So you want to learn physics (2021)(susanrigetti.com)
susanrigetti.com
So you want to learn physics (2021)
https://www.susanrigetti.com/physics
169 comments
You might be interested in Kip Thorne (of Gravitation fame) and Roger Blandford's book Modern Classical Physics, which is designed to cover the elements of non-quantum physics that are generally ignored in the first year PhD curriculum. Part headers: statistical physics; optics; elasticity; fluid dynamics; plasma physics; general relativity
I second the recommendation of this book -- it really is quite excellent and covers at an advanced level most of what is commonly left out of a modern physics curriculum (though it is quite imposing in its size/weight).
Idiot who transferred from physics to computer science after year 1 here, so please make allowances. But all of those phenomena are emergent. Shouldn’t physics focus much more on the underlying micro states and micro processes than the emergent phenomena?
Obviously there needs to be a transition, but at some point you go from physics to engineering. I suppose it depends what specialty in physics you go into. Nobody can specialise in everything.
Obviously there needs to be a transition, but at some point you go from physics to engineering. I suppose it depends what specialty in physics you go into. Nobody can specialise in everything.
> Shouldn’t physics focus much more on the underlying micro states and micro processes than the emergent phenomena? Obviously there needs to be a transition, but at some point you go from physics to engineering.
1. The boundaries between disciplines are where they are in part by historical accident, and in part because that's what the people working in them find useful - there is no actual fact of the matter.
2. We don't actually know the underlying microprocesses of anything. Effective theories are all we have, and there's no fundamental difference between an effective theory for the vacuum (if it is a vacuum) and one for, say, the bulk of a semiconductor.
1. The boundaries between disciplines are where they are in part by historical accident, and in part because that's what the people working in them find useful - there is no actual fact of the matter.
2. We don't actually know the underlying microprocesses of anything. Effective theories are all we have, and there's no fundamental difference between an effective theory for the vacuum (if it is a vacuum) and one for, say, the bulk of a semiconductor.
> there is no actual fact of the matter.
This is true of all categories, so not a helpful comment. I suspect someone has a good enough definition.
This is true of all categories, so not a helpful comment. I suspect someone has a good enough definition.
Physics: research, theorize
Engineering: practical implementation
That’s how it goes in my brain. It’s physics until we can build it reliably, then it’s engineering.
Engineering: practical implementation
That’s how it goes in my brain. It’s physics until we can build it reliably, then it’s engineering.
As GP said, continuum mechanics is often used for physics research. While not the Truth, the models can often be accurate. My own research involving transport in the quantum domain utilized some models from continuum mechanics.
(I didn't introduce it - it was already being used).
(I didn't introduce it - it was already being used).
You could say that about a lot of topics. Heck you could say that chemistry is just an emergent phenomenon of physics.
The benefit of taking such a class or reading such a textbook is that these things have been studied extensively, we have good models for them, and it is useful to know because people are still doing fundamental research on it to this day or working on phenomena that are closely related.
The benefit of taking such a class or reading such a textbook is that these things have been studied extensively, we have good models for them, and it is useful to know because people are still doing fundamental research on it to this day or working on phenomena that are closely related.
Reminds me of a student sketch from my days in nerd school, parodying Star Trek. A student dressed as one of the physics professors demonstrated that FTL travel was impossible, causing the Enterprise’s warp drives to stop functioning. It was fixed when Scotty said, “Wait, I’m an engineer: I don’t need to understand physics!”
I think solid state continuum mechanics are also the optimal place to introduce tensors. For some reason, the first tensors many physics students encounter are very abstract. It would be like if the first vectors you encountered were quantum mechanical states. Stress and strain are, in my opinion, the ideal "prototypical rank-2 tensors", and it's useful to spend time really elaborating what that means, the same way we teach students to think of vectors as "things that look like displacement/velocity".
That’s an interesting idea. The best class involving tensors I ever took was an introductory course on differential geometry, and I still think the coordinate-free approach of thinking of tensors as multilinear functions from some number of vectors to some other number of vectors (or a scalar) is great. Everything else just involves picking coordinates and figuring out where the numbers to :)
But I probably like abstractions like this more than most people.
Oddly, undergraduate physics also seems to be missing another, arguably even more fundamental, tensor: the moment of inertia. You can get quite far (in three dimensions, and only in three dimensions) by thinking of rotation as a vector. (Or a quaternion if that floats your boat.) But you can’t get very far by pretending that the moment of inertia is a scalar, and you get very confused very quickly if you treat it as three scalars in the magical coordinate system in which you can write it like that.
But I probably like abstractions like this more than most people.
Oddly, undergraduate physics also seems to be missing another, arguably even more fundamental, tensor: the moment of inertia. You can get quite far (in three dimensions, and only in three dimensions) by thinking of rotation as a vector. (Or a quaternion if that floats your boat.) But you can’t get very far by pretending that the moment of inertia is a scalar, and you get very confused very quickly if you treat it as three scalars in the magical coordinate system in which you can write it like that.
Hydraulics are everywhere. Ever used a sink? Flushed a toilet? Contemplated an air filter? Felt both sides of a small fan? Wondered how, exactly, a utility pump causes water to go in the inlet and out the outlet, and tried to read the manufacturer’s spec? Contemplated that the ripples when you throw a rock in an actual pond really don’t resemble the average “look I made water in WebGL” animation very much?
if you can understand the PDEs of GR and QFT, you can apply it to this too
if you can understand the PDEs of GR and QFT, you can apply it to this too
I noticed that too, and my explanation was that physics education needs to set itself apart from engineering.
Classical ( non relativistic ) field theories by now are undergrad engineering topics, but there are only a few quantum engineers.
Most of the non quantum topics in modern undergrad physics curricula, is needed to make sense of quantum[ thermodynamics, filed theory, optics, something ]
Classical ( non relativistic ) field theories by now are undergrad engineering topics, but there are only a few quantum engineers.
Most of the non quantum topics in modern undergrad physics curricula, is needed to make sense of quantum[ thermodynamics, filed theory, optics, something ]
Do you have text/other sources suggestions for this? I agree with you, would like to learn more.
Halliday & Resnick Fundamentals of Physics is what we used in AP as well as in freshman year at college. Covers most sections one needs to be familiar with to be physics literate (solid/fluid mechanics, waves, thermo, electromagnetism, optics, relativity).
Is that still in print? That was the physics book we used my freshman year, in 1974. It was a great book. I’m still sorry I sold it.
That was my first year text book in 1998. Sounds like it's still going strong!
Still used in as an undergraduate in 2013
Jearl Walker (of Cleveland State and PBS’s Kinetic Carnival) was added as an author.
I don’t know much about continuum mechanics (unless you count stat mech but I wouldn’t), however Goldstein has a few chapters on the topic that might serve as an introduction
The best book I came across is this
https://www.amazon.com/Continuum-Mechanics-Foundations-Appli...
It has a slightly solid mechanics bent, but the fundamentals are the same for fluids and solids (conservation laws, tensor formulation)
For the mathematically inclined, the best I've seen is An Introduction to Continuum Mechanics by Morton Gurtin from 1981. At one point, it could be purchased from Google books directly as a pdf.
You've described the core of a usual Chemical Engineering curriculum. A school with a good engineering program would definitely offer these classes, maybe under a name like "transport phenomena" (in my experience).
The undergraduate Physics program is, in my opinion, heavily influenced by the working physicists in the field. Lots of physicist who work in fundamental physics is either particle physicists or work with models that are in particles. Those are the ones who teach physics in undergrad.
This is simply not true, condensed matter physics makes up the largest sub-field of physics (about half by some estimates).
I think the more relevant aspect is that to reach the frontier in a wide array of fields you a solid grounding quantum physics (and several other "new" -- i.e. within the last century or so -- topics) that have displaced more "old-fashioned" topics like continuum mechanics.
I think the more relevant aspect is that to reach the frontier in a wide array of fields you a solid grounding quantum physics (and several other "new" -- i.e. within the last century or so -- topics) that have displaced more "old-fashioned" topics like continuum mechanics.
Introduction to the Physics of Fluids and Solids by James Trefil might be interesting for you.
