# Approaches for teaching Modern Physics in Grade School and University

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Both Feynman and Einstein have famous quotes about explaining physics concepts to those not well schooled in physics.(freshman undergrad and a six year old respectively). Yet both hedged a bit on this: Einstein Things should be made as simple as possible but not simpler and Feynman: We have this terrible struggle to try and explain things to people who have no reason to want to know. But we all recognize the difficulty of being burdened by the formalism and challenging concepts with which we understand physics and the lack of familiarity of these by the general public.

Some think that modern physics can be taught in eighth grade in primary school. One such program (link to the abstract) has been tried and with apparent success. I have no access to this article, but there are several questions in my mind; how much classical physics did the students have, what particular concepts were taught, what were the expectations of the program, how did they assess comprehension?

Would you have tried this (of course I am thinking about the USA)? I am sure some students would benefit but getting back to Feynman's issue mentioned above, any student? Thoughts?

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vanhees71 and Astronuc

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Some think that modern physics can be taught in eighth grade in primary school. One such program (link to the abstract) has been tried and with apparent success. I have no access to this article,...
Here is a preprint
https://arxiv.org/abs/2109.00598
Physics for the masses: teaching Einsteinian gravity in primary school
Matteo Luca Ruggiero, Sara Mattiello, Matteo Leone

KedarMhaswade, hutchphd, vanhees71 and 2 others
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Some think that modern physics can be taught in eighth grade in primary school. One such program (link to the abstract) has been tried and with apparent success. I have no access to this article, but there are several questions in my mind; how much classical physics did the students have, what particular concepts were taught, what were the expectations of the program, how did they assess comprehension?

I think the real test here is, now that the study is over, are those schools still teaching physics like this?

vanhees71
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I think the real test here is, now that the study is over, are those schools still teaching physics like this?
On a related note, this book was recently published.

Teaching Einsteinian Physics in Schools
An Essential Guide for Teachers in Training and Practice
By Magdalena Kersting, David Blair

https://www.routledge.com/Teaching-...-Teachers/Kersting-Blair/p/book/9781760877712
https://www.taylorfrancis.com/books...hysics-schools-magdalena-kersting-david-blair

The senior author (David Blair) [who is referenced in the earlier article] is actively pursing this.
https://www.einsteinianphysics.com/media/
https://www.uwa.edu.au/news/Article...an-Science-on-offer-for-teachers-and-everyone

[disclaimer: I contributed Ch 7 of that book]

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If the choice is between a solid understanding of SUVAT and a belief that a rubber sheet model of gravity explains GR then I would choose SUVAT every time

PhDeezNutz and vanhees71
Finished the article. Is this just another "new math" scenario? The curriculum will be developed by experts who have a deep understanding of the subject and handed off there ideas to the general education community to implement.

In the article it noted that the students had little classical physics. It would seem very challenging to teach modern physics as a foundation for physics. It noted too that the students naïve concepts of gravity showed confusion since the experience of the student did not confirm the classical explanation, e.g., all bodies attract one another so why aren't all objects glommed together and not just to the earth?

How is curved space easier than action at a distance? How easy is it for them to generalize from two dimensions to three dimensions? It not saying that some students will not benefit from this program but primary education curriculum is usually foundational, skill building and homogeneous. Stretching space seems a little off the track as useful as it may seem to us.

A few years back there was talk of "Physics First" for HSs the thinking being that physics being the most fundamental of the physical science would be most useful if taught before chemistry or biology. So, how many schools offer a good physics introduction in the freshman or sophomore year? How many have teachers with a physics background? How many primary school teachers have taken at least one physics course?

My grandson (eighth grade) is in an advance program, called the Cambridge Program. This includes courses in math, science and computers not offered in the general curriculum. I will have to find out if they discuss gravity and to what extent.

vanhees71
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(Maybe this thread on trying to teach modern physics to kids
the abstract-translation website (which has been under maintenance for some time now) )

Here's "the case" that the senior author ( https://en.wikipedia.org/wiki/David_Blair_(physicist) )
of the book that I mentioned a few posts back ( in
makes for teaching Einsteinian Physics
https://www.routledge.com/blog/article/the-case-for-teaching-einsteinian-physics-in-schools

