Discussed yesterday:
Particle mystery: physicists confirm the muon is more magnetic than predicted - https://news.ycombinator.com/item?id=26726269 - April 2021 (282 comments)
Muon G-2 Experiment at Fermilab Finds Hint of New Particles
41–50 of 65 posts
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#42Regardless 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…
Despite its complexity, the model has been remarkably successful during the last decades.
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#43Earlier quoted context omitted.
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
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 fr…
> 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.
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#44Regardless 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…
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.
This is a deep philosophical debate: Is mathematics invented or discovered?
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#45Earlier quoted context omitted.
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 fr…
> 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.
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?
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#46Earlier quoted context omitted.
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.
This is a deep philosophical debate: Is mathematics invented or discovered? 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.
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#47Earlier quoted context omitted.
> 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. 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.
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#48Regardless 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…
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.)
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#49Earlier quoted context omitted.
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'v…
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…
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.)
Re: Muon G-2 Experiment at Fermilab Finds Hint of New Particles
#50There have been a bunch of articles near the top of HN on this result, but I found this one from Quanta magazine to be one of the best non-technical explanations. 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…
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....).