A point that's rightfully emphasized by the author:
> Solving problems is the only way to understand physics. There's no way around it.
This generalizes well to other fields. I don't want to discourage anybody from trying to educate themselves in a difficult field (be it physics or something else), but that's a very common and immediately visible problem with autodidacts. If you haven't worked through enough hard problems you lack the intuition that ties together theory.
> Solving problems is the only way to understand physics. There's no way around it.
This generalizes well to other fields. I don't want to discourage anybody from trying to educate themselves in a difficult field (be it physics or something else), but that's a very common and immediately visible problem with autodidacts. If you haven't worked through enough hard problems you lack the intuition that ties together theory.
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That’s a POV I’ve grown to adopt as I got older (like many, perhaps). I used to heavily privilege theory, believing that everything could (and maybe should) be derived from first principles.
Now I place the concrete over everything else; theory is nice when it can illuminate why the practice works. Otherwise, it’s just words.
The most frustrating is when I have friends who have derived their entire understanding of a subject I know as a practitioner (typically something tech/programming related) from watching YouTube videos/listening to podcasts.
Because they’ve heard hours and hours from experts, they have a feeling of deep understanding. But talking to them about this topic is extremely frustrating because their knowledge clearly has never had to be applied to the real world, and is grounded in nothingness, so they misunderstand lots, but they feel like they know what they’re talking about as much as you do.
Now I place the concrete over everything else; theory is nice when it can illuminate why the practice works. Otherwise, it’s just words.
The most frustrating is when I have friends who have derived their entire understanding of a subject I know as a practitioner (typically something tech/programming related) from watching YouTube videos/listening to podcasts.
Because they’ve heard hours and hours from experts, they have a feeling of deep understanding. But talking to them about this topic is extremely frustrating because their knowledge clearly has never had to be applied to the real world, and is grounded in nothingness, so they misunderstand lots, but they feel like they know what they’re talking about as much as you do.
> That’s a POV I’ve grown to adopt as I got older (like many, perhaps). I used to heavily privilege theory, believing that everything could (and maybe should) be derived from first principles.
> Now I place the concrete over everything else; theory is nice when it can illuminate why the practice works. Otherwise, it’s just words.
That mirrors the trajectory of all humankind, doesn’t it? From lofty Platonic ideals to nitty gritty empiricism and experimentation.
> Now I place the concrete over everything else; theory is nice when it can illuminate why the practice works. Otherwise, it’s just words.
That mirrors the trajectory of all humankind, doesn’t it? From lofty Platonic ideals to nitty gritty empiricism and experimentation.
An odd hypothesis, I think. I don't think our ancestors were any less practical than us. Probably a great deal more practical, in fact.
You reference Plato, but you could easily phrase it in the other direction. "From Roman engineering to Wittgenstein blithering on about meaning."
You reference Plato, but you could easily phrase it in the other direction. "From Roman engineering to Wittgenstein blithering on about meaning."
antegamisou(1)
Yes, and I'd take it further. What I'd like to see more of in physics texts is presenting a problem before offering the solution. Too often you get what amounts to a laundry list of techniques and ideas, which are the components to the answers to hard problems, but the student isn't motivated to learn them. If you present the hard problem first, the student may flail around and realize: I need something to help with this! Now that they know they need it, and why, you can give them the tool that fits the bill. For example, I think calculus is probably better learned after trying to write down some force laws, and perhaps doing some numerical analysis. Then when you learn them you realize those nice closed-form solutions aren't busywork, they are huge labor saving tools that eliminate ad hoc labor intensive analysis.
I would also deemphasize the more mathy parts of calculus - do you really need a deep dive into continuity or the fundamental theorem of calculus? Eventually, yes. But it's just like programming: you're not going to need to understand language theory or ADTs or category theory or lambda calculus to write your first program. Or your second. And, IMHO, you should only reach for this understanding when you realize you need it. Otherwise, it won't integrate well into your toolkit.
I would also deemphasize the more mathy parts of calculus - do you really need a deep dive into continuity or the fundamental theorem of calculus? Eventually, yes. But it's just like programming: you're not going to need to understand language theory or ADTs or category theory or lambda calculus to write your first program. Or your second. And, IMHO, you should only reach for this understanding when you realize you need it. Otherwise, it won't integrate well into your toolkit.
> If you present the hard problem first, the student may flail around and realize: I need something to help with this!
As I've grabbed my horse and lance and rushed at this windmill from assorted directions, I quickly run into my limitations that prevent the problem being solved. I run into vocabulary problems with the math, the fact that I simply don't have the math to approach the problem (which appears to be some vector calculus -- I think. "No, you idiot, it's XYZ instead", but I don't know enough to know that it's not vector calculus, if, indeed, it isn't). I try to apply basic kinematics to the problem, but I don't know if that's enough. And, finally, it could be all of those things plus, oh, some optimization issues and, also, would you like to be introduced to the several different techniques for computing numeric integration and the differential equation solvers?
"Eeep!"
To quote the film "Addams Family Values":
Wednesday: Pugsley, the baby weighs 10 pounds, the cannonball weighs 20 pounds. Which will hit the stone walkway first?
Pugsley: I'm still on fractions.
You might dig “The Theoretical Minimum” by Susskind, as well as his follow-on books. And he has associated lectures on YouTube.
I don’t recommend the first book. At least in my edition the typesetting is just odd, which makes it harder to read than it should be. The front matter indicates it was typeset in Mathematica, which probably explains it. The later books in the series don’t suffer from this problem.
The videos that it was essentially transcribed from are great tho.
If it exists, you could probably replace most of the first book with just a really good explanation of the Lagrangian, with lots of examples, I think.
The videos that it was essentially transcribed from are great tho.
If it exists, you could probably replace most of the first book with just a really good explanation of the Lagrangian, with lots of examples, I think.
> What I'd like to see more of in physics texts is presenting a problem before offering the solution.
Yes.
> If you present the hard problem first, the student may flail around and realize: I need something to help with this! Now that they know they need it, and why, you can give them the tool that fits the bill.
No.
If an instructor deliberately gives a student a problem that they know the student _cannot_ solve, then it rightfully destroys trust.
I never taught at the university level, but with middle and high school math students I taught them to how (re)discover the solutions, rather than teaching them the solutions directly.
As a practical matter, many of my college classes went too quickly to do anything _but_ teach the solution -- or tell us to learn it between classes and bring questions back.
Yes.
> If you present the hard problem first, the student may flail around and realize: I need something to help with this! Now that they know they need it, and why, you can give them the tool that fits the bill.
No.
If an instructor deliberately gives a student a problem that they know the student _cannot_ solve, then it rightfully destroys trust.
I never taught at the university level, but with middle and high school math students I taught them to how (re)discover the solutions, rather than teaching them the solutions directly.
As a practical matter, many of my college classes went too quickly to do anything _but_ teach the solution -- or tell us to learn it between classes and bring questions back.
I don't think it breaks trust, if you tell them what's going on. "Hey kids, I'm going to give you a problem that went unsolved until Newton. I don't expect you to find his answer, which I'll teach you later, but I want you to try to solve it your own way."
> If an instructor deliberately gives a student a problem that they know the student _cannot_ solve, then it rightfully destroys trust.
This does not destroy trust, but gives the student an important lesson: we only have the techniques to solve, say, 0.0000001% of the problems. So you have to learn brutally hard for the next many years (or rather decades) to have the minimal qualifications to be able to invent whole new techniques that no person has ever come up in history before to increase this ratio from, say,to 0.000000100000000001% (even this would trigger a whole new aera in the history of science).
This does not destroy trust, but gives the student an important lesson: we only have the techniques to solve, say, 0.0000001% of the problems. So you have to learn brutally hard for the next many years (or rather decades) to have the minimal qualifications to be able to invent whole new techniques that no person has ever come up in history before to increase this ratio from, say,to 0.000000100000000001% (even this would trigger a whole new aera in the history of science).
> As a practical matter, many of my college classes went too quickly to do anything _but_ teach the solution
I dropped that class. I always felt it was a mistake not taking calculus in High School. I had a very good relationship with the math teacher there, and we could have done it, to some level, casually between classes. I just didn't take him up on it.
I've never learned calculus.
