22 ms·

Particle mystery: physicists confirm the muon is more magnetic than predicted

560 points by furcyd 6y ago

gus_massa 6y ago
Only 4.2 sigmas. ;) That is really a lot. It's less than the official arbitrary threshold of 5 sigmas to proclaim a discovery, but it's a lot. In the past, experiments with 2 or 3 sigmas were later classified as flukes, but AFAIK no experiment with 4 sigmas has "disappeared" later.
- comboy 6y ago
  Neutrinos faster than light had 6 sigma. It just shows probabilistic significance. Confirmation by independent research teams helps eliminate calculation and execution errors.
  - thepangolino 6y ago
    This is the second separate experiment giving similar value.
    - XorNot 6y ago
      The use of a secret frequency source not known to the experimenters is also a very good way to deal with potential bias.
    - Robotbeat 6y ago
      That does help a lot! Of course, this is still not good enough. But the nice thing about things that are real is they eventually stand up to increasing levels of self-doubt and 3rd party verification... it’s an extraordinary result (because, of course, the Standard Model seems to be sufficient for just about everything else... so any verified deviation is extraordinary), and so funding shouldn’t be a problem. A decent heuristic: Real effects are those that get bigger the more careful your experiment is (and the more times it is replicated by careful outsiders), not smaller.
      - deleted 6y ago
        [deleted]
    - davrosthedalek 6y ago
      "Separate" for slightly small values of separate. It's the same measurement approach, and using many components from the first experiment, so there could be correlated errors. But they made many fundamental improvements to the experiment, so it's great to see that the effect hasn't gone away.
      - ISL 6y ago
        The primary shared component is the ring/yoke. I worked in the same lab as a substantial team of g-2 scientists for the last decade and watched them come to this result. The level of re-characterization of the properties of the entire instrument was extremely extensive. If anything, one should regard the lessons that they have learned along the way as providing extra insight into the properties of the original BNL measurement. To use a car analogy: This is as if you took someone's prize-winning race car, kept the moderately-priceless chassis, installed upgraded components in essentially every other sense (remove the piston engine, install a jet engine, remove the entire cockpit and replace with modern avionics, install entirely new outer shell, replace the tires with new materials that are two-decades newer...), put the car through the most extensive testing program anyone has ever performed on a race car, filled the gas tank with rocket fuel, and took it back to Le Mans. I believe that the likelihood of a meaningful ring-correlated systematic, while still possible, is quite low in this case. The magnetic-field mapping, shimming, and monitoring campaigns, in particular, should give people confidence that any run-to-run correlated impact of the ring ought to be very small.
  - selectodude 6y ago
    Ideally they have all their fiber optic cables screwed on tight at Fermilab.
  - gizmo686 6y ago
    As I recall, FTL neutrinos were the result of experimental error, not chance; and so are outside the scope of what sigma screen for.
    - theptip 6y ago
      In scope for the context of this thread though; your GP claimed that 4 sigmas means “it’ll probably pan out as being real”, your parent provided a 6-sigma counter example.
      - ianai 6y ago
        Or the title of this topic as it is right now is misleading. It says they’ve confirmed the stronger magnetic field. Ie it was either predicted elsewhere or seen elsewhere. The later would build confidence in the testing apparatus.
      - deleted 6y ago
        [deleted]
      - kbelder 6y ago
        "It's 99.99% significant, if we assume the 10% case that we haven't fucked up somewhere."
      - a1369209993 6y ago
        > your GP claimed that 4 sigmas means "it'll probably pan out as being real" No they didn't; they claimed that 4 sigmas means it will probably turn out to be something other than statistical noise. They made no claims about "it's real" versus "it's a systematic, non-statistical error". See also https://www.explainxkcd.com/wiki/index.php/2440 https://www.explainxkcd.com/wiki/index.php/2440
    - mhh__ 6y ago
      It's probably worth saying that even "chance" is still a little misleading in the sense that the quantification of that chance is still done by the physicists and therefore can be biased
    - 6y ago
- sgt101 6y ago
  Oh sweet summer physicist, what do you know of reality? Reality is for the markets, lovely mathey person, when a one in a million chance comes every month, and investment portfolios lie scattered over the floor like the corpses on a battlefield. Reality is for when your mortgage and the kid's school fees are riding on it, and quantitative strategies are borne and die with the fads of last summers interns pet projects. In some domains 7 sigma events come and go - statistics is not something to be used to determine possibility in the absence of theory. If you go shopping you will buy a dress, just because it's a pretty one doesn't mean that it was made for you.
misiti3780 6y ago
What is everyones favorite book on quantum mechanics (I would love understand more of the 3 generations of matter)?
- thisiscorrect 6y ago
  Mine is Sakurai's "Modern Quantum Mechanics." But it sounds like you're really asking which book would be good for you to learn about quantum mechanics and also the Standard Model of particle physics.
  - selimthegrim 6y ago
    I would not just throw someone into Sakurai starting from scratch.
- andrepd 6y ago
  Cohen-Tannoudji, Sakurai.
- martincmartin 6y ago
  Quantum Mechanics and the three generations of matter are slightly different. Quantum Mechanics is like Newton's laws at small scales, in that if you know what things are like at time t, and you know all the potentials (forces), it tells you how they evolve. It also tells you what states are physically allowed (e.g. only certain energies for electrons orbiting an atom). You can study QM for years without any real look at the standard model, which is where the three generations come from. If you want an undergraduate class in QM, edX has MIT's classes on line: https://learning.edx.org/course/course-v1:MITx+8.04.1x+3T2017/home https://learning.edx.org/course/course-v1:MITx+8.04.1x+3T201... If you want a textbook, Griffth's "Introduction to Quantum Mechanics" is the standard answer. It's very much a "shut up and calculate" book, you'll learn how to compute expected values of commutators without much intuition for what they mean. Update: Others point out Griffth's "Introduction to Elementary Particles", read their recommendations, sounds like the way to go. If don't want to spend 12 hours a week for 3 months and still not have learned much about the 3 generations, then ... I don't know, maybe QED: The Strange Theory of Light and Matter? I don't know if it has the 3 generations, but it only assumes high school math, yet gets into the quantum version of electricity and magnetism.
1-6 6y ago
Must be background radiation day at HN.
- whatshisface 6y ago
  This is not a collider experiment, so it doesn't have that particular failure mode.
wrnr 6y ago
Live from the Fermilab: https://www.youtube.com/watch?v=81PfYnpuOPA https://www.youtube.com/watch?v=81PfYnpuOPA
beezle 6y ago
The Quanta write up is a bit more neutral on this announcement. There is a computational result that was not included in the theoretical value used to bench the test against. Once reviewed, this difference may yet go back to oblivion. https://www.quantamagazine.org/muon-g-2-experiment-at-fermilab-finds-hint-of-new-particles-20210407 https://www.quantamagazine.org/muon-g-2-experiment-at-fermil...
- ssivark 6y ago
  To clarify, for those not familiar with this topic, this experiment is making measurements at such exquisite precision that even the calculations for the theoretical prediction are extremely non-trivial and require careful estimation of many many pieces which are then combined. Which is to say that debugging the theoretical prediction is (almost) as hard as debugging the experiment. So I would expect the particle physics community to be extremely circumspect while the details get ironed out. The Quanta article explains it quite nicely. To quote their example of what has happened in the past: > ”A year after Brookhaven’s headline-making measurement, theorists spotted a mistake in the prediction. A formula representing one group of the tens of thousands of quantum fluctuations that muons can engage in contained a rogue minus sign; fixing it in the calculation reduced the difference between theory and experiment to just two sigma. That’s nothing to get excited about.”
  - platz 6y ago
    it's not good to cherry-pick paragraphs from the whole artile. > But as the Brookhaven team accrued 10 times more data, their measurement of the muon’s g-factor stayed the same while the error bars around the measurement shrank. The discrepancy with theory grew back to three sigma by the time of the experiment’s final report in 2006.
    - eloff 6y ago
      > it's not good to cherry-pick paragraphs from the whole artile Isn't that exactly what you just did? There's nothing wrong with showing only small quotes, the problem would be cherry picking them in a way that leads people to draw incorrect conclusions about the whole.
treyh 6y ago
With 19 free parameters in the standard model, can't they fit any experimental result by adjusting a "constant"?
- PeterisP 6y ago
  Sure they can fit any experimental result that way, they can probably fit any 19 experimental results that way, but in general if you would freely adjust a constant to fit one experiment then it would stop fitting other experiments.
  - tW4r 6y ago
    Do we need TDD for particle physics so CI could run tests on what experiments break when merging a theory
    - tux3 6y ago
      Are you volunteering to write the YAML for it? =) Should be pretty much trivial! Exercise left to the reader.
    - whatshisface 6y ago
      That's done by hand. I guess you could automate it. Maybe we'll see that some time in the next century.
    - ISL 6y ago
