Muon G-2 Experiment at Fermilab Finds Hint of New Particles(quantamagazine.org)
quantamagazine.org
Muon G-2 Experiment at Fermilab Finds Hint of New Particles
https://www.quantamagazine.org/muon-g-2-experiment-at-fermilab-finds-hint-of-new-particles-20210407
9 comments
Someone linked to this Twitter thread in the other discussion, from a theorist (one I happen to know a very little, from back in the day): https://mobile.twitter.com/GordanKrnjaic/status/137983430884...
Not a lattice theorist, but I can tell you lattice stuff is very hard, and also very cool to be calculating such bare bones nature on a computer. Lattice results can be hard to parse for the outsiders, and I know there is often debate over how trustworthy the results are when it is so hard to check (you don't just build and perform another experiment). That's not to say the people doing it aren't very smart and capable, but it is an unbelievably difficult problem to do, and just like experiments have problems and errors, so to does lattice calculations. Treating them like almost another form of experiment is perhaps best (how does it fit in with other experiments? with theory expectations? how can we know if it is correct or not and correlate with other results? etc.). In other words, theorists and model makers (like work I used to do), may or may not include lattice results based on how they feel about some result (or what it does to their own model....).
Not a lattice theorist, but I can tell you lattice stuff is very hard, and also very cool to be calculating such bare bones nature on a computer. Lattice results can be hard to parse for the outsiders, and I know there is often debate over how trustworthy the results are when it is so hard to check (you don't just build and perform another experiment). That's not to say the people doing it aren't very smart and capable, but it is an unbelievably difficult problem to do, and just like experiments have problems and errors, so to does lattice calculations. Treating them like almost another form of experiment is perhaps best (how does it fit in with other experiments? with theory expectations? how can we know if it is correct or not and correlate with other results? etc.). In other words, theorists and model makers (like work I used to do), may or may not include lattice results based on how they feel about some result (or what it does to their own model....).
[deleted]
Can’t upvote you enough. This is driving me crazy-curious. It must be eating at the HEP folks... unless it isn’t, hah.
If this becomes a quagmire nested with the muon quagmire within the new physics quagmire. I will surely have to find a way to renormalize my self energy.
If this becomes a quagmire nested with the muon quagmire within the new physics quagmire. I will surely have to find a way to renormalize my self energy.
The class of integrals that QCD solutions belong to is known to be NP-hard. It is not known specifically that QCD itself is NP-hard but it is suspected to be by many.
Would this mean that either the strong Church-Turing thesis(any model of computation based on physical reality gives the same class of problems solvable in polynomial time as a Turing machine) is wrong or P=NP?
If what is suspected is true, then yes, strong Church-Turing is false. If there's a symmetry in QCD that makes simulation possible in polynomial time, i.e. a helpful property that is true of QCD specifically but absent from the more general class of integrals its solutions belong to, then no.
If you're looking for something to raise your hair even farther, some suspect that gravity is outright uncomputable[0] due to the unclassifiability of 4-manifolds and the expectation that quantum gravity will require summing over possible spacetimes.
Since all of our computers are built with QED, it should come as no surprise that everything else made out of QED-obeying-matter, like Turing machines are imagined to be, is equally difficult to compute and equally powerful at computing. I don't see why you'd expect the other field theories to fall in to the same computational class.
[0]https://arxiv.org/pdf/gr-qc/0506019.pdf
If you're looking for something to raise your hair even farther, some suspect that gravity is outright uncomputable[0] due to the unclassifiability of 4-manifolds and the expectation that quantum gravity will require summing over possible spacetimes.
Since all of our computers are built with QED, it should come as no surprise that everything else made out of QED-obeying-matter, like Turing machines are imagined to be, is equally difficult to compute and equally powerful at computing. I don't see why you'd expect the other field theories to fall in to the same computational class.
[0]https://arxiv.org/pdf/gr-qc/0506019.pdf
PBS Spacetime just released a video on this experiment. https://www.youtube.com/watch?v=O4Ko7NW2yQo
So did Fermilab ;) https://youtu.be/ZjnK5exNhZ0
Definitely worth checking out the rest of the videos on both those channels.
While we’re at it, check out 60 Symbols’ channel for great physics discussions that hardly ever (thanks Brady!) include equations https://youtube.com/user/sixtysymbols
Definitely worth checking out the rest of the videos on both those channels.
