How do you learn physics correctly ?

[sshai45]

How do you learn physics "correctly"?

Hi.

I was wondering about this. I saw this thread:

https://www.physicsforums.com/showthread.php?t=372653&page=2

I saw this:

I roughly agree here. With sufficient background information and context, the Rutherford experiment is clean enough to strongly disfavor certain ideas. My concern is that students often lack the relevant background and context to make such a determination. If you've never done the classical mechanics calculations for different types of scattering, if you've never thought hard about the assumptions and mechanism underlying scattering experiments, etc then just being told that Rutherford conclusively proved this or that isn't necessarily very convincing.

(highlight mine)

Does this mean that if you go to a school to learn physics, or any other method of learning physics, chances are you're not getting what you need? If so, how do you get it? How do you get ALL the relevant background and context for a particular point? How can you make sure you have ALL the relevant background and context before moving up to a higher level of physics? It seems that physics is full of all kinds of catches and "gotchas" which one has to be careful of, and which may easily mislead the student. What should you do? Does this mean the schools aren't teaching it right? If "yes", what should you do?

 

[ZapperZ]

This is why there is no short cuts to learning physics.

I see people on here all the time wanting to know how to learn quantum mechanics, or how to understand Relativity. They think they can pick up just the bits and pieces that they need and that's that. This is a fallacy!

Whether we like it or not, the tedious curriculum of a typical physics program is often necessary to give you the broad background in physics needed. You do need classical mechanics, classical E&M, and then QM, which will lead to Statistical mechanics/Thermodynamics, QFT, Special/General Relativity, etc. One just can't pick up a QM textbook and thinks that one can understand that without going through the rigors of doing basic classical mechanics and E&M. How else will you know where the potential term for the H atom came from in the Schrodinger equation?

There is a difference between learning physics and learning about physics. You cannot do the former in bits and pieces. Physics is not a series of disjointed and disconnected pieces of information.

Zz.

 

[sshai45]

This is why there is no short cuts to learning physics.

I see people on here all the time wanting to know how to learn quantum mechanics, or how to understand Relativity. They think they can pick up just the bits and pieces that they need and that's that. This is a fallacy!

Whether we like it or not, the tedious curriculum of a typical physics program is often necessary to give you the broad background in physics needed. You do need classical mechanics, classical E&M, and then QM, which will lead to Statistical mechanics/Thermodynamics, QFT, Special/General Relativity, etc. One just can't pick up a QM textbook and thinks that one can understand that without going through the rigors of doing basic classical mechanics and E&M. How else will you know where the potential term for the H atom came from in the Schrodinger equation?

There is a difference between learning physics and learning about physics. You cannot do the former in bits and pieces. Physics is not a series of disjointed and disconnected pieces of information.

Zz.

"There is no royal road to physics." :) Just as there is no royal road to geometry. :)

So does that mean the "students" mentioned in the quoted text are then those trying to do it "piecemeal"?

Also, I'm curious about that progression -- is that really the order you'd use? In particular, the bit about Quantum Mechanics before Thermodynamics and Relativity. Isn't Special Relativity a natural outgrowth from Classical EM, so wouldn't it make sense to go to it first after finishing classical EM?

 

[ZapperZ]

"There is no royal road to physics." :) Just as there is no royal road to geometry. :)

So does that mean the "students" mentioned in the quoted text are then those trying to do it "piecemeal"?

I wouldn't know. I'm responding to the more general situation that I see very often in this forum, where people think learning a particular part of physics is like picking up a novel and reading.

Also, I'm curious about that progression -- is that really the order you'd use? In particular, the bit about Quantum Mechanics before Thermodynamics and Relativity. Isn't Special Relativity a natural outgrowth from Classical EM, so wouldn't it make sense to go to it first after finishing classical EM?

I used CM, E&M, and QM as the "pillars" of physics. I consider the other areas as building on top of those three. Some may lean more on one than the others, but to get a true knowledge of physics, one must master those three without question and without exception. I mentioned this in my "So You Want To Be A Physicist" essay.

Zz.

 

[Forensics]

If you are an autodidact and very disciplined then it's possible. The question the OP asked is dependent on how driven, intelligent, and disciplined the person in question is.

I will go ahead and say that for most people it is not possible to teach yourself anything as advanced and in depth as physics.

