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Ask HN: How to self-study physics?

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Re: Ask HN: How to self-study physics?

#181

Post by stared »

ska wrote: post #114
AnthonBerg wrote: post #111

Earlier quoted context omitted.

We all learn differently. Please don't deal in pedagogical certainties that may close doors unventured. Feynman's lectures were crucially eye-opening for me and many others.

It's pretty well established now that Feynman is not a good general approach for introductory physics. Plenty of talented teachers have tried it, and moved on to something more effective. This doesn't contradict your point. A particular individual may find them very helpful in learning and understanding the foundational stuff. By all means try, and if it works for you, great. However, it shouldn't be at the top of an…

> It's pretty well established now that Feynman is not a good general approach for introductory physics.

Citation needed.

For people at the Physics Olympiad level, it is hard to find something as eye-opening and insightful as Feynman Lectures on Physics.

For more "general audience", I guess that a more step-by-step is preferred. I know many people (usually not the Olympiad tribe) who preferred Halliday & Resnick.

Re: Ask HN: How to self-study physics?

#182

Post by stared »

scottlocklin wrote: post #74

For the love of God, don't use Feynman lectures to learn physics. That's something you read after you know physics, for relaxation and conceptual stuff. Resnick & Halliday is a much better freshman/sophomore book. Susskind's "theoretical minimum" is actually pretty good. http://theoreticalminimum.com/courses Fowler gives a pretty conventional undergraduate physics curriculum (adding Feynman in there somehow). If it w…

This piece of advice is wrong on so many levels, from the general context. I cannot believe it got 1st place here.

(I got a Ph.D. in theoretical quantum optics, and I do have over a decade of experience teaching gifted high-school students. There is a lot of experience that works, and doesn't work, on people without prior background.)

Feynman Lectures are much a more lively, insightful, overview of physics (I started reading when I was 14 or 15 y.o.; jumped there after reading one advanced high-school textbook). While I do know people who preferred Halliday & Resnick, these were people who liked a more straightforward, even if less insightful or colorful, approach.

> learn the math tools first.

Nope. You can spend 2 years (not a joke) to get mathematics to prove Stokes theorem, in one of the more general versions. Or draw a few cubes and squares, and get there is 15 mins or so. For regular 1 dim integrals, it is a one year course of mathematical analysis, if you want to do it rigorously.

For many tools (e.g. Fenman Path Integrals) there is no rigorous math approach that is in use (at all). While, sure, you need to continuously improve your mathematical skills, my strong suggestion is first physics, then maths. Same Dirac Delta first as a trick, only later (and if you wish for math's sake) learn about distributions, Radon measures, etc.

For E&M: for introduction, totally start with Griffiths. It is much more approachable as the introduction.

> There's very little difference in undergraduate vs graduate quantum mechanics.

I don't know where to get started, but it is nor true. For quantum information - yes, you can start with undergraduate maths. For anything going into quantum field theory, you would need to know much more about Lagrangian mechanics, group representations, symmetries, differential geometry, etc.

Re: Ask HN: How to self-study physics?

#183

Post by dtornabene »

stared wrote: post #181
ska wrote: post #114

Earlier quoted context omitted.

It's pretty well established now that Feynman is not a good general approach for introductory physics. Plenty of talented teachers have tried it, and moved on to something more effective. This doesn't contradict your point. A particular individual may find them very helpful in learning and understanding the foundational stuff. By all means try, and if it works for you, great. However, it shouldn't be at the top of an…

> It's pretty well established now that Feynman is not a good general approach for introductory physics. Citation needed. For people at the Physics Olympiad level, it is hard to find something as eye-opening and insightful as Feynman Lectures on Physics. For more "general audience", I guess that a more step-by-step is preferred. I know many people (usually not the Olympiad tribe) who preferred Halliday & Resnick.

I'm a logician and the Feynman lectures were incomprehensible when I tried to work through them. I for one am glad to see people pushing students toward more approachable texts.

Re: Ask HN: How to self-study physics?

#184

Post by ukj »

joel_ms wrote: post #180
ukj wrote: post #179

Earlier quoted context omitted.

