10 ms·

The electron is so round that it’s ruling out potential new particles

179 points by martincmartin 4y ago

dogma1138 4y ago
So the TLDR is that the electric dipole moment of electron seem to match the one predicted by the Standard Model at least as far as our current measurement capability goes and as we get more and more accurate measurements the wiggle room shrinks so the likelihood that the EDM predicted by the SM is correct increases which lowers the likelihood of post SM physics?
- zmgsabst 4y ago
  I think more accurate to say: “Lowers the probability of particular models” We still have open questions the standard model doesn’t answer — like what’s up with gravity? …why didn’t we have equal parts antimatter? …does braiding have wider implications than anyons? Etc.
- MengerSponge 4y ago
  Yes and no. First off, "the sm is correct" isn't how to think about this. Newtonian mechanics is "correct" for airplane flight, or even to calculate rocket trajectories. It's a low order approximant of relatavistic mechanics, though. It's incomplete, and you need to add higher order effects to correctly describe the orbit of Mercury, for example. The SM is incomplete. Among many other things, it dramatically misses the amount of matter generated during the big bang (by about 10^7). To read about the generation of matter over antimatter, check out the Sakharov criteria. (Sakharov was also an interesting dude, but that's for another day.) Matter/antimatter asymmetry is coupled to symmetry violating processes, which also inevitably generate nonzero EDMs. The SM includes a bit of this asymmetry, which is why it predicts an eEDM at all. The SM's prediction is so small that any detection has to come from beyond SM sources.
  - dogma1138 4y ago
    That was what I wanted to raise, SM doesn’t have an allowance for Dark Matter, and also doesn’t not have an explanation for the matter anti matter asymmetry so the article was quite confusing.
    - MengerSponge 4y ago
      The SM does have a bit of matter/antimatter asymmetry, as this asymmetry was first observed in the 60's by Cronin and Fitch (1980 Nobel). It's just not a big enough asymmetry to account for all this matter we see.
    - elashri 4y ago
      By now, there is a concessions among the particle physics community that SM is incomplete. The same way that we all agree that Newtonian mechanics is incomplete and doesn't describe anything on atomic/quantum level so we don't use it or talk about Newton mechanics when we are in this scale. The same thing happens here, people mostly talk about SM for what it predict and have an answer for not what it lacks (again because it is obviously incomplete).
      - dogma1138 4y ago
        Hence my confusion with the title and the article at large. We know we need new particles if for nothing else than to explain dark matter (unless we will come with a non-MOND non-matter theory that fits current observations and hopefully is compatible with other well tested theories too). We also have “known” for a while that the standard model is incomplete but so far actual physics beyond it has been eluding us. That was to me missing in this article.
shonenknifefan1 4y ago
preprint is here: https://arxiv.org/abs/2212.11841 https://arxiv.org/abs/2212.11841
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jethkl 4y ago
The Standard Model predicts a vanishingly tiny EDM for the electron — nearly a million times smaller than what current techniques can probe. This is a big achievement, but a lot more work in this direction remains.
flimflamflem 4y ago
[flagged]
kortex 4y ago
This leads me to the logical question about EDM of protons and neutrons. The electron and neutron are mentioned, but nothing for proton EDM. What's up with that? Also apparently the EDM for the neutron has yet to be detected, despite it being a composite particle. Our sensitivity is about five orders of magnitude away from the predicted value. https://en.m.wikipedia.org/wiki/Electron_electric_dipole_moment https://en.m.wikipedia.org/wiki/Electron_electric_dipole_mom... https://en.m.wikipedia.org/wiki/Neutron_electric_dipole_moment https://en.m.wikipedia.org/wiki/Neutron_electric_dipole_mome... Also of note, here's a pEDM experiment with a 50m radius (the eEDM experiment is lab scale). https://aip.scitation.org/doi/10.1063/1.4967465 https://aip.scitation.org/doi/10.1063/1.4967465
- MengerSponge 4y ago
  EDM experiments are sensitive to electric field strength and observation time. For electrons, you can get much higher fields inside a molecule. For neutrons, you either need a very cleverly designed crystal or a bottle with ultracold neutrons. The crystal lets you get huge fields and huge particle counts, but relatively short observation times. Ultracold neutrons let you have long observation times (100-300 seconds) but lower fields and much lower particle counts. Protons are probably the hardest of the lot. They need external fields, but they're charged so you can't just bottle them. You're stuck with a holding ring, and needing to make all those v x E corrections.
- vihren 4y ago
