Particle Physics' Most Famous Anomaly (almost) Solved
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- Опубликовано: 27 мар 2024
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Three years ago, there was a frenzy over an experiment at Fermilab that confirmed anomaly of the muon - a fundamental particle in the standard model. Since then, physicists have debated whether the theory needs to be revised or whether there is something wrong with the calculation. A new paper now says it's neither.
Paper: journals.aps.org/prl/abstract...
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Well, they opened a can of Pions, you mean ?
I opened a can of Pringles the other day, same?
Well played
Were they tasty?
@@Nulley0 Not really, but it was better than the can of wurms we had a while ago.
@@Nulley0 yes.
Muon, not to be confused with a spherical cow in a vacuum which is a moo-on.
They're not spherical. That's just an approximation. The cows exist in a cloud of improbability and can only be detected by injecting a load of bull. You can see that I'm milking this for all I have...
@@simongross3122 Buffalo can you go?
@@zoetropo1 When I get my wings, maybe
A muon does not distribute it's milk uniformly. It also rotates between whole, %2, and skim.
@@fehmeh6292 That's a really good point and thank you for raising it.
It probably means that muons don't have spin, but have degrees of skim instead.
And it reveals the possibility of other particles such as soyons, almons, etc. These might prove to be virtual and not real, although it might depend on the observer.
Then there are other families of particles involving goats or sheep which would give rise to baa-ons.
The particle zoo is so exciting!
As a software developer, when I hear of this sort of "we found the bug 6 steps back" kind of problem, I start wanting to see the "build graph" for all of physics. It would be an interesting project to try to aggregate all the calculations everything is built on in a form that would allow researchers to re-run them, either in their original form (giving access to all the intermediate values) or in modified form (simplifying checks of how changes in fundamental assumption alter other things).
It's spread over lots of bottom drawers and shoe boxes.
@@BANKO007 I'd love to see people working to fix that.
@@benjaminshropshire2900: Would be good, yes. Of course, those calculations in many cases have probably _only_ been done by hand, and properly rerunning them all on a computer probably calls for C/C++ for speed, but Prolog for behavior...
It's like finding a numerical methods/catastrophic cancellation bug in one of the core statistical packages they all use.
@@absalomdraconis Likely true, to some extent, but anything done by hand doesn't need really fast code for a computer to do it in a negligible amount of time. Writing the code is the hard part. (Side note: things like symbolic math manipulations are hard for computers, but even there, it's not that hard to get them to check works that humans already did, e.g. proof checkers.)
What always made me slightly uncertain/dubious (beyond never having been a physicist nor able to do the math myself ;) about this experiment was, while it was conducted in two different places, Brookhaven and Fermi labs, it was done on the same piece of equipment which was shipped from Brookhaven to Fermi labs. I'm sure that was top on the experimental physicists' minds but wouldn't this cut into the 5 sigma level of certainty?
I have always wondered about this as well. Because its nice that this Equipment predicts the same result with 5sigma but what if there is an general systematic error involved.
there are much more experiments than shown in the video. Muonic hydrogen type experiments were like 5-10. Plus few experiments on e^+e^- colliders in Russia and Japan.
@@Mrluk245 That's precision versus accuracy. The measurements are very precise ( up to 3 sigma) but might not be accurate. Yet the only reasonable way to measure accuracy without reusing similar equipment is to calculate the same property from a different set of axioms. In this case, with the help of the pair of pions.
Ofcourse, then you can restate your question of accuracy of the pion/muon experiments compared to any other axiom used in the paper. But the end result will be that eventually, all known experiments will have values that are precise and accurate, at least relative to each other. This is why the meter is defined as the speed of light over time instead of any form of absolute distance that we cannot measure.
And all their experiments operated with anti-muons, not with muons.
Agreed. It would be a lot more convincing if the equipment had been built from scratch in both cases.
This smells like experimental error to me.
1:13 we engineers be like: that's literaly the same number!!!
2:04 Funny, I personally know one of the authors right in the middle of the block. He's a geodesist (handles alignment of the instrument). "7" means Fermilab, I assume.
For Sabines relativity course on Brilliant: make sure your math is fresh, although a good basis at high school is sufficent (I mean: the schooling from 16 till 18 years, so not higher eduction). However, you have to know how to multiply matrices.