While we’re at it, check out 60 Symbols’ channel for great physics discussions that hardly ever (thanks Brady!) include equations https://youtube.com/user/sixtysymbols
Warning. Sixty symbols is a black hole. It will devour all your free time.
Check out this phyics.stackexchange answer:
https://physics.stackexchange.com/a/627852/386
I've been involved in one of the light-by-light theory groups a long time ago. The situation with theoretical prediction is not as clear.
Regardless of whether this is a real result, I always had trouble "trusting" the "Standard Model" when I was at university. There are too many knobs to twiddle, and levers to pull in order to get the results. The mathematics is non-trivial. Just reading the article gives you an idea of how difficult it is to make predictions from the model.
Compare it to this comment about General Relativity:
"Widely acknowledged as a theory of extraordinary beauty, general relativity has often been described as the most beautiful of all existing physical theories." (via wikipedia - Landau & Lifshitz 1975, p. 228).
(ignoring the cosmological constant, of course).
Compared to most, or all, other physical theories, the Standard Model feels like there's something much simpler set of equations underneath waiting to be discovered.
Compare it to this comment about General Relativity:
"Widely acknowledged as a theory of extraordinary beauty, general relativity has often been described as the most beautiful of all existing physical theories." (via wikipedia - Landau & Lifshitz 1975, p. 228).
(ignoring the cosmological constant, of course).
Compared to most, or all, other physical theories, the Standard Model feels like there's something much simpler set of equations underneath waiting to be discovered.
On this point, you might enjoy "A Fortunate Universe (Life in a Finely Tuned Cosmos)" by Lewis and Barnes. It discusses this "fine-tuning" problem in a detailed and up-to-date way, and avoids the theological speculation found in some other treatments. (That is, fine-tuning is sometimes presented as evidence for God.)
It doesn't seem obvious that the fundamental models of reality would just happen to match up with the mathematical constructs that we humans have come up with.
On the flip side, it wouldn't be entirely surprising if mathematical constructs that we have thought of are in fact very good models of fundamental reality. We should remember that, after all, nothing exists outside of fundamental reality, and if certain basic patterns can be encoded such that the encoding is both high-fidelity and simple, that won't be shocking. It might be awe-inspiring, but not really surprising.
>nothing exists outside of fundamental reality
A bold assertion.
A bold assertion.
This is a deep philosophical debate: Is mathematics invented or discovered?
https://www.pbs.org/wgbh/nova/article/great-math-mystery/
https://www.pbs.org/wgbh/nova/article/great-math-mystery/
I think it's a bit less deep than that. It's more, "is the language we use to describe mathematics invented or discovered", which I would put myself (and most people) firmly in the invented camp.
[deleted]
Most of the standar model complexity comes from the variety of particles, forces, and aggregations thereof that need to be contended with.
GR likewise becomes a brutal computational mess with these many body problems.
What will be interesting in these new experimental results is whether we’re reaching the limits where determining the correctness of our approximations becomes impractical.
GR likewise becomes a brutal computational mess with these many body problems.
What will be interesting in these new experimental results is whether we’re reaching the limits where determining the correctness of our approximations becomes impractical.
If its turtles all the way down, and physics goes on forever like a fractal, you'll find domains where you can approximate with relatively simple mathematics ("beautiful") and domains that require much more mathematical machinery to describe
Nature doesn't care how complicated it is. A bias towards beauty is a trap that any serious scientist will not fall for.
https://www.youtube.com/watch?v=xFKgIOX8IRE
https://www.youtube.com/watch?v=xFKgIOX8IRE
A bias towards "beauty" or simplicity of some form is inevitable and part of good science.
For every theory, you can generate a more complicated theory with more moving parts that generates the exact same predictions. For instance, my theory of gravity is the same as general relativity, except that at 3 PM April 9th, 2021, all gravity will be reversed.
You have to appeal to some principle to sort out such theories from good descriptions of how the world works.
For every theory, you can generate a more complicated theory with more moving parts that generates the exact same predictions. For instance, my theory of gravity is the same as general relativity, except that at 3 PM April 9th, 2021, all gravity will be reversed.
You have to appeal to some principle to sort out such theories from good descriptions of how the world works.
> A bias towards "beauty" or simplicity of some form is inevitable and part of good science.
> For every theory, you can generate a more complicated theory with more moving parts that generates the exact same predictions.
I agree with the second point, but disagree with the first.
Yes, by Occam's razor, a simpler theory with fewer moving parts should be preferred over a complex theory, if both produce correct answers. But the most accurate theory might not be "beautiful".