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There is, of course, a dilemma here. On the one hand from the point of view of a physicist it doesn't make sense to try to teach general relativity or quantum mechanics to anybody who is not familiar with classical mechanics and electrodynamics, because it's simply impossible to understand modern physics without at least some understanding of classical physics, which makes contact with everyday experience but also modifies it and makes it quantitative. E.g., everyday experience concerning moving bodies deals always with dissipative effects, and thus indeed ancient philosophy lead to Aristotelian physics. Now already Newtonian mechanics is in this sense an abstraction, because it teaches us that friction is a force and if you can set up things such that there is almost no friction anymore, the body will go on in uniform motion if that state of motion isn't changed by the influence of forces and so on. Then also it's for sure at least of advantage to learn about the equality of inertial and gravitational mass and Newton's theory of gravity before starting to discuss the equivalence principle. For GR in addition you need SR, because otherwise there's no way to understand, how gravity can be described by a dynamical spacetime metrical description. To use the rubber sheet model is a nogo, because it's completely wrong and establishes wrong concepts that make it even more difficult to understand GR than it already is without wrong pictures taught at school. The same holds of everything related with "old quantum mechanics", leading to a completely wrong concept of photons (it took me a while to eliminate the thinking of a photon as a little particle-like bullet) or Bohr orbits in a (hydrogen) atom (it took me a while to eliminate the thinking that electrons move in an atom in it's stationary states).

On the other hand, maybe it's disappointing for school pupils when they first encounter physics only via the subjects of classical physics, which is in some tension with what's communicated about it in the public, where it is usually about exciting subjects like spaceflights (well, here's perhaps a nice opportunity to start discussing Newtonian physics in explaining how a rocket launches and how the space telescope or other satellites precisely travel along trajectories accurately calculated before), cosmlogy, quantum computers, Schrödinger's cats and other "weirdness" of quantum mechanics. So maybe there should be some "modern physics" already at the beginning as a teaser to make sure that these more intersting topics will be treatable later after one has gained some knowledge about the "old stuff" named classical physics.

So the dilemma is, how to teach some modern physics without bad analogies like this unfortunate rubber-sheet model or Bohr's electron orbits in the old atomic model, which is known to work just by chance for only the hydrogen atom.

Oldman too, PhDeezNutz, Klystron and 6 others
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So the dilemma is, how to teach some modern physics without bad analogies like this unfortunate rubber-sheet model or Bohr's electron orbits in the old atomic model, which is known to work just by chance for only the hydrogen atom.

Indeed, one needs to revise various models.

But I think it's too harsh to criticize these first/early attempts because some old models persist.
One needs some combination of something to catch their interest,
followed by a development of better ways to think about things.

However, I would argue it's
better to try to move forward with imperfect models of 20th-century physics
rather than
just sit with pre-20th-century models of the world.

As more folks try, models get refined.

of pre-20th century physics for two semesters...
likely burnt out before seeing what the 20th-century and beyond has to offer.
(High schoolers typically follow a simplified version of that sequence.)

Do Biology and Chemistry courses do that?
Or do they treat modern topics sooner?

I've taught at some small liberal arts colleges that try to bring the modern physics up earlier.
I wasn't at Pomona, but here's Tom Moore's idea
http://www.physics.pomona.edu/sixideas/AAPTW20.pdf
(from his Six Ideas That Shaped Physics website http://www.physics.pomona.edu/sixideas/ )

Similarly, Matter and Interactions (used in my current institution)
tries to bring atomic thinking (and computational thinking) into introductory physics
https://matterandinteractions.org/

Certainly, one won't go at full speed and full coverage of modern physics at this level.
But the modes of thinking are updated from the really-old models.

We don't have to
just think like Newton, Galileo, Lagrange, etc.. to do intro mechanics
or like Ampere, Faraday, Gauss Maxwell to do electrodynamics,
or like Einstein and Lorentz to do relativity,
or like Bohr, Schrodinger, and Heisenberg to do quantum physics.

(I like this quote by Synge:
"...insisting that the time has come in relativity to abandon an historical order and to present the subject as a completed whole, completed, that is, in its essentials.
In this age of specialisation, history is best left to historians."
- JL Synge.)

Although there might be references to the rubber-sheet model
in the Kersting-Blair book I mentioned a few posts back,
there is also reference to these "Sector Models" https://www.spacetimetravel.org/sectormodels1/sectormodels1.html
as well as attempts to develop quantum theory with Feynman's Paths (as in his QED book).
I, along with some others, contributed ideas to develop "spacetime thinking".