      Yes. This would be extremely helpful for experimentalists who spend a lot of their time pointing out, for example, that one's new theory can't violate the equivalence principle by very much at all. Similarly, it would be helpful for people planning new experiments to know whether or not their proposed experiment will probe new ground (i.e. CERN's anti-hydrogen experiments are of intense value for spectroscopic studies, but existing experiments [1] show that antimatter, at the 10^-8 level or better, obeys the equivalence principle and therefore will reliably fall in every experiment of which CERN is capable.). As a sibling comment points out, it is difficult to implement the markup that spans the space of all possible theories. Kostelecky's parametric Standard Model Extension offers one avenue to do so. One could implement such a test as a checklist, too, which might already make a difference. [1] https://arxiv.org/pdf/1207.2442.pdf https://arxiv.org/pdf/1207.2442.pdf
davidivadavid 6y ago
Physics noob question: is there any physical framework that does away with the concept of "force"? I know a bit about how it is reconceptualized as space-time deformation in the context of general relativity, but that's about it. It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different?
- outworlder 6y ago
  > It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different? This is something I struggle with. I know that physics originated from an experimental framework. We observe phenomena, then we try to come up with explanations for said phenomena, formulate hypothesis, then test them. That is fine. But this breaks down when the 'fundamental forces' are involved. What _is_ a force? All the explanations I've ever seen (apart from gravity) seem to treat a 'force' as an atomic concept. They will describe what a force 'does', but not what it 'is'. Maybe that's something unknowable, but it bothers me. F* magnets, how do they work.
  - l33tman 6y ago
    At its essence, in the modern understanding, a force is an emergent phenomena arising out of the fact that a world (a spacetime filled with your particles) where two particles of opposite charge seem to move towards each other is more probable than a world where they don't. This sounds silly but it's exactly the root cause in the current understanding and shoehorning in the word "force" in "force-carrying particles" is a stretch and causes this confusion. It's true that there would be no electromagnetic force without the photons. But photons and their likes are not the only way a "force" arises. For example, the Pauli exclusion principle can be seen as a "force" and it arises without photons with just electrons.
  - alexlarsson 6y ago
    From feynman: https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8
- 6y ago
nyc640 6y ago
There was a nice explanation of the finding in comic format from APS & PhD Comics: https://physics.aps.org/articles/v14/47 https://physics.aps.org/articles/v14/47
- BlueTemplar 6y ago
  Oh, so it's a bit like electron screening, but with virtual particles ? Fine structurally neat !
- lgrebe 6y ago
  This sound like the hypothesized „subtle-matter“ as proposed by Dr. Klaus Volkamer [1]? - still looking for a better link than the Book… I’ll update this later [1] https://amzn.to/3mvvsWW https://amzn.to/3mvvsWW
  - dan-robertson 6y ago
    But if muons are inanimate, why would they be affected by this hypothesised “subtle matter” which makes up the soul of living things?
    - lgrebe 6y ago
      heres is a paper [1] from 1994 here the results of weighing thermodynamically closed reactions are "interpreted to reveal the existence of a heretofore unknown kind of non-bradyonic, cold dark matter with two different forms of interaction with normal matter" [1] http://klaus-volkamer.de/wp-content/uploads/2014/11/1994-Volkamer-Journal-of-Scientific-Exploration.pdf http://klaus-volkamer.de/wp-content/uploads/2014/11/1994-Vol...
  - gct 6y ago
    lol
  - kjs3 6y ago
    Maybe the muons are hitting the angels at a good fractions of the speed of light and the difference is the angel-splat. Maybe FERMI can contract Dr Klaus to come up the an experiment to measure the angel-goo and true the difference right up. Thanks for the link to an 'authoritative source'. :-)
ipnon 6y ago
Nature seems to have this interesting property of always increasing in perceived complexity.
- BiteCode_dev 6y ago
  Wouldn't that be amazing if the universe developed more and more characteristics as you look for them? Or even, that it's pushed to create something when you do? Infinite playground.
  - BlueTemplar 6y ago
    Godel kind of proved that about Mathematics.
    - schmorptron 6y ago
      That sounds wild, do you have a link where I can read more about this, or is wikipedia fine to learn about it?
      - ArnoVW 6y ago
        https://en.m.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_theorems https://en.m.wikipedia.org/wiki/G%C3%B6del%27s_incompletenes... TLDR: you can have a mathematics that always gives true answers (but that cannot answer everything). Or you can have a mathematics that can answer every possible question (but some answers are wrong, you do not know which). Choose. This dispaired mathematicians of the early 20th century, who had hoped to create 'one mathematics to rule them all'. Of course you can have several disjunct mathematics, each one for the problem you like.
        schmorptron 6y ago
        Oh, cool!
      - jl6 6y ago
        Axioms are the foundational assumptions from which formal systems of mathematics are built. Some systems of axioms are unable to prove the truth or falsity of some statements within that system. But you can add such statements to your set of axioms to form a new, larger formal system, which in turn has other indeterminate statements, and so on, thus building, in GP’s terms, an infinite playground of mathematics. Book recommendation: Gödel, Escher, Bach by Douglas Hofstadter.
gautamcgoel 6y ago
Honestly feel sorry for particle physicists... Their entire gig is spending billions on fancy equipment, and hoping that observe something unexpected. If they see exactly what they expected to see, all that effort was basically wasted. Also, a lot of "discoveries" turn out to be equipment miscalibration - remember those particles which supposedly moved faster than light a few years back? Always struck me as an odd way to do science.
- astrophysician 6y ago
  From a physicists standpoint, not seeing something unexpected is not a waste at all.
  - gautamcgoel 6y ago
    Can you expand on that? I was under the impression that many thought of it as a waste (Sabine Hossenfelder comes to mind, for example).
    - CrazyDave 6y ago
      I assume it helps trim off the branches of research that become unviable with the new evidence.
    - bluGill 6y ago
      Some do I'm sure. However if we see something unexpected and it turns out to be true that means our ideas of physics are fundamentally wrong. While it is long term good to correct our understanding, in the mean time a lot of the real world depends on us being right, and so until we correct the theory who knows what will work. I'd hate to find our margin of safety on nuclear bombs was too small and it is only luck that they haven't all blown up in their silos over the years.
    - aqme28 6y ago
      Theorizing a phenomenon and having experimental evidence of a phenomenon are very different things.
    - 6y ago
aworkerbee 6y ago
Can anyone recommend any pop-sci books? I haven't taken a science class since high school, and that is barely remembered. Mostly interested in getting philosophically up to date with the state of matter(?), it's different types, how these objects interact.
- throw1234651234 6y ago
  The only update that I got since was high school was that electrons aren't on concrete orbitals around the nucleus, but that there is a probability distribution saying that they are likely somewhere around the area where the concrete "orbital" concept is usually drawn. That and quantum shenanigans, but that comes down to "we can't transport information faster than light."
  - keanebean86 6y ago
    Just mention pilot wave theory and someone on this site might reply with a very detailed explanation of quantum mechanics. https://en.wikipedia.org/wiki/Pilot_wave_theory https://en.wikipedia.org/wiki/Pilot_wave_theory
- sdedovic 6y ago
  My personal favorite: - Thirty Years that Shook Physics: The Story of Quantum Theory Other great books: - The Theory Of Everything - The Quark and the Jaguar - Six Easy Pieces
- Zanni 6y ago
  Recommended up thread, but Feynman's QED: The Strange Theory of Light and Matter [0] is fantastic and very accessible. It's not particularly "up to date" (dating back to 1985), but it's not obsolete. [0] https://en.wikipedia.org/wiki/QED:_The_Strange_Theory_of_Light_and_Matter https://en.wikipedia.org/wiki/QED:_The_Strange_Theory_of_Lig...
goatcode 6y ago
>the strong force and the weak force. Is there a reason we're leaving "nuclear" off these forces' names now?
- rocqua 6y ago
  I have indeed often seen the names referred to without the term "nuclear".
  - goatcode 6y ago
    Weird. This must have changed in the past 10 years or so, since I've been out of college.
    - dylan604 6y ago
      It's something you never get used to. As you get older, this will just keep happening. We used to put commas before the last item in a list back in like the stone ages when I was in school. My SAT score looked really lame for a bit of time when those suddenly changed.
      - goatcode 6y ago
        I understand the grumpy old person archetype now. I feel like I've been one for a long time, but it's really hitting home over the past decade.
    - dukwon 6y ago
      This (very important) paper from 1967 calls them "weak interaction" and "strong interaction": https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.19.1264 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.19... Putting the word "nuclear" in the middle seems to just be done in textbooks and classrooms.
  - a9h74j 6y ago
    This might be a new variant of: You can tell how old a national lab is by what they study in the "physics" division.
zbendefy 6y ago
Is this the same thing that this 2016 article is about? Or is it a new finding with a similiar conclusion? https://www.nature.com/news/has-a-hungarian-physics-lab-found-a-fifth-force-of-nature-1.19957 https://www.nature.com/news/has-a-hungarian-physics-lab-foun...