  I'm working on the search for the EDM of the muon. Essentially it's much harder to search for the proton EDM than the neutron EDM. All EDM searches rely on a strong electric field applied to the particles. Because neutrons are neutral they are easily stored in some volume for a long time. You cannot so easily store protons because the moment you apply some E-field you start accelerating them. That's why you need to build a large storage ring with magnetic/electric focusing and so on. This brings numerous challenges that you don't have for the neutron. This, combined with the fact that we don't expect much different novel physics for the proton that won't be seen in the neutron has led to the focus on the neutron EDM, while the proton was left behind. The usual quote is that for the proton we can reach sensitivities up to 10^-29 (around three orders of magnitude lower than the current nEDM limit), but thats only the statistical sensitivity. The systematic effects that would spoil that come much earlier and this limit is close to science fiction at this point. For example, if you have a magnetic field in the order of attotesla in the region of the storage ring it will dominate the measurement. Would be happy to answer more edm questions :)
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m3kw9 4y ago
"Imagine an electron as a spherical cloud of negative charge" sorry man, you lost me on the very first sentence
- Waterluvian 4y ago
  Fine. Oblate spheroidal cloud with a Lakitu in it* There’s many abstractions. None of them are right. They’re useful for different things. You cannot reject the simpler ones because you have adopted a still wrong but more complex one.
  - MengerSponge 4y ago
    All models are wrong, but some are useful.
- eitau_1 4y ago
  Some argue that metaphor is more fundamental to science than math.
- asplake 4y ago
  Imagine a spherical cow, then make it really, really tiny
vehemenz 4y ago
It’s tangential, but I don’t know how physicists understand the “why is there something rather than nothing?” question. At best, it’s quantification without a predicate. At worst, it’s metaphysical gobbledygook of the same variety that physicists constantly deride philosphers for.
- vaidhy 4y ago
  But the answer to "why" is always gobbledygook. We try to answer how there is something instead of nothing. I do not think anyone can answer why it is flooding in Florida now. Many can answer the how, multiple levels deep. 'Why" is trying to assign a higher order causality and that is religion. But, if you are using "why" as a way to probe into inner workings, here is one possible hypothesis - https://www.youtube.com/watch?v=3SxowRIc20M&t=761s https://www.youtube.com/watch?v=3SxowRIc20M&t=761s
  - carrozo 4y ago
    This was beautiful thank you.
  - vehemenz 4y ago
    The same point applies to the phrase "something rather than "nothing." It's not a general concern about "why" questions but a concern about applying quantification to non-specific things. Quantification in the abstract typically falls under mathematics. This is what we have numbers for. But people make sense of "something rather than nothing" as if it's more than abstraction. People think they understand what they're talking about, but they really don't (literally, not figuratively).
sdfghswe 4y ago
> If an electron were the size of Earth, the experiment could detect a bump the size of a sugar molecule. Makes sense, as the electrostatic force is about 10^36 times stronger than the gravitational force.
p1esk 4y ago
Can someone explain what an electron is? I remember from my high school physics that electrons are "point-like" particles, which are "elementary" (not built out of any smaller particles). And electron clouds are like all possible or probable trajectories of how electrons move around an atom's nucleus. Or something like that, it was many years ago. Then what is a "cloud of negative charge"?
- notfish 4y ago
  My model for understanding phenomena where quantum effects matter is this: if you think of the universe like a big sheet of something stretchy, an electron/proton/particle is just a knot tied in the sheet. Outside of some small region local to the knot the sheet looks flat.
  - jacquesm 4y ago
    It looks flat but the tension isn't flat. That's why that analogy is so beautiful because it suggests the existence of another force that works at any distance and weakens the further away you get from the point of the knot (gravity).
- scotty79 4y ago
  There is an "electron field" everywhere. Electron is a persistent, energetic disturbance of this field that can travel and interact through electroweak force. It's most convenient mathematical description is as if it was a "cloud" of probability of all of it's charge and mass being concentrated at a single point in space. If we forcefully interact with electron we can reshape this "cloud" to be as small as we need to at the cost of imparting on it random monentum through uncertainty principle. I think what they measure is that when you interact with electron then its electric field seems to be very spherical to the point that we can rule out a lot of ideas about electron having any internal substructure that might cause the field to be a little bumpy.
  - p1esk 4y ago
    This cloud of probability you're talking about - is it different from the cloud of probabilities of electron's position relative to the atomic nucleus?
revolvingocelot 4y ago
I find this result satisfying. Of course an electron is as a Platonic solid, that's very sensible. God does not play dice -- God plays with marbles.
- klyrs 4y ago
  Hot take, a marble is a D1.
  - andygeorge 4y ago
    *D-infinity
inportb 4y ago
If an electron were the size of Earth... did its mass increase or did its density decrease? Would it be a black hole with a planet-sized event horizon? What would happen to a sugar molecule on the north pole of a planet-sized electron with infinitesimal density?
