smash apart particles? That's oscillatory motion over the oscillating field.

    Postulate 1) If the shrapnel matter from your collision moves in an oscillatory way, so does the matter of the cloud in the chamber. The tracks that you see are the net effect of the two oscillations.

    Supporting evidence 1) See the tracks that appear to go spiral backwards in time, back towards the collision? That would violate causality and time direction and be impossible. However the net effect of two oscillating fields appearing to go backwards in time is a common effect, see car wheels in TV programs appearing to turn backwards caused by the net effect of the camera shutter rate and the rotation rate.

    P2) Electric as you know it is an oscillating force.

    S2) If matter moves and electrons move in the field, then the electric fields you produce also oscillate.

    P3) Light moves by the same mechanism.

    S3) It interacts with matter, e.g. travels through glass it slows down. It only has electric effects, so that interaction must be electric. It behaves like a particle, is produced and absorbed by matter, at what point would its motion be difference that matters?

    P4) Electric_h0, the non-oscillating version of electric, propagates infinitely fast.

    S4) It binds light, travelling at C, it cannot therefore travel at C itself. It's oscillating version P2, (oscillating over the same field as light is oscillating over that field), unsurprisingly moves at the same apparent velocity as light.

    P5) The electro magnetic wavelength of light is the net effect of its interaction with the detector. Just like P1 matter on matter oscillations, so light on matter is a net effect).

    S5) Matter is oscillation, at zero Hz electro-magnetic frequency light would have to be moving the same way. i.e. If matter was oscillating at some universal F frequency then 0Hz EM frequency corresponds to that F oscillation. The frequency of light (and its polarization and all other components of oscillatory motion) are also the net effect of the two oscillations.

    P6) If light at position R1 has the same propeties at position R2 and all its properties did not travel with it because they are the net effect of the detector and the light, then the detector at R1 is oscillating the same way as the detector at R2.

    S6) Yep, everything is in resonance, because P4 propagates infinitely fast, you could not stop the oscillations equalizing out over time. It is not magic that you atomic clocks oscillate at the same rate if at the same temperature and velocity, it is the underlying resonant frequency that drives it.

    P7) Magnetic is an oscillating force too, and is resonant with electric. ( F/2)

    S7) Again the electron connects magnetic and electric forces, but only if there is motion involved. If there is no motion then there is no force. i.e. it must be resonant. Magnetic and electric applying to an electron creates velocity at right angles to both, this is impossible, the velocity should be in the plane of the forces. It is impossible with static forces, it connects these forces even in a vacuum, and the the electron would have to be anchored to the vacuum to push against it! However its trivial to have a net 'waddle' and no net effect over time.

    P8) Magnetic has a clumping force too. ALL the harmonics of F have clumping variants.

    S8) Put magnets in a bag, shake them up, they clump together.

    Do you wanna take a guess at gravity? Or why some atoms are gasses and some solids?

    Go try assembling the nucleus without strong force, using only resonance:

    P9) When you do, you'll find there are no neutrons and protons, there is +ve monopoles, and a binding donut and it's mirror image. A binding donut is an oscillation looping back on itself. I use the shorthand of calling it by its loop size. e.g. electron has F2 {-ve monopole} F2', these F2's return to their same position after 2 oscillations, F2' is the same donut mirrored, the anti-donut if you wish. F2 is why magnetic is F/2 oscillating electric force, the F2 gives it an F/2 waddle. When you break apart the nucleus, e.g. knocking an +ve using an F1 oscillation, the F2 becomes wrapped in the twists of the binding donut that were holding the +ve and forms a neutron.

    S9) See that magic connection between the number of neutrons and +ve protons? They were literally part of the binding holding the +ves together.

    So, from the above, the size of the proton (you measure the +ve, a free travelling proton also has binding donut wrappers) is the net effect of the oscillation in the matter of the proton, and the detector. It's size will vary depending on how you chose to measure it.

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