- dukwon 6y ago
  It's unrelated
Arjuna144 6y ago
hahah all this for some what? 10^(-6) or 10^(-5) discrepancy?! What about this age old 10^120 discrepancy that eveyone seems to be just fine about... https://en.wikipedia.org/wiki/Cosmological_constant_problem https://en.wikipedia.org/wiki/Cosmological_constant_problem
- podiki 6y ago
  People aren't "just fine" about dark energy. It is an entire field of study in physics/astronomy. A problem there is that we are quite stuck; some future experiments might tell us something (if it has changed over time for instance), but theoretically there aren't any stand out answers or ones that can see experimental confirmation soon.
  - Arjuna144 6y ago
    Please read up on Dark Energy. It is quite fascinating that people do not make the connection. Dark Energy was invented because the theory does predict not enough energy. Meaning observation requires there to be WAAY more energy than what the theory predicts! This vacuum catastrophe is completely different! The theory does predict WAAAAY, I mean WAAAAAAAAYYYYYY more energy than what was found in observations.
    - podiki 6y ago
      Perhaps I should have mentioned I am (was) a theoretical physicist and have worked a little on dark energy. But perhaps you meant the comment to others in general.
aaomidi 6y ago
Everytime I see news like this, it just reminds me of the three body problem and the extremely unique Sophons in them.
nimish 6y ago
It'll be a huge victory for lattice-QCD if the computational result is true.
zzzeek 6y ago
bottom line this for me. can we have levitating cars or not ?
podiki 6y ago
As a particle physicist (no longer working in the field, sadly), this is one of the more exciting results in a long time. Muon g-2 has been there, in some form of another for debate and model building, for many years (taken somewhat seriously for 15+?), waiting for better statistics and confirmation. At over 4 sigma this is much more compelling than it has ever been, and the best potential sign of new (non-Standard Model) physics. I'm not current on what models people like to explain this result, but it has been factored in (or ignored if you didn't trust it) in particle physics model building and phenomenology for years. This result makes it much more serious and something I imagine all new physics models (say for dark matter or other collider predictions or tensions in data) will be using. Whether or not anything interesting is predicted, theoretically, from this remains to be seen. I don't know off hand if it signals anything in particular, as the big ideas, like supersymmetry, are a bit removed from current collider experiments and aren't necessarily tied to g-2 if I remember correctly.
- manspacetar 6y ago
  re "what models people like to explain": There was some good discussion of lepton universality violation at the end of the announcement talk. tl;dr - electrons and muons are leptons, but what if they don't interact with photons the same way? (ie the rules of physics aren't universal to all leptons)
atty 6y ago
Alexey Petrov, quoted in the article, subbed in to teach one day in my quantum mechanics class :) It was the first day we were being introduced to the theory of scattering, and I will never forget his intro. He asked the class, “what is scattering?”, waited a moment, and then threw a whiteboard marker against the wall, and answered his own question: “that’s scattering”. Lots of times, physics classes can be so heavy on math that it’s hard to even remember that you’re trying to describe the real world sometimes, and moments like that were always very memorable to me, because it helped remind me I wasn’t just solving equations for the hell of it :)
- kache_ 6y ago
  An old professor of mine loved the "Throw something at the blackboard" technique. Great way to get the class potheads to wake up
  - forgotmysn 6y ago
    how many potheads did you have in your quantum mechanics class?
    - kache_ 6y ago
      It was an algorithms class. But I'm 100% certain there was at least one ;)
    - xzel 6y ago
      Hmm probably about a third of my graduate level QED class and considerably less in my undergraduate QM but you'd be surprised at the cross over between potheads and high level physics.
      - slenk 6y ago
        I don't see any reason that would cause them to be mutually exclusive.
    - jefft255 6y ago
wnevets 6y ago
I can't wait for PBS Spacetime to tell me what to think about this.
- terramex 6y ago
  They already did, 15 minutes ago: https://www.youtube.com/watch?v=O4Ko7NW2yQo https://www.youtube.com/watch?v=O4Ko7NW2yQo For those who do not know - PBS Spacetime is YouTube channel hosted by astrophysics Ph.D Matt O'Dowd, aimed at casual physics enthusiasts without oversimplifying underlying physics too much.
- MperorM 6y ago
  Am I the only one who barely understands anything from that show? Every episode I hear a dozen barely explained confusing terms with quantum this and higgs-field that. I feel like they care more about impressing me with how complicated this stuff is than they do about actually teaching me much. Maybe I'm just not the target audience :(
  - wnevets 6y ago
    There are a lot of quantum mechanics episodes from 1-2 years ago that cause my eyes to just glaze over from all of the math and technical terms. However I feel like the newer episodes are much better at explaining things to the casual viewer rather than math nerds.
  - smegger001 6y ago
    honestly i some times have the same problem sometimes, but I think it is because there is just so much background that you have to grok before you understand the discussion being had. And as that is not part of my knowledge domain I haven't spent enough time to pick it up as it will probably never effect me my daily life.
  - megablast 6y ago
    No. I imagine lots of children don’t understand anything said on that show as well.
  - 6y ago
uhtred 6y ago
Can anyone explain in layman's terms why this is important?
- 1-6 6y ago
  3D point clouds and x-rays! More research can be done on low-cost devices. It puts LiDAR to shame but there are also great privacy implications. Muon tomography: https://en.wikipedia.org/wiki/Muon_tomography https://en.wikipedia.org/wiki/Muon_tomography
  - whatshisface 6y ago
    Extremely precise measurements of the muon magnetic moment are not going to be useful for those applications.
- Jeff_Brown 6y ago
  From another comment, there's this PBS Space Time video on Youtube. https://www.youtube.com/watch?v=O4Ko7NW2yQo https://www.youtube.com/watch?v=O4Ko7NW2yQo
- whatshisface 6y ago
  If you take the current sum of all human knowledge and calculate something called g, and then subtract two, you get something different from the the real value of g-2. Therefore, we have identified something that lies beyond the sum of all human knowledge. That's kind of the whole idea behind being a physicist so understandably anyone remotely related to the area this belongs to is pretty excited. If you are wondering, "why does this one single number matter so much, who cares if we didn't know it before," it is because it hints at a great new theory that could change everything. Nobody knows what theory, but in the past small discrepancies in fundamental measurements have been the seeds of great theories.
- gus_massa 6y ago
  The electrons and the muons are very similar. We can measure the magnetic moment and make some calculations and calculate a number g. If they were perfectly ideal particles, then g must be exactly 2, so it's interesting to measure g-2. The real particles have a lot of virtual particles that appear around them and are impossible to detect directly. It's like a cloud of more electrons, positrons, photons, and other particles. They are impossible to detect directly, but they affect slightly the result of the experiments, so when you go to a lab and measure g, you don't get exactly 2. We have a very good model for all the virtual particles that appear around them, i.e. the electrons, positrons, photons, and other particles. It's call the "Standard Model". (But I don't like the name.) We can use the "Standard Model" to calculate the correction of g of an electron, and the theoretical calculation agree with the experiments up to the current precision level. We[1] can use the "Standard Model" to calculate the correction of g of a muon, and the theoretical calculation does not agree with the experiments!!! The disagreement is very small, and there is still a small chance that the disagreement is a fluke, but people is optimistic and think that it they continue measuring they can be confident enough that it is not a fluke. [1] Actually not me, this is not my research area, but I know a few persons that can. --- Back to your question: > *Why is this important? If the theoretical calculation and the experimental value disagree, it means that the "Standard Model" is wrong. Physicist would be very happy to prove that it is wrong, because they can study variants of this experiment and try to improve the model. (And be famous, and get a Nobel prize.) Physicist are very worried because they are afraid that the "Standard Model" is so good that to prove it is wrong they need to build a device that is as big as the Solar system. (And they can't be famous, and the Nobel prize will go that work in other areas.) If this result is "confirmed", the idea is to add a new particle to the "Standard Model" and get the "Standard Model II". (IIRC it already has a few corrections, so we will call the new version the "Standard Model".) It's difficult because the new particle must change the predictions for this experiment, but not change too much the predictions for other experiments. It may take a few years or decades to find the new theoretical particle that match the experiments. If you are pessimistic, the new particle will be useful only to explain a small correction that is only relevant in very accurate experiments in the lab, or inside a big star, or other unusual events. If you are optimistic, in 100 year every moron on Earth will have in the pocket a device that will use this new particle for something amazing. Or perhaps something in between. Nobody has any clue about this.
glofish 6y ago