What matters most is if the theory correctly predicts reality. If it has a weird arbitrary format, but correctly predicts everything, it's better than a theory that's beautiful but incorrect.
Most of science has been using "beauty" as a way to help guide it to the correct answers. For example, there's been a lot of work on string theory because it has a kind of mathematical beauty. But it may turn out that a search for "beauty" in this sense was misguided. Beauty is not the goal, truth is.
> For every theory, you can generate a more complicated theory with more moving parts that generates the exact same predictions.
I agree with the second point, but disagree with the first.
Yes, by Occam's razor, a simpler theory with fewer moving parts should be preferred over a complex theory, if both produce correct answers. But the most accurate theory might not be "beautiful".
What matters most is if the theory correctly predicts reality. If it has a weird arbitrary format, but correctly predicts everything, it's better than a theory that's beautiful but incorrect.
Most of science has been using "beauty" as a way to help guide it to the correct answers. For example, there's been a lot of work on string theory because it has a kind of mathematical beauty. But it may turn out that a search for "beauty" in this sense was misguided. Beauty is not the goal, truth is.
"the most accurate theory might not be 'beautiful' "
Welcome to Biology! :-)
(Except DNA -> RNA -> Protein, but it's still sloppy along the way)
Welcome to Biology! :-)
(Except DNA -> RNA -> Protein, but it's still sloppy along the way)
> You have to appeal to some principle to sort out such theories from good descriptions of how the world works.
Yes: testable predictions followed by experimental evidence.
Beyond that I don't see how what you're talking about is anything other than an appeal to aesthetics.
Yes: testable predictions followed by experimental evidence.
Beyond that I don't see how what you're talking about is anything other than an appeal to aesthetics.
> Yes: testable predictions followed by experimental evidence.
But there are an infinite number of theories matching the current evidence. Some predictions of the theories might not be testable, what do you do then?
But there are an infinite number of theories matching the current evidence. Some predictions of the theories might not be testable, what do you do then?
Simple: you label them as fiction rather than science. The scientific method has experimental feedback built into the loop.
Well then you have to label everything as fiction rather than science because if you don't single out the simplest theory you can't say that general relativity is science and general relativity plus sun turns into cake tomorrow isn't science.
And if someone tells you the sun will turn into cake tomorrow and claims that your theory where the sun doesn't turn into a cake tomorrow is fiction and unscientific cause it doesn't make predictions to distinguish it from their theory, you don't have any principled philosophical ground to disagree whith them .
And that's not so clearly bad there because they are obiously wrong, but then you get to complicated topics where everyone has hard to resolve disagreements about which theory should be the default from a big pool of theories that seem to agree whith the evidence.
And that's not so clearly bad there because they are obiously wrong, but then you get to complicated topics where everyone has hard to resolve disagreements about which theory should be the default from a big pool of theories that seem to agree whith the evidence.
Doing something clearly outside of empiricism then saying “why doesn’t empiricism cover this” is complete nonsense. What is the ontological explanation for your hypothesis that the sun will turn into cake? Misunderstanding the scientific method is not an issue with the scientific method.
[deleted]
Despite its complexity, the model has been remarkably successful during the last decades.
Question for physicists: Are the G-2 results more groundbreaking than discovering the Higgs particle to moving physics forward?
I would agree with the other commenters. g-2 has been a debate for a long time, but fundamentally points to something new if the result holds. The Higgs was expected, and given the mass and properties we've seen, doesn't point to anything new. "New" meaning not the Standard Model.
If physics is climbing a mountain.
G-2 result is seeing the next hand hold (hoping its not a mirage).
Higgs discovery and its subsequent precision measurement is resting your toe into a hold and flexing your calf upwards.
G-2 result is seeing the next hand hold (hoping its not a mirage).
Higgs discovery and its subsequent precision measurement is resting your toe into a hold and flexing your calf upwards.
I'm not a physicist, I just pay some attention to these things.
The Higgs particle was expected, and so finding it within expected ranges was confirmation of the standard model.
The G-2 results are showing deviations from the expected ranges from the standard model.
In the former case, Higgs, the standard was further, strongly confirmed. In the latter case, G-2, there's a strong indication that the standard model is fundamentally missing something.
I think that's pretty exciting!
The Higgs particle was expected, and so finding it within expected ranges was confirmation of the standard model.
The G-2 results are showing deviations from the expected ranges from the standard model.