tonymillion 4y ago
It’s simple. Antimatter goes the other direction in time. Just as you can go forwards and backwards in the X dimension. Matter can only go in one direction through time, antimatter the other. So at the point of the Big Bang matter went on its direction through time saying buh-bye to antimatter that went in the opposite direction. Note: I didn’t say forward and backwards because from their perspective we are the ones who went in the opposite direction. This accounts for the lack of antimatter, the “missing mass” of the universe and why time travel (other than into the future for us) is impossible as the only way you could go in the opposite direction (the past) would be to convert yourself to antimatter which would be very very bad. This also doesn’t mean there is an antimatter earth somewhere out there (in the other time direction so we’d never know anyway) because at the point of the Big Bang an entire series of events / interactions would have occurred. There’s no interacting link between the two times (t+1 vs t-1) Figure out the maths for yourself…
- mrkeen 4y ago
  Physicists are able to produce small quantities of matter and antimatter, which then annihilate each other, releasing energy. It was a big deal when they were able to trap the antimatter so that it didn't do this. If the two particles travelled different directions in time, how would they meet?
  - dragonwriter 4y ago
    > Physicists are able to produce small quantities of matter and antimatter, which then annihilate each other, releasing energy. […] If the two particles travelled different directions in time, how would they meet? The anti-matter would travel backwards in time from the event we see as the “mutual annihilation” to the event we see as the “creation of paired particles”, while the matter would travel the other direction. Simple. When they don’t meet is a little trickier to explain, but its still the anti-particle coming back from somewhere in the future (possibly where it coincided with a different matter particule coming forward in time) and coinciding with the particle at the point we consider the “creation” point, and the same vice versa with the matter particle. I’m not saying it’s right, I’m saying that’s how you explain them “meeting” in the “anti-matter goes back in time” framework.
ThinkBeat 4y ago
I do not understand this. May someone help me with an ELI16? An electron is a cloud that is contained with a perfectly round sphere. Does cloud mean a thing that contains a particle that travels very fast in a perfect sphere? What does cloud entail in this instance? If we have determined that an electronic cannot be made up of other particles then there should only be one particle in the cloud? Or is the particle a gas / cloud? I thought that the general consensus was that the precise location of an electron was impossible (?) to fully predict? If you can't predict where an electron is with a high degree of certainty How can you measure it ? This might be outdated, or just my brain pulling tricks on me again.
- dave333 4y ago
  I think the measurements don't say anything about the size or how the electron is distributed in the probability distribution other than that it's spherically symmetric to a very small tolerance. It's interesting that there is another model of the electron orbit in atoms that is a spinning fluid shell of charge with an exact radius. See https://brilliantlightpower.com/theory-overview/ https://brilliantlightpower.com/theory-overview/
  - ThinkBeat 4y ago
    > I think the measurements don't say anything about the size or how the electron is distributed in the probability distribution I fully admit i dont understand most of what I hear about particle physics anymore A lot seems non intuitive with the (dumb) model I have in my head. (That doesn't say much about tis accuracy) If you are to make such extremely detailed measurements of anything you need to be able to observe it over time? (Though how much time varies a lot) Presumably, a constantly moving electron whose location cannot established is a difficult thing measure?
    - dave333 4y ago
      Well it depends how it is moving. Think of a spinning axle that is featureless - does it appear to move? How about a featureless disc bike wheel that is spinning? And the Mills model of the electron "orbitsphere" is a spherical fluid shell of charge that is spinning along all great circle routes. The charge distribution is not changing but the charge is spinning.
cperciva 4y ago
Can someone tell me what version of "shape" we're talking about here? I thought electrons were point charges.
- JonyEpsilon 4y ago