Also: after you've done a lesson, study it. You have to grasp it well enough to be able to do the next one. In the beginning it will work out, but especially the later lessons of the course will become hard if you don't know enough of the first ones.
Except for that, I would like to see that in a book.
I have often wondered if one or some combination of the consensus rules of mathematics might begin to introduce noise at these levels of precision. The reason being the difference between proving something is necessarily the case and proving something is necessary for "well-functioning" use of further mathematical approximation.
Physicists often enough have a creative way to interpret mathematical theorems.
Well, I can only hope this paper was published on 3/14.
Thanks, Sabine! 😊
Stay safe there with your family! 🖖😊
1st April, that is today
Im half way through your book "existential physics" and I'm loving it. Its a nice change up from reading books written buy people who lived 1500 years and ruled roman empires haha. Also, my anxiety has decreased. Its amazing what a little extra understanding of the big picture does for the restless troubled mind.
You are an amazing presenter who can breathe life for the 'every-day person' into a highly complex and specialised area. Well done Sabine.
It's no coincidence that the problem is PI-ons making the calculation only aROUND the experimental finding.
Your joke deserves better fortune. 👍
@@MassimoAngotzi This joke should have been made on March 14
I love the humor in the presentation.
The problem has been solved for a while, it's called lattice QFT, because it actually works with proper QFT and not just scattering approximations (of course both are perturbative)
I truly enjoy catching up with science news from your channel.👍🤠
2:22 does not show the prediction vs the observation. It shows the data-driven result from the new paper vs the previous results obtained from lattice QCD.
exactly! well spotted. lattice-QCD predictions fit well with the measure value in fact
That makes me think they got the slides out of order somehow. That slide clearly belongs, just not at that exact moment.
@@mal2ksc the labeling is wrong though
Having done the plot, I couldn't agree more :)
Yes, good catch!
My modest physics knowledge literally grew up with this. Is there a calculation for the decay of twitter discussions, too? Navier-Stokes?
I suspect there is, may be only available to Twitter insiders.
_"Is there a calculation for the decay of twitter discussions, too?"_ - Probably Dunning-Kruger.
@@renedekker9806 😆
@@aniksamiurrahman6365I assume, they are still calculating and therefore not to find on those debates.🙃
Well this is a real problem. The only way to calculate the decay of twitter discussions is to participate in the the twitterverse. This adds uncertainty as the observer becomes an actor and it becomes impossible to work out what would happen without that observation. Oh dear, I've just gone cross-eyed.
I love your channel! Your presentation style is charming, and your accent is addictive to what little hearing I still have. Sabine, you have really brightened my days, since I became disabled.
It's very easy to solve this problem with a simple new partical, a mewon would fit perfectly.
Mewtwo would fit even better!
2:21
"..testicules.. " 🤫🤣🤣
If a mathematician thinks your calculations might be incorrect, it's probably a good idea to check again.
It is definitely important to care more about the quality of our calculations and data, than an end goal new physics scenario!
I think this topic is most interesting because of its immediate applications in Lattice QCD, but it’s always good to have that back motivation too!
"If a mathematician thinks your calculations might be incorrect"
That's not what happened in this case.
@@bjornfeuerbacher5514 but it is. Might I assume you are relatively new to following Sabine?
@@timhaldane7588 "but it is."
No, it isn't. Sabine explained in the video that the problem is with _data_ which goes into the calculations. _Not_ with the calculations themselves.
Additionally, no mathematicians were involved here, this was a discussion among physicists.
"Might I assume you are relatively new to following Sabine?"
No, I've been watching her videos for several years.
Particle physics is not based on solid mathematics, there is a lot of heuristics and hand weaving. This is a fact which most (?) physics are well aware of since decades. However, nobody found a solution since decades. Because the results fits quite well, this pseudo mathematics is usually accepted. The mathematican Folland, the writer of the well estadlished book „Quantum Field Theory: A Tourist Guide for Mathematicans“ calls this „bargin with the devil“.
Thank you for telling us this wonderful information as a scientist. We hope that the number of scientists who not only focus on their field and work, but also raise awareness of people like you will increase.
I wonder if the 4.2 sigma deviation in -2 muons corresponds well with the difference in the universe's mass for normal matter as opposed to dark matter and dark energy.
