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I'm taking on an interesting task: explaining to an extremely advanced 11 year old that much of what he hears and reads from the "popular physics" videos and TV programs isn't accurate, and some of it is just wrong. I know I have a problem here however - once he moves on to high school physics he's going to come across many of these same incorrect explanations from his teachers. I need to decide if I go so far as to explain that there is ZERO evidence showing or theorizing that an electron (for instance) is ever a wave.

He's bright as heck, and I can certainly explain a probability function, and can explain that it's a solution to a wave equation. And I can explain that this probability function is NOT the electron itself. And that this probability function can be plotted in a way that it can look like a wave or a superposition of waves. But do I stop there or continue and say simply "this does not in any way imply that the electron itself is a wave!"

??

If I was that kid I would have LOVED it if someone explained this to me at an early age. But I know I would have upset some teachers. Maybe only once or twice though. I'd like to know what everyone else thinks.

Thanks!!

From the comments I realize there's a need to modify my question with the following statement:

The probability function (or superposition thereof) has meaning because it is the solution to a very special wave equation that has proven to glean incredible meaning. The electron is and never has been a solution to such a special wave equation. We can learn things about electron behavior from the solutions to this wave equation, but it makes no sense to say that the electron is a solution to this same wave equation.

Furthermore, to posit that ANY localized entity is a wave is disingenuous and misleading: Propose any thing which can be plotted and/or described as a function, and I will show you a superposition of orthogonal solutions of SOME equation that will describe it to whatever precision that seems reasonable (let's say "measurable" for these purposes). If I choose that equation to be a wave equation then I allow myself the right to call the thing a wave and give it a wavelength which quantifies some average spatial distribution. Is that meaningful? Does that help us to understand an electron? I say no.

Yes - I do strongly believe that there is NO reason to call the electron a wave ever, because there is no evidence and no theory showing it to be such a thing. There IS however much evidence showing that an electron is a particle, and that's because we measure it to be such a thing. To state that it is also a wave is nothing but disingenuous babble. If it's an electron then it's measured always as a particle.

So do you think the electron IS ever a wave? If so please state your evidence and/or theories which prove it to be such a thing.

John Ahearn
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    This site is about physics, not the teaching of physics, so this might go better somewhere else. My personal opinion is that one should never make strong statements either way ("the electron is / is not a wave") because "wave" is just a vague word. It's better just to say what electrons do, i.e. give a solid introduction to the math. That will also allow the kid to evaluate other peoples' claims himself, later in life. – knzhou May 24 '17 at 20:48
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    I'm voting to close this question as off-topic because questions about physics pedagogy are not in the scope of the site. – tpg2114 May 24 '17 at 20:49
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    If you went so far as to explain there is zero evidence showing that an electron has wave-like properties, YOU would be telling him something patently false. Also in my experience most introductory physics classes taught by good teachers haven't gone so far as to do the same. – IntuitivePhysics May 24 '17 at 21:12
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    Er ... electrons can (and do if you rig the experiment correctly) diffract. While there is an ontological argument that the electron fails to be a wave, it's wave-like properties are of non-trivial physical consequence. As a greasy-handed, soldering-iron and wrench physicist I always figure that ontology can take a flying leap if it obscures consequential behaviors. – dmckee --- ex-moderator kitten May 24 '17 at 21:16
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    I'm voting to close this question as off-topic because the OP wrote "A great part of the reason for posting my question was to OUT the misconceptions so often perpetuated." In other words, this was apparently never intended as a question in the first place. – WillO May 24 '17 at 21:39
  • You might rethink your response to the young person taking into consideration that an electron is neither, at least using conventional definitions of "wave" and "particle". Especially so since the young person is likely to be thinking in conventional terms. – garyp May 24 '17 at 22:34
  • @dmckee you never responded to my question. something is diffracting yes - and it's a solution to a very special wave equation. the electron is not that solution. if you're sure it's the electron then you are the one taking the ontological approach. you want it to be a wave because your brain won't let it be something else? ok - show me evidence that some fractional part of it with fractional mass and fractional charge was responsible for this diffraction in the location where it diffracted. – John Ahearn May 26 '17 at 01:57

2 Answers2

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Whether an electron's probability function should be thought of as distinct from the electron itself is pretty much a completely philosophical question with very little physical content, and so saying that its "DEFINITELY NOT" true is wrong. (Note I'm not saying that it's true that an electron is the same thing as its probability function. I'm saying that it's not true that an electron is definitely not the same thing as its probability function.) Presenting this as a "common misconception" is just going to confuse him and set back his physics understanding.