Amusingly - fittingly for our times - in the same issue of the exact same journal (Nature) another paper has been published that indicates that the prior, so much "hyped" discrepancy might be due to the theory having being applied inaccurately in the past. When computed with the new method, the experimental and theoretical models align far more accurately. So now all that matters is what kind of article do your want to write. A sensationalist one to get eyeballs or a realistic one that is far less exciting. Thus the exact same discovery can be presented via two radically different headlines: BBC goes with "Muons: 'Strong' evidence found for a new force of nature" https://www.bbc.com/news/56643677 https://www.bbc.com/news/56643677 > "Now, physicists say they have found possible signs of a fifth fundamental force of nature" ScienceDaily says: "The muon's magnetic moment fits just fine" https://www.sciencedaily.com/releases/2021/04/210407114159.htm https://www.sciencedaily.com/releases/2021/04/210407114159.h... > "A new estimate of the strength of the sub-atomic particle's magnetic field aligns with the standard model of particle physics." There you have it, the mainstream media is not credible even when they attempt to write about a physics experiment ...
- gameswithgo 6y ago
  What were the times when journalism was better?
- devb 6y ago
  This is an incredibly complicated and abstract subject, yet you have somehow managed to boil it down into a sweeping generalization about the basics of media and reporting. Masterfully done.
Anon84 6y ago
I’m getting a “faster than light neutrinos” feeling about this one
mjevans 6y ago
I read the release written by the lab. https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/ https://news.fnal.gov/2021/04/first-results-from-fermilabs-m...
j4yav 6y ago
There is a nice video explanation from PBS at https://youtu.be/O4Ko7NW2yQo https://youtu.be/O4Ko7NW2yQo
- seventytwo 6y ago
  PBS, man. Just steadily and reliably educating everyone for years now. Good shit.
  - dimator 6y ago
    SpaceTime (that channel) in general is of impeccable quality and production value. Definitely worth subscribing.
    - Crash0v3rid3 6y ago
      Worth the patreon contribution also.
atty 6y ago
As someone who has worked in fields that use lattice calculations (on the experimental side), the new calculation is interesting, but I would not say it’s particularly convincing yet. Lattice calculations are VERY difficult, and are not always stable. I am not questioning whether they did their work well or not, just pointing out that in high energy physics and high energy nuclear physics, many times our experimental results are significantly better constrained and also undergo significantly more testing via reproduction of results by other experiments than our theory counterparts’ work. Is it possible that all of our previous experiments have had some sort of correlated systematic error in them? Unlikely, but yes. Is it more likely that this lattice calculation may be underestimating its errors? Much more likely. Another interesting option is that one of the theoretical calculations was actually done slightly wrong. My first guess would be the lattice result, since it’s newer, but both procedures are complicated, so it could be either.
- glofish 6y ago
  I am not sure I follow the logic. The new computation aligns with the experiment. Why is it more likely for it to be wrong than the calculation that shows the theory deviating from experiment.
  - atty 6y ago
    The old calculation relies on older experimental results that have been verified by multiple experiments - so if the older value is wrong, it means either the calculation was done wrong (possible), or the experiments all have had a significant correlated systematic error that has never been caught (also possible). However, I’d say both of those things are relatively unlikely, when compared to the probability of some small error in a new paper that was just released that uses a new method that involves lattice calculations. This is all a balance of probabilities argument, but from my experience in the field, I’d say it’s more likely that any errors in calculation or missed systematics would be in the new paper. However, I’m an experimentalist who has worked close to a lot of this stuff, not an actual theorist, so I’d love to get a theorists interpretation as well.
    - 6y ago
gonational 6y ago
Science is a never ending series of incorrect observations, each disqualifying the penultimate while asserting the ultimate is axiomatic. When you're young you get excited each time a new breakthrough is happening. If you manage to grow up, you get tired of the pattern, and the signal to noise ratio starts to look like a good statistical P value.
- imvetri 6y ago
  That is very true. Knowledge – expands, Space exploration knowledge – expands, Sub atomic exploration – expands, (muon and we may even find its sub atomic particles as well) Space – expands, Number series – expands, Fibonacci – expands. Science expands external knowledge and shrinks self-knowledge, Spirituality shrinks external-knowledge and expands self-knowledge. Be warned when something expands. Be warned when something shrinks. E=mc^2 where c is not just the speed of light, c is the speed of space expansion as well. Mass expands to form energy (science) Energy shrinks to form mass (spirituality)
deleted 6y ago
[deleted]
eevilspock 6y ago
> "The concordance shows the old result was neither a statistical fluke nor the product of some undetected flaw in the experiment, says Chris Polly, a Fermilab physicist and co-spokesperson for the g-2 team. “Because I was a graduate student on the Brookhaven experiment, it was certainly an overwhelming sense of relief for me,” he says." A committed scientist should worry about having such feelings, even though it is very human. It represents a possible source of non-independence of tests and of scientific bias.
tompagenet2 6y ago
Genuine question from ignorance. Is this related to this work at CERN? https://www.theguardian.com/science/2021/mar/23/large-hadron-collider-scientists-particle-physics https://www.theguardian.com/science/2021/mar/23/large-hadron...
- dukwon 6y ago
  Maybe. There are plenty of attempts to explain g-2 and LFUV in B decays in one go. But really there's no way to know for sure yet.
- yk 6y ago
  Yes and no. It is two very different experimental situations, the magnetic moment is at rest (well, in an accelerator but the rest frame is defined by the muon) and the R_k anomaly is in an collision. On the other hand, as a theorists the immediate thing one thinks about is lepton universality, that the only difference between a electron and a muon is its mass, is violated. So there will be a lot of work this year on trying to explain both results at the same time.
yaya69 6y ago
And the gluon is the opposite
mkaic 6y ago
I highly recommend the YouTube channel PBS Space Time's coverage of this, it's informative, well organized, and accessible even to someone like me who doesn't have any background in physics.
cambalache 6y ago
https://www.math.columbia.edu/~woit/wordpress/?p=12292 https://www.math.columbia.edu/~woit/wordpress/?p=12292 This just PR fluff, with the paper published today in Nature there is no discrepancy with the SM. Mother Nature loves Ockham's razor.
lolthishuman 6y ago
It’s simple. The universe is electromagnetic. The Bose-Einstein condensate is the aether in most dense form. Everything evaporates into lower densities by means of rotation via the torus and vortices. Everything is pressure finding equilibrium spread throughout densities in fluid. Easy to reason about. The sun is hollow and incompressible aether inside, which is why it’s cold. The surface is electromagnetic activated by the currents spread throughout the galaxy. Every sun is like a lamp. Every sun is a plasmoid. Outer space is least dense form of the aether. Sound makes matter. Fun!
- shrimpx 6y ago
  Is there legitimate support for this hollow sun theory, or is this a fringe theory like flat earth and so on?
  - Arjuna144 6y ago
    I dont know about hollow suns and stuff. But what he said in the beginning has some reason. Check some of this guys papers: https://file.scirp.org/Html/8-2180368_91083.htm https://file.scirp.org/Html/8-2180368_91083.htm
  - SAI_Peregrinus 6y ago
    The EM universe hypothesis is not much better than the flat Earth one. Similar levels of agreement with observed behavior.
    - lolthishuman 6y ago
      Not much is published that makes sense unfortunately. The EM universe hypothesis has its flaws because it’s not United on first principles connecting the aether and primitive constructs like the torus and hyperboloid. It’s dangerous for many easy to reason about considerations. Most people’s lives are reputation based and confined to incentives of pay that prevent such topics being published or discussed. Hard problem.
wombatmobile 6y ago
I read the headline wrong and came here to find out how mutton is magnetic at all.
- imvetri 6y ago
  hahaha
irjustin 6y ago
The NYTimes[0] article takes a more measured tone and reports 1 in 40,000 confidence, ~5 sigma. 5 sigma results have disappeared (even 6-sigma) upon independent testing, so more testing is needed. [0] https://www.nytimes.com/2021/04/07/science/particle-physics-muon-fermilab-brookhaven.html https://www.nytimes.com/2021/04/07/science/particle-physics-...
dtrain2017 6y ago
Why is it called a particle accelerator when it's possible for the particle to go both ways: forwards and backwards? Don't they measure the difference in the direction of the particle as determined by its virtual cloud? more energy emitted from the cloud = forward and vice-versa. Loved the explanation and accompanying illustrations.
imvetri 6y ago
Knowledge - expands, Space exploration knowledge - expands, Sub atomic exploration - expands, (muon and we may even find its sub atomic particles as well) Space - expands, Number series - expands, Fibonacci - expands. Be warned when something expands, you can never reach. Its not the destination, its the journey :D
peter303 6y ago
The muon was the first non-standard matter particle and 2nd transient particle discovered in 1937. It lead to new physics then and continues to suggest there is new physics.
ngcc_hk 6y ago
Very interesting indeed. But if one read again all depends the idea of quantum field theory or "like all charged particle it interacts with its own field to create virtual particles" etc. It is hard to understand for old guy learning basic physics long time ago.