 

[mal4mac]

What's the problem? If the student lacks the relevant background and context to perform scattering calculations, then the student needs to hit the books. If you've never done the classical mechanics calculations for different types of scattering, if you've never thought hard about the assumptions and mechanism underlying scattering experiments, then go away and do it now!

Indeed, just being told that Rutherford conclusively proved this or that isn't very convincing - you could say the same about everything. Realising we take most everything for granted is crucial. We also need the maturity to know that, if we are paid to do scattering calculations, we should start from the basics and do the job as thoroughly as possible. This maturity might be gained through doing a physics degree and doing some very basic stuff very thoroughly... it may not leave us equipped to do serious scattering calculations, but it should leave us equipped with knowing how to teach ourselves to do them. So "Forensics" is wrong, at some stage, if you keep in the game, you will have to teach yourself some very hard physics!

 

[IGU]

Whether we like it or not, the tedious curriculum of a typical physics program is often necessary to give you the broad background in physics needed.

I understand your basic position, but I thought that much of the "tedious curriculum" was structured to get around the students' expected inadequacies in math. What if we posit students who know all the math needed already -- what would you suggest as a streamlined curriculum then? Surely the no calculus into to mechanics could be dropped -- start with Landau & Lipschitz's Mechanics? Maybe toss intro to E&M and go straight for the grad level class based on Jackson? Other things?

I guess I'm wondering what's a good path for a grad student in mathematics who has never had a physics class to learn physics to a Ph.D. level? Surely there's something more efficient than the full "tedious curriculum".

 

[WannabeNewton]

Surely the no calculus into to mechanics could be dropped -- start with Landau & Lipschitz's Mechanics? Maybe toss intro to E&M and go straight for the grad level class based on Jackson?

Why would knowing more advanced math make either of these a good alternative to the standard curriculum? L&L mechanics isn't a book you learn mechanics from. It's a book from which you appreciate the elegance and glory of symmetries in physics and as such is something you reserve after you've had a proper course in mechanics. A book like Kleppner and Kolenkow can give you a deep understanding of mechanics and makes use of nothing more than basic calculus; from here L&L would be a more logical next step. Going straight to Jackson isn't a great route either-you don't get any physical insight from Jackson. The book is meant to reinforce your computational fluency and spontaneous utilization of electromagnetism not teach you the fundamentals, foundations, and physical concepts of EM. An EM book more on the level of Kleppner and Kolenkow would be Purcell's masterpiece.

More advanced math $\neq$ more physical insight or deeper physical understanding.

 

[mfb]

Abstruse Goose: Prerequisites
Click on the images to proceed

@IGU: You can certainly skip some mathematical parts of the physics lectures, but I doubt skipping full lectures would be possible just based on math knowledge.

 

[AlephZero]

More advanced math $\neq$ more physical insight or deeper physical understanding.

That is not an "either/or" dichotomy. The best insight into Lagrange multipliers that I have come across in 30 years explained them using Rube Goldberg machines. And I once demolished a plausible looking two-year experimental research project in mech eng with a three-line argument using group theory (though it took more than 3 lines of math to explain it to the other people involved!)

You can't have too many tools in your intellectual tool-box, but it's easy not to know you have too few.

 

[sshai45]

If you are an autodidact and very disciplined then it's possible. The question the OP asked is dependent on how driven, intelligent, and disciplined the person in question is.

I will go ahead and say that for most people it is not possible to teach yourself anything as advanced and in depth as physics.

Would I be right in saying that it also requires a lot of "discipline" even if you're having it taught to you by someone else?

 

[sshai45]

Also, I saw this:

https://www.physicsforums.com/showthread.php?t=144950#post1170129

Yes, that was the point. The usual textbook arguments of the "need" for photons are wrong (in that you have "immediate" emission, that there is a threshold in frequency and all that, are usually presented as *necessary conditions* to have photons, and these are the things that are also obtained in the semiclassical approximation, as shown by Mandl and Wolf). This is not so widely known. Of course, for more sophisticated setups, the semiclassical approximation doesn't work well anymore, but these are not the arguments usually brought up in elementary textbooks to require the *need* for photons.

(emphasis mine)

If this is true, and the textbooks can be wrong on that, what else can they be wrong on? If you can't trust a textbook, what can you trust? Can you trust your physics teacher? What if he inherited some of these misconceptions? What do you do about stuff like this?

Doing more searching I've found others talking about misconceptions promoted by textbooks, including (especially?) introductory ones. What should one do?