In fact, based on the confidence with which you present the incorrect statement in your question, I would recommend thinking twice about clearing up the "misconceptions" that his physics teachers are spreading and letting the professionals do their job.

ACuriousMind
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tparker
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  • Physics.SE comments are not the place to discuss ontological convictions, and I've removed a comment thread that did not really try to address or improve this answer. I'd also remind everyone that we try to be nice even to people with which we disagree. – ACuriousMind May 25 '17 at 22:02
  • @ACuriousMind Thank you. Of course I walk a fine line here, but your comment begs the question "with respect to Q.M. where does ontology begin and where does it end?". Bohr stopped a lot of this speculation, not because of the ontological nature of it, but because it wasn't useful and it didn't appear to go anywhere. And yet he was too late - cat was out of the bag and everyone started calling electrons (for instance) waves. But isn't THAT the very ontological conviction which I'm attacking with my non-ontological approach? – John Ahearn May 25 '17 at 22:20
  • @tparker - you write "I'm saying that it's not true that an electron is definitely not the same thing as its probability function.". You would be alone here. A prob function is useful to present expectation values for what might be measured when some effect due to an electron's presence is measured. You seem to misunderstand that the electron may be a solution to the Schrodinger's Eq? Regardless, there is no evidence that electron is or ever has been a wave. Expectation values would need to imply fractional mass/charge in that case. – John Ahearn May 29 '17 at 20:45
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And electron is not a wave. However, describing matter with the use of wave functions has proven to be very effective in giving a mathematical framework for quantifying empirical observations regarding the probabilistic nature of interactions of small particles, and our uncertainty of their momentum/position, or energy/time relationship.

To say "an electron is not a wave" is not going to clear up any misconceptions - it is likely to perpetuate them in the same way that you seem to be having some misconceptions (and strongly held opinions masquerading as facts).

If this 11 year old is so bright, you might want to take him through some of the experimental work that has been done to explain optical diffraction (is a photon a particle or a wave?), the photoelectric effect, and electron diffraction. Three beautiful experiments that cannot, between them, be explained unless you accept that particles "sometimes are like particles, and at other times are like waves". Note - I don't say "are waves"; I say "like waves".

At the age of 11, having a clear and well grounded intuition for the behavior of the world (including some of that "fuzzy duality") is appropriate; telling a child something "absolute" when you are not actually an expert is likely to set them back.

I applaud your desire to help this child grow; please consider the advice given in the sense it was given - we both want the next generation to be equipped to deal with the challenges of their time, and we'll need some first class scientists...