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vela and vanhees71
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Do Biology and Chemistry courses do that?
Or do they treat modern topics sooner?

When I first took biology, in grade school, in the 1960's, there was a lot of historical presentation.
This was interesting to me because it presented interesting narratives of the discoveries, how succeeding concepts built on each other, and where the original meanings of certain words came from.

On the other hand, it presents a tangled and more complex exposure to the basic concepts.

On the other, other hand, the state of biological knowledge (especially for primary school teachers) was not so well developed in the 1960's as it is now.
Although the important concepts of evolution and the cellular basis of life were well known, the powerful and unifying concepts of molecular and cellular biology were just being developed.
I would expect that today, these simplifying concepts would be presented earlier in the process now.

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Klystron, vanhees71, robphy and 1 other person
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I think in learning and teaching physics one must distinguish between different goals. On the one hand one wants to learn or teach physics as a natural science, and there it is useful to just find a way to convey a subject from the point of view of our current knowledge. Then it makes a lot of sense to present (at least for theoretical physics) the subject in a deductive way, i.e., arguing with a few key heuristical elements for some fundamental principles underlying this subject. E.g., in classical mechanics you don't start with Aristotle and his theory only to tell the students later that this is all outdated and we rather switch to Newtonian mechanics. You rather start right away with Newtonian mechanics, but you'd also not use the version of this very successful theory as written up by Newton in the Principia. First of all you'll use modern mathematics, i.e., vector analysis. Second from the physics point of view you don't introduce absolute space and time but argue aiming at the modern understanding that the description of motion is always relative to some reference frame and that there are inertial frames and then start from the three postulates, discussing the subtle interrelations between them and how this introduces the fundamental dynamical elements, mass (characterizing a body) and forces (describing interactions between bodies) etc.

On the other hand, such a teaching is also utterly incomplete, because it does not tell the students, that physics is not just a collection of postulates and mathematical concepts to describe Nature but that's rather the result of physics as a process in learning about Nature by observe it in a quantitative way and then trying to find "natural laws" and mathematical descriptions in terms of models and finally a theory. For this the study of the history of physics is of course of the greatest value and, at least for me, it's an utmost interesting subject in its own right. I even think that for a full understanding of the physics of today you need to study the history of its discovery.

The important point, I think, is to strictly separate these two goals of physics teaching. I think ideal examples in this context are the textbooks by Steven Weinberg. He usually starts with a chapter on the history, but it is not used to explain the theory the textbook is teaching us but just to give an idea how the theory has developed from previous knowledge. Then he explains the theory from a modern point of view in a clear deductive way. E.g., in his marvelous books about "The Quantum Theory of Fields" he starts from the representation theory of the Poincare group and not with the pretty confusing historical order trying to establish a "first quantization relativistic wave mechanics" first, only to find out later that you always have to deal with many-body systems and finally use "second quantization" aka "quantum field theory". Of course he has all this in the first chapter on the history of the subject. So you have the best of both approaches, the historical and the deductive one.

hutchphd, Klystron, Ibix and 2 others
(Maybe this thread on trying to teach modern physics to kids
the abstract-translation website (which has been under maintenance for some time now)

I strongly support this. The title of this thread hides some good content and maybe some more to come.

vanhees71 and berkeman
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(Maybe this thread on trying to teach modern physics to kids
the abstract-translation website (which has been under maintenance for some time now) )

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vanhees71
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We can certainly do that. Should it be in the open forums instead of the Advisor Lounge? Academic Advising, or is there too much open-the-kimono content to post in the open forums?