> IMHO, you should only reach for this understanding when you realize you need it
Issue is that often times people don't know that a certain tool exists, so they re-invent a 100x worse version and just hack something.
Issue is that often times people don't know that a certain tool exists, so they re-invent a 100x worse version and just hack something.
I only became reasonably proficient in physics when I took the summer off between undergrad and graduate school and spent three months, six days a week, ten hours a day, doing nothing but working through four years of undergraduate physics curriculum by solving problems from my textbooks.
There is no substitute for solving problems.
There is no substitute for solving problems.
That is some dedication, well done. Interesting to know more about your career and where this lead to if you continued down the physics path.
I went on to earn a doctorate in biophysics and then began a career developing instrumentation for biomedical research. While I no longer work directly in the field of physics, the physical intuition and reasoning abilities honed by a physics education has allowed me to successfully lead teams consisting of electrical and mechanical engineers, while serving as the liaison to biologists and doctors. I regard a physics education as a modern-day ‘liberal arts’ technical degree.
> I regard a physics education as a modern-day ‘liberal arts’ technical degree.
Some anecdotal evidence for this:
https://www.dwarkeshpatel.com/p/dario-amodei#details
> Dario Amodei: We have generally found that if we hire someone who is a Physics PhD or something, that they can learn ML and contribute just very quickly in most cases.
Some anecdotal evidence for this:
https://www.dwarkeshpatel.com/p/dario-amodei#details
> Dario Amodei: We have generally found that if we hire someone who is a Physics PhD or something, that they can learn ML and contribute just very quickly in most cases.
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Like another commenter, I'm curious what drove you to this. Seems like clearly A Good Idea I Could Have Benefited From, but my attitude was always: I finished the class, whatever I need to learn through application, life will point me toward. Yet I wish I had done something similar to what you did. What gave you the impetus?
We were required (by the state I believe) to take a comprehensive test assessing our competency at physics. I struggled with test and was disheartened that four years of strenuous effort would be all for naught. I knew I needed to do something to shore up my understanding of physics if I was going to retain the knowledge decades onwards. The other reason was a simple love for the beauty and underlying simplicity of the subject.
> I finished the class, whatever I need to learn through application, life will point me toward.
In math/physics, it often won't. Solving lots of problems serves two particular purposes: To really solidify the concepts in your mind so you won't forget, and ensuring you learn the techniques and not just the knowledge.
For the former, you may find yourself in the position where you find yourself way over your head, and won't know where to start. You usually will not have a single gap, but many. You'll find yourself realizing you'll need to look up material from several textbooks to regain the knowledge you've lost. Once you begin that process, you'll pick up one of your old textbooks and while the physics knowledge may be absorbed, you'll realize you've forgotten much of the math needed to solve such problems. In the unlikely event you'll retain enough to follow the textbook, it is very unlikely you'll know the techniques well enough to solve the real world problem.
And your colleagues will. You'll be alone, and you'll drop out of that group. With physics/math, there often are hard boundaries in these groups. Those who meet the bar are in. Those who don't drop out, because it really sucks being the only person in the group who is struggling with what everyone else considers as basic.
SW engineering has a much more gradual change in skills amongst people, and usually the problems most people work on are fairly learnable in a short amount of time.
In math/physics, it often won't. Solving lots of problems serves two particular purposes: To really solidify the concepts in your mind so you won't forget, and ensuring you learn the techniques and not just the knowledge.
For the former, you may find yourself in the position where you find yourself way over your head, and won't know where to start. You usually will not have a single gap, but many. You'll find yourself realizing you'll need to look up material from several textbooks to regain the knowledge you've lost. Once you begin that process, you'll pick up one of your old textbooks and while the physics knowledge may be absorbed, you'll realize you've forgotten much of the math needed to solve such problems. In the unlikely event you'll retain enough to follow the textbook, it is very unlikely you'll know the techniques well enough to solve the real world problem.
And your colleagues will. You'll be alone, and you'll drop out of that group. With physics/math, there often are hard boundaries in these groups. Those who meet the bar are in. Those who don't drop out, because it really sucks being the only person in the group who is struggling with what everyone else considers as basic.
SW engineering has a much more gradual change in skills amongst people, and usually the problems most people work on are fairly learnable in a short amount of time.
Plus, at various times, I’ve had to revisit things I learned years ago and ended up understanding it much better because I could connect it to a swath of things I hadn’t learned the first time I saw the material.
Math and its applications are a contact sport. You don’t truly appreciate it until you try to use it yourself.
Math and its applications are a contact sport. You don’t truly appreciate it until you try to use it yourself.
This is really interesting perspective -- thanks for sharing it. I think there's something to the idea that some fields are more 'binary' than others -- that if you can't make it past some threshold of _true understanding_ that you will be denied experiences that could push that threshold further. Such a field would warrant a different strategy for learning / mastery than a less binary field.
I'm going to ruminate on this.
I'm going to ruminate on this.
> There is no substitute for solving problems
But you will spend the rest of your life arguing with people who insist that there must be a ("quick and dirty") substitute and you're responsible for finding it.
But you will spend the rest of your life arguing with people who insist that there must be a ("quick and dirty") substitute and you're responsible for finding it.
Totally 100% with this. When younger I thought I could read the material and say "Oh, okay that makes sense I understand this." Only to fail miserably when on a test or somewhere I had to apply what I "knew" and realizing I didn't actually know it. I lean strongly toward autodidacticism and learned that if I could solve problems with the technique then I knew it.
My calculus 1 professor gave the advice that the best way to study is to do every problem in the book, then go and get another book and do every problem in that book, and keep doing that until you look at a problem and know exactly every step to do immediately.
Time consuming but I can see this being really really effective.
There’s certainly fields of math where I’ve seen a twist on the advice. Differential geometry, for example, is a big field with a lot of notation. Different textbooks end up using very different notations and covering non-overlapping sections of the field. Therefore, the advice I got was to not just do the problems, but translate the definitions and theorems into a unified notation that you feel is natural.
That's how I learned probability theory. I studied from one book and solved all problems, then moved to the next, until it became second nature. Probability theory is one of the topics that you will never learn by only reading, it is necessary to develop the necessary intuition.
Which exactly describes the problem with today's culture of people watching a 10 minute youtube clip and then thinking they are experts on the subject matter.
Be it microservices, coronavirus or taxation.
Be it microservices, coronavirus or taxation.
In college, I was always the first one out of my friends to “get” a concept, like fast Fourier transforms, anything with signal processing or even coding or any labs we had to do etc so I would spend time teaching them in the library. However I never did any of the exercises, mostly due to laziness and not arrogance. They would get A’s and I would get C’s and D’s.
I emphasize this story to my kids because knowing isn’t important because everyone eventually figure it out. It’s the ones who can do the problems and get good marks that succeed in the end.
I emphasize this story to my kids because knowing isn’t important because everyone eventually figure it out. It’s the ones who can do the problems and get good marks that succeed in the end.
I think this shows a lack of self-doubt, which can be deadly. Those problems acted as verification to yourself that you understood the theory and its application. If you truly understood the material, then the problems would be zero effort. However, if you struggled with them it's a signal that you don't know what you think you know.
As someone who had an a similar experience to whom you are replying to, this was definitely not the case. The problems were easy, but were not "zero effort". Even if it takes you only a few minutes to do the steps and show the work per problem, then that could still take you 30-60 minutes to complete the assignment. That was time I'd spend doing things I wanted to do (fun in the short term, a nightmare in the long term).
I think usually the easy problems are just the "burn-in" time to solidify understanding, but there's usually a couple hard problems that take way longer to work through and those will teach you the intuition. Doing simple calculation is different than being forced to conceptualize the entire path from starting information to system to evolution to result.
This is kind of interesting to hear because I was the other way around. I found the best way to understand something was to teach it to others. That way I took what I already understood and was able to see what other people misunderstood, which was often something I'd never expected to be an issue, and add their experience in learning the topic on to what I already knew which expanded my overall understanding.
Then again, in the process of teaching I always found myself teaching people to work problems, which required me to be able to work the problems myself. In a way, it's kind of impressive you managed to avoid doing that.