So as a brief summary: laziness leaks time. Whether that's a good or a bad thing depends on what you want/need. It may be a bad thing if you are doing cryptography because time leaks allow side-channel attacks ( https://en.wikipedia.org/wiki/Timing_attack ). As with all philosophical squabbles - there are arguments for each side. It's up to you to make up your mind based on your particular use-case. And so in context…

Thank you! I was more wondering how time leaks and laziness relates to denotational vs operational semantics? I couldn't find anything about either in the links (they seem to be general descriptions of haskell and laziness..?).

Trivially. For any given system 'safety' is an operational concept, not a denotational one.

You can't formalize the notion of 'safety' let alone prove (in the Mathematical sense) that your code has it without examining its runtime behaviour.

In the words of Donald Knuth: Beware of bugs in the above code; I have only proved it correct, not tried it.

In one context lazy evaluation may be 'safe' - it another it may be 'dangerous' - the context in which this assertion is made is always about human needs and expectations, not mathematics.

With particular example being that lazy evaluation allows for side-channel attacks in cryptographic systems. That's undesirable - hence operationally 'unsafe'.

Re: Ask HN: How to self-study physics?

#185

Post by scottlocklin »

stared wrote: post #182
scottlocklin wrote: post #74

For the love of God, don't use Feynman lectures to learn physics. That's something you read after you know physics, for relaxation and conceptual stuff. Resnick & Halliday is a much better freshman/sophomore book. Susskind's "theoretical minimum" is actually pretty good. http://theoreticalminimum.com/courses Fowler gives a pretty conventional undergraduate physics curriculum (adding Feynman in there somehow). If it w…

This piece of advice is wrong on so many levels, from the general context. I cannot believe it got 1st place here. (I got a Ph.D. in theoretical quantum optics, and I do have over a decade of experience teaching gifted high-school students. There is a lot of experience that works, and doesn't work, on people without prior background.) Feynman Lectures are much a more lively, insightful, overview of physics (I started…

> You can spend 2 years (not a joke) to get mathematics to prove Stokes theorem, in one of the more general versions.

You're out of your mind. You don't need to prove Gauss-Stokes in the general version to understand Maxwell's equations; you just need 3-d calculus, and you're done. Bike shedding the process further is silly: I could claim you don't really understand GR (or for that matter, E&M) without Hatcher-level understanding of Algebraic topology. All you need is the simple calculus theorem, such as is presented in Jackson.

> For anything going into quantum field theory....

This is a rubbish argument: yes, you need more math to do quantum field theory. You also need basic quantum mechanics first, which is what I'm talking about for a self study program. If you want to go on to fiddle with QED, you can fool around with Itzykson and Zuber (and Griffiths book) later, when you actually know how non-relativistic QM works, and how relativity works. First learn basic Schroedinger stuff and something like S-matrix theory. Don't learn the shitty undergrad training wheels crapola; do the real thing. That's my advice in general. If you work your way through a differential equations book; there is no point in doing the intermediate stuff and a great argument (it's a waste of time; a make work program for physics professors, and a weeder for people with low dedication to the subject) for skipping it.

FWIIW I was not a theorist, though I had some theory papers queued up on quantum dynamics. I think what everyone knows after first year of grad school is a pretty good basket of knowledge, which is why the 1st year grad school program is virtually identical everywhere in the world. It's like a gentleman learning Latin in the old days. There is a direct line from advanced calculus to completed first years of grad school physics; one which I outlined above. The imbecile make-work program of doing a bunch of intermediate problems in junior and senior year; it's really not worth it if you're an adult with a functioning cerebral cortex. Or if you're trying to pass prelims/GREs which test you on these subjects. Otherwise; skip it -do the important bits, and revisit the training wheels versions later when you need them. That's all.

Re: Ask HN: How to self-study physics?

#186

Post by stared »

scottlocklin wrote: post #185
stared wrote: post #182

Earlier quoted context omitted.

This piece of advice is wrong on so many levels, from the general context. I cannot believe it got 1st place here. (I got a Ph.D. in theoretical quantum optics, and I do have over a decade of experience teaching gifted high-school students. There is a lot of experience that works, and doesn't work, on people without prior background.) Feynman Lectures are much a more lively, insightful, overview of physics (I started…

> You can spend 2 years (not a joke) to get mathematics to prove Stokes theorem, in one of the more general versions. You're out of your mind. You don't need to prove Gauss-Stokes in the general version to understand Maxwell's equations; you just need 3-d calculus, and you're done. Bike shedding the process further is silly: I could claim you don't really understand GR (or for that matter, E&M) without Hatcher-level…

To be frank, I don't get what you are up to. I sense a lot of anger, mixed with somehow chaotic notes.