I don’t see anything that should
prevent it from moving it to the open forum.
But that’s just from what I see.
My $0.02. Oldman too, vanhees71 and gleem Science Advisor Education Advisor I agree and suggest the STEM Educators and Teaching forum. Oldman too, berkeman, vanhees71 and 1 other person Mentor I agree and suggest the STEM Educators and Teaching forum. Done. Oldman too and robphy Science Advisor Education Advisor [...] Feynman: We have this terrible struggle to try and explain things to people who have no reason to want to know. But we all recognize the difficulty of being burdened by the formalism and challenging concepts with which we understand physics and the lack of familiarity of these by the general public. [...] (boldface added). I think this is the central issue, it certainly is rarely discussed. In a similar vein, the endless arguments over how much math should be in a physics course. Rationales based on applications (GPS, for example) miss the point. I do think modern physics can be taught in 8th grade... as long as the teacher understands the material and is able to offer an audience-appropriate presentation. Science Advisor Gold Member 2022 Award Some newer studies by the physics diactitians tell us that one has to start very early to generate some interest in the natural sciences. Best is starting to play around with simple things already in kindergarten and elementary school. There of course you have no math at all, but you can provide some idea about the fact that there are natural laws in the sense that there are regular patterns in the behavior of the stuff around us. To make math interesting I think you have to start somewhat later, because you need a more advanced ability to think in more abstract terms, but also here you can start early on with presenting math in a more appealing way than to just let the pupils learn some basic ways to solve standard problems, which do not even refer to anything they are interested in. BillTre Science Advisor Education Advisor Some of the info online about teaching Einsteinian Physics leaves me a little perplexed and scratching my head. Remarks such as students get bored with Newtonian Physics, or Newtonian Physics is obsolete would seem to devalue learning classical physics in the eyes of the students. [disclaimer: I contributed Ch 7 of that book] Perhaps you can shed more light on how this program is integrated into or replaces the traditional physics curriculum. Just call me old fashioned (or is that obsolete) but certainly, concepts as energy, momentum and force are consider in a classical physics context. This program begins in primary school starting as early as grade three (AUS) and children are not very receptive to abstract concepts. Science Advisor Homework Helper Gold Member robphy said: [disclaimer: I contributed Ch 7 of that book] Perhaps you can shed more light on how this program is integrated into or replaces the traditional physics curriculum. Just call me old fashioned (or is that obsolete) but certainly, concepts as energy, momentum and force are consider in a classical physics context. This program begins in primary school starting as early as grade three (AUS) and children are not very receptive to abstract concepts. I'm aware of David Blair's efforts on teaching Einsteinian Physics in K-12 but not closely associated with it. I contributed a chapter (which was peer reviewed and accepted by them) which uses new methods to teach relativity that I feel could be implemented in a K-12 setting. I hope they find a way to incorporate aspects of it... but I don't know enough of how they go about things. In general, my feeling is that we should introduce fundamental concepts, starting with classical concepts... but not to leave it there... but to gently weave in Einsteinian concepts (involving relativity and quantum mechanics) not to say that the classical concepts are wrong and should be abandoned... ... but to refine them towards what relativity and quantum mechanics says (which is confirmed by experiments). The Correspondence Principle suggests that classical concepts got some things correct. What classic physics got wrong is extrapolating many of its features to situations where it fails. So, in threads like this and others in the Relativity forum, my approach is not to reject and discard everything classical but to refine (slowly), by clarifying what features they got correct and persist and how we should think of things in order to meet up with relativistic and quantum concepts. In addition, I think it is a good thing to introduce modern ideas in K-12 (not waiting until college or later). Mastery of modern ideas is of course not expected as this level. But I think it is good to shine a light in that direction. [I got interested in physics in 6th grade and relativity in 7th grade after watching a video on public television. I didn't acquire mastery at that level... but it gave me direction... it suggested a plan towards understanding relativity... that led me to get degrees in physics. Without that, maybe I would have been an engineer [since that is what my father did... and he was nudging me in that direction].] Oldman too Science Advisor Gold Member 2022 Award Some of the info online about teaching Einsteinian Physics leaves me a little perplexed and scratching my head. Remarks such as students get bored with Newtonian Physics, or Newtonian Physics is obsolete would seem to devalue learning classical physics in the eyes of the students. This is of course utter nonsense. There's no doubt that one needs to start to learn physics with learning Newtonian mechanics. Of course, as any subject in the natural sciences, it should not be taught in "historical order" but in terms of clear concepts from a modern point of view. E.g., at the university level Newtonian mechanics can be used to introduce into the