Then again, in the process of teaching I always found myself teaching people to work problems, which required me to be able to work the problems myself. In a way, it's kind of impressive you managed to avoid doing that.
Especially these days, the bar for “knowing” Fourier transforms is simply a 7 minute video from 3blue1brown.
The gap between knowers and doers will only get larger as math explainers improve their content.
The gap between knowers and doers will only get larger as math explainers improve their content.
It used to pose as a difficulty for self leaners because they did not have access to assignments, exams and solutions unless they register for classes.
Nowadays it's a lot easier when there are so many free materials from top school online. And stack exchange and reddit is available almost 24-7 if one ever has a question.
Nowadays it's a lot easier when there are so many free materials from top school online. And stack exchange and reddit is available almost 24-7 if one ever has a question.
> It used to pose as a difficulty for self leaners because they did not have access to assignments, exams and solutions unless they register for classes.
Many textbooks still employ the deplorable practice of not presenting the answer to all exercises at the end, unfortunately.
Many textbooks still employ the deplorable practice of not presenting the answer to all exercises at the end, unfortunately.
Yeah, but I think there is a teacher's edition we can grab online from somewhere?
>> Solving problems is the only way to understand physics. There's no way around it.
The reason is that you think you understand what you read, but as Richard Feynman said:
> The first principle is that you must not fool yourself, and you are the easiest person to fool.
You think you understand 90% of what you read, but in reality it's probably only 20-30%. By doing the exercises, at the very least you'll know that you don't know that much. And if you then reread the materials a few pages before, you'll realize that you have skimmed (or worse, skipped) some parts because you mistakenly thought you already understood it.
Another tips from my personal experience: When you're reading a textbook, keep asking in your mind questions with the types of "what if" and "how about," which are sometimes not yet explained in the section you're reading. Also, keep associating what you've recently learned with what you've already known (days ago, years ago).
Be curious and validate that you really understand what you think you understand.
The reason is that you think you understand what you read, but as Richard Feynman said:
> The first principle is that you must not fool yourself, and you are the easiest person to fool.
You think you understand 90% of what you read, but in reality it's probably only 20-30%. By doing the exercises, at the very least you'll know that you don't know that much. And if you then reread the materials a few pages before, you'll realize that you have skimmed (or worse, skipped) some parts because you mistakenly thought you already understood it.
Another tips from my personal experience: When you're reading a textbook, keep asking in your mind questions with the types of "what if" and "how about," which are sometimes not yet explained in the section you're reading. Also, keep associating what you've recently learned with what you've already known (days ago, years ago).
Be curious and validate that you really understand what you think you understand.
Although, I think what you're describing doesn't completely lie on the reader. Oftentimes, the author has plain just not explained things clearly or even remotely well, and the reader has to play a little bit of 20 questions to get to the meat of something. When a book is properly written, then the shared load between the reader and the writer is much more balanced.
It's kind of a tautology though. Physics isn't remotely special in this regard at all, and it doesn't need generalizing from physics. One needs to work through anything to truly learn it: music, sports, gardening, life, writing, etc.
> Classical Electrodynamics by Jackson (essential). This is the bible of classical electrodynamics, and everyone who works through either loves it or hates it (I loved it).
I agree that there is a division between who loves that book (like the author) and the majority of the graduate students who had nightmares (and sometimes still gets). I like this goodreads review of the book [1]
> A soul crushing technical manual written by a sadist that has served as the right of passage for physics PhDs since the dawn of time. Every single one of my professors studied this book, and every single one of them hates it with a passion. While I've no intention of becoming a professor, I still wonder, will my colleagues also inflict this torture on their students? Will the cycle be perpetuated ad infinitum? How many more aspiring physicists will we leave battered and bruised at the gates of insanity before switching to a textbook that seeks to make electrodynamics clear and intuitive rather than a mind-numbing trip through the seventh circle of hell?
[1] https://www.goodreads.com/review/show/1266180525
* personal note: If this book is really the bible of classical mechanics, then I'm atheist.
I agree that there is a division between who loves that book (like the author) and the majority of the graduate students who had nightmares (and sometimes still gets). I like this goodreads review of the book [1]
> A soul crushing technical manual written by a sadist that has served as the right of passage for physics PhDs since the dawn of time. Every single one of my professors studied this book, and every single one of them hates it with a passion. While I've no intention of becoming a professor, I still wonder, will my colleagues also inflict this torture on their students? Will the cycle be perpetuated ad infinitum? How many more aspiring physicists will we leave battered and bruised at the gates of insanity before switching to a textbook that seeks to make electrodynamics clear and intuitive rather than a mind-numbing trip through the seventh circle of hell?
[1] https://www.goodreads.com/review/show/1266180525
* personal note: If this book is really the bible of classical mechanics, then I'm atheist.
Well yes, but curious what book you would recommend instead for graduate electrodynamics? Note that she already recommends first studying Griffith's Introduction to Electrodynamics at the undergraduate level (and that one is a true pleasure to read imho).
I'm happy that many professors start to use Zangwill's Modern Electrodynamics [1] textbook. It seems more focused on explaining things and don't assume that you know too much (which you usually have no idea if you should have known something or you just an idiot) like Jackson.
[1] https://www.amazon.com/dp/0521896975/
[1] https://www.amazon.com/dp/0521896975/
From what I've heard, the value of Jackson is not the EM you'll learn, but the mathematical techniques you'll learn, which are widely applicable beyond EM.
Zangwill should be the new Jackson. Covers mostly the same problems and topics but you can actually get through it.
It is interesting that 2 years later the same reviewer changes their mind a bit:
> Now, a few years after writing that review, I must return to say that as much as I hate this book, it's probably the best textbook that I have. I constantly return to it to reteach myself basic concepts or math. The problem with the text is that in order for it to be useful, you pretty much have to already understand the material. It's a dense, technical manual that, when paired with an easier to understand text such as Griffiths, grants tremendous power. Don't get me wrong, if there is a hell, I personally hope John David Jackson is burning in it right now, but I also have to tip my hat to him
> Now, a few years after writing that review, I must return to say that as much as I hate this book, it's probably the best textbook that I have. I constantly return to it to reteach myself basic concepts or math. The problem with the text is that in order for it to be useful, you pretty much have to already understand the material. It's a dense, technical manual that, when paired with an easier to understand text such as Griffiths, grants tremendous power. Don't get me wrong, if there is a hell, I personally hope John David Jackson is burning in it right now, but I also have to tip my hat to him
the author's IQ is high enough that I don't think this opinion is applicable to anyone reading it
Classical Electrodynamics by Jackson (essential). This is the bible of classical electrodynamics, and everyone who works through either loves it or hates it (I loved it).
If you're smart enough that advanced college physics comes as easily as learning to talk, I guess this would be true. The author of this guide is such a huge outlier in every respect of life. I have seen and read many smart people and she's easily in Witten or Tao territory of just being otherworldly smart. I don't think she ever encountered anything being hard. Jackson for her is like a walk in park, which is otherwise regarded as a formidably hard text.
Classical Electrodynamics by Jackson (essential). This is the bible of classical electrodynamics, and everyone who works through either loves it or hates it (I loved it).
If you're smart enough that advanced college physics comes as easily as learning to talk, I guess this would be true. The author of this guide is such a huge outlier in every respect of life. I have seen and read many smart people and she's easily in Witten or Tao territory of just being otherworldly smart. I don't think she ever encountered anything being hard. Jackson for her is like a walk in park, which is otherwise regarded as a formidably hard text.
The title should probably be: "So you want to learn theoretical physics".
While generally little known and appreciated among modern theorists and mathematical physicists, physics is actually an empirical science. In other words, every single section of that reading list is based directly or indirectly on a diverse and sophisticated set of devices and measurement configurations (aka experiments). Also, most progress in our understanding the physical universe follows simply from inventing ever better probes and opening new observation windows.
A computer analogy of the theoretical/empirical physics relation might be fun: You can spend your whole life writing application software and never even know what digital devices you are actually using. That's totally legit. But if you want to write a new computer language (= a new theory) you most likely will have to dig into memory architectures and caches and all that stuff. If you want to dramatically increase the speed of computation (= a new observation window) you have to design a new chip. And if you want to go really deep and invent new computing paradigms, well then you need to learn quantum mechanics :-)
In fairness, she does have a final sentence about that weird place called laboratory (= a place of labor).