> why the 1st year grad school program is virtually identical everywhere in the world

Certainly, it isn't. In the US usually starts with heavy regular coursework. In many European, there is some coursework. Unlike undergraduate physics, which is less varied, the subjects vary heavily on the place (specialization, the focus of concrete groups). In my case, it was purely research, no classes or teaching (it is less common, though).

Source: quite a lot of my friends did graduate-level physics in various places worldwide.

Re: Ask HN: How to self-study physics?

#188

Post by andrepd »

ukj wrote: post #113
andrepd wrote: post #100

Earlier quoted context omitted.

>The observer effect in physics can be trivially expressed and evaluated as a mutating getter in any programming language. >It cannot be expressed in any Mathematical grammar. What on earth are you trying to say...? There is a whole mathematical treatment of quantum mechanics, measurement effect included (several treatments). More to the point, any algorithm can be formalised in e.g. a Turing machine, or any other eq…

>Any algorithm can be formalised in e.g. a Turing machine, or any other equivalent universal model of computation Quoting http://math.andrej.com/2006/03/27/sometimes-all-functions-ar... >>The lesson is for those “experts” who “know” that all reasonable models of computation are equivalent to Turing machines. This is true if one looks just at functions from N toN. However, at higher types, such as the type of our func…

The link you has its fallacy in the premise. It's defining "function" as "computable function", then complaining that many results that follow do not agree with the former definition! Either I'm really missing something or this is some poor attempt at trolling / bait-and-switch. Of course you have problems with that "computable function" definition when dealing with functions from Real -> Real, since many (in fact, almost all) real numbers are not computable!

Re mutating getter:

Monads for example are a standard way of formalising state in a pure-function universe. You seem to have some fundamental misconception about what "mathematics" is, since you keep repeating something about purity. Mathematics is merely the rigorous study of formal systems, of which your mystical "mutating getter" is one such system.

Re: Ask HN: How to self-study physics?

#189

Post by andrepd »

ubercow13 wrote: post #153
ukj wrote: post #113

Earlier quoted context omitted.

>Any algorithm can be formalised in e.g. a Turing machine, or any other equivalent universal model of computation Quoting http://math.andrej.com/2006/03/27/sometimes-all-functions-ar... >>The lesson is for those “experts” who “know” that all reasonable models of computation are equivalent to Turing machines. This is true if one looks just at functions from N toN. However, at higher types, such as the type of our func…

What is special about a mutating getter? It operates on the state of the object S and outputs a new state S' and some value x. Some programming languages allow you to write 'functions' without explicitly passing all input state into the function, but does that imply anything fundamental or interesting about mathematics or computation? Is that anything more than a type of syntactic sugar?

Of course it isn't. OP seems to have some kind of misconception about what "mathematics" means, since they keep fixating on a vague concept of purity of notation.

Re: Ask HN: How to self-study physics?

#190

Post by ukj »

andrepd wrote: post #188
ukj wrote: post #113

Earlier quoted context omitted.

>Any algorithm can be formalised in e.g. a Turing machine, or any other equivalent universal model of computation Quoting http://math.andrej.com/2006/03/27/sometimes-all-functions-ar... >>The lesson is for those “experts” who “know” that all reasonable models of computation are equivalent to Turing machines. This is true if one looks just at functions from N toN. However, at higher types, such as the type of our func…

The link you has its fallacy in the premise. It's defining "function" as "computable function", then complaining that many results that follow do not agree with the former definition! Either I'm really missing something or this is some poor attempt at trolling / bait-and-switch. Of course you have problems with that "computable function" definition when dealing with functions from Real -> Real, since many (in fact, a…

You have some deeply flawed (or entirely absent) philosophical upbringing. There are no "foundations" to anything - all definitions are arbitrary.

To assert that a premise is fallacious mandates that you have some prior notion of "fallaciousness".

You don't have an objective criterion for asserting whether one definition is better than another because you don't have a notion of "betterness" - it's all conventional.

It's precisely because I am an over-zealous formalist is why I see Mathematics for what it is - grammar, syntax and semantics.

It's just language.

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