  I think it's the usual meaning of shape, it's just perhaps that we don't typically think about what that really means. [I was an author of the Imperial study mentioned in the article, and I had some long arguments with my collaborators about whether it was right to describe our measurement as the "shape of the electron", so I feel compelled to defend the point!] If I pick something up on my desk and feel what shape it is, what I'm really doing is mapping out the interaction between the density of electrons in the object under test and those in my fingers. I might infer that the electrons of the object are distributed in a spherically symmetric way (it's round), or perhaps something more complex (all the other less symmetric shapes). So shape in the context of the electron shape measurements means how it interacts electromagnetically. If it interacted perfectly spherically symmetrically, I think it would be reasonable to say it was round. If it interacted in a more complex way (as in, you could grab it and rotate it, because it has some non-spherically symmetric interactions) then it's not round. Interestingly, the electromagnetic interactions of an electron are extremely tightly constrained by it having only 1/2 unit of spin. You can expand any field around a point in terms of spherical harmonics, and you can show the with spin 1/2, the electron can only interact in the manner of the first two spherical harmonics - monopole and dipole. So it can be round (monopole), or round + a more negative and less negative end (dipole). Nothing more complicated than that. (Assuming you believe quantum mechanics. The Wigner-Eckart theorem is the thing to look up if you're interested.) These measurements, then are measuring the dipolar component of the electron's electromagnetic interaction. The only way in which it could be not round. As to the point charge thing: well, that's like your opinion man :-) Which is to say, the electron is what the electron is, and it cares not how humans decide to describe it! These experiments are fine examples of a long tradition of measuring and observing to make sure our theoretical descriptions are actually faithful to reality. You might be tempted so say that if one of these measurements discovered that the electron was not round, then maybe that would be evidence for the electron being not a point particle. It's complicated though ... and you'd find many physicists would start arguing with you if you did say that, because the current description of the electron - while being a point particle in a certain sense - is already pretty complicated (basically, because of interactions between all of the different quantum fields) and many people would say it's already not point-like. Many wouldn't though. Maybe the point here it's quite tricky to be precise about these things without just doing it properly with maths!
noncoml 4y ago
Explain like I’m five follow up question: is this electron able to exist in infinite places in space or only in predetermined slots? I.e. does space consists of pixels?
- DoubleFree 4y ago
  Space is not quantized, so yes, the electron has infinite possible locations. There are, however, places the electron cannot be, depending on its energy. See, the electron's energy is quantized, meaning it can only have a predetermined set of values (see atoms' electron shells). The energy determines the wave function and the wave function squared is the probability distribution for the electron's location. This wave function has roots, indicating where the electron cannot be.
tachyon5 4y ago
It's interesting to consider the parallels between the electron's roundness and the cosmic microwave background (CMB) radiation's uniformity. Both seem to defy our expectations of asymmetry, with the electron's shape ruling out new particles and the CMB's uniformity challenging our understanding of the early universe. As we explore these seemingly unrelated phenomena, perhaps there lies a deep, underlying connection that could unite our understanding of the microcosm and the macrocosm, offering a fresh perspective on the laws governing our universe.
- nuccy 4y ago
  For the CMB we predict (or rather invent) "inflation" - a rapid expansion of the space-time to preserve uniformity of early Universe [1]. Inflation lasted for 0.00000000000000000000000000000001s but the size of the Universe increased by 10^30 times. 1. https://www.esa.int/Science_Exploration/Space_Science/Planck/The_cosmic_microwave_background_and_inflation https://www.esa.int/Science_Exploration/Space_Science/Planck... Edit: I wanted to come up with an analogy of increasing some object to the size of Earth (as it is the biggest object we can experience in real life). Though 10^30 times is so mindbogglingly large that we don't really have any sense of that small sizes at all. The object would have to be smaller than an electron by a trillion times (10^12).
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martincmartin 4y ago
The experiments are now so sensitive that if an electron were the size of Earth, they could detect a bump on the North Pole the height of a single sugar molecule. This new bound is sensitive to energies above roughly 10^13 electron-volts — more than an order of magnitude beyond what the LHC can currently test. Wow.
- JumpCrisscross 4y ago
  It reminds me of Aristotelian physics’ perfect ætherial heavenly bodies. Ironinic they were on the terrestrial sphere in the end.
- wkat4242 4y ago
  Yeah how do they manage to get that kind of accuracy. Mind boggling.
  - moron4hire 4y ago
    That's precision, not accuracy.
    - lifeisstillgood 4y ago
      hang on - what? Yes it is precise ... to 17 decimal places or whatever. But it is also I believe accurate? I mean are they wrong and the electron is as bumpy as my chin on a weekend?
      - delecti 4y ago
        It's not that the experiment is not accurate, "accuracy" is simply not the aspect of the measurement being discussed. The sentence "That's precision, not accuracy." should be read to mean "we are discussing precision, we are not discussing accuracy" rather than "it's precise, but inaccurate".
        Wowfunhappy 4y ago