> And, finally, a note on learning in a laboratory vs. learning from textbooks. Physics is both an experimental and theoretical science, and while research happens in laboratories and on blackboards and computers, the majority of any physics education does not take place in a laboratory but in lecture classes that teach from textbooks and assign homework problems that are found in textbooks.
My recommendation for a comprehensive intro into theoretical physics is The Road to Reality by Roger Penrose. Alas there is no such profound review of all experimental physics.
While generally little known and appreciated among modern theorists and mathematical physicists, physics is actually an empirical science. In other words, every single section of that reading list is based directly or indirectly on a diverse and sophisticated set of devices and measurement configurations (aka experiments). Also, most progress in our understanding the physical universe follows simply from inventing ever better probes and opening new observation windows.
A computer analogy of the theoretical/empirical physics relation might be fun: You can spend your whole life writing application software and never even know what digital devices you are actually using. That's totally legit. But if you want to write a new computer language (= a new theory) you most likely will have to dig into memory architectures and caches and all that stuff. If you want to dramatically increase the speed of computation (= a new observation window) you have to design a new chip. And if you want to go really deep and invent new computing paradigms, well then you need to learn quantum mechanics :-)
In fairness, she does have a final sentence about that weird place called laboratory (= a place of labor).
> And, finally, a note on learning in a laboratory vs. learning from textbooks. Physics is both an experimental and theoretical science, and while research happens in laboratories and on blackboards and computers, the majority of any physics education does not take place in a laboratory but in lecture classes that teach from textbooks and assign homework problems that are found in textbooks.
My recommendation for a comprehensive intro into theoretical physics is The Road to Reality by Roger Penrose. Alas there is no such profound review of all experimental physics.
After reading this blog, I'm ashamed. I just graduated from college. In my high school, the education of physics was so boring and tiresome that I even hated it at one point. For this reason, I chose computer science rather than physics as my major in college. Later, I gradually became interested in physics, however, due to the lack of good enough study habits, atmosphere and courage (which is a self-deprecating way of saying cowardice and laziness), until now I have not taken a step forward. This is the decision I regret most in my life. I am going to the United States to study for a master's degree in CS. Maybe I can learn some physics during the freetime of the two-year program because the educational resources in the United States are more abundant(perhaps).
I feel the same way about pursuing CS instead of Physics. But at some point, a pragmatic solution had to be made. So don’t go hard on yourself for that, you probably would have felt the same way about CS too.
Yeah thanks. The difference of CS and physics, and other natural science, I think, is that it's more about engineering even though it's name is computer "science". However the pupolar deep learning may satisfy the needs of a natural science enthusiast. Since Hinton sayed the way neural network workss resembles the mechanism of human brain[^1]. It's quite exciting.
[^1]: https://www.youtube.com/watch?v=2EDP4v-9TUA&t=2418s
[^1]: https://www.youtube.com/watch?v=2EDP4v-9TUA&t=2418s
I dropped out of Physics back in the day, because I loved computers a bit more, and now that I'm kind of fed up with computers I'd like to remove the thorn and do something like this.
But I find that so much time has passed that I would need to brush up parts of my high school maths first, and this kind of discourages me before even starting.
But I find that so much time has passed that I would need to brush up parts of my high school maths first, and this kind of discourages me before even starting.
Using math to model a system instead of learning math qua math does wonders for ease of understanding. Derivates and integrals become easy if you're using them to model the relationship between position/velocity/acceleration. I don't think I really got linear algebra until using it to learn quantum computing.
I decided to start self learning theoretical physics late last year. I have been now studying physics every day for almost a year (before and after work). I did have to brush up on calculus and matrices but it came back very quickly (within a few days) after a 25 year gap so I'd say don't let that discourage you.
Excellent discipline. What topic are you focussing on?
I have been working on quantum physics since March of this year and am hoping to complete the whole text book (Townsend) by end of the year. Then on to special relativity -> classical field theory in 2024, general relativity and QFT in 2025 and 2026 - at least that's the plan.
Enjoy the journey.
I'm preparing to do something similar but attack a lesser beast that is the general relativity. I had a Master's degree in Statistics but unfortunately 1) Statistics does not really match Pure Mathematics and 2) I forgot most of it.
A beast it still is, I think it is contained in its own walls. I can skip any topic in Quantum Physics and others that is irrelevant.
I'm wondering if it's helpful to you too to focus on something smaller.
A beast it still is, I think it is contained in its own walls. I can skip any topic in Quantum Physics and others that is irrelevant.
I'm wondering if it's helpful to you too to focus on something smaller.
Brushing up on high school maths is easy using Khan Academy, if that's all that's stopping you.
Rather than 27 (or however many) books, an ambitious student may be able to use just one big-ish book: Ian D. Lawrie's "A Unified Grand Tour Of Theoretical Physics". This even has a little 18 page "Snapshots of the Tour" which might be a trip down memory lane for those who studied physics long ago.
Of course, it might also be impenetrable if you haven't had prior exposure to most of the material.. I have zero experience trying to teach physics from it.
Of course, it might also be impenetrable if you haven't had prior exposure to most of the material.. I have zero experience trying to teach physics from it.
It will be impossible to learn physics from this book, even in the unlikely event that you already have all the requisite mathematical background (partial differential equations, vector calculus, tensors, etc.). Degree of “ambition” doesn’t come into it; you just can’t start out with special and general relativity and spacetime and quantum fields; you need to solve a lot of problems in newtonian mechanics and electromagnetism and thermodynamics and get a solid foundation in classical physics first. There is no royal road to this stuff: Susan’s list lays out the standard curriculum and it’s really the only way we know to produce physicists.
That said, this book does look like a great text for someone with a graduate level physics knowledge who wants to refresh their memory.
That said, this book does look like a great text for someone with a graduate level physics knowledge who wants to refresh their memory.
It was mostly just a recommendation to check out. I did not actually do it myself, but I tend to think I could have right after lin.alg./multivar calc freshman year and would have preferred it. Can't prove that, of course, since I didn't do it, but a year later I was loving Landau's Classical Theory of Fields which has a very similar relativity-first approach, and I did know a lot of relativity in high school. Wolfram went right from high school to grad school in physics at Caltech. The only very recently deceased late great Ed Fredkin got to be head of the MIT CS department with naught but a high school degree due to various life interventions and had some interesting "digital physics" ideas.
There are lots of pathways to learn & do. That is especially true of people coming to topics later in life, as I might expect is more common for HN comment thread readers. I know someone who learned to program in x86 assembly before they learned C (in fact one of the best programmers I know). If you talk to such people, I think you will find that their more varied backgrounds / ages in life when they approach things make anyone's dogmas more suspect. A great numerical relativist didn't study physics until his 30s. No idea what order he did things in, but I heard it was very non-standard.
So, I would encourage you to have more imagination of what might be possible / be less dismissive / jumping to conclusions. That is needlessly discouraging to many here were bemoaning "soooo many books/years/etc". "Ambition" might be "first learn diffgeo, then learn physics". I've been recommending that lately to a friend with extreme mathematical sophistication (a professor even) but no physics exposure, actually, but already some diffgeo exposure.
And, of course, "to learn physics" is maybe not to be a "produced physicist" any more than "to learn networks" means to "build a hardware router". It all depends. IMO, there are too many levels (& even directions/dimensions) of "having learned" to really even make "just can't", "only way" statements like you did. Elsethread, the diversity of even what "physicists" wind up having learned is shown to vary considerably (e.g. continuum mechanics). I find such absolutist statements needlessly discouraging to someone who might be hopeful to do it in "fewer steps". The way for most need not be the way for all or even the recommended way for any one person. People vary.
There are lots of pathways to learn & do. That is especially true of people coming to topics later in life, as I might expect is more common for HN comment thread readers. I know someone who learned to program in x86 assembly before they learned C (in fact one of the best programmers I know). If you talk to such people, I think you will find that their more varied backgrounds / ages in life when they approach things make anyone's dogmas more suspect. A great numerical relativist didn't study physics until his 30s. No idea what order he did things in, but I heard it was very non-standard.
