Comment by Maro | Hacker News Reader

Comment by Maro | Hacker News Reader

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One thing I wish would happen: create a nice, asthetic, smooth way for a smart student to go from the two-slit experiment to QED/QCD [in 2-3 years], while having clarity what the input parameters are in the model (=needs to be measured), what is predicted by the model (=this comes out and is measurable), where an approximation is being made, what the current spacetime model is assumed to be, etc. Also, a mathematician should be able to look at this "journey" and approve that it's not too handwavy.

Given that there's "not much to do", it's weird that there isn't a 1% group somewhere out there who thinks this is worthwhile.

Context = I studied particle/astro physics 15 years ago and then "dodged the bullet" as the OP nicely puts it. I felt the way we were taught modern phsyics was quite poor/handwavy, esp. once the cross was made to QFT territory, and led to a lot of misunderstanding/confusion, which I still see in comment threads today, incl. between academics (!). Also, when I speak to mathematicians about this, they deeply disapprove of the way physics is taught/run today in this respect, and can routinely point to misunderstandings/confusion that hinders progress.

A good example (but probably too mathy) is the work of Tamas Matolcsi: `Spacetime without reference frames` and `Ordinary thermodynamics`.

https://www.amazon.com/s/ref=dp_byline_sr_book_1?ie=UTF8&tex...

It's handwavy because no one really knows what they're doing. Even Feynman said that no one understands QM, and things have hardly improved since then. Some details have been filled in, but there's a lot of hostility to the idea that science should even be thinking about quantum fundamentals, because it's such a philosophical tar pit.

Modern QFT is like being given a laptop with an Excel spreadsheet that does some clever things, without having any idea what a processor is, what memory is, how a hard drive works, or why the case is that funny shape.

The kinder way to put this is to say there's a lot of educated guessing going on. But the fundamental problem - reconciling GR and QFT - can't be solved without a completely new mental model. And academic research isn't funded in ways that reward the generation of creative new models.

It's become a bit of a cargo-culty pursuit. You're rewarded if you know the words to the songs that everyone else is singing, but if you try to invent a new genre you'll probably be told it's career suicide and Don't Go There.

No the problem is that any new model needs to be more then "interesting" - plenty of those kicking around. What it needs to do is generate a testable prediction - either explain something we currently can't explain, and ideally point the way to something we should expect to see if it's correct in a convincing way.

The entire argument against string theory, is, in many ways, founded on the fact that as a group of hypotheses, none of them predict anything that would rule them in or out that's within a practically reachable detection limit.

I think this is very unfair.

>no one really knows what they're doing. Even Feynman said that no one understands QM

Quantum field theory makes possible the single most accurate predictions in all of science. Time and time again people whip out the Feynman (mis)quote to try to argue "oh we don't really know what's happening", but just cannot see why they think that way. Science is about finding observing reality and formulating descriptions with predictive power, and qft is objectively the best description any person has figured out so far.

>Modern QFT is like being given a laptop with an Excel spreadsheet that does some clever things, without having any idea what a processor is, what memory is, how a hard drive works, or why the case is that funny shape.

Again, preposterous. We know how qft works (we've come up with it, after all), and we know how to use it to make predictions and confirm them experimentally. If you mean know in a deeper, fuzzy sense, they maybe, maybe not.

>the fundamental problem - reconciling GR and QFT - can't be solved without a completely new mental model

>It's become a bit of a cargo-culty pursuit.

If you come up with a better idea than the current understanding, publish your findings and you will instantly become the most respected, popular, and influential physicist alive.

I will concede though that sadly funding is allocated more to "safer" avenues of research than novel ones. That's certainly a problem.

I don't think this is about reconciling QM and GR.

Even without gravity, modern particle physics theory is a big mess imo.

What's interesting is that this is happening in aerodynamics today as students and researchers rediscover on youtube the amazing Shell Oil-sponsored "High Speed Flight" videos from the 1950's - they're like an instant Masters Degree:

https://www.youtube.com/watch?v=bELu-if5ckU

Watching this now. It is great!

The unfortunate truth is that even among good theoretical physicists there are few who would be able to teach such a course. The main reason is that a mathematical description of some of these things is still scattered in the research literature. The best attempt that I am aware of is the special year at Princeton in the 90s it produces a fantastic two volume collection of lectures “quantum fields and strings: a course for mathematicians”. Weinberg’s three part book on QFT is also pretty nice.

I (tried to) used Vol. 1 and 2 of Weinberg for QFT courses back 12 years ago, I don't agree that they're good in the sense of being clear / not handwavy.

Matolcsi’s books are available here for those interested: http://szofi.elte.hu/~szaboa/MatolcsiKonyvek/

Thanks! The 7 page preface of the Spacetime book gives a good argument/overview of my original point.

I wonder whether using computers more (whether numerical or symbolic calculations) could remove some of the burden of understanding mathematical techniques and make this process smoother. Or maybe it would just obscure the fundamental assumptions to software and increase the burden on learning computational techniques.

Does it matter whether mathematicians think it is handwavy? If any two trained practitioners can get to the same result of a calculation and it matches experiment to appropriate approximations that seems good enough to me.

> If any two trained practitioners can get to the same result of a calculation and it matches experiment to appropriate approximations that seems good enough to me.

I think that's already true today. The problem is, when theorists are out manufacturing new theories, I think it gets very confusing/handwavy (because everybody is brought up on handwavy fundamentals).

Disclaimer: I'm not a practicing physicist.

There are no "handwavy" fundamentals. The theory is well-studied, well-understood, sound, and produces verifiable results. It is, however, incomplete, in that it does not provide an explanation for certain phenomena.

I took introductory lectures in physics and one prof would repeatedly state that quantum mechanics just cannot be understood, which was probably true for the scope of the audience, but still struck me as cringe-worthy. If I remember correctly that came up with wavefunction collapse, which is indeed just one model, that's begging for an explanation, and with fixed energy bands. The conclusion that there's a lot to memorize by heart is true nevertheless for any advanced science.

Whereas, I'm currently hearing an introductory philosophy lecture and, while physics informs my view in large parts, it's mostly about knocking down misconceptions.

The basic fundamentals, the first principles deriving conclusions, should be basic common knowledge. I don't actually need a mysterious slit experiment to be able to tell that my life, so to speek, is unpredictable, yet very regular, in the bigger picture. One common problem is language and there's almost no focus on that in physics education--if I may leave at least one lament--and since I can't say that the assembly of quantum states that is me is very likely to diverge, disentagle and grow decoherent ... philosophy still puts up with concepts like soul; or free will which is in the end not about inherent physical properties but just about regret and commitment.

>create a nice, asthetic, smooth way for a smart student to go from the two-slit experiment to QED/QCD

Not quite sure what you mean by this. This is (part of) the standard curriculum for a physics degree. Of course physics is a vastly bigger field than quantum mechanics, so it takes 4 years to do this journey.

> A good example (but probably too mathy) is the work of Tamas Matolcsi:

Good examples as cautionary tales, or worth a look as how it should be done?

It's good, but very dry.

Look at the spacetime one and read the Preface, it gives a good overview of the "program". Read the first chapter and see what you think.

http://szofi.elte.hu/~szaboa/MatolcsiKonyvek/pdf/konyv/Matol...

Disclaimer: I took these courses 10+ years ago from Matolcsi.

Thanks, I already started reading it. Initially my impression was that it's a fairly standard geometric formulation of physics, but I really appreciate the simple explanations.

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