179 points by martincmartin 4y ago

So the TLDR is that the electric dipole moment of electron seem to match the one predicted by the Standard Model at least as far as our current measurement capability goes and as we get more and more accurate measurements the wiggle room shrinks so the likelihood that the EDM predicted by the SM is correct increases which lowers the likelihood of post SM physics?

zmgsabst 4y ago
I think more accurate to say: “Lowers the probability of particular models” We still have open questions the standard model doesn’t answer — like what’s up with gravity? …why didn’t we have equal parts antimatter? …does braiding have wider implications than anyons? Etc.
MengerSponge 4y ago
Yes and no. First off, "the sm is correct" isn't how to think about this. Newtonian mechanics is "correct" for airplane flight, or even to calculate rocket trajectories. It's a low order approximant of relatavistic mechanics, though. It's incomplete, and you need to add higher order effects to correctly describe the orbit of Mercury, for example. The SM is incomplete. Among many other things, it dramatically misses the amount of matter generated during the big bang (by about 10^7). To read about the generation of matter over antimatter, check out the Sakharov criteria. (Sakharov was also an interesting dude, but that's for another day.) Matter/antimatter asymmetry is coupled to symmetry violating processes, which also inevitably generate nonzero EDMs. The SM includes a bit of this asymmetry, which is why it predicts an eEDM at all. The SM's prediction is so small that any detection has to come from beyond SM sources.
- dogma1138 4y ago
  That was what I wanted to raise, SM doesn’t have an allowance for Dark Matter, and also doesn’t not have an explanation for the matter anti matter asymmetry so the article was quite confusing.
  - MengerSponge 4y ago
    The SM does have a bit of matter/antimatter asymmetry, as this asymmetry was first observed in the 60's by Cronin and Fitch (1980 Nobel). It's just not a big enough asymmetry to account for all this matter we see.
  - elashri 4y ago
    By now, there is a concessions among the particle physics community that SM is incomplete. The same way that we all agree that Newtonian mechanics is incomplete and doesn't describe anything on atomic/quantum level so we don't use it or talk about Newton mechanics when we are in this scale. The same thing happens here, people mostly talk about SM for what it predict and have an answer for not what it lacks (again because it is obviously incomplete).
    - dogma1138 4y ago
      Hence my confusion with the title and the article at large. We know we need new particles if for nothing else than to explain dark matter (unless we will come with a non-MOND non-matter theory that fits current observations and hopefully is compatible with other well tested theories too). We also have “known” for a while that the standard model is incomplete but so far actual physics beyond it has been eluding us. That was to me missing in this article.

shonenknifefan1 4y ago

preprint is here: https://arxiv.org/abs/2212.11841 https://arxiv.org/abs/2212.11841

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jethkl 4y ago

The Standard Model predicts a vanishingly tiny EDM for the electron — nearly a million times smaller than what current techniques can probe. This is a big achievement, but a lot more work in this direction remains.

flimflamflem 4y ago

[flagged]

kortex 4y ago

This leads me to the logical question about EDM of protons and neutrons. The electron and neutron are mentioned, but nothing for proton EDM. What's up with that? Also apparently the EDM for the neutron has yet to be detected, despite it being a composite particle. Our sensitivity is about five orders of magnitude away from the predicted value. https://en.m.wikipedia.org/wiki/Electron_electric_dipole_moment https://en.m.wikipedia.org/wiki/Electron_electric_dipole_mom... https://en.m.wikipedia.org/wiki/Neutron_electric_dipole_moment https://en.m.wikipedia.org/wiki/Neutron_electric_dipole_mome... Also of note, here's a pEDM experiment with a 50m radius (the eEDM experiment is lab scale). https://aip.scitation.org/doi/10.1063/1.4967465 https://aip.scitation.org/doi/10.1063/1.4967465