Floris
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  • Comments are not for extended discussion; this conversation has been moved to chat. – ACuriousMind May 25 '17 at 21:58
  • dude. i think it's really uncool the way you blew me off. you aren't qualified to do that to me. instead of stopping to figure out why I might be right on with my post, you took the easy route and chose to assume i meant something incorrect. You were incorrect to do that. I'd be tremendously embarrassed if I was you. – John Ahearn Nov 14 '17 at 23:46
  • @Floris - I am SO SORRY. My comment was for ACuriousMind. It seems to me that you are the only one that understood my points here. My post wasn't given the chance to see an entire day's worth of responses from people across the globe that were never allowed to read it - many were still at work or sleeping when it was voted down! What's incredible to me is how you and I are trying to be careful with our words, while others are just incorrect with regard to their logic AND their physics. You and I are saying the SAME things written by some of the most esteemed members on S.E! – John Ahearn Nov 18 '17 at 15:37
  • @JohnAhearn no worries and thank you for the clarification. I will delete my earlier comment. Civility seems to be in short supply on the internet... best to just move on. Be the change you want to see. – Floris Nov 18 '17 at 17:33
  • @Floris - I am astounded that after reading the following post with so many great contributers agreeing with what I've written, that I was so quickly downvoted and outcast on this post. Where do most people on this site get their physics "knowledge" anyhow? https://physics.stackexchange.com/questions/41892/what-does-a-de-broglie-wave-look-like – John Ahearn Dec 06 '17 at 19:51
  • @Floris what really urks me is that ACuriousMind has decided to "wave me off" as inconsequential without bothering to explain why he doesn't respond. Is his allegiance to the "downvoters" or the physics? – John Ahearn Dec 06 '17 at 19:53
  • @JohnAhearn I am not sure how you think ACM "waved you off". Moving comments to chat is normal procedure (and the job of a moderator). This allows discussions (which are intended to be transient in nature) to stay off the main question page, but they are still accessible (for a time - three months IIRC) for anyone who clicks on the "moved to chat" link. As for downvoting - that's a community thing; and the question was closed by 5 different users, none of whom were ACM. So I think you are being a bit too focused on one person. Still - I sympathize with you. "Drive by shootings" do happen here. – Floris Dec 06 '17 at 21:17
  • @Floris He waved me off by not responding to any of my attempts to understand what goes on here. My first attempts were directly to those who explained that, by the result of voters, my post was going to (and eventually was) closed. When I realized these are not physicists but ACM is, I tried to make contact to see just how such a thing could happen. I was trying to get ACM's reasoning as to why I'm not allowed to have my post up for an entire day so actual physicists that think could vote on it, rather than the gang that I ended up with during what was a 4-5 hour span. continued ... – John Ahearn Dec 07 '17 at 00:31
  • @Floris Honestly, if he can read some of the comments from these egomaniacs how can he disagree with me? I'm still not sure why ACM isn't willing to make contact. I think my post makes it clear that I understand the topic more deeply than those that voted it down. There's some pathetic silliness going on here. I see this guy tparker (below) making many errant comments on PSE, and yet by virtue of him being here first he's allowed to spew his non-sense while my first attempt ever gets silenced? – John Ahearn Dec 07 '17 at 00:32
  • @Floris My original question to anyone in charge here is "What is the goal of PSE?" Is it to gain as many members as possible, or to have accurate, objective, meaningful and educational dialogue? – John Ahearn Dec 07 '17 at 00:32
  • @Floris BTW, you also appear to misunderstand something about this topic. to say i have "misconceptions" is to disagree with similar viewpoints of Feynman and many others in PSE. Please tell me - which viewpoint are you misunderstanding as a misconception? – John Ahearn Dec 07 '17 at 01:31
  • Your statement "...nothing but disingenuous babble. If it's an electron then it's measured always as a particle." - the wavelike behavior is demonstrated and useful for describing certain aspects of electron behavior (like diffraction and the motion of electrons in periodic crystalline structures) . When you simply dismiss that as "babble" you are not helping your case even though you are correct with the latter part of that statement. – Floris Dec 07 '17 at 01:36
  • I think "disingenuous" points out the correct flavor of my position, although it is a bit strong. It implies intent to deceive, and I think that's exactly what attempts at trying to understand this concept often are from those unable or unwilling to think it through. – John Ahearn Dec 07 '17 at 22:25
  • If it's the word "babble" that bothers you, then fine. I'll retract it, but it does have a purpose. It points out that many of these same attempts lack detail. They're sloppy. To say outright that the electron is or ever was a wave is to project one's own ontological beliefs onto natural observations which have no need for it. It's misplaced fluff which gets in the way IMO. It's obfuscation. – John Ahearn Dec 07 '17 at 22:25