That's strange. Even in Switzerland - NB outside of CERN - pions are studied now for 40 years. So enough trustworthy data should be around.
I wonder if they have tried redoing the calculation over and over with inputs that are slightly different but still within the measurement confidence intervals from experiments
Yes, that was why confidence intervals had to be shrunk,so that we could rule out the possibility that we just had to use values that weren't considered the most likely, but still possible. That took some time but was eventually successful.
So a sensitivity analysis? I'm sure they wouldn't have forgotten to do that.
I'm just waiting for them to discover the moron alongside lepton, boson, and muon.
Interesting, keep us informed Doll
*oboe music plays*
I could tell she was bad news as soon as she mentioned statistical analysis, but I guess I always have been a sucker for a dame with with a p-value lower than 0.05... or at least that's what I thought.
Thanks for the shortened intro theme. PBS Eons also does a good job with this.
Thanks for the explanation, far more complicated than what I think....
What I've learned today is that Physicists make a lot of assumptions and this is an easy way to fail. In software development there is a technique called 'branching', we safeguard against the ways our assumptions could go wrong.
Hi Sabine, huge fan of yours, my Dad and I love watching all your videos together!
In my very uneducated opinion it seems as though there are more and more theory’s being proposed that are missing a solid “base”.
A “recent” (2010 I believe) example that comes to mind is the theory of Entropic Gravity which is reliant on the assumption that the Holographic Univers theory is correct.
How can we attempt to understand how space-time curves if we aren’t even sure what space-time is? (If space is emergent or fundamental, or if it is continuous or discrete)
Similar to a point you made about astronomy, where the phrase “something that shouldn’t exist” seems to come up a lot, how can we create a tower of knowledge if we are unsure that we are building on the right base?
Thanks for everything you do
An issue is that science isn't like building a tower of knowledge,starting from fundamental true things and adding to it; it's more like inventing new building materials and having to rebuild our houses anew each time.
We didn't go from stuff, to atoms to subatomic particles, with each step proceeding logically from the last and adding to what we knew. Instead we asked questions about what we knew, looked for things we couldn't prove and our new discoveries changed what we already knew entirely. We didn't com across atoms because someone saw one and built a theory on it. Rather we took the two options,atoms exist or they don't, and asked what we could look for and find in either case.
All theories must start without a solid base, or they'd immediately be proven. First you assume, then you look and test. You search *for* the solid base for your theory and if you find it then everything that came before must be rebuilt according to this new understanding.
There should be a multitude of theories with their own strange assumptions;that shows that we are thinking. There should be experiment to test them, that shows we are working. A theory becomes worthless only when people cling to it after it has been shown to be false,something science is certainly not immune to.
She describes the trouble with mainstream physics and scientific establishment very accurately in her book 'Lost in Math'. Her books are a pleasure to read.💚
What numerical type did the calculations use? Eight-byte floats have about 17 digits of precision; the accumulated roundoff error could overwhelm the errors in the data. I'd like to get a Power9 box, which has sixteen-byte floats.
Which would you rather have? 1. the correct answer to a physics problem that has stumped the academic world...or 2. the ability to levitate.
4:27
I think the step order of the process is wrong.
The experimentation step should be the last step.
1- prediction
2- approximation
3- calculation
4- experimentation/testing
This always bothered me honestly, even though I'm far from an expert the desire for what seemed to me to be an obvious mathematical or experimental error to be a gateway to some grand new physics always felt like desperation to me. It seems like physicists just really want there to be more to discover than there is to wiggle out of the uncomfortable thought that we might actually have things mostly figured out with a few small holes to iron out and then what's left is a purely deterministic universe with no free will, no many-worlds multiverses, no extra dimensions, and no special mysteries
I strongly suspect that free will is an illusion, and the many-worlds interpretation of quantum theory just sounds silly to me.
However, I expect there is still some new Physics to discover, or else proper explanations of dark matter, dark energy and some other phenomena that aren't really understood yet.
With any luck there may even be something entirely unexpected, like faster-than-light travel. It wouldn't be the first time that Physics seemed almost completed, only for whole new areas to open up. We won't know unless we look.
You missed the part where quantum mechanics is the opposite of being deterministic.