 

[Forensics]

Would I be right in saying that it also requires a lot of "discipline" even if you're having it taught to you by someone else?

I will agree with that. While my degree is not in Physics I have a great deal of respect for the difficulty of majoring in it.

The way I see it, the more intelligence you have the less you will need discipline. Look at it this way, if you are an extremely brilliant person you will possibly pick things up much quicker than others around you, allowing you to gain a masterful knowledge base with minimal effort.

Now, with that said, people like the example above are rare. With average and even above average intelligence, you will need to have the discipline and commitment to study the material until you've mastered it. I was in a class with an engineering student that was about to graduate for mechatronics engineering. He was taking a motors and control class with me. Now, when we spoke about calculus he said he memorized his calculus book and worked through it until he could do any and all of it.

That is the dedication that you need to teach yourself a topic like physics, in my opinion.

 

[sshai45]

I will agree with that. While my degree is not in Physics I have a great deal of respect for the difficulty of majoring in it.

The way I see it, the more intelligence you have the less you will need discipline. Look at it this way, if you are an extremely brilliant person you will possibly pick things up much quicker than others around you, allowing you to gain a masterful knowledge base with minimal effort.

Now, with that said, people like the example above are rare. With average and even above average intelligence, you will need to have the discipline and commitment to study the material until you've mastered it. I was in a class with an engineering student that was about to graduate for mechatronics engineering. He was taking a motors and control class with me. Now, when we spoke about calculus he said he memorized his calculus book and worked through it until he could do any and all of it.

That is the dedication that you need to teach yourself a topic like physics, in my opinion.

So does that mean you have to sit there are rote-memorize everything, rote-memorize the entire text of the calculus book, and every other textbook you use until you can recite it word for word exactly as written? But isn't there more to learning than just rote memorization, even if rote memorization does play a role (in particular, you need to understand, not just rote drill), and so if you decided to sit down and rote memorize everything like that word-for-word, you wouldn't have any time for the other parts of the learning? Or am I interpreting that wrong? E.g. do you mean something more like "memorize the content of every definion, theorem, and proof in the book while understanding them, but not necessarily the exact and specific words the author used, so that, if quizzed, you would be able to produce a statement of the theorem and its proof in your words that would be correct?"

 

[WannabeNewton]

If this is true, and the textbooks can be wrong on that, what else can they be wrong on?

Textbooks can be sloppy and even outright incorrect frequently. There are countless examples of textbooks promoting misconceptions, even famous and well-regarded textbooks. I could give you examples I found of this not two weeks ago. Your best bet is to consult multiple textbooks on the subject.

What do you do about stuff like this?

Your professors obviously know what they're doing. If something doesn't make sense to you then ask them. If you find later on that something was misinterpreted then just correct it for yourself. You're making this harder on yourself by worrying so much. It's not a big deal.

 

[Vanadium 50]

You're the only person who mentioned rote memorization. You are setting up a straw man.

 

[Forensics]

So does that mean you have to sit there are rote-memorize everything, rote-memorize the entire text of the calculus book, and every other textbook you use until you can recite it word for word? But isn't there more to learning than just rote memorization, even if rote memorization does play a role (in particular, you need to understand, not just rote drill), and so if you decided to sit down and rote memorize everything like that word-for-word, you wouldn't have any time for the other parts of the learning? Or am I interpreting that wrong?

Oh, I don't mean that to be how everyone has to learn, just an example of his dedication to learning what he needed to learn to excel at what he wanted to do. He wanted to excel in calculus for his degree so he went the extra mile and memorized every equation in the entire book and understood their application thoroughly.

For me, I am in an EET degree so everything I learn is hands on. When I took my motors and control class (I am getting a 2 year degree at a CC then transferring to a 4 year ABET accredited uni) I memorized everything I could. I took the class a year ago but I can still write you out a ladder logic, troubleshoot it and it's order, then wire it up for you. I got all of that from a 2 month summer class because I learned what they were teaching in the class, then learned all the things related to the class that they didn't cover.

 

[sshai45]

You're the only person who mentioned rote memorization. You are setting up a straw man.

Thanks. I have a problem of interpreting things in a strict, literal way some times. But if that is straw, then what is the correct interpretation? Was I right when I added that addendum?:

"memorize the content of every definion, theorem, and proof in the book while understanding them, but not necessarily the exact and specific words the author used, so that, if quizzed, you would be able to produce a statement of the theorem and its proof in your words that would be correct? "