So, I would encourage you to have more imagination of what might be possible / be less dismissive / jumping to conclusions. That is needlessly discouraging to many here were bemoaning "soooo many books/years/etc". "Ambition" might be "first learn diffgeo, then learn physics". I've been recommending that lately to a friend with extreme mathematical sophistication (a professor even) but no physics exposure, actually, but already some diffgeo exposure.
And, of course, "to learn physics" is maybe not to be a "produced physicist" any more than "to learn networks" means to "build a hardware router". It all depends. IMO, there are too many levels (& even directions/dimensions) of "having learned" to really even make "just can't", "only way" statements like you did. Elsethread, the diversity of even what "physicists" wind up having learned is shown to vary considerably (e.g. continuum mechanics). I find such absolutist statements needlessly discouraging to someone who might be hopeful to do it in "fewer steps". The way for most need not be the way for all or even the recommended way for any one person. People vary.
This guide does contain the books that are usually recommended in a university course setting! So, it will require significant amount of time and effort to master it. One of the series of books that physicists religiously stick to is Landau and Lifschitz. But my experience has been that it's worth it only if you already have some basic understanding.
I never got on very well with Landau and Lifschitz it's pretty intense. I mostly used pdf lecture notes from different courses. They can be a bit mixed but many are very good quality and you can easily pick up a couple for the same topic if you don't understand some part of one of them
Landau and Lifschitz are terrible books, pedagogically speaking. They're good only in that they're exhaustive and rigorous.
Surprised to not find Tong's notes for qft [1] (his other notes are great too). That's the only clear source of introductory QFT (and I have none for advanced QFT). Of course the only real way to learn QFT is to learn it multiple times from various sources, but you usually have exam after the first one, and Tong may get you through it.
[1] https://www.damtp.cam.ac.uk/user/tong/qft.html
[1] https://www.damtp.cam.ac.uk/user/tong/qft.html
So happy to see the love for Griffith’s Intro to Electrodynamics. I know it gets dinged for not being sufficiently rigorous, but I’ve never read another math or science textbook that did as good a job of getting a beginner to truly understand the subject.
In what way is it not rigorous? I've never read it but it definitely seems interesting to have a "good" but non-rigorous science book. Does it just hand-wave over some things to get to other important topics?
I didn’t think so, but it’s the text I used as an undergrad, so I don’t have a basis for comparison. I just have seen that criticism pop up on HN when this topic has arisen in the past.
It's pretty rigorous, and is perhaps the best EM book to get the intuition. I'm guessing the GP meant challenging in terms of the problem set.
The author is aka Susan Fowler and author of three books and has a degree in physics.
The Post is basically about how to get a degree or at least the equivalent and would require an effort of years.
https://en.wikipedia.org/wiki/Susan_Rigetti
The Post is basically about how to get a degree or at least the equivalent and would require an effort of years.
https://en.wikipedia.org/wiki/Susan_Rigetti
Previous posts, if you want to take a look at the comments there:
https://news.ycombinator.com/from?site=susanrigetti.com
https://news.ycombinator.com/from?site=susanrigetti.com
Thanks! Macroexpanded:
So You Want to Learn Physics (2016) - https://news.ycombinator.com/item?id=24088985 - Aug 2020 (124 comments)
So You Want to Learn Physics (2016) - https://news.ycombinator.com/item?id=18374994 - Nov 2018 (122 comments)
So You Want to Learn Physics - https://news.ycombinator.com/item?id=12691963 - Oct 2016 (129 comments)
So You Want to Learn Physics (2016) - https://news.ycombinator.com/item?id=24088985 - Aug 2020 (124 comments)
So You Want to Learn Physics (2016) - https://news.ycombinator.com/item?id=18374994 - Nov 2018 (122 comments)
So You Want to Learn Physics - https://news.ycombinator.com/item?id=12691963 - Oct 2016 (129 comments)
It seems like we're in a sort of 'autodidacticism boom'. I see this so much in almost everything now--physics, math, MIT courses online, etc. I think this is symptomatic of how people have lost faith in institutions--be it colleges, schools, govt, etc.--and see the DIY route as being better, or maybe schools are doing a poor job teaching or costs are too high, such as tuition. But why the sudden, huge interest in DIY math and physics especially? I dunno.
Even though Susan Rigetti says you don’t need to learn calculus first, I would recommend it -— or learn it concurrently with the introductory mechanics course. Mechanics is so much more enriching when you learn the mathematical language that was created to describe it.
You’ll already be one step ahead by the time you get to the second course, which is good, because you can strongly benefit from learning vector calculus at that time. I really enjoyed the text “Div, Grad, Curl and all that”.
You’ll already be one step ahead by the time you get to the second course, which is good, because you can strongly benefit from learning vector calculus at that time. I really enjoyed the text “Div, Grad, Curl and all that”.
One problem with approaching physics without any calculus is that you're more or less in the place in which most people taking high school physics are. Here are a bunch of formulas. Memorize them and don't worry about why they are what they are or how they relate to all the other formulas that you also have to memorize.
This post comes in at a very good time because I have recently begun to become interested in particle physics and have so far only resorted to watching YouTube videos. This is a sign that it is maybe time for me to jump into a textbook.
However, I seem to be interested in a few particular questions about particle physics as a science rather than facts about particle physics. For instance, I am interested in the instruments and methods that physicists use to verify their theoretical claims empirically. I am also interested in how theorists are able to come up with theories so early on, such that they are confirmed by evidence many years later. What are the assumptions that they were able to make? I am curious about where they derived the creativity to be able to bring in so many assumptions together and the come up with their models. Now that I write this, I realize that before theories were validated there were probably competing models.
Therefore, I am not exactly sure I want to study particle physics per se, or whether a book on the history of particle physics will do. I am ok with having a popular understanding of the subject, I mostly want to gain inspiration from following the work of famous scientists.
However, I seem to be interested in a few particular questions about particle physics as a science rather than facts about particle physics. For instance, I am interested in the instruments and methods that physicists use to verify their theoretical claims empirically. I am also interested in how theorists are able to come up with theories so early on, such that they are confirmed by evidence many years later. What are the assumptions that they were able to make? I am curious about where they derived the creativity to be able to bring in so many assumptions together and the come up with their models. Now that I write this, I realize that before theories were validated there were probably competing models.
Therefore, I am not exactly sure I want to study particle physics per se, or whether a book on the history of particle physics will do. I am ok with having a popular understanding of the subject, I mostly want to gain inspiration from following the work of famous scientists.
I see no mention of Landau and Lifshitz! On a less joking tone, I don't know many of these books. I was kinda surprised. guess i am outdated.
Landafschitz is kinda hard to self teach from. Fantastic supplement, though
It’s a decent list but thermodynamics is introduced way too late in the list (after modern and quantum wtf) and fluid dynamics and fluid mechanics including aerodynamics is entirely missing.
If you have a physics education (I have an engineering education) can you tell me if you can really get a physics degree without bumping into Bernoulli or Navier-Stokes?
At least just to see the lay of the land.
If you have a physics education (I have an engineering education) can you tell me if you can really get a physics degree without bumping into Bernoulli or Navier-Stokes?
At least just to see the lay of the land.
I am writing my physics PhD thesis and I did not study fluid mechanics (other than the few chapters in the standard general physics).
It will really be dependent on what is your physics field but you can definitely survive in physics without deep knowledge of fluid mechanics except when your study require it
PS: I am a particle physicist.
It will really be dependent on what is your physics field but you can definitely survive in physics without deep knowledge of fluid mechanics except when your study require it
PS: I am a particle physicist.
A professor remarked that it was a bit sad that physics students nowadays have a better understanding of quantum field theory than fluid mechanics. He mentioned this while lecturing on QFT.
[deleted]
But fluid mechanics is haarrddddd (Aeronautical Engineer). Compressible fluids can go suck it. I rue the day Navier-Stokes became a thing.
Agreed, I studied Materials Engineering - Fluid Dynamics was one of the hardest subjects in my opinion. I liked thermodynamics it made sense to me, solid mechanics was a bit of a slog to get through (endless amounts of beam deflection) but fluid dynamics arrghh.