In the former case, Higgs, the standard was further, strongly confirmed. In the latter case, G-2, there's a strong indication that the standard model is fundamentally missing something.
I think that's pretty exciting!
Physicist. Some people in the community are quite excited because it hints at something beyond SM. The problem is that the quoted theoretical prediction for g-2 is not a settled issue and is a subject of a long controversy between various groups of theorists.
https://physics.stackexchange.com/a/627852/386
Discussed yesterday:
Particle mystery: physicists confirm the muon is more magnetic than predicted - https://news.ycombinator.com/item?id=26726269 - April 2021 (282 comments)
Particle mystery: physicists confirm the muon is more magnetic than predicted - https://news.ycombinator.com/item?id=26726269 - April 2021 (282 comments)
The muon was the first non-standard matter particle and second transient particle discovered in 1937. It lead to much new physics in mid-20th century. And continues to suggest new physics.
The most exciting news in quite a while!
Why does it take physicists so long to find the complete foundation of the universe? I want an answer in my lifetime.
I blame the mathematicians anf the engineers.
So far we're struggling to reverse engineer all the perl it was hacked together with
I know you’re joking around but does the universe seem hacked together to you?
I feel like it’s incredibly elegant. All these low level rules are able to create such complex structures with beautiful order to it.
It’s so orderly, we can play things backwards billions of years. We can look back to how things were just a fraction of a second after this version of the universe began.
It’s astonishing.
I feel like it’s incredibly elegant. All these low level rules are able to create such complex structures with beautiful order to it.
It’s so orderly, we can play things backwards billions of years. We can look back to how things were just a fraction of a second after this version of the universe began.
It’s astonishing.
But can we explain just what exactly quantum mechanics is?
It's too bad we'll almost certainly never be able to answer the meta question of how or why we ended up with the rules we did.
These questions are more metaphysics than science.
I, personally, am partial to the idea that the anthropic principle has a pretty big role to play, at least in terms of the fundamental constants.
I, personally, am partial to the idea that the anthropic principle has a pretty big role to play, at least in terms of the fundamental constants.
That's why I didn't say metaphysics specifically. I really mean the scientific answer to the question rather than a philosophical one. How did we end up with bosons, gluons, etc as opposed to anything else? Maybe it was totally random. A combo of it being random, the anthropic principle being true, and the possibility that the big bang was actually proceeded by the collapse of $current_universe - 1 due to heat death seems plausible. It could turn out we're actually on universe number 1 trillion and this was the first one where the randomness worked out where it'd support life. Or maybe it's even the second. We'd never be able to figure it out either way.
Maybe. The fact that a treatment of particle physics based on Symmetry groups works so well is rather odd, but equally why should it be that way? Elegance is subjective, mathematical elegance even more so.
the container that runs the simulation is extremely hard to escape from
Hilbert's tomb:
Wir müssen wissen
Wir werden wissen
You should not be downvoted. Spare the world a little cruelty where we can.
You should not be downvoted. Spare the world a little cruelty where we can.
He/she is being downvoted for demanding an answer, as if they're entitled to one but all the physicists out there are just too dumb to figure it out or refuse to give them what they are owed.
Perhaps that is not how this person actually feels. If so, a little humility and empathy in their communication would go a long way to rectify that.
Perhaps that is not how this person actually feels. If so, a little humility and empathy in their communication would go a long way to rectify that.
Physicist here:
1. One should be rather specific about what 'the complete foundation' might comprise. The depth of questions one can ask is infinite, but some questions are more important than others. The g-2 experiment is asking a specific question: "Does the anomalous magnetic moment of the muon open a door to discoveries that are inaccessible with modern colliders?"
It is tempting to regard fundamental physics as a study of "Why are we here?", but it is really a study of "How are we here?" The difference is subtle but substantial. If "Why?" is what you're seeking, you are more likely to find that answer within, rather than within the study of physics.
2. Physicists can do a lot more in these directions with greater institutional support. With great sadness, I recently departed a lab, where colleagues next-door were working on this very experiment, precisely because a collision between funding rules and administrative priorities made further progress within my specialty unsustainable. I was the third postdoc in a row to do the same; not for lack of scientific promise nor ability to attract grants.
1. One should be rather specific about what 'the complete foundation' might comprise. The depth of questions one can ask is infinite, but some questions are more important than others. The g-2 experiment is asking a specific question: "Does the anomalous magnetic moment of the muon open a door to discoveries that are inaccessible with modern colliders?"