MengerSponge 4y ago
EDM experiments are sensitive to electric field strength and observation time. For electrons, you can get much higher fields inside a molecule. For neutrons, you either need a very cleverly designed crystal or a bottle with ultracold neutrons. The crystal lets you get huge fields and huge particle counts, but relatively short observation times. Ultracold neutrons let you have long observation times (100-300 seconds) but lower fields and much lower particle counts. Protons are probably the hardest of the lot. They need external fields, but they're charged so you can't just bottle them. You're stuck with a holding ring, and needing to make all those v x E corrections.
vihren 4y ago
I'm working on the search for the EDM of the muon. Essentially it's much harder to search for the proton EDM than the neutron EDM. All EDM searches rely on a strong electric field applied to the particles. Because neutrons are neutral they are easily stored in some volume for a long time. You cannot so easily store protons because the moment you apply some E-field you start accelerating them. That's why you need to build a large storage ring with magnetic/electric focusing and so on. This brings numerous challenges that you don't have for the neutron. This, combined with the fact that we don't expect much different novel physics for the proton that won't be seen in the neutron has led to the focus on the neutron EDM, while the proton was left behind. The usual quote is that for the proton we can reach sensitivities up to 10^-29 (around three orders of magnitude lower than the current nEDM limit), but thats only the statistical sensitivity. The systematic effects that would spoil that come much earlier and this limit is close to science fiction at this point. For example, if you have a magnetic field in the order of attotesla in the region of the storage ring it will dominate the measurement. Would be happy to answer more edm questions :)

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m3kw9 4y ago

"Imagine an electron as a spherical cloud of negative charge" sorry man, you lost me on the very first sentence

Waterluvian 4y ago
Fine. Oblate spheroidal cloud with a Lakitu in it* There’s many abstractions. None of them are right. They’re useful for different things. You cannot reject the simpler ones because you have adopted a still wrong but more complex one.
- MengerSponge 4y ago
  All models are wrong, but some are useful.
eitau_1 4y ago
Some argue that metaphor is more fundamental to science than math.
asplake 4y ago
Imagine a spherical cow, then make it really, really tiny

vehemenz 4y ago

It’s tangential, but I don’t know how physicists understand the “why is there something rather than nothing?” question. At best, it’s quantification without a predicate. At worst, it’s metaphysical gobbledygook of the same variety that physicists constantly deride philosphers for.

vaidhy 4y ago
But the answer to "why" is always gobbledygook. We try to answer how there is something instead of nothing. I do not think anyone can answer why it is flooding in Florida now. Many can answer the how, multiple levels deep. 'Why" is trying to assign a higher order causality and that is religion. But, if you are using "why" as a way to probe into inner workings, here is one possible hypothesis - https://www.youtube.com/watch?v=3SxowRIc20M&t=761s https://www.youtube.com/watch?v=3SxowRIc20M&t=761s
- carrozo 4y ago
  This was beautiful thank you.
- vehemenz 4y ago
  The same point applies to the phrase "something rather than "nothing." It's not a general concern about "why" questions but a concern about applying quantification to non-specific things. Quantification in the abstract typically falls under mathematics. This is what we have numbers for. But people make sense of "something rather than nothing" as if it's more than abstraction. People think they understand what they're talking about, but they really don't (literally, not figuratively).

sdfghswe 4y ago

> If an electron were the size of Earth, the experiment could detect a bump the size of a sugar molecule. Makes sense, as the electrostatic force is about 10^36 times stronger than the gravitational force.

p1esk 4y ago

Can someone explain what an electron is? I remember from my high school physics that electrons are "point-like" particles, which are "elementary" (not built out of any smaller particles). And electron clouds are like all possible or probable trajectories of how electrons move around an atom's nucleus. Or something like that, it was many years ago. Then what is a "cloud of negative charge"?

notfish 4y ago
My model for understanding phenomena where quantum effects matter is this: if you think of the universe like a big sheet of something stretchy, an electron/proton/particle is just a knot tied in the sheet. Outside of some small region local to the knot the sheet looks flat.
- jacquesm 4y ago
  It looks flat but the tension isn't flat. That's why that analogy is so beautiful because it suggests the existence of another force that works at any distance and weakens the further away you get from the point of the knot (gravity).
scotty79 4y ago
There is an "electron field" everywhere. Electron is a persistent, energetic disturbance of this field that can travel and interact through electroweak force. It's most convenient mathematical description is as if it was a "cloud" of probability of all of it's charge and mass being concentrated at a single point in space. If we forcefully interact with electron we can reshape this "cloud" to be as small as we need to at the cost of imparting on it random monentum through uncertainty principle. I think what they measure is that when you interact with electron then its electric field seems to be very spherical to the point that we can rule out a lot of ideas about electron having any internal substructure that might cause the field to be a little bumpy.
- p1esk 4y ago
  This cloud of probability you're talking about - is it different from the cloud of probabilities of electron's position relative to the atomic nucleus?

revolvingocelot 4y ago

I find this result satisfying. Of course an electron is as a Platonic solid, that's very sensible. God does not play dice -- God plays with marbles.