560 points by furcyd 6y ago

Only 4.2 sigmas. ;) That is really a lot. It's less than the official arbitrary threshold of 5 sigmas to proclaim a discovery, but it's a lot. In the past, experiments with 2 or 3 sigmas were later classified as flukes, but AFAIK no experiment with 4 sigmas has "disappeared" later.

comboy 6y ago
Neutrinos faster than light had 6 sigma. It just shows probabilistic significance. Confirmation by independent research teams helps eliminate calculation and execution errors.
- thepangolino 6y ago
  This is the second separate experiment giving similar value.
  - XorNot 6y ago
    The use of a secret frequency source not known to the experimenters is also a very good way to deal with potential bias.
  - Robotbeat 6y ago
    That does help a lot! Of course, this is still not good enough. But the nice thing about things that are real is they eventually stand up to increasing levels of self-doubt and 3rd party verification... it’s an extraordinary result (because, of course, the Standard Model seems to be sufficient for just about everything else... so any verified deviation is extraordinary), and so funding shouldn’t be a problem. A decent heuristic: Real effects are those that get bigger the more careful your experiment is (and the more times it is replicated by careful outsiders), not smaller.
    - deleted 6y ago
      [deleted]
  - davrosthedalek 6y ago
    "Separate" for slightly small values of separate. It's the same measurement approach, and using many components from the first experiment, so there could be correlated errors. But they made many fundamental improvements to the experiment, so it's great to see that the effect hasn't gone away.
    - ISL 6y ago
      The primary shared component is the ring/yoke. I worked in the same lab as a substantial team of g-2 scientists for the last decade and watched them come to this result. The level of re-characterization of the properties of the entire instrument was extremely extensive. If anything, one should regard the lessons that they have learned along the way as providing extra insight into the properties of the original BNL measurement. To use a car analogy: This is as if you took someone's prize-winning race car, kept the moderately-priceless chassis, installed upgraded components in essentially every other sense (remove the piston engine, install a jet engine, remove the entire cockpit and replace with modern avionics, install entirely new outer shell, replace the tires with new materials that are two-decades newer...), put the car through the most extensive testing program anyone has ever performed on a race car, filled the gas tank with rocket fuel, and took it back to Le Mans. I believe that the likelihood of a meaningful ring-correlated systematic, while still possible, is quite low in this case. The magnetic-field mapping, shimming, and monitoring campaigns, in particular, should give people confidence that any run-to-run correlated impact of the ring ought to be very small.
- selectodude 6y ago
  Ideally they have all their fiber optic cables screwed on tight at Fermilab.
- gizmo686 6y ago
  As I recall, FTL neutrinos were the result of experimental error, not chance; and so are outside the scope of what sigma screen for.
  - theptip 6y ago
    In scope for the context of this thread though; your GP claimed that 4 sigmas means “it’ll probably pan out as being real”, your parent provided a 6-sigma counter example.
    - ianai 6y ago
      Or the title of this topic as it is right now is misleading. It says they’ve confirmed the stronger magnetic field. Ie it was either predicted elsewhere or seen elsewhere. The later would build confidence in the testing apparatus.
    - deleted 6y ago
      [deleted]
    - kbelder 6y ago
      "It's 99.99% significant, if we assume the 10% case that we haven't fucked up somewhere."
    - a1369209993 6y ago
      > your GP claimed that 4 sigmas means "it'll probably pan out as being real" No they didn't; they claimed that 4 sigmas means it will probably turn out to be something other than statistical noise. They made no claims about "it's real" versus "it's a systematic, non-statistical error". See also https://www.explainxkcd.com/wiki/index.php/2440 https://www.explainxkcd.com/wiki/index.php/2440
  - mhh__ 6y ago
    It's probably worth saying that even "chance" is still a little misleading in the sense that the quantification of that chance is still done by the physicists and therefore can be biased
  - 6y ago
sgt101 6y ago
Oh sweet summer physicist, what do you know of reality? Reality is for the markets, lovely mathey person, when a one in a million chance comes every month, and investment portfolios lie scattered over the floor like the corpses on a battlefield. Reality is for when your mortgage and the kid's school fees are riding on it, and quantitative strategies are borne and die with the fads of last summers interns pet projects. In some domains 7 sigma events come and go - statistics is not something to be used to determine possibility in the absence of theory. If you go shopping you will buy a dress, just because it's a pretty one doesn't mean that it was made for you.

misiti3780 6y ago

What is everyones favorite book on quantum mechanics (I would love understand more of the 3 generations of matter)?

thisiscorrect 6y ago
Mine is Sakurai's "Modern Quantum Mechanics." But it sounds like you're really asking which book would be good for you to learn about quantum mechanics and also the Standard Model of particle physics.
- selimthegrim 6y ago
  I would not just throw someone into Sakurai starting from scratch.
andrepd 6y ago
Cohen-Tannoudji, Sakurai.
martincmartin 6y ago
Quantum Mechanics and the three generations of matter are slightly different. Quantum Mechanics is like Newton's laws at small scales, in that if you know what things are like at time t, and you know all the potentials (forces), it tells you how they evolve. It also tells you what states are physically allowed (e.g. only certain energies for electrons orbiting an atom). You can study QM for years without any real look at the standard model, which is where the three generations come from. If you want an undergraduate class in QM, edX has MIT's classes on line: https://learning.edx.org/course/course-v1:MITx+8.04.1x+3T2017/home https://learning.edx.org/course/course-v1:MITx+8.04.1x+3T201... If you want a textbook, Griffth's "Introduction to Quantum Mechanics" is the standard answer. It's very much a "shut up and calculate" book, you'll learn how to compute expected values of commutators without much intuition for what they mean. Update: Others point out Griffth's "Introduction to Elementary Particles", read their recommendations, sounds like the way to go. If don't want to spend 12 hours a week for 3 months and still not have learned much about the 3 generations, then ... I don't know, maybe QED: The Strange Theory of Light and Matter? I don't know if it has the 3 generations, but it only assumes high school math, yet gets into the quantum version of electricity and magnetism.

1-6 6y ago

Must be background radiation day at HN.

whatshisface 6y ago
This is not a collider experiment, so it doesn't have that particular failure mode.

wrnr 6y ago

Live from the Fermilab: https://www.youtube.com/watch?v=81PfYnpuOPA https://www.youtube.com/watch?v=81PfYnpuOPA

beezle 6y ago

The Quanta write up is a bit more neutral on this announcement. There is a computational result that was not included in the theoretical value used to bench the test against. Once reviewed, this difference may yet go back to oblivion. https://www.quantamagazine.org/muon-g-2-experiment-at-fermilab-finds-hint-of-new-particles-20210407 https://www.quantamagazine.org/muon-g-2-experiment-at-fermil...

ssivark 6y ago
To clarify, for those not familiar with this topic, this experiment is making measurements at such exquisite precision that even the calculations for the theoretical prediction are extremely non-trivial and require careful estimation of many many pieces which are then combined. Which is to say that debugging the theoretical prediction is (almost) as hard as debugging the experiment. So I would expect the particle physics community to be extremely circumspect while the details get ironed out. The Quanta article explains it quite nicely. To quote their example of what has happened in the past: > ”A year after Brookhaven’s headline-making measurement, theorists spotted a mistake in the prediction. A formula representing one group of the tens of thousands of quantum fluctuations that muons can engage in contained a rogue minus sign; fixing it in the calculation reduced the difference between theory and experiment to just two sigma. That’s nothing to get excited about.”
- platz 6y ago
  it's not good to cherry-pick paragraphs from the whole artile. > But as the Brookhaven team accrued 10 times more data, their measurement of the muon’s g-factor stayed the same while the error bars around the measurement shrank. The discrepancy with theory grew back to three sigma by the time of the experiment’s final report in 2006.
  - eloff 6y ago
    > it's not good to cherry-pick paragraphs from the whole artile Isn't that exactly what you just did? There's nothing wrong with showing only small quotes, the problem would be cherry picking them in a way that leads people to draw incorrect conclusions about the whole.

treyh 6y ago

With 19 free parameters in the standard model, can't they fit any experimental result by adjusting a "constant"?