  • Regardless, you never explained any "misconceptions" I might have. I assure you I do not unless Feynman and the Physics departments at Berkeley, Boulder and Arizona all have the same misconception. You've led me to believe that you're offended by my language and somehow that led you to believe I have a misconception. If so, you have convinced me that you simply don't understand the subject matter and probably should have never tried to weigh in on it in the first place. – John Ahearn Dec 16 '17 at 16:48
  • You are very insistent - but I am not offended by your language. I believe your statement "If it's an electron then it's measured always as a particle." is an oversimplification - and thus borders on misconception. For example, when you observe the behavior of electrons in a periodic solid (semiconductor), including the strange behavior of "holes" in a magnetic field (Hall effect), it is hard to say "these electrons are just particles". They really do behave like waves - or rather, without the wavelike (quantum) nature of electrons you could not explain the presence of a conduction band. – Floris Dec 16 '17 at 17:32
  • Incidentally, quoting Feynman: "Historically, the electron, for example, was thought to behave like a particle, and then it was found that in many respects it behaved like a wave. So it really behaves like neither. Now we have given up. We say: “It is like neither.”" - see this lecture – Floris Dec 16 '17 at 17:33
  • My insistence originates from years of observations of how badly this idea is interpreted, and you are proving my point that it IS very badly interpreted. Feynman said many things on this topic, none more important than that the electron is never observed to BE a wave. Always a particle. You are making the common mistake of associating wavelike behavior with with some sort of inference that the quanta itself IS a wave. This is the point where MANY PhD physicists often take a sort of personal ontological leap of overconfidence and bestow a wave nature to the quanta itself. When confronted ... – John Ahearn Dec 16 '17 at 20:44
  • I never said anywhere "the electron is a wave". Please re-read my original post - which was suggesting ways to talk about this difficult topic to an above-average intelligent 11 year old. – Floris Dec 16 '17 at 20:47
  • The response is often the sam: a claim that the difference is a semantic one. It is not. There are many ways to visualize the distinction: One ex. while it's important to note the non-QM nature of beach balls, if one were to observe a billion of them floating on the ocean from far away one might be inclined to note their wavelike properties and behavior. But clearly they never are waves. A non quantum mechanical ex. yes, but in one respect a good analogy - find out more about what's really going on and each measurement results in the individual beach balls or the quanta bouncing off them. – John Ahearn Dec 16 '17 at 20:50
  • Two points. 1: i am responding to your misguided and apparently very confident claim that I have a misconception or misconceptions. You have yet to explain even one to me. 2. The 11 year old is way way above average intelligence. My point was that at his age I would have been greatly assisted with knowledge of all the fluffy thinking imparted as actual knowledge. That fluffiness slowed me down because it made me think I was missing something. That was not helpful. I maintain my position - it is NOT smart to insinuate to someone like this that an electron is actually a wave. Ever. – John Ahearn Dec 16 '17 at 20:52
  • Let us continue this discussion in chat. – Floris Dec 16 '17 at 20:52
  • Tried to move it to chat. Apparently there is a bug when I tried to edit an incomplete answer - some of the discussion has been cut off. I'll try to copy things over now ... – John Ahearn Dec 16 '17 at 21:03
  • Floris. Not surprising that I want to contact you but PSE gets in my way. Seems like this is the only way. Are you getting this comment? – John Ahearn Jan 11 '18 at 02:18
  • Yes I got it @JohnAhearn – Floris Jan 11 '18 at 02:18
  • so how to start a new discussion? i am troubled by something you wrote. – John Ahearn Jan 11 '18 at 02:20
  • More accurately two former physics profs (one currently at LBL and one teaching at Stanford) also have trouble with something you've written. In fact they have trouble with almost everything that others have written here in opposition to my post. In your case we are all questioning this statement you wrote: "you know that electron diffraction demonstrates that single quanta have wavelike behavior." Their response is the same as mine: if it's a quanta then it doesn't behave like a wave. I'm going further and saying that a quanta is not a wave. Never was and never will be. – John Ahearn Jan 18 '18 at 22:33
  • @JohnAhearn I am just going to say I disagree but I am no authority in this regard. Feel free to follow the teachings whomever you want. I said my piece. To argue with a body of knowledge requires a carefully constructed argument - beyond the scope of this question or site. I hope your efforts to mentor the bright child at the heart of your question are fruitful. – Floris Jan 19 '18 at 03:59
  • that's amazing. sad even. unquestionable confirmation that PSE is "science according to the masses". – John Ahearn Jan 19 '18 at 14:45
  • I don't see how you interpret my comment in that way. I just don't think that a question about how to mentor an 11 year old can reasonably be expected to be turned into a careful scientific exploration of the issue you bring up. If that is what you want to do, and you want to do it on this site, I would recommend that you write a focused question (and self-answer it); that would be the only way to get traction here. Or you could take a look at physicsoverflow which seems to be where some people like yourself have better luck with this kind of topic. – Floris Jan 19 '18 at 16:03