@@zray2937 Thats one interpretation, the one that leads to most of the seemingly weird contradictory things in quantum physics. Other versions like the pilot wave interpretation are deterministic and the deterministic models seem to iron out a lot of weirdness. I think Sabine even has a video about it.
Yes, she has, and she herself works on superdeterminism to solve the measurement problem. Also she describes the hole error stuff in physics very accurately in her book 'Lost in Math'.
I love this channel. The nerd in me is sooo happy
3:14
It's pronounced " Let us "
Please don't start a war, I just want the known facts as they pertain to these calculations. I just want to know this, please just stick to the facts and have anyone trying to start a war dealt with in the most unbiased manner that commenters are capable of:
Did they use the traditional definition of pi?
Or was it 2 pi r
Or some other definition that Sabine did not elaborate on in this video?
These complications are complicated!!!
I was hoping for new physics but thought it was something like this. So in summary various physicists become pi-eyed after mu-sing over this problem for (of?) a moment...
Yup fixing a bug often leads to a cascade of other issues.
Hi Sabine. If you read this comment, I hope you are a friend of the good mood 😊
Hi hottie.
Muon has always been my favorite particle
I woke up this morning to two different videos claiming Betelgeuse was going supernova now. I remember thinking, "Oh, Sabine is going to rip these yahoos a new one."
Did they release this on 14 March?
Anyone else bothered by the fact that the g-2 (at 1:13) in this video is off by a factor of about 200 million ? There are way too many zeroes after the decimal point AND 0.00116... corresponds to (g-2)/2, not g-2. The forest for the trees...
its also amazing how these are preoccupied over a 0.000000000000000000x difference, whereas in other fields we are basically at O(1) discrepancy and we are totally fine.
Thanks for increasing the frequency of your videos - I watch almost every one now - a daily scientific vitamin shot.
Even Richard Feynman had a problem with infinity and how it's dealt with in mathematics and it's the same today and I really like him due to the fact that he's really humble in the way he speaks and it says it said that he only had an IQ of 128 so that really says something about that particular measure of intelligence.
At almost the same time as Fermilab announced the original results for their g-2 result, another team announced the results from a different technique to make the prediction. They claimed their result agreed with the measurement (and there was no discrepancy). I believe it was called the BMW prediction based on the university teams involved. Has there been any advancement in this prediction, or is the prediction discussed here related to the BMW prediction.
Goes a Muon to a bar...
(already funny enough)
an electron comes out and the neutrino is missing.
@@steffenbendel6031 And the barman, in error, offers it some pi
I was thinking recently about whether this g-2 tension has been resolved. After a short search, I found the possibility that electron-positron collision data may be wrong, a thing Castelvecchi described in his piece in Nature on August 17, 2023. But that came from Novosibirsk, and somehow I do not trust anything Russian, nowadays. Sorry, but I can't. So I definitely prefer the pion solution
I am not an expert , but our Russian colleagues in pure Science deserve our respect I think.
@@carlbrenninkmeijer8925 Too many of them support the imperial politics of the Kremlin murderer. I speak Russian so I know what they say to each other. Anyway, this result needs certainly independent confirmation.
@@arctic_haze It is all a tragedy ! It is a dark haze for humanity !
@@carlbrenninkmeijer8925 Agreed. By the way, I know you are not a Russian troll. They always vanish if their clown president is mentioned in the way I did 🤡
I cannot see the correlation between politicsl opinions and doing science?
\
This is exciting. A ripple in a pond, that causes an avalanche across the world.
butterfly-effect
Always a pleasure.
My layman outside impression is that in the last couple of decades there's been an inflation of confidence in fuzzy methods across many scientific disciplines and that there's a lot of cleanup ahead of us.
Exactly my experience as interested layperson. Reading Sabine's book 'Lost in Math' cleaned up my brain. It explains a lot.
I disagree completely, these dispersive methods and lattice QCD both have very understandable errors, it would be very wrong in my opinion to classify them as “fuzzy” methods. If anything our errors were more conservative, not less.
@@genessabUnderstand, I think it really depends on the special topic.
