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Ask HN: How to self-study physics?

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

#171

Post by godelski »

neutronicus wrote: post #156
propter_hoc wrote: post #126

Earlier quoted context omitted.

I can't believe I am reading a recommendation that someone with little background in E&M self-studies with Jackson. That book is incredibly difficult even with a great graduate-level professor.

It all depends on your background in PDEs. I think the undergrad physics curriculum is pretty weak relative to some engineering disciplines here and Jackson is what really exposes this. Coming from Nuclear Engineering I thought it was fine.

I think PDEs are just weak in all undergrad curriculum. Most engineers I know could only do very basic PDEs. Physicists could do a little more because they learned it from Griffiths E&M. PDEs are typically more a grad school thing. The idea is to form a strong understanding first.

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

#172

Post by gowld »

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…

> Plenty of talented teachers have tried it, and moved on to something more effective.

Including, you know, Richard Feynman.

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

#173

Post by godelski »

zinclozenge wrote: post #86
Simon_says wrote: post #69

Earlier quoted context omitted.

How does Halliday + Resnick compare to Young + Freedman?

At that level, the textbooks are more or less the same. So neither is superior than the other.

I found in my undergrad I used both. Sometimes one would explain a specific topic better. Sometimes I just needed to hear the topic explained from a different voice. With the number of old editions and online copies floating around, I don't think it is bad to recommend both.

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

#174

Post by ukj »

davidivadavid wrote: post #158
ukj wrote: post #150

Earlier quoted context omitted.

Yeah! So you know that read:T call that you have implemented in Scala? You know that it could produce a different result on consecutive calls, right? Because the notion of a mutex/lock doesn’t exist in Math. Mathematics doesn’t allow that, because it is not a “pure function”. https://en.wikipedia.org/wiki/Pure_function Non-determinism is the norm in distributed systems. e.g any networked Turing machine.

You seem to imply that there's no mathematical model/theory of non-deterministic/distributed systems. Surely you don't believe that?

I am implying that Mathematical semantics are broken/incomplete.

Mathematics uses denotational semantics. It implies pass by-value and pass-by-reference are equivalent. They are in theory, they aren't in practice. That is why Haskell's lazy evaluation leaks time.

Engineers/physicists intuitively rely at least on operational semantics. It's a higher order logic, and since Linear Logic time is localized.

https://ncatlab.org/nlab/show/Geometry+of+Interaction

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

#175

Post by cannabis_sam »

ukj wrote: post #174
davidivadavid wrote: post #158

Earlier quoted context omitted.

You seem to imply that there's no mathematical model/theory of non-deterministic/distributed systems. Surely you don't believe that?

I am implying that Mathematical semantics are broken/incomplete. Mathematics uses denotational semantics. It implies pass by-value and pass-by-reference are equivalent. They are in theory, they aren't in practice. That is why Haskell's lazy evaluation leaks time. Engineers/physicists intuitively rely at least on operational semantics. It's a higher order logic, and since Linear Logic time is localized. https://ncatla…

> That is why Haskell's lazy evaluation leaks time.

Could you maybe illustrate this with an example?

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

#176

Post by hriir0 »

throwqwerty wrote: post #161
hriir0 wrote: post #135

Earlier quoted context omitted.

Interesting. To me that’s just a subjective list the author likes. The replies seem a bit on the level of “...but everyone knows really.” I always took notions like “expert” virtue signaling to mean experts seem convinced we should all learn via the timelines they did. Uni students versed in textbook physics, linear timelines for learning cause that’s how society taught them, are also experts in working cognitive the…

>To me that’s just a subjective list the author likes. but the prompt isn't "list some books you like" but "how should I learn" so there's obviously intent in picking those books.

“Likes for learning” is not an unreasonable acquiescence for the reader to consider.

English is a terrible language and taking how we use it so literally is as bad as the language itself.

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

#177

Post by ukj »

diegoperini wrote: post #160
ukj wrote: post #154

Earlier quoted context omitted.

Assume that it is a black box to you, even though it is a white box to me. Every time you call read() on it - you get a different result. It has side-effects. This violates the “purity” of Mathematics.

I just explained three different models to represent side-effects without leaving the purity. I'm not sure if you are trolling, throwing random big words or simply have a really misguided impression about how computer science connects with math.

Your monad(WorldState, Value) example assumes shared global state. So not a networked system then?

That's not a train-smash for your argument if you can show me a Mathematical model for a global mutex.

When the discussion turns to control-flow you are inevitably in the land of well-ordered imperatives, not Mathematical, lazy-evaluated declaratives.

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

#178

Post by [deleted] »

davidivadavid wrote: post #91
ukj wrote: post #88

Earlier quoted context omitted.

I am to really glad to hear commentary like this coming from physicists. (read: glad to see others siding with my biases). Ceteris paribus there is one significant distinction between Mathematics and Computer Science: state. The Mathematical Universe is immutable/stateless/timeless. The Computational Universe is mutable/stateful/time-bound. The observer effect in physics can be trivially expressed and evaluated as a…

It seems likely that anything that can be expressed in "any programming language" is isomorphic to something that exists in math and can be expressed in that language (automata theory, type theory, category theory, pick your poison).

[deleted]

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

#179

Post by ukj »

cannabis_sam wrote: post #175
ukj wrote: post #174

Earlier quoted context omitted.

I am implying that Mathematical semantics are broken/incomplete. Mathematics uses denotational semantics. It implies pass by-value and pass-by-reference are equivalent. They are in theory, they aren't in practice. That is why Haskell's lazy evaluation leaks time. Engineers/physicists intuitively rely at least on operational semantics. It's a higher order logic, and since Linear Logic time is localized. https://ncatla…

> That is why Haskell's lazy evaluation leaks time. Could you maybe illustrate this with an example?

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 of crypto + Haskell, have a look at these two posts:

https://crypto.stanford.edu/~blynn/c/haskell.html

https://crypto.stanford.edu/~blynn/haskell/lazy.html

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

#180

Post by joel_ms »

ukj wrote: post #179
cannabis_sam wrote: post #175

Earlier quoted context omitted.

> That is why Haskell's lazy evaluation leaks time. Could you maybe illustrate this with an example?

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..?).

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