klyrs 4y ago
Hot take, a marble is a D1.
- andygeorge 4y ago
  *D-infinity

inportb 4y ago

If an electron were the size of Earth... did its mass increase or did its density decrease? Would it be a black hole with a planet-sized event horizon? What would happen to a sugar molecule on the north pole of a planet-sized electron with infinitesimal density?

tonymillion 4y ago

It’s simple. Antimatter goes the other direction in time. Just as you can go forwards and backwards in the X dimension. Matter can only go in one direction through time, antimatter the other. So at the point of the Big Bang matter went on its direction through time saying buh-bye to antimatter that went in the opposite direction. Note: I didn’t say forward and backwards because from their perspective we are the ones who went in the opposite direction. This accounts for the lack of antimatter, the “missing mass” of the universe and why time travel (other than into the future for us) is impossible as the only way you could go in the opposite direction (the past) would be to convert yourself to antimatter which would be very very bad. This also doesn’t mean there is an antimatter earth somewhere out there (in the other time direction so we’d never know anyway) because at the point of the Big Bang an entire series of events / interactions would have occurred. There’s no interacting link between the two times (t+1 vs t-1) Figure out the maths for yourself…

mrkeen 4y ago
Physicists are able to produce small quantities of matter and antimatter, which then annihilate each other, releasing energy. It was a big deal when they were able to trap the antimatter so that it didn't do this. If the two particles travelled different directions in time, how would they meet?
- dragonwriter 4y ago
  > Physicists are able to produce small quantities of matter and antimatter, which then annihilate each other, releasing energy. […] If the two particles travelled different directions in time, how would they meet? The anti-matter would travel backwards in time from the event we see as the “mutual annihilation” to the event we see as the “creation of paired particles”, while the matter would travel the other direction. Simple. When they don’t meet is a little trickier to explain, but its still the anti-particle coming back from somewhere in the future (possibly where it coincided with a different matter particule coming forward in time) and coinciding with the particle at the point we consider the “creation” point, and the same vice versa with the matter particle. I’m not saying it’s right, I’m saying that’s how you explain them “meeting” in the “anti-matter goes back in time” framework.

ThinkBeat 4y ago

I do not understand this. May someone help me with an ELI16? An electron is a cloud that is contained with a perfectly round sphere. Does cloud mean a thing that contains a particle that travels very fast in a perfect sphere? What does cloud entail in this instance? If we have determined that an electronic cannot be made up of other particles then there should only be one particle in the cloud? Or is the particle a gas / cloud? I thought that the general consensus was that the precise location of an electron was impossible (?) to fully predict? If you can't predict where an electron is with a high degree of certainty How can you measure it ? This might be outdated, or just my brain pulling tricks on me again.

dave333 4y ago
I think the measurements don't say anything about the size or how the electron is distributed in the probability distribution other than that it's spherically symmetric to a very small tolerance. It's interesting that there is another model of the electron orbit in atoms that is a spinning fluid shell of charge with an exact radius. See https://brilliantlightpower.com/theory-overview/ https://brilliantlightpower.com/theory-overview/
- ThinkBeat 4y ago
  > I think the measurements don't say anything about the size or how the electron is distributed in the probability distribution I fully admit i dont understand most of what I hear about particle physics anymore A lot seems non intuitive with the (dumb) model I have in my head. (That doesn't say much about tis accuracy) If you are to make such extremely detailed measurements of anything you need to be able to observe it over time? (Though how much time varies a lot) Presumably, a constantly moving electron whose location cannot established is a difficult thing measure?
  - dave333 4y ago
    Well it depends how it is moving. Think of a spinning axle that is featureless - does it appear to move? How about a featureless disc bike wheel that is spinning? And the Mills model of the electron "orbitsphere" is a spherical fluid shell of charge that is spinning along all great circle routes. The charge distribution is not changing but the charge is spinning.

cperciva 4y ago

Can someone tell me what version of "shape" we're talking about here? I thought electrons were point charges.