@@genessab Of course, my stated impression is itself fuzzy and a jumble of many different reports reaching me over the years. I don't have the expertise to personally evaluate the merit of a lot of them, and I'm not confident that it applies in this case. That being said, across many fields of research, especially those of interest to the public, the heuristic of gauging the level of certainty by the confidence expressed in the conclusions doesn't work as well for me as it used to.
1:13 I am afraid of the small misplacement between the two numbers in the graphic.
Assumptions are the bane of science.
Impressed.
I dont get why there are so few fundamental particles. Like why is the universe so simplified.
Really only 3 that make stuff, 4 max.
on the other hand, I don't get why there are so many? whats the point of all the muons and taus and strange quarks when they all just immediately decay into like 3 particles that actually do things. So much additional complexity is just strange when you think about it And then in that case, why only 3 generations? why can't it just keep going up infinitely?
@@soasertsus there could indeed be more generations of matter, their would need to be quite large at this point in order to be suppressed enough that we wouldn’t see their influence in our experiments. But yeah, this question of why there are only 3 generations of matter is one of the most fundamental unsolved problems in particle physics.
For all that difficult math those dang muons better have a real good song and dance😊
@SabineHossenfelder finally I can comment on your channel with something more than just fan mail :)
When I studied physics at university I actually had Fred Combley as one of my tutors in Sheffield, he was famous (it turned out) for one of the big "muon g-2 experiments" I think in 1974 so 50 years ago this year, he was a lovely lovely man, sadly he died of illness some years ago but I have fond memories of being taught by him, I even had the pleasure of having him as a mentor for my experimental masters project building a water moderated neutron detector.
Try reversing the analogy input. Use a measure of regular data minus the change, then subtract a full unchanged data from unchanged. Of course it seems simple. If amaebas are the course of balanced energy and not micro organisms, then how many are left to keep a balance sheet?
What does the test say about unchanged neurons, neutrons or well you get it. We can ask why it carries special weight. Is it airs filter or growth of the magnetics?
Didn‘t I have learned in recent video from Sabine that gravity is *not* a force… 😉
I saw something on RUclips about muons and their decay. The lady said the muons lasted longer than expected while travelling through the atmosphere to hit the earth. If I got it right she said it was because of their speed. They are moving so fast they experience time dilation and don't decay as predicted. She also said something about it was E=mc, and not E=mc squared. So I guess that's why I stay so confused about science stuff. Lol. One channel says this is so and another channel says that is so. I guess I should find another hobby.😊
"the muons go in circles until they decay, a process that you can also observe in Twitter discussion". Who says particle physics isn't relevant to everyday life?
That guy sporting a spiffy hat and pipe was bohemian.
1:30 на что распадаются мюоны, они же элементарные частицы, на что распадаются элементарные частицы?!
"... 5-sigma; that's less than a 1 in 3 million chance of it being a fluctuation...". I really enjoy this channel for the most part, but the one thing Sabine consistently gets wrong is properly interpreting and communicating p-values. Please, Sabine, if you read this-get this right! -Tom (physicist and statistician)
Lattice Calculations: Bethe? Or others? I would like to hear more!
Shortly thought that my local automotive OEM was doing some physics experiment and was disappointed when I saw the original paper
will all this help me get a better fast food Hamberger or what ?
With each video of Sabine my IQ rise by 10 points
Haha, that surely is the reason, why she works so hard.😊
It always irks me when i hear quantum physicists say "GR is at best incomplete and may be wrong" and then I see how many assumptions are just made and treated like fact in QM.
Well yes, QM is also incomplete and may be wrong; both theories cover complementary physics but cannot handle the other's domain.
@@garethdean6382 A bit like Yin and Yang but with more numbers.
Err, particle physicists also say all the time that the standard model of particle physics is at best incomplete and may be wrong, so what's your problem?
Additionally, even with the assumptions made in particle physics, most of the results are still __way__ more precise than those in GR.
@bjornfeuerbacher5514 I've never heard that. It's always "this is the best model of the universe and the natural world" and "matches perfectly down to fifteen decimal places"
@@garrett6064 That it's the best model we have and that it matches observations to ten (not fifteen!) decimal places does not contradict that particle physicists are well aware that the standard model is incomplete.
And again, they say that all the time! What do you think the LHC was built for?!? Yes, one of the reasons was the search for the Higgs boson, but all of the other reasons was searching for extensions of the standard model!