important concept of symmetry and (Lie) group theory using the action principle, Poisson brackets and all that (Noether's theorems). With a good grasp of this in Newtonian mechanics you've a great advantage when it comes to learning quantum mechanics. Nevertheless I think it's of advantage to also introduce special relativity early on, i.e., already in the classical-mechanics lecture as another spacetime model with another symmetry group realizing the special principle of relativity. I know at least one (German) high school physics book, where this is done in an excellent way (of course not explicitly arguing with group theory). It's of course more challenging to make classical physics attractive at the school level. I think, here an experimental approach is most promising. The problem is that in the popular coverage of physics only the newest discoveries are "hyped" (usually quantum theory as "something weird" and cosmology, black holes etc.). But also this can be used to motivate the study of classical physics: E.g., why the Webb telescope is put at the Lagrange point L2 (to begin with what is the Lagrange point). Then you have a nice intro for covering Newton's theory of gravity, the motion of the planets and moons in the solar system, spaceflights, and all that. robphy Science Advisor Gold Member Here's something this thread made me remember. It's a clip from WKRP in Cincinnati where Venus Flytrap (one of the DJ's and a certified science teacher) explains the basics of an atom to a gang member who says that he is too dumb to learn anything and that is why he's a gang member. This was probably the reason why I wanted to become a teacher... Astronuc, BillTre, robphy and 2 others Science Advisor Homework Helper Gold Member Here's something this thread made me remember. It's a clip from WKRP in Cincinnati where Venus Flytrap (one of the DJ's and a certified science teacher) explains the basics of an atom to a gang member who says that he is too dumb to learn anything and that is why he's a gang member. Got it... that's electrons, neutrons, and protrons. ( I had to check: https://translate.google.com/?hl=en&sl=sw&tl=en&text=tron ) (Still a great clip!) Science Advisor Education Advisor The authors of this program did a study of the response of teachers (25), parents (20) and student (20) to the pilot implementation of it. https://ui.adsabs.harvard.edu/abs/2019PhyEd..54a5001F/abstract However, a remark by the authors at the end of the article seemed a little optimistic. "The comments analyzed above clearly represent a self-selected audience. Many comments were useful in identifying difficulties. However, overall, the lack of opposition implies strong public support." (My emphasis) There was only one review of the book on Amazon. The reviewer (ex-physics teacher) thought the program was more appropriate for HS and that secondary teachers without a physics background (I think that would be most) would not be sufficiently prepared. One of the reasons for this program as the authors note is dwindling interest ins STEM subjects hoping that this program will rekindle that interest. We must also remember that when STEM subjects were initially emphasized that the about half of entering STEM majors did not get a degree in a STEM field. vanhees71 Mentor Has anyone started with the results of relativity and quantum mechanics Saying this is the way things really are and then expanding outward or slower and say this is how we experience them in everyday. As an example, traveling at close to light speed, our clocks run normal but everyone we pass has a clock that runs slower. When we measure our yardsticks, they are 36” but when we measure everyone else’s yardstick it’s shorter. Then we make the speeds slower and closer to our own and what do we see. in a sense, flipping the notion of common sense to a person living in a relativistic world and interpreting it that way. vanhees71 Science Advisor Homework Helper Gold Member Has anyone started with the results of relativity and quantum mechanics Saying this is the way things really are and then expanding outward or slower and say this is how we experience them in everyday. As an example, traveling at close to light speed, our clocks run normal but everyone we pass has a clock that runs slower. When we measure our yardsticks, they are 36” but when we measure everyone else’s yardstick it’s shorter. Then we make the speeds slower and closer to our own and what do we see. in a sense, flipping the notion of common sense to a person living in a relativistic world and interpreting it that way. I would say that Bondi's k-calculus approach ( https://www.amazon.com/dp/0486240215/?tag=pfamazon01-20 ) is along these lines for relativity in the sense that Bondi gives operational definitions of assigning coordinates via radar measurements... then pointing out later various "effects" that disagree with our common sense. (I haven't read https://en.wikipedia.org/wiki/Mr_Tompkins .. but this could be along those lines. This might be enlightening... I just stumbled upon it. ) For quantum... the only thing that comes to mind is the "quantum baby" idea developed by a professor at my PhD institution... but it's not quite ready for a general audience. https://arxiv.org/abs/quant-ph/9702055 Bringing Up a Quantum Baby A.P. Balachandran Parable of the Quantum Baby Entertain the conjecture of a time, long long ago, when there lived a quantum baby of cheerful semblance and sweet majesty. It was brought up by its doting parents on a nourishing diet of self-adjoint operators on a Hilbert space. All it could experience as it grew up were their mean values in quantum states. It did not have a clue when it was little that there is our classical world with its topology, dimension and metric. It could not then tell a torus from a hole in the ground. Yet the baby learned all that as it