JonyEpsilon 4y ago
I think it's the usual meaning of shape, it's just perhaps that we don't typically think about what that really means. [I was an author of the Imperial study mentioned in the article, and I had some long arguments with my collaborators about whether it was right to describe our measurement as the "shape of the electron", so I feel compelled to defend the point!] If I pick something up on my desk and feel what shape it is, what I'm really doing is mapping out the interaction between the density of electrons in the object under test and those in my fingers. I might infer that the electrons of the object are distributed in a spherically symmetric way (it's round), or perhaps something more complex (all the other less symmetric shapes). So shape in the context of the electron shape measurements means how it interacts electromagnetically. If it interacted perfectly spherically symmetrically, I think it would be reasonable to say it was round. If it interacted in a more complex way (as in, you could grab it and rotate it, because it has some non-spherically symmetric interactions) then it's not round. Interestingly, the electromagnetic interactions of an electron are extremely tightly constrained by it having only 1/2 unit of spin. You can expand any field around a point in terms of spherical harmonics, and you can show the with spin 1/2, the electron can only interact in the manner of the first two spherical harmonics - monopole and dipole. So it can be round (monopole), or round + a more negative and less negative end (dipole). Nothing more complicated than that. (Assuming you believe quantum mechanics. The Wigner-Eckart theorem is the thing to look up if you're interested.) These measurements, then are measuring the dipolar component of the electron's electromagnetic interaction. The only way in which it could be not round. As to the point charge thing: well, that's like your opinion man :-) Which is to say, the electron is what the electron is, and it cares not how humans decide to describe it! These experiments are fine examples of a long tradition of measuring and observing to make sure our theoretical descriptions are actually faithful to reality. You might be tempted so say that if one of these measurements discovered that the electron was not round, then maybe that would be evidence for the electron being not a point particle. It's complicated though ... and you'd find many physicists would start arguing with you if you did say that, because the current description of the electron - while being a point particle in a certain sense - is already pretty complicated (basically, because of interactions between all of the different quantum fields) and many people would say it's already not point-like. Many wouldn't though. Maybe the point here it's quite tricky to be precise about these things without just doing it properly with maths!

noncoml 4y ago

Explain like I’m five follow up question: is this electron able to exist in infinite places in space or only in predetermined slots? I.e. does space consists of pixels?

DoubleFree 4y ago
Space is not quantized, so yes, the electron has infinite possible locations. There are, however, places the electron cannot be, depending on its energy. See, the electron's energy is quantized, meaning it can only have a predetermined set of values (see atoms' electron shells). The energy determines the wave function and the wave function squared is the probability distribution for the electron's location. This wave function has roots, indicating where the electron cannot be.

tachyon5 4y ago

It's interesting to consider the parallels between the electron's roundness and the cosmic microwave background (CMB) radiation's uniformity. Both seem to defy our expectations of asymmetry, with the electron's shape ruling out new particles and the CMB's uniformity challenging our understanding of the early universe. As we explore these seemingly unrelated phenomena, perhaps there lies a deep, underlying connection that could unite our understanding of the microcosm and the macrocosm, offering a fresh perspective on the laws governing our universe.

nuccy 4y ago
For the CMB we predict (or rather invent) "inflation" - a rapid expansion of the space-time to preserve uniformity of early Universe [1]. Inflation lasted for 0.00000000000000000000000000000001s but the size of the Universe increased by 10^30 times. 1. https://www.esa.int/Science_Exploration/Space_Science/Planck/The_cosmic_microwave_background_and_inflation https://www.esa.int/Science_Exploration/Space_Science/Planck... Edit: I wanted to come up with an analogy of increasing some object to the size of Earth (as it is the biggest object we can experience in real life). Though 10^30 times is so mindbogglingly large that we don't really have any sense of that small sizes at all. The object would have to be smaller than an electron by a trillion times (10^12).

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martincmartin 4y ago

The experiments are now so sensitive that if an electron were the size of Earth, they could detect a bump on the North Pole the height of a single sugar molecule. This new bound is sensitive to energies above roughly 10^13 electron-volts — more than an order of magnitude beyond what the LHC can currently test. Wow.

JumpCrisscross 4y ago
It reminds me of Aristotelian physics’ perfect ætherial heavenly bodies. Ironinic they were on the terrestrial sphere in the end.
wkat4242 4y ago
Yeah how do they manage to get that kind of accuracy. Mind boggling.
- moron4hire 4y ago
  That's precision, not accuracy.
  - lifeisstillgood 4y ago
    hang on - what? Yes it is precise ... to 17 decimal places or whatever. But it is also I believe accurate? I mean are they wrong and the electron is as bumpy as my chin on a weekend?
    - delecti 4y ago
      It's not that the experiment is not accurate, "accuracy" is simply not the aspect of the measurement being discussed. The sentence "That's precision, not accuracy." should be read to mean "we are discussing precision, we are not discussing accuracy" rather than "it's precise, but inaccurate".
      - Wowfunhappy 4y ago