At some point, the nested Feynman diagrams must be attenuated in order to return a meaningful vacuum energy. Finding a clue for that would mean progress.
Muons and pions have similar masses as compared to protons and neutrons, but they are utterly different from each other. A muon is a simple pointlike entity which only knows the electroweak interaction. A pion is a composite entity apparently made of two quarks which is dominated by the strong interaction. I can well believe that a calculation of the muon g-2 overlooked the contribution made by pions. Is that what has happened?
Maybe there was some editing to condense this video as there seems to be a confusion between the lattice calculation and the data driven estimate where the video makes it sound like these are both steps in one calculation to get the theory prediction. Instead these are two different methods for obtaining theory predictions in the standard model. The data driven prediction gives this very large ( now ~ 5 sigma) deviation from the experimentally measured value, while the lattice result which is fairly new (2020) is closer to the measured value. Since it was the first time a lattice calculation had been carried out at this level of precision the first step was to get comparisons from other lattice collaborations. This happened even more recently so it really looks like there is a tension between lattice and data driven estimates. The new paper is comparing a particular part of that calculation in the data driven method to the same part of the calculation from the lattice method and that has led them to identify a particular contribution as a likely cause of the discrepancy between the data driven method and the lattice result.
And as far as I as told by colleagues, lattice calculations agree with experiments so muon anomaly issue is kind of considered solved for the last few years.
Just hold on there a magnetic moment...
If that’s not one of Sheldon’s lines from the Big Bang Theory, it really should have been!
"and that's why people are afraid of particle physics"
Bless you
In the end, physics is just a programmatic quirk in the simulation we live in, and the chap who wrote it goes between "whoopsies" and "haha let them figure it out".
Wasn't this tension already solved by the BMW calculation of the HVP contribution ? (see 2002.12347)
"The 𝝅s! The 𝝅s!" - As they say in Liverpool.
Bad measurements, bad observers? Has anyone seen my peanut butter and jelly sandwich?
It's in orbit next to Russell's Teapot.
I find it hilarious how many people actually get their names thrown on these papers now! There are specific rules in scientific methodology about naming conventions and I seriously doubt that every single one of those people actually had a significant role in that actual research!
If information goes into twitter but doesn't come out, that makes it a black hole. The trick is efficiently harvesting the brief burst of energy emitted when somebody rage quits.
It's been long known that when enough heavy particles known as morons congregate in one place, their shared force creates a resent horizon. There's no way to get anything useful out of it.
if those authors are the Sherlocks of particle physics, who gets the title of "Batman" of theoretical physics?
Well the point of Lattice is that you do not need that other data that we know is controversial
Let me rewatch and see if I can get a better grasp
'a process also observed in Twitter discussions' - love it
It’s like making a mistake after the first simplification
So basically, the existence of the universe is due to a rounding error.
I love the way you. Sound.
gravity isn't a force. it's a property of space. x,y,z,g. while x,y,z can be measured with a ruler, gravity also needs a clock
Actually, it's a propery of spacetime, not of space alone.
Why you condescend previously about gravity not being a force and then continue calling it a force afterward?
Physicists do it all the time. I guess it's like saying sunrise instead of earthdown.
Gravity is intriguing. If you are curious, then Bing image search "Bode's Galaxy Poster" and "Giant Biggest Whirlpool" by whirlpoolhitman. I've found that galaxies in general are strikingly similar to vortexes.
Whichever way it goes; wrong theory or wrong calculation, this is very exciting!
There's a third option: Wrong interpretation.
The pion ripple effect - or it may turn out to be a tidal wave.
When your relative error is 0.00019727% and you're worried about it, I'm thinking you're procrastinating on your admin paperwork...
I didn’t get her before but now I love her
My math stayed in a pre twitter world when there were only protons neutrons and electrons and the Earth was flat.🤣
Wait? So they measured the decay products? Doesn't that release energy? Did they account for that energy or am I missing something about these particles? Like that energy turns into one of the decay products but doesn't release energy?
"Did they account for that energy"
What do you mean? This is about a magnetic property, not about energy.
It releases energy in the form of particles, that these detectors are designed to measure. It is very well understood how energetic the muons initially are, and what decays they will go into.
And I thought the [p]rinciple [i]nvestigators did it..