It is tempting to regard fundamental physics as a study of "Why are we here?", but it is really a study of "How are we here?" The difference is subtle but substantial. If "Why?" is what you're seeking, you are more likely to find that answer within, rather than within the study of physics.
2. Physicists can do a lot more in these directions with greater institutional support. With great sadness, I recently departed a lab, where colleagues next-door were working on this very experiment, precisely because a collision between funding rules and administrative priorities made further progress within my specialty unsustainable. I was the third postdoc in a row to do the same; not for lack of scientific promise nor ability to attract grants.
> It is tempting to regard fundamental physics as a study of "Why are we here?", but it is really a study of "How are we here?" The difference is subtle but substantial. If "Why?" is what you're seeking, you are more likely to find that answer within, rather than within the study of physics.
I don't want to know why, I just want to know the complete set of rules at the lowest level.
I don't want to know why, I just want to know the complete set of rules at the lowest level.
It is unlikely that we will ever grasp the complete set of rules at the lowest level. I don't say this to be defeatist, but rather as a statement of pragmatism.
To do so would be to have a convincing grasp of Planck-scale physics -- a detailed understanding of physics at and above energy-densities reached in the Big Bang. Some precision experiments and astrophysical measurements do constrain certain Planck-scale models, but a true test of whether or not we understand early-universe physics is likely to necessitate creating a few Big Bangs ourselves. Doing so, with known technology, seems impossible. If it were possible, doing so would seem fraught with actual risk.
(N.B. for the non-expert reader: there are cosmic rays that strike the Sun at least once every five minutes (and Earth, at least once a month) with energies 10,000,000 times greater than anything humans have ever achieved. Those collisions, over the last 4,500,000,000 years, have not yet resulted in the disruption of spacetime or the formation of a black hole. You are very, very, very safe from physicists breaking the universe as you know it. :).)
Edit to add: You, mseepgood, aren't alone in your desire for knowledge. One Stephen Hawking once stated, “My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.”
To do so would be to have a convincing grasp of Planck-scale physics -- a detailed understanding of physics at and above energy-densities reached in the Big Bang. Some precision experiments and astrophysical measurements do constrain certain Planck-scale models, but a true test of whether or not we understand early-universe physics is likely to necessitate creating a few Big Bangs ourselves. Doing so, with known technology, seems impossible. If it were possible, doing so would seem fraught with actual risk.
(N.B. for the non-expert reader: there are cosmic rays that strike the Sun at least once every five minutes (and Earth, at least once a month) with energies 10,000,000 times greater than anything humans have ever achieved. Those collisions, over the last 4,500,000,000 years, have not yet resulted in the disruption of spacetime or the formation of a black hole. You are very, very, very safe from physicists breaking the universe as you know it. :).)
Edit to add: You, mseepgood, aren't alone in your desire for knowledge. One Stephen Hawking once stated, “My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.”
dumb q I was never smart enough to ask when I was doing a physics degree: how do we know the big bang required enormous energy and thus is impossible? in the few peeks we got at grad school physics, I walked with away with the likely erroneous impression that the best guess was the big bang happened due to "quantum fluctuations in a vacuum" which sounded suspiciously close to "at random" - and I won't lie, since, I've just assumed that at any point there could be another big bang and we'd be blown away!
I think the safest answer regarding the Big Bang is that we don't really understand the mechanism. In particular, anything regarding inflation stands on truly dubious ground (It gets the necessary outcomes right, but we have no presently-testable theory regarding the mechanism. Any mechanism that does must defy the laws of physics as we know them).
I can't pretend to be an expert here, but the quantum-fluctuations in a vacuum that we all experience at all times do, over longer times ("long" here is generally unfathomably short), need to satisfy energy-conservation. To do otherwise requires paying an overwhelming probabilistic cost (a much bigger nigh-infinity than your garden-variety nigh-infinity). If you're worried about unexpected instantaneous death from the universe, I would argue that one should be far more concerned with, say, a gamma-ray burst nearby from within the galaxy (or, far more likely yet, a nuclear war) than being overrun by a Big-Bang-like event.
For that same reason (energy conservation), perhaps the central question one might ask of the Big Bang theory is, "How did it come to pass that all of that energy wound up in such a tiny volume?" There are plenty of theories out there, the best of which attempt to confront inflation at the same time, but I am unaware of a clear leader.