PeterisP 6y ago
Sure they can fit any experimental result that way, they can probably fit any 19 experimental results that way, but in general if you would freely adjust a constant to fit one experiment then it would stop fitting other experiments.
- tW4r 6y ago
  Do we need TDD for particle physics so CI could run tests on what experiments break when merging a theory
  - tux3 6y ago
    Are you volunteering to write the YAML for it? =) Should be pretty much trivial! Exercise left to the reader.
  - whatshisface 6y ago
    That's done by hand. I guess you could automate it. Maybe we'll see that some time in the next century.
  - ISL 6y ago
    Yes. This would be extremely helpful for experimentalists who spend a lot of their time pointing out, for example, that one's new theory can't violate the equivalence principle by very much at all. Similarly, it would be helpful for people planning new experiments to know whether or not their proposed experiment will probe new ground (i.e. CERN's anti-hydrogen experiments are of intense value for spectroscopic studies, but existing experiments [1] show that antimatter, at the 10^-8 level or better, obeys the equivalence principle and therefore will reliably fall in every experiment of which CERN is capable.). As a sibling comment points out, it is difficult to implement the markup that spans the space of all possible theories. Kostelecky's parametric Standard Model Extension offers one avenue to do so. One could implement such a test as a checklist, too, which might already make a difference. [1] https://arxiv.org/pdf/1207.2442.pdf https://arxiv.org/pdf/1207.2442.pdf

davidivadavid 6y ago

Physics noob question: is there any physical framework that does away with the concept of "force"? I know a bit about how it is reconceptualized as space-time deformation in the context of general relativity, but that's about it. It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different?

outworlder 6y ago
> It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different? This is something I struggle with. I know that physics originated from an experimental framework. We observe phenomena, then we try to come up with explanations for said phenomena, formulate hypothesis, then test them. That is fine. But this breaks down when the 'fundamental forces' are involved. What _is_ a force? All the explanations I've ever seen (apart from gravity) seem to treat a 'force' as an atomic concept. They will describe what a force 'does', but not what it 'is'. Maybe that's something unknowable, but it bothers me. F* magnets, how do they work.
- l33tman 6y ago
  At its essence, in the modern understanding, a force is an emergent phenomena arising out of the fact that a world (a spacetime filled with your particles) where two particles of opposite charge seem to move towards each other is more probable than a world where they don't. This sounds silly but it's exactly the root cause in the current understanding and shoehorning in the word "force" in "force-carrying particles" is a stretch and causes this confusion. It's true that there would be no electromagnetic force without the photons. But photons and their likes are not the only way a "force" arises. For example, the Pauli exclusion principle can be seen as a "force" and it arises without photons with just electrons.
- alexlarsson 6y ago
  From feynman: https://www.youtube.com/watch?v=MO0r930Sn_8 https://www.youtube.com/watch?v=MO0r930Sn_8
6y ago

nyc640 6y ago

There was a nice explanation of the finding in comic format from APS & PhD Comics: https://physics.aps.org/articles/v14/47 https://physics.aps.org/articles/v14/47

BlueTemplar 6y ago
Oh, so it's a bit like electron screening, but with virtual particles ? Fine structurally neat !
lgrebe 6y ago
This sound like the hypothesized „subtle-matter“ as proposed by Dr. Klaus Volkamer [1]? - still looking for a better link than the Book… I’ll update this later [1] https://amzn.to/3mvvsWW https://amzn.to/3mvvsWW
- dan-robertson 6y ago
  But if muons are inanimate, why would they be affected by this hypothesised “subtle matter” which makes up the soul of living things?
  - lgrebe 6y ago
    heres is a paper [1] from 1994 here the results of weighing thermodynamically closed reactions are "interpreted to reveal the existence of a heretofore unknown kind of non-bradyonic, cold dark matter with two different forms of interaction with normal matter" [1] http://klaus-volkamer.de/wp-content/uploads/2014/11/1994-Volkamer-Journal-of-Scientific-Exploration.pdf http://klaus-volkamer.de/wp-content/uploads/2014/11/1994-Vol...
- gct 6y ago
  lol
- kjs3 6y ago
  Maybe the muons are hitting the angels at a good fractions of the speed of light and the difference is the angel-splat. Maybe FERMI can contract Dr Klaus to come up the an experiment to measure the angel-goo and true the difference right up. Thanks for the link to an 'authoritative source'. :-)

ipnon 6y ago

Nature seems to have this interesting property of always increasing in perceived complexity.

BiteCode_dev 6y ago
Wouldn't that be amazing if the universe developed more and more characteristics as you look for them? Or even, that it's pushed to create something when you do? Infinite playground.
- BlueTemplar 6y ago
  Godel kind of proved that about Mathematics.
  - schmorptron 6y ago
    That sounds wild, do you have a link where I can read more about this, or is wikipedia fine to learn about it?
    - ArnoVW 6y ago
      https://en.m.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_theorems https://en.m.wikipedia.org/wiki/G%C3%B6del%27s_incompletenes... TLDR: you can have a mathematics that always gives true answers (but that cannot answer everything). Or you can have a mathematics that can answer every possible question (but some answers are wrong, you do not know which). Choose. This dispaired mathematicians of the early 20th century, who had hoped to create 'one mathematics to rule them all'. Of course you can have several disjunct mathematics, each one for the problem you like.
      - schmorptron 6y ago
        Oh, cool!
    - jl6 6y ago
      Axioms are the foundational assumptions from which formal systems of mathematics are built. Some systems of axioms are unable to prove the truth or falsity of some statements within that system. But you can add such statements to your set of axioms to form a new, larger formal system, which in turn has other indeterminate statements, and so on, thus building, in GP’s terms, an infinite playground of mathematics. Book recommendation: Gödel, Escher, Bach by Douglas Hofstadter.

gautamcgoel 6y ago

Honestly feel sorry for particle physicists... Their entire gig is spending billions on fancy equipment, and hoping that observe something unexpected. If they see exactly what they expected to see, all that effort was basically wasted. Also, a lot of "discoveries" turn out to be equipment miscalibration - remember those particles which supposedly moved faster than light a few years back? Always struck me as an odd way to do science.

astrophysician 6y ago
From a physicists standpoint, not seeing something unexpected is not a waste at all.
- gautamcgoel 6y ago
  Can you expand on that? I was under the impression that many thought of it as a waste (Sabine Hossenfelder comes to mind, for example).
  - CrazyDave 6y ago
    I assume it helps trim off the branches of research that become unviable with the new evidence.
  - bluGill 6y ago
    Some do I'm sure. However if we see something unexpected and it turns out to be true that means our ideas of physics are fundamentally wrong. While it is long term good to correct our understanding, in the mean time a lot of the real world depends on us being right, and so until we correct the theory who knows what will work. I'd hate to find our margin of safety on nuclear bombs was too small and it is only luck that they haven't all blown up in their silos over the years.
  - aqme28 6y ago
    Theorizing a phenomenon and having experimental evidence of a phenomenon are very different things.
  - 6y ago

aworkerbee 6y ago

Can anyone recommend any pop-sci books? I haven't taken a science class since high school, and that is barely remembered. Mostly interested in getting philosophically up to date with the state of matter(?), it's different types, how these objects interact.

throw1234651234 6y ago
The only update that I got since was high school was that electrons aren't on concrete orbitals around the nucleus, but that there is a probability distribution saying that they are likely somewhere around the area where the concrete "orbital" concept is usually drawn. That and quantum shenanigans, but that comes down to "we can't transport information faster than light."
- keanebean86 6y ago
  Just mention pilot wave theory and someone on this site might reply with a very detailed explanation of quantum mechanics. https://en.wikipedia.org/wiki/Pilot_wave_theory https://en.wikipedia.org/wiki/Pilot_wave_theory
sdedovic 6y ago
My personal favorite: - Thirty Years that Shook Physics: The Story of Quantum Theory Other great books: - The Theory Of Everything - The Quark and the Jaguar - Six Easy Pieces
Zanni 6y ago
Recommended up thread, but Feynman's QED: The Strange Theory of Light and Matter [0] is fantastic and very accessible. It's not particularly "up to date" (dating back to 1985), but it's not obsolete. [0] https://en.wikipedia.org/wiki/QED:_The_Strange_Theory_of_Light_and_Matter https://en.wikipedia.org/wiki/QED:_The_Strange_Theory_of_Lig...

goatcode 6y ago

>the strong force and the weak force. Is there a reason we're leaving "nuclear" off these forces' names now?

rocqua 6y ago
I have indeed often seen the names referred to without the term "nuclear".
- goatcode 6y ago
  Weird. This must have changed in the past 10 years or so, since I've been out of college.
  - dylan604 6y ago
    It's something you never get used to. As you get older, this will just keep happening. We used to put commas before the last item in a list back in like the stone ages when I was in school. My SAT score looked really lame for a bit of time when those suddenly changed.
    - goatcode 6y ago
      I understand the grumpy old person archetype now. I feel like I've been one for a long time, but it's really hitting home over the past decade.
  - dukwon 6y ago
    This (very important) paper from 1967 calls them "weak interaction" and "strong interaction": https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.19.1264 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.19... Putting the word "nuclear" in the middle seems to just be done in textbooks and classrooms.
- a9h74j 6y ago
  This might be a new variant of: You can tell how old a national lab is by what they study in the "physics" division.