grew up... Science Advisor Education Advisor Has anyone started with the results of relativity and quantum mechanics Saying this is the way things really are and then expanding outward or slower and say this is how we experience them in everyday. I vaguely recall a story that (IIRC) John Wheeler tried this approach, or tried to structure an introductory course sequence like this, and it was a total failure. Nonetheless, attempts continue, for example: https://physics2000.com/PDF/RelWkOne.pdf vanhees71 Science Advisor Gold Member One of my old professors wrote an introductory mechanics text starting from relativistic mechanics and taking the small velocity limit to get Newton's laws. I found it kind of funny that he would teach an honors physics course from that aspect. He published his text and it was never really received well, because the text went out of print almost immediately and he never taught that class again. robphy, Andy Resnick and vanhees71 Science Advisor Gold Member 2022 Award I also don't know, how you can think that students who have never heard about physics in a quantitative way can understand relativistic mechanics. I think there is no other way than to start with Newtonian mechanics, which is already more difficult than most of us might think, because we are just too familiar with it. On the other hand, I think it's possible to start with SR very early. In the standard theory course almost all professors bring the introduction to it at the end of the 1st semester on mathematical methods and mechanics (part 1). This seems to work very well. It opens the opportunity to teach electrodynamics from the very beginning as relativistic field theory, which I think is indeed making the concepts simpler, though the 4D Minkowskian vector calculus is of course slightly a bit more challenging than the usual 3D vector calculus, which you need of course in addition to get a better intuition about the physical meaning of the equations. Astronuc, paralleltransport and gleem andresB Maybe I'm too old school and close-minded, but I rather prefer the general public to have a solid conceptual grasp of inertia, Newton's Laws, and some basics of thermal physics and electromagnetism than a nebulous knowledge of the neutron double-slit experiment, the Schrodinger cat, or black holes. gentzen, Astronuc, paralleltransport and 1 other person paralleltransport I think @vanhees71 hits on the point. The physics education has 2 parts, one is general knowledge (cultural) one would say where knowing what topics are "out there" enriches you culturally. Teaching that people think about black holes, schrodinger cats etc... in that context to inspire young students is fine. The other part is to teach problem solving skills students can use later in life (most people don't end up professional physicists). Personally, it's the latter that attracted me to physics as a student. I was taught to think about the world in a precise quantitative way. The best way to do so was through classical physics, which at the high school level is just an exercise of crystallizing day to day intuition into equations. Trying to do so with modern physics seems out of order since there's not intuitive crutch and the students haven't built enough math technology to use that for problem solving (which is the key goal here). Astronuc and vanhees71 Science Advisor Homework Helper Gold Member Trying to do so with modern physics seems out of order since there's not intuitive crutch and the students haven't built enough math technology to use that for problem solving (which is the key goal here). Some thoughts about modern physics: • Does each generation have to endure 17th, 18th, 19th, 20th century physics before 21st century physics? • "Therefore, I apologise, if apology is necessary, for departing from certain traditional approaches which seemed to me unclear, and for insisting that the time has come in relativity to abandon an historical order and to present the subject as a completed whole, completed, that is, in its essentials. In this age of specialisation, history is best left to the historians."- J.L. Synge in Relativity: The Special Theory (1956), p. vii • There may be new intuitions.. new ways of looking at old topics (and new topics) that can be developed. The next generation doesn't have to learn things the way the previous generation did, possibly stumbling over the same the roadbumps and conceptual barriers. [For example, I think relativity should be taught with Minkowski spacetime diagrams, which have been traditionally considered too mathematical... But, instead many books reason with moving boxcars... the way Einstein did... the physicist's way... not that mathematical way. Geometric intuition from high school could be modified and developed for relativity... but no... we're stuck in boxcars with cryptic transformation equations... and can't see the geometry of spacetime. Along these lines, I often wonder about electromagnetism... When in the history of introductory textbooks did we start drawing field vectors? They haven't always been there. At some point in the future, could we have drawings of differential forms or tensors... or is the vector field the last word in teaching electrodynamics? I wonder if someone told the first textbook author using vector field diagrams... that's too mathematical. Sadly, that's what Edwin Taylor told me about rapidity in relativity... why it was omitted from the 2nd edition of Spacetime Physics... some felt it was too mathematical. ] • There may be someone out there who catches onto something important about some modern physics topic without having the traditional prerequisites or isn't tied down to a classical viewpoint ... someone who thinks differently from the crowd. Sure, it could be argued as unlikely. Maybe folks should just stay in their [classical] lanes. My$0.03.