I chose to take a particle physics course as an elective in my final year - I was planning to specialize in battery and capacitor technologies and wanted to learn more.
The lectures were very different to Engineering much, much more theory focused(almost nothing on applications) it was my introduction to things like Hamiltonians, Wave Functions and Fermi-Dirac statistics. I'm glad I took the course I learnt a heap especially about semi-conductors it gave me a better appreciation and understanding of things we covered in my engineering degree like magnetism and phonons/heat transfer as well. But I will say it did feel like another world compared to Engineering - there was much less in common than I would have thought.
I chose to take a particle physics course as an elective in my final year - I was planning to specialize in battery and capacitor technologies and wanted to learn more.
The lectures were very different to Engineering much, much more theory focused(almost nothing on applications) it was my introduction to things like Hamiltonians, Wave Functions and Fermi-Dirac statistics. I'm glad I took the course I learnt a heap especially about semi-conductors it gave me a better appreciation and understanding of things we covered in my engineering degree like magnetism and phonons/heat transfer as well. But I will say it did feel like another world compared to Engineering - there was much less in common than I would have thought.
at least fluid mechanics in the context of engineering is only 3 dimensions. QFT needs more.
There is a more practical reason for that. QFT has become essential to learn for many Condensed matter physicists. And they always are with particle physicists which will span most of the physics community, at least comparing with whose work involve in-depth knowledge of fluid mechanics. Not to mention that QFT seems easy in comparison.
That is a very "pure physics" way to approach physics, and I think it's right if you want to build up the underlying principles. That was how my college taught physics, and it helped to make many otherwise unintuitive parts of thermodynamics understandable.
Also, physicists don't necessarily include fluid dynamics as a core discipline. It is almost mechanical engineering to them. I'm not surprised to see it missing.
Also, physicists don't necessarily include fluid dynamics as a core discipline. It is almost mechanical engineering to them. I'm not surprised to see it missing.
I have a B.S. Physics from NMT graduated in 2009 (they changed some of the courses a year or two after my cohort) but the main series progression was Modern Physics -> Waves -> Classical Mechanics, E/M/Optics -> Quantum -> Thermo. Never really did much of anything fluids-wise other than some viscosity/drag stuff in Mechanics
NS is too applied and seems akin to including the beam equation.
Would you also say Maxwell's equations are "too applied"?
They're both pretty firmly physics things rather than applied or engineering things, in their purest forms...
They're both pretty firmly physics things rather than applied or engineering things, in their purest forms...
I've noticed before that "physics" as in what is taught for a physics degree has gaps which make little sense to me as a mechanical engineer. Continuum mechanics (including both fluid and solid mechanics) is unfortunately nearly entirely absent aside from some basic things like Hooke's law and Bernoulli's principle.
In my view, what's taught for a physics degree is more of a historical accident than a selection of the most important principles. In an extraterrestrial civilization, the boundaries between engineering, physics, and chemistry may be entirely different.
Dismissing Navier-Stokes as just a consequence of Newton's laws and thus unimportant can be extended further towards dismissing a large fraction of what's taught in physics degree programs. An undergraduate physics student may get more education on Bose-Einstein condensates (which are just a consequence of quantum mechanics :-) than they do on Navier-Stokes. The Navier-Stokes equations are a lot more important than Bose-Einstein condensates in my view.
In my view, what's taught for a physics degree is more of a historical accident than a selection of the most important principles. In an extraterrestrial civilization, the boundaries between engineering, physics, and chemistry may be entirely different.
Dismissing Navier-Stokes as just a consequence of Newton's laws and thus unimportant can be extended further towards dismissing a large fraction of what's taught in physics degree programs. An undergraduate physics student may get more education on Bose-Einstein condensates (which are just a consequence of quantum mechanics :-) than they do on Navier-Stokes. The Navier-Stokes equations are a lot more important than Bose-Einstein condensates in my view.
A physics undergraduate degree is different than a lot of degrees in that it's 100% incomplete for the purpose of training towards a real profession. Nobody hires physics bachelors. It's just the four year mark of your studies to be a 8+ year trained physicist.
And for that purpose of being an intermediate degree to becoming a physics PhD, Navier-Stokes isn't relevant. You don't use it in most fields that are generating physics PhDs in the 2000s and beyond.
There's only so much time to teach somebody in four years and there are significantly more important things that are also being left out (e.g. more thorough courses on group theory).
And for that purpose of being an intermediate degree to becoming a physics PhD, Navier-Stokes isn't relevant. You don't use it in most fields that are generating physics PhDs in the 2000s and beyond.
There's only so much time to teach somebody in four years and there are significantly more important things that are also being left out (e.g. more thorough courses on group theory).
> You don't use [Navier-Stokes] in most fields that are generating physics PhDs in the 2000s and beyond.
That's because physics degrees don't include much on fluid dynamics. If someone wants to get a PhD in fluid dynamics, they probably get a PhD in some variety of engineering. This goes back to what I said about the physics curriculum seeming weird to me, as it it's not about "physics" in itself. It's more a random selection of topics that exists for historical reasons.
> There's only so much time to teach somebody in four years and there are significantly more important things that are also being left out (e.g. more thorough courses on group theory).
In another comment, you said that you don't know what the Navier-Stokes equations are. Given that, I don't think you're in a good position to judge their value.
I have a couple of group theory books myself, and I don't agree with your assessment that group theory should get priority over fluid dynamics.
That's because physics degrees don't include much on fluid dynamics. If someone wants to get a PhD in fluid dynamics, they probably get a PhD in some variety of engineering. This goes back to what I said about the physics curriculum seeming weird to me, as it it's not about "physics" in itself. It's more a random selection of topics that exists for historical reasons.
> There's only so much time to teach somebody in four years and there are significantly more important things that are also being left out (e.g. more thorough courses on group theory).
In another comment, you said that you don't know what the Navier-Stokes equations are. Given that, I don't think you're in a good position to judge their value.
I have a couple of group theory books myself, and I don't agree with your assessment that group theory should get priority over fluid dynamics.
> In another comment, you said that you don't know what the Navier-Stokes equations are. Given that, I don't think you're in a good position to judge their value.
It was an exaggeration given that it never came up during my studies once. And I think that's a fantastic assessment of their value that I made it through most of a decade of studies without having to know a thing about fluid dynamics.
> I have a couple of group theory books myself, and I don't agree with your assessment that group theory should get priority over fluid dynamics.
...why? You're commenting on a physics line of education here. We don't use fluid dynamics and we extensively use group theory.
It was an exaggeration given that it never came up during my studies once. And I think that's a fantastic assessment of their value that I made it through most of a decade of studies without having to know a thing about fluid dynamics.
> I have a couple of group theory books myself, and I don't agree with your assessment that group theory should get priority over fluid dynamics.
...why? You're commenting on a physics line of education here. We don't use fluid dynamics and we extensively use group theory.
You are missing my main point. Physics education tends to exclude fluid dynamics, so of course you wouldn't hear much about it or do research in it if you only have physics degrees. If a physics degree were about physics as defined in the dictionary, fluid dynamics would be more prominent. But "physics" as studied in a "physics" department is much more narrow than the dictionary definition.
Fluid phenomena is ubiquitous. You live in a fluid. You probably drive a car through a fluid and may occasionally take a plane through a fluid at higher speed. You surely use plumbing. I don't see how you can claim that fluid dynamics is not valuable given that. It's a lot more relevant to most people than quantum mechanics.
Fluid phenomena is ubiquitous. You live in a fluid. You probably drive a car through a fluid and may occasionally take a plane through a fluid at higher speed. You surely use plumbing. I don't see how you can claim that fluid dynamics is not valuable given that. It's a lot more relevant to most people than quantum mechanics.
Physics education focuses on exciting areas of research. There isn't much interesting work currently taking place in fluids. We consider it a solved problem. The fact that we drive cars through fluids is completely irrelevant.
The physics curriculum prepares people to do research on stuff that is published in "physics journals". You may not think that should be the goal but it is. Doing work on Navier-Stokes lands you in a math journal on PDEs.