zbendefy 6y ago

Is this the same thing that this 2016 article is about? Or is it a new finding with a similiar conclusion? https://www.nature.com/news/has-a-hungarian-physics-lab-found-a-fifth-force-of-nature-1.19957 https://www.nature.com/news/has-a-hungarian-physics-lab-foun...

dukwon 6y ago
It's unrelated

Arjuna144 6y ago

hahah all this for some what? 10^(-6) or 10^(-5) discrepancy?! What about this age old 10^120 discrepancy that eveyone seems to be just fine about... https://en.wikipedia.org/wiki/Cosmological_constant_problem https://en.wikipedia.org/wiki/Cosmological_constant_problem

podiki 6y ago
People aren't "just fine" about dark energy. It is an entire field of study in physics/astronomy. A problem there is that we are quite stuck; some future experiments might tell us something (if it has changed over time for instance), but theoretically there aren't any stand out answers or ones that can see experimental confirmation soon.
- Arjuna144 6y ago
  Please read up on Dark Energy. It is quite fascinating that people do not make the connection. Dark Energy was invented because the theory does predict not enough energy. Meaning observation requires there to be WAAY more energy than what the theory predicts! This vacuum catastrophe is completely different! The theory does predict WAAAAY, I mean WAAAAAAAAYYYYYY more energy than what was found in observations.
  - podiki 6y ago
    Perhaps I should have mentioned I am (was) a theoretical physicist and have worked a little on dark energy. But perhaps you meant the comment to others in general.

aaomidi 6y ago

Everytime I see news like this, it just reminds me of the three body problem and the extremely unique Sophons in them.

nimish 6y ago

It'll be a huge victory for lattice-QCD if the computational result is true.

zzzeek 6y ago

bottom line this for me. can we have levitating cars or not ?

podiki 6y ago

As a particle physicist (no longer working in the field, sadly), this is one of the more exciting results in a long time. Muon g-2 has been there, in some form of another for debate and model building, for many years (taken somewhat seriously for 15+?), waiting for better statistics and confirmation. At over 4 sigma this is much more compelling than it has ever been, and the best potential sign of new (non-Standard Model) physics. I'm not current on what models people like to explain this result, but it has been factored in (or ignored if you didn't trust it) in particle physics model building and phenomenology for years. This result makes it much more serious and something I imagine all new physics models (say for dark matter or other collider predictions or tensions in data) will be using. Whether or not anything interesting is predicted, theoretically, from this remains to be seen. I don't know off hand if it signals anything in particular, as the big ideas, like supersymmetry, are a bit removed from current collider experiments and aren't necessarily tied to g-2 if I remember correctly.

manspacetar 6y ago
re "what models people like to explain": There was some good discussion of lepton universality violation at the end of the announcement talk. tl;dr - electrons and muons are leptons, but what if they don't interact with photons the same way? (ie the rules of physics aren't universal to all leptons)

atty 6y ago

Alexey Petrov, quoted in the article, subbed in to teach one day in my quantum mechanics class :) It was the first day we were being introduced to the theory of scattering, and I will never forget his intro. He asked the class, “what is scattering?”, waited a moment, and then threw a whiteboard marker against the wall, and answered his own question: “that’s scattering”. Lots of times, physics classes can be so heavy on math that it’s hard to even remember that you’re trying to describe the real world sometimes, and moments like that were always very memorable to me, because it helped remind me I wasn’t just solving equations for the hell of it :)

kache_ 6y ago
An old professor of mine loved the "Throw something at the blackboard" technique. Great way to get the class potheads to wake up
- forgotmysn 6y ago
  how many potheads did you have in your quantum mechanics class?
  - kache_ 6y ago
    It was an algorithms class. But I'm 100% certain there was at least one ;)
  - xzel 6y ago
    Hmm probably about a third of my graduate level QED class and considerably less in my undergraduate QM but you'd be surprised at the cross over between potheads and high level physics.
    - slenk 6y ago
      I don't see any reason that would cause them to be mutually exclusive.
  - jefft255 6y ago

wnevets 6y ago

I can't wait for PBS Spacetime to tell me what to think about this.

terramex 6y ago
They already did, 15 minutes ago: https://www.youtube.com/watch?v=O4Ko7NW2yQo https://www.youtube.com/watch?v=O4Ko7NW2yQo For those who do not know - PBS Spacetime is YouTube channel hosted by astrophysics Ph.D Matt O'Dowd, aimed at casual physics enthusiasts without oversimplifying underlying physics too much.
MperorM 6y ago
Am I the only one who barely understands anything from that show? Every episode I hear a dozen barely explained confusing terms with quantum this and higgs-field that. I feel like they care more about impressing me with how complicated this stuff is than they do about actually teaching me much. Maybe I'm just not the target audience :(
- wnevets 6y ago
  There are a lot of quantum mechanics episodes from 1-2 years ago that cause my eyes to just glaze over from all of the math and technical terms. However I feel like the newer episodes are much better at explaining things to the casual viewer rather than math nerds.
- smegger001 6y ago
  honestly i some times have the same problem sometimes, but I think it is because there is just so much background that you have to grok before you understand the discussion being had. And as that is not part of my knowledge domain I haven't spent enough time to pick it up as it will probably never effect me my daily life.
- megablast 6y ago
  No. I imagine lots of children don’t understand anything said on that show as well.
- 6y ago

uhtred 6y ago

Can anyone explain in layman's terms why this is important?

1-6 6y ago
3D point clouds and x-rays! More research can be done on low-cost devices. It puts LiDAR to shame but there are also great privacy implications. Muon tomography: https://en.wikipedia.org/wiki/Muon_tomography https://en.wikipedia.org/wiki/Muon_tomography
- whatshisface 6y ago
  Extremely precise measurements of the muon magnetic moment are not going to be useful for those applications.
Jeff_Brown 6y ago
From another comment, there's this PBS Space Time video on Youtube. https://www.youtube.com/watch?v=O4Ko7NW2yQo https://www.youtube.com/watch?v=O4Ko7NW2yQo
whatshisface 6y ago
If you take the current sum of all human knowledge and calculate something called g, and then subtract two, you get something different from the the real value of g-2. Therefore, we have identified something that lies beyond the sum of all human knowledge. That's kind of the whole idea behind being a physicist so understandably anyone remotely related to the area this belongs to is pretty excited. If you are wondering, "why does this one single number matter so much, who cares if we didn't know it before," it is because it hints at a great new theory that could change everything. Nobody knows what theory, but in the past small discrepancies in fundamental measurements have been the seeds of great theories.
gus_massa 6y ago
The electrons and the muons are very similar. We can measure the magnetic moment and make some calculations and calculate a number g. If they were perfectly ideal particles, then g must be exactly 2, so it's interesting to measure g-2. The real particles have a lot of virtual particles that appear around them and are impossible to detect directly. It's like a cloud of more electrons, positrons, photons, and other particles. They are impossible to detect directly, but they affect slightly the result of the experiments, so when you go to a lab and measure g, you don't get exactly 2. We have a very good model for all the virtual particles that appear around them, i.e. the electrons, positrons, photons, and other particles. It's call the "Standard Model". (But I don't like the name.) We can use the "Standard Model" to calculate the correction of g of an electron, and the theoretical calculation agree with the experiments up to the current precision level. We[1] can use the "Standard Model" to calculate the correction of g of a muon, and the theoretical calculation does not agree with the experiments!!! The disagreement is very small, and there is still a small chance that the disagreement is a fluke, but people is optimistic and think that it they continue measuring they can be confident enough that it is not a fluke. [1] Actually not me, this is not my research area, but I know a few persons that can. --- Back to your question: > *Why is this important? If the theoretical calculation and the experimental value disagree, it means that the "Standard Model" is wrong. Physicist would be very happy to prove that it is wrong, because they can study variants of this experiment and try to improve the model. (And be famous, and get a Nobel prize.) Physicist are very worried because they are afraid that the "Standard Model" is so good that to prove it is wrong they need to build a device that is as big as the Solar system. (And they can't be famous, and the Nobel prize will go that work in other areas.) If this result is "confirmed", the idea is to add a new particle to the "Standard Model" and get the "Standard Model II". (IIRC it already has a few corrections, so we will call the new version the "Standard Model".) It's difficult because the new particle must change the predictions for this experiment, but not change too much the predictions for other experiments. It may take a few years or decades to find the new theoretical particle that match the experiments. If you are pessimistic, the new particle will be useful only to explain a small correction that is only relevant in very accurate experiments in the lab, or inside a big star, or other unusual events. If you are optimistic, in 100 year every moron on Earth will have in the pocket a device that will use this new particle for something amazing. Or perhaps something in between. Nobody has any clue about this.

glofish 6y ago

Amusingly - fittingly for our times - in the same issue of the exact same journal (Nature) another paper has been published that indicates that the prior, so much "hyped" discrepancy might be due to the theory having being applied inaccurately in the past. When computed with the new method, the experimental and theoretical models align far more accurately. So now all that matters is what kind of article do your want to write. A sensationalist one to get eyeballs or a realistic one that is far less exciting. Thus the exact same discovery can be presented via two radically different headlines: BBC goes with "Muons: 'Strong' evidence found for a new force of nature" https://www.bbc.com/news/56643677 https://www.bbc.com/news/56643677 > "Now, physicists say they have found possible signs of a fifth fundamental force of nature" ScienceDaily says: "The muon's magnetic moment fits just fine" https://www.sciencedaily.com/releases/2021/04/210407114159.htm https://www.sciencedaily.com/releases/2021/04/210407114159.h... > "A new estimate of the strength of the sub-atomic particle's magnetic field aligns with the standard model of particle physics." There you have it, the mainstream media is not credible even when they attempt to write about a physics experiment ...

gameswithgo 6y ago
What were the times when journalism was better?
devb 6y ago
This is an incredibly complicated and abstract subject, yet you have somehow managed to boil it down into a sweeping generalization about the basics of media and reporting. Masterfully done.