  • @Floris I am specifically and ONLY referring to the point about a quanta behaving like a wave. Maybe we mis-communicated here in which case I apologize. Regarding that question in particular I see no room for an understanding driven by ontology. A quanta is a discrete thing. It is not spread out. It is not a wave. In short, it is a quanta. There is no mathematical idea or formalism of Q.M. which even hints that it is anything but this. I don't know where this idea comes from that it is a wave or behaves like a wave. Furthermore I think this is an excellent thing to teach this unique young man. – John Ahearn Jan 20 '18 at 03:51
  • A quantum (singular of quanta - sorry six years of Latin in school...) is a wavefunction observed. At the moment of observation it is exactly a particle. The behavior of an ensemble of particles strongly suggest that at times when it was not observed this quantum had wave-like properties. I never intended to say “was a wave”. My point always was: be careful to take young people too far outside of conventional wisdom unless you really know what you are doing - and ask yourself if you are doing them a favor. That’s all. I am no expert and I won’t judge for choices you make. Peace. – Floris Jan 20 '18 at 03:58
  • You are confusing at least two ideas. Again, we are addressing your statement "you know that electron diffraction demonstrates that single quanta have wavelike behavior." You just correctly stated that a quanta is a wavefunction observed. EXACTLY !! At that point it is NOT a wavefunction - its mathematical equivalent is the expectation value of the wavefunction. This value represents a discrete entity. NOT spread out. It cannot diffract -it is OBSERVED! – John Ahearn Jan 20 '18 at 15:47
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    @Floris FWIW I just visited a "page" about you specifically and was about to type the following "My interactions with Floris have proved him to be an invaluable PSE member. Very knowledgeable and very patient. Always fair and unbiased. Keep it going Floris;-)". However, I'm not allowed to post because of some rule related to my overall "score". Good luck to you regardless. – John Ahearn Feb 07 '18 at 23:30
  • @Floris I think I read an entry by you in which you write that E&M propagation "along" a conducting wire is moving near the speed of light only outside and within the insulator. J.D. Jackson proves this wives-tale to be untrue. I've spent most of my weekend tracking down the origination of the error. You might be interested to know what I've found. J – John Ahearn Mar 19 '18 at 19:11
  • Can you post a link? – Floris Mar 19 '18 at 19:13
  • I have done a lot of work, and the result is many fairly involved emails. I can break that down to two emails though. I don't know how to get you all the info. If I put it in a blog, where would I post a link? – John Ahearn Mar 19 '18 at 20:36
  • Do you have a copy of J.D. Jackson? That would help quite a bit. – John Ahearn Mar 19 '18 at 20:37
  • i will, but let me try this first. i've created a blog posting on this topic. let's see if I can paste the link to that here: – John Ahearn Mar 19 '18 at 20:59
  • http://everphase.net/2018/03/19/displacement-current-within-good-conductors-gone-mia-but-why/#comment-749 – John Ahearn Mar 19 '18 at 20:59
  • Link works! I will read it when I have time. – Floris Mar 19 '18 at 21:55
  • I've contributed quite a bit to that blog post in just the last two hours. I'll likely stop now for awhile. So after this moment is a good time to consider everything mentioned there. Especially two things not necessarily in this order: 1.) The very last entry describes a modified coax cable such that TEM mode can likely exist inside the conductor. I'll be looking into this later. 2.) there is still the very strong hint from Jackson about the small electric field existing inside a good conductor in the normal direction. For the case of large skin depth, I believe this is our TEM. – John Ahearn Mar 20 '18 at 20:25
  • Now it's just a matter of choosing the correct geometry so that TEM mode can exist inside the conductor. – John Ahearn Mar 20 '18 at 20:30
  • I left this last comment out. Now at bottom of the post ... "Since all I want to know is whether an E&M wave can propagate within a good conductor at a good % of the speed of light, I will proceed to consider only the following case for now which concentrates on TEM mode only ... – John Ahearn Mar 20 '18 at 21:05
  • A modified coax cable, where both the inner and outer conductors are hollow cylinders with thickness smaller than the skin depth. The inner conductor is filled with the same dielectric as everywhere else in the coax cable. We now have a case where neither of the conductors satisfy the "singular waveguide" case (i.e. the case where TEM mode is not allowed)." – John Ahearn Mar 20 '18 at 21:06
  • You have to admit it's interesting. I've now tried to contact 5 physics PhDs, 11 EE PhDs and 1 legendary author (Balanis) who all state that E&M doesn't travel at light speed axially within a conductor. Only 2 admit they had no idea what they were thinking when ignoring displacement current inside. The rest just ignore the issue - no response! – John Ahearn Apr 13 '18 at 02:02
  • I didn't respond because I have been extremely busy with a new job (see my recent inactivity on SE...) and I don't have the book you referenced in your blog. That left me at a disadvantage, and it didn't seem worth my (or anyone's) time to add my ignorance to your inquiry. – Floris Apr 13 '18 at 02:35
  • shifting gears ... like your new job? i'd like to know more about it. – John Ahearn Apr 28 '18 at 22:00