On a more important note, the actual topics are completely irrelevant. What's important is learning to "think like a physicist". That's what has value even for those who don't go on to do academic research, which is most students. For any given physics topic that is relevant to real-life applications, there are engineers who actually know how to use it, something that would be ridiculous to expect from the superficial treatment a physics degree has to give any one topic.
On a more important note, the actual topics are completely irrelevant. What's important is learning to "think like a physicist". That's what has value even for those who don't go on to do academic research, which is most students. For any given physics topic that is relevant to real-life applications, there are engineers who actually know how to use it, something that would be ridiculous to expect from the superficial treatment a physics degree has to give any one topic.
Fluid dynamics is published in physics, engineering, and math journals, even if focused specifically on Navier-Stokes.
To do fluid dynamics research in a physics department, sometimes one has to spin it in some way that people with physics degrees care about. For example, saying that it's to understand chaos theory.
To do fluid dynamics research in a physics department, sometimes one has to spin it in some way that people with physics degrees care about. For example, saying that it's to understand chaos theory.
>can you tell me if you can really get a physics degree without bumping into Bernoulli or Navier-Stokes?
Bernoulli principle was covered in my bachelor degree but Navier Stokes wasn't; true-blue fluid dynamics was either an optional course that I didn't take or a grad student course, I don't remember now.
Bernoulli principle was covered in my bachelor degree but Navier Stokes wasn't; true-blue fluid dynamics was either an optional course that I didn't take or a grad student course, I don't remember now.
As a physicist, fluid mechanics was the most glaring gap in my undergraduate preparation, despite its centrality to most physics applications. Somehow it is always a “time permitting” topic at the end of an already-cramped curriculum.
I first encountered the Euler equation in the context of GR — absurd. In another decade or two, I suspect its rightful place early in the physics curriculum will be emphasized.
I first encountered the Euler equation in the context of GR — absurd. In another decade or two, I suspect its rightful place early in the physics curriculum will be emphasized.
The order seems fine to me.
Thermodynamics/statistical mechanics was taught as a junior level class at my undergraduate alma mater. During that year, students would take electrodynamics, classical mechanics, and statistical mechanics as separate classes in some loose order, although of course simpler versions of these topics would have been introduced in first year physics.
The lack of fluid mechanics also, unfortunately, tracks with my experience.
Thermodynamics/statistical mechanics was taught as a junior level class at my undergraduate alma mater. During that year, students would take electrodynamics, classical mechanics, and statistical mechanics as separate classes in some loose order, although of course simpler versions of these topics would have been introduced in first year physics.
The lack of fluid mechanics also, unfortunately, tracks with my experience.
Thermodynamics is usually (and rightfully so) taught together with statistical physics for which quantum mechanics is essential, so the order does make sense.
again, if you can get a good grasp of the differential equations of GR and QFT, then you can make the leap to other topics. it's not like starting from zero. there is a large base of knowledge
I think this is, at least in part, specific to the US/Western tradition. US physics curriculum is built to get people up to speed with quantum physics ASAP, because this is the core of most physics research in US physics departments. If you look at Landau-Lifshitz's Theoretical Physics curriculum, you will find plenty of classical physics: from fluid dynamics, to elasticity, and plasma physics. For example, Landau-Lifshitz Vol. 6 is an excellent introduction to Navier-Stokes equations and their applications.
I love HN for thing like these that I wouldn't have otherwise found out. I used to think often about physics but not seriously enough to search for resources on how to get started and learn. But now that I have this guide (thank you Susan), I think I will start and no longer wonder or plan for learning physics in the future.
> they are and have been dreadfully underserved and underestimated by the academic physics community (who do not take them seriously because they aren’t studying at colleges and universities)
This stuck out, pretty rigorous if all you want to satisfy your curiosity. If you want to actually apply any of the hard work you put in, you need a degree.
I think that is the most interesting part of learning anything, applying it interesting ways. Doing that within so many of the areas of study is still gated behind academics.
That killed my motivation for putting effort into most things, pretty much except computer science where we are still ok with trusting self taught people for some reason. But to do anything interesting physics, astronomy, philosophy too you need to be in school. sucks
This stuck out, pretty rigorous if all you want to satisfy your curiosity. If you want to actually apply any of the hard work you put in, you need a degree.
I think that is the most interesting part of learning anything, applying it interesting ways. Doing that within so many of the areas of study is still gated behind academics.
That killed my motivation for putting effort into most things, pretty much except computer science where we are still ok with trusting self taught people for some reason. But to do anything interesting physics, astronomy, philosophy too you need to be in school. sucks
> That killed my motivation for putting effort into most things, pretty much except computer science where we are still ok with trusting self taught people for some reason.
100% same, except computers bore me to death now. I would even be willing to go back to school at this point if it wasn’t tens of thousands of dollars.
100% same, except computers bore me to death now. I would even be willing to go back to school at this point if it wasn’t tens of thousands of dollars.
“ But to do anything interesting physics, astronomy, philosophy too you need to be in school.” Why would you say that? I am curious. Imagine you are into a specific physics subject and knows what to do with some of contemporary problems that are puzzling people, work on it to provide your solution, etc., and publish your findings. I would think no one could prevent you. Right?
To help with some of the math required by general relativity, there's a good series on YouTube by the user "eigenchris" on tensor calculus, which I found helpful for a geometric intuition of what's going on. He also has a series on GR itself, which I haven't watched yet. If you're interested in learning GR and want specific information on the area of differential geometry you'll need to understand it, then this series is a great start.
> there's a good series on YouTube by the user "eigenchris" on tensor calculus
To save someone else a search: https://www.youtube.com/watch?v=8ptMTLzV4-I&list=PLJHszsWbB6...
To save someone else a search: https://www.youtube.com/watch?v=8ptMTLzV4-I&list=PLJHszsWbB6...
“Resnik- Halliday” and “IE Irodov” the two books changed physics for me. One simplified physics for everyday and made it relatable and one showed me how to think about solving physics problems.
P.S I mostly self taught physics for my own interest. Not sure if these books are under grad level.
P.S I mostly self taught physics for my own interest. Not sure if these books are under grad level.
Dexter Chua's notes merit a mention IMO for supporting material/summary notes:
https://dec41.user.srcf.net/notes/
I took physics in high school and college. It's has, and always has been, my most difficult class and it's because I have the hardest time trying to solve physics problems. I may give this one a go!
Also see Gerard 't Hooft's site on how to become a good theoretical physicist (https://goodtheorist.science).
Is there a guide like this but for learning astronomy and/or astrophysics? I would love to learn more about astronomy, but I don't know where to start.
I am surprised that condensed matter and solid state physics is considered a supplement/elective.
Learn Landau’s course in original Russian. Pass The Test. You are ahead of most PhDs now.
I just realised I had seen the first version of this and thought there’s too much and would take a long time. 6 years passed, I guess enough to have read the majority of those but I haven’t. Hope in 6 years I won’t be thinking the same. Started with some Susskind tonight.
Can we have one of these with probability and stats?
[deleted]
(2021)
anything new here?
anything new here?
All of it, to the users who haven't seen it posted here before.
Undergraduate physics hasn't changed much in the past two years.
It was mentioned in another comment thread[0] this morning. These things happen[1].
[0]: https://news.ycombinator.com/item?id=37199307
[1]: https://news.ycombinator.com/item?id=32795559
[0]: https://news.ycombinator.com/item?id=37199307
[1]: https://news.ycombinator.com/item?id=32795559
- insert relevant XKCD comic -
[comic]
https://xkcd.com/1053/
[/comic]
[comic]
https://xkcd.com/1053/
[/comic]
Hydraulics are everywhere. Ever used a sink? Flushed a toilet? Contemplated an air filter? Felt both sides of a small fan? Wondered how, exactly, a utility pump causes water to go in the inlet and out the outlet, and tried to read the manufacturer’s spec? Contemplated that the ripples when you throw a rock in an actual pond really don’t resemble the average “look I made water in WebGL” animation very much?
And more fancily, and very much in “Physics”, cosmological models usually model the universe as being full of a spatially varying continuous fluid. Stars are plasma or weirder things, and those are fancy fluids.
Yet, for some reason, the basics are missing from “Physics”. You can sometimes find them in mechanical engineering departments, and Feynman covers it a bit in his lectures.