Anon84 6y ago

I’m getting a “faster than light neutrinos” feeling about this one

mjevans 6y ago

I read the release written by the lab. https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/ https://news.fnal.gov/2021/04/first-results-from-fermilabs-m...

j4yav 6y ago

There is a nice video explanation from PBS at https://youtu.be/O4Ko7NW2yQo https://youtu.be/O4Ko7NW2yQo

seventytwo 6y ago
PBS, man. Just steadily and reliably educating everyone for years now. Good shit.
- dimator 6y ago
  SpaceTime (that channel) in general is of impeccable quality and production value. Definitely worth subscribing.
  - Crash0v3rid3 6y ago
    Worth the patreon contribution also.

atty 6y ago

As someone who has worked in fields that use lattice calculations (on the experimental side), the new calculation is interesting, but I would not say it’s particularly convincing yet. Lattice calculations are VERY difficult, and are not always stable. I am not questioning whether they did their work well or not, just pointing out that in high energy physics and high energy nuclear physics, many times our experimental results are significantly better constrained and also undergo significantly more testing via reproduction of results by other experiments than our theory counterparts’ work. Is it possible that all of our previous experiments have had some sort of correlated systematic error in them? Unlikely, but yes. Is it more likely that this lattice calculation may be underestimating its errors? Much more likely. Another interesting option is that one of the theoretical calculations was actually done slightly wrong. My first guess would be the lattice result, since it’s newer, but both procedures are complicated, so it could be either.

glofish 6y ago
I am not sure I follow the logic. The new computation aligns with the experiment. Why is it more likely for it to be wrong than the calculation that shows the theory deviating from experiment.
- atty 6y ago
  The old calculation relies on older experimental results that have been verified by multiple experiments - so if the older value is wrong, it means either the calculation was done wrong (possible), or the experiments all have had a significant correlated systematic error that has never been caught (also possible). However, I’d say both of those things are relatively unlikely, when compared to the probability of some small error in a new paper that was just released that uses a new method that involves lattice calculations. This is all a balance of probabilities argument, but from my experience in the field, I’d say it’s more likely that any errors in calculation or missed systematics would be in the new paper. However, I’m an experimentalist who has worked close to a lot of this stuff, not an actual theorist, so I’d love to get a theorists interpretation as well.
  - 6y ago

gonational 6y ago

Science is a never ending series of incorrect observations, each disqualifying the penultimate while asserting the ultimate is axiomatic. When you're young you get excited each time a new breakthrough is happening. If you manage to grow up, you get tired of the pattern, and the signal to noise ratio starts to look like a good statistical P value.

imvetri 6y ago
That is very true. Knowledge – expands, Space exploration knowledge – expands, Sub atomic exploration – expands, (muon and we may even find its sub atomic particles as well) Space – expands, Number series – expands, Fibonacci – expands. Science expands external knowledge and shrinks self-knowledge, Spirituality shrinks external-knowledge and expands self-knowledge. Be warned when something expands. Be warned when something shrinks. E=mc^2 where c is not just the speed of light, c is the speed of space expansion as well. Mass expands to form energy (science) Energy shrinks to form mass (spirituality)

deleted 6y ago

[deleted]

eevilspock 6y ago

> "The concordance shows the old result was neither a statistical fluke nor the product of some undetected flaw in the experiment, says Chris Polly, a Fermilab physicist and co-spokesperson for the g-2 team. “Because I was a graduate student on the Brookhaven experiment, it was certainly an overwhelming sense of relief for me,” he says." A committed scientist should worry about having such feelings, even though it is very human. It represents a possible source of non-independence of tests and of scientific bias.

tompagenet2 6y ago

Genuine question from ignorance. Is this related to this work at CERN? https://www.theguardian.com/science/2021/mar/23/large-hadron-collider-scientists-particle-physics https://www.theguardian.com/science/2021/mar/23/large-hadron...

dukwon 6y ago
Maybe. There are plenty of attempts to explain g-2 and LFUV in B decays in one go. But really there's no way to know for sure yet.
yk 6y ago
Yes and no. It is two very different experimental situations, the magnetic moment is at rest (well, in an accelerator but the rest frame is defined by the muon) and the R_k anomaly is in an collision. On the other hand, as a theorists the immediate thing one thinks about is lepton universality, that the only difference between a electron and a muon is its mass, is violated. So there will be a lot of work this year on trying to explain both results at the same time.

yaya69 6y ago

And the gluon is the opposite

mkaic 6y ago

I highly recommend the YouTube channel PBS Space Time's coverage of this, it's informative, well organized, and accessible even to someone like me who doesn't have any background in physics.

cambalache 6y ago

https://www.math.columbia.edu/~woit/wordpress/?p=12292 https://www.math.columbia.edu/~woit/wordpress/?p=12292 This just PR fluff, with the paper published today in Nature there is no discrepancy with the SM. Mother Nature loves Ockham's razor.

lolthishuman 6y ago

It’s simple. The universe is electromagnetic. The Bose-Einstein condensate is the aether in most dense form. Everything evaporates into lower densities by means of rotation via the torus and vortices. Everything is pressure finding equilibrium spread throughout densities in fluid. Easy to reason about. The sun is hollow and incompressible aether inside, which is why it’s cold. The surface is electromagnetic activated by the currents spread throughout the galaxy. Every sun is like a lamp. Every sun is a plasmoid. Outer space is least dense form of the aether. Sound makes matter. Fun!

shrimpx 6y ago
Is there legitimate support for this hollow sun theory, or is this a fringe theory like flat earth and so on?
- Arjuna144 6y ago
  I dont know about hollow suns and stuff. But what he said in the beginning has some reason. Check some of this guys papers: https://file.scirp.org/Html/8-2180368_91083.htm https://file.scirp.org/Html/8-2180368_91083.htm
- SAI_Peregrinus 6y ago
  The EM universe hypothesis is not much better than the flat Earth one. Similar levels of agreement with observed behavior.
  - lolthishuman 6y ago
    Not much is published that makes sense unfortunately. The EM universe hypothesis has its flaws because it’s not United on first principles connecting the aether and primitive constructs like the torus and hyperboloid. It’s dangerous for many easy to reason about considerations. Most people’s lives are reputation based and confined to incentives of pay that prevent such topics being published or discussed. Hard problem.

wombatmobile 6y ago

I read the headline wrong and came here to find out how mutton is magnetic at all.

imvetri 6y ago
hahaha

irjustin 6y ago

The NYTimes[0] article takes a more measured tone and reports 1 in 40,000 confidence, ~5 sigma. 5 sigma results have disappeared (even 6-sigma) upon independent testing, so more testing is needed. [0] https://www.nytimes.com/2021/04/07/science/particle-physics-muon-fermilab-brookhaven.html https://www.nytimes.com/2021/04/07/science/particle-physics-...

dtrain2017 6y ago

Why is it called a particle accelerator when it's possible for the particle to go both ways: forwards and backwards? Don't they measure the difference in the direction of the particle as determined by its virtual cloud? more energy emitted from the cloud = forward and vice-versa. Loved the explanation and accompanying illustrations.

imvetri 6y ago

Knowledge - expands, Space exploration knowledge - expands, Sub atomic exploration - expands, (muon and we may even find its sub atomic particles as well) Space - expands, Number series - expands, Fibonacci - expands. Be warned when something expands, you can never reach. Its not the destination, its the journey :D

peter303 6y ago

The muon was the first non-standard matter particle and 2nd transient particle discovered in 1937. It lead to new physics then and continues to suggest there is new physics.

ngcc_hk 6y ago

Very interesting indeed. But if one read again all depends the idea of quantum field theory or "like all charged particle it interacts with its own field to create virtual particles" etc. It is hard to understand for old guy learning basic physics long time ago.