I don't mean to entirely disregard the importance of quantum fluctuations in cosmology. Indeed, the large-scale structure of the cosmic-microwave background is very consistent with pure quantum fluctuation, as if the fluctuations of a tiny volume of space had been magnified to cosmic scale. It is simply this experimentalist's opinion that there is probably substantially more to the story than the universe having won the lottery of all lotteries in order to exist at all.
I can't pretend to be an expert here, but the quantum-fluctuations in a vacuum that we all experience at all times do, over longer times ("long" here is generally unfathomably short), need to satisfy energy-conservation. To do otherwise requires paying an overwhelming probabilistic cost (a much bigger nigh-infinity than your garden-variety nigh-infinity). If you're worried about unexpected instantaneous death from the universe, I would argue that one should be far more concerned with, say, a gamma-ray burst nearby from within the galaxy (or, far more likely yet, a nuclear war) than being overrun by a Big-Bang-like event.
For that same reason (energy conservation), perhaps the central question one might ask of the Big Bang theory is, "How did it come to pass that all of that energy wound up in such a tiny volume?" There are plenty of theories out there, the best of which attempt to confront inflation at the same time, but I am unaware of a clear leader.
I don't mean to entirely disregard the importance of quantum fluctuations in cosmology. Indeed, the large-scale structure of the cosmic-microwave background is very consistent with pure quantum fluctuation, as if the fluctuations of a tiny volume of space had been magnified to cosmic scale. It is simply this experimentalist's opinion that there is probably substantially more to the story than the universe having won the lottery of all lotteries in order to exist at all.
What do you feeling is wrong with "the universe having won the lottery of all lotteries in order to exist at all"? Our existence seems consistent with some multiverse picture where we just end up observing one out of many universes that was capable of supporting life. After all, if any of a number of fundamental constants gets tweaked by a small amount, then we end up in situations like e.g. hydrogen being the only naturally occurring element.
(I'm purposely being a bit provocative here because I haven't heard an explanation for fine-tuning that doesn't rely on multiverses or divine intervention.)
(I'm purposely being a bit provocative here because I haven't heard an explanation for fine-tuning that doesn't rely on multiverses or divine intervention.)
If the anthropic principle is at work, then there might be very little (accessible at our energies) left to learn that is truly fundamental. It might be an article of faith, but I believe that there is more to know.
If you elect to believe in the anthropic principle, one might continue to delve into fundamental research in order to ask the question, "What configuration of all possible universes is required in order to win the lottery of all lotteries?" That is a pretty awesome question, too. It is the lottery of all lotteries, after all.
In either case, deeper research is likely to turn up new and deeply-interesting surprises. Those surprises are likely to be resolved with improved theories with greater predictive power regarding the universe in which we live.
If you elect to believe in the anthropic principle, one might continue to delve into fundamental research in order to ask the question, "What configuration of all possible universes is required in order to win the lottery of all lotteries?" That is a pretty awesome question, too. It is the lottery of all lotteries, after all.
In either case, deeper research is likely to turn up new and deeply-interesting surprises. Those surprises are likely to be resolved with improved theories with greater predictive power regarding the universe in which we live.
120 years ago, we had no model of the atom, no quantum theory, no relativity, and only the first hints of figuring out radioactivity. Yet we were able to split the atom in 1942, create the MOSFET in 1959, and started launching the first GPS satellites in 1978.
It's hard to express how much progress we've made in such a small amount of time relative to the rest of history. It's a god damn miracle.
It's hard to express how much progress we've made in such a small amount of time relative to the rest of history. It's a god damn miracle.
screwed up half of biosphere as well...
It's theories galore out there that aim to describe everything. Proving them right/wrong via experiments is the hard part.
Particularly interesting was the focus on an alternative theoretical calculation for the muon magnetic moment: the “BMW” approach, which uses a numerical lattice model and produces a number much closer to the Fermilab experiment.
For an outsider, one of the surprising things here must be just how hard the theoretical calculation actually is, especially as you get deeper into the decimal places and have to include the vacuum effects on the muon of basically all particles in the standard model, including hadrons which means trying to calculate the Strong Force. Back when I studied quantum field theory in college we never got anywhere near actually producing numbers for strong force effects; the equations weren’t soluble with the usual perturbation theory techniques. But it’s interesting to read about how it is possible to get useful numbers with these different cutting-edge theoretical/computational methods - but with some uncertainty about whether they’re actually right!
Curious to hear any practicing physicists on HN weigh in on the BMW calculation versus the orthodox theoretical approach that everyone’s comparing the Fermilab result against.