andresB
• Does each generation have to endure 17th, 18th, 19th, 20th century physics before 21st century physics?

I don't remember studying living forces, caloric theory, or aether theory. Things like mechanics, thermodynamics, and classical electrodynamics are 21st century physics, explaining phenomena that each generation encounters when seeing nature, and with innumerable applications to current technology.

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• Does each generation have to endure 17th, 18th, 19th, 20th century physics before 21st century physics?
Yes and no. There is no way to learn physics without first learning Newtonian mechanics and with it starting to build up a "tool box" of mathematical methods. Of course, nobody would teach Newtonian mechanics using the Principia as a "textbook" but rather will use modern vector analysis and (in my opinion as soon as possible) the action principle and the geometrical point of view in the sense of Klein's Erlanger program (groups, symmetries, Noether). That's what proved useful for "modern physics". E.g., I don't think that one can really understand quantum theory without a good knowledge in the group-theoretical methods to explain why the specific algebra of observables look the way they look for either non-relativistic QM or special-relativistic QFT or to understand the step from special to general relativity (making global symmetries local and the "gauge principle" helps a great deal).

• "Therefore, I apologise, if apology is necessary, for departing from certain traditional approaches which seemed to me unclear, and for insisting that the time has come in relativity to abandon an historical order and to present the subject as a completed whole, completed, that is, in its essentials. In this age of specialisation, history is best left to the historians."- J.L. Synge in Relativity: The Special Theory (1956), p. vii
Sure, the historical approach is never a good one to present the logical order of a subject. It should be talk with the view on the most successful methods to be used to understand contemporary physics. On the other hand a good knowledge of the historical development of those methods is of great use to understand the subject too, but it should be separated. The best way for me is how Weinberg used to write his textbooks, starting with a historical overview, which is independent of the development of the subject itself, which then is explained in a logical order.

• There may be new intuitions.. new ways of looking at old topics (and new topics) that can be developed. The next generation doesn't have to learn things the way the previous generation did, possibly stumbling over the same the roadbumps and conceptual barriers.

[For example, I think relativity should be taught with Minkowski spacetime diagrams, which have been traditionally considered too mathematical... But, instead many books reason with moving boxcars... the way Einstein did... the physicist's way... not that mathematical way. Geometric intuition from high school could be modified and developed for relativity... but no... we're stuck in boxcars with cryptic transformation equations... and can't see the geometry of spacetime.
I see Minkowski diagrams as ambivalent. They are harder to read than one might think. Particularly you have to switch off your Euclidean thinking you are used to from hammering in this subject starting from elementary school. On the other hand they can help to visualize the algebraic (or rather analytical-geometry) treatment of special-relativistic spacetime.

• Along these lines, I often wonder about electromagnetism... When in the history of introductory textbooks did we start drawing field vectors? They haven't always been there. At some point in the future, could we have drawings of differential forms or tensors... or is the vector field the last word in teaching electrodynamics? I wonder if someone told the first textbook author using vector field diagrams... that's too mathematical.

Sadly, that's what Edwin Taylor told me about rapidity in relativity... why it was omitted from the 2nd edition of Spacetime Physics... some felt it was too mathematical.
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Vectors have been introduced into physics by Gibbs and Heaviside, and we can be thankful for that great step forward. I find a picture with field lines pretty intuitive.

Of course in some sense it's good to teach classical electromagnetism with "relativity first", i.e., as a classical relativistic field theory. After all it's the paradigmatic example for exactly this, and many formal derivations are much easier in the four-tensor formalism than in the tradiational one (the retarded propagator/potentials/fields, the conservation laws of energy, momentum, angular momentum and the center-of-energy theorem, the homopolar generator, Faraday's Law, constitutive relations in moving media,...). Also here, however, you must make some compromise, because it's hardly a good approach for completely starting to learn the subject. You need to build some intuition about "traditional" 3D Euclidean vector calculus first ("div, grad, curl, and all that").

• There may be someone out there who catches onto something important about some modern physics topic without having the traditional prerequisites or isn't tied down to a classical viewpoint ... someone who thinks differently from the crowd. Sure, it could be argued as unlikely. Maybe folks should just stay in their [classical] lanes.
My \$0.03
Feynman!