Hello everyone! It seems like this video has gotten a flood of recent activity, (a bit surprising since it's three years old, but a welcome surprise) and I just wanted to, first, say "hello" to all you new people. Great to see you. And, second, it seems like there's been a sort of new wave of reactions, some negative some positive, to the content of this video so I just wanted to, in a central place, maybe provide some important additional context and discussion. Namely: 1) The human mind thinks in "concepts" but ultimately a physical theory is not a collection of concepts but a collection of math, math that either does or does not match experimental data. And within math it is possible to have so-called DUALISMS. A mathematical dualism is when two sets of equations on the surface look very different, but when you mathematically manipulate them in a certain way you find out that they are actually EXACTLY the same bit of math. Whenever you have such a dualism it is thus the case that ANY and ALL predictions of the one set of equations will be exactly the same in the other, again, because they're secretly the same bit of math, just in a different form. 2) The central set of equations of the classical theory of electromagnetism is often said to be what are called Maxwell's equations. However, these Maxwell's equations have a couple alternative formulations that can be shown to be mathematically DUAL. Thus, any such formulation will exactly make the same predictions and there is no basis for saying one is "correct" and the other is "incorrect" as they are secretly the same thing. 3) One such mathematical dual formulation is what is called a formulation in terms of "retarded potentials" (retarded meaning slowed or time-delayed): en.wikipedia.org/wiki/Retarded_potential 4) The content of this video is basically just introducing this "retarded potentials" approach to people who may not be familiar with it. This approach should be covered in any good undergraduate textbook on electrodynamics, and is certainly not in any way "my" idea. I am not Lienard, Wiechert or Green, those were the ones who came up with it over a century ago. There also seems to be some notion that this formulation is "fringe". That is definitely not the case, as I said, the content of this video will also be found in any good undergrad textbook, for example, my personal (and I'm sure many others) favorite Introduction to Electrodynamics by Griffiths. 5) When learning a new subject, not everyone "clicks" with the material in the same way and having alternative conceptual and mathematical formulations can be of great benefit to some in learning. If you personally prefer the Maxwell formulation and find it intuitive, then "great!". If you've always found it a bit opaque, well then here's an alternative formulation that, again, is ultimately identical (i.e. mathematically dual) but may "click" a bit better. 6) As many have pointed out, this approach does not carry to a quantum mechanical treatment, but neither does Maxwell's equations and one CAN formulate quantum in a similar way, this is in essence what a so-called Green's functions approach is. Anyways, hello again to all you new people. Please check out some of the other videos and welcome. Also, there have been some asking about my qualifications and background. Of course the work should speak for itself but for the curious I have a Ph.D. in Physics (specifically in what is called Condensed Matter Theory, which is basically the field that deals with what happens when you have many quantum objects in something like a solid, or novel solid states like unconventional superconductors or "spin liquids" and such and how they behave) then moved to a more Applied Physics focus when I did a Post Doc for many years (where I worked on everything from new solar cell designs, new approaches to renewable energy and new computer memories to stuff like better ways of formulating electron transport in semiconductor devices in order to better take quantum effects into account). I am now a Senior Staff Physicist at a research-adjacent private company in the field of emerging semiconductor technology.

Brilliant work! Now I need to go pick up and reassemble the pieces of my mind so I can continue down this rabbit hole!

People often confuse map for the territory. It's like when quantum physics was explained in terms of matrices, then same theory was explained equally well with functions (Schrödinger). Then it was shown both approaches are valid and interchangeable. People asked - so is it matrices or functions then? The answer is: "both and neither" - the defining point for quantum physics is actually non-commuting operators (A•B ≠ B•A)- we can construct them with matrices or functions, either will do - because these are just tools to describe the thing. We often even forget that physical laws are descriptive, not prescriptive. People say "laws that govern the universe" - but it's more like "rules that seem to more or less describe what we observe".

I just discovered this channel, and I absolutely love it. SO helpful. I work in graphics programming, and as a result I both think about light a lot, and have a pretty decent understanding of vector fields and things like that. But I have always been so confused when I tried to actually understand whats *actually* happening with light, and whenever I've tried to look stuff up I always get just countless unending piles of the same old basic explanations. This is has been extraordinarily helpful. Your channel needs more views.

I think you're going a bit hard on these "misconceptions". After all, that a Magnetic field is caused by a changing electric field is basically a Maxwell equation. Of course your interpretation is not wrong, in your interpretation this just means that they coincide because of the way they are generated instead of being causally related. So basically the interpretation of the Maxwell equation goes from "changing magnetic fields cause an electric field" to "a changing magnetic field is always accompanied by an electric field". The way I see it this is just a shift in perspective and depending on the situation you're trying to understand different perspectives might be more or less useful. If we're talking about light from the sun for example I find it more convenient to think of radiation as its own thing and the details of the charges in the sun would only be distracting. In the end, the math is clear and unambiguous, the way we conceptualize can differ. A good physicist can conceptualize the same phenomenon from several perspectives. Understanding comes from being able to translate between different perspectives.

You either do or do not accept the 4 Maxwell/Heaviside equations are a valid starting point from which to better understand nature .If you do , one equation says that a magnetic field curls about a current or changing electric field , another says an electric field curls about a changing magnetic field .They are coupled ; they co-exist . From these equations one can derive the Wave equation and show that the fields ( electric and magnetic ) are propagating waves that are orthogonal , in phase , and spatially in quadrature , further that they propagate at one speed , c . From this understanding we have been able to build , broadcast radio and TV,sattelite communications , cell phone networks etc . We have also gone on to expand and improve this knowledge bringing it into alignment with relativity . This in turn has enabled us to build the GPS networks and large distance communications. All of this has been rendered possible because our fundamental understanding was correct. Many of the points made in this video are flat out nonsense and if adopted by a viewer , that would be unfortunate .

That's interesting, and I can see it working in some contexts, but not in most. If you are teaching a future physicist, you want him to have an understanding of how physics is made. The classical explanation using Maxwell's equations does that quite well. The student sees how physics is produced not by just experimenting and figuring out mathematical functions that describe the results, but also by trying to unify different theories and ending up having made accurate predictions about reality. The story of Maxwell's correction and how that allows the model to support electromagnetic waves, how these waves turned out to have the same speed as light, and how the attempt to salvage this theoretical model lead to Relativity is quite powerful. How would a student get the intuition behind the Liénard-Wiechert potential (or simply the force) if that's what they see when they are first taught the topic. If you are teaching a future engineer, who mainly wants to know electromagnetism to do calculations, how would an unwieldy formula like that be of more use than Maxwell's equations? This approach can be useful (in an educational setting) when you want somebody to understand the basic idea behind electromagnetism, without really going far with it and really diving into them math. It could also be used complementarily to the classical approach, to test the students' understanding by having them figure out why the two ways are equivalent, and how the same phenomena can be described differently. This is just my opinion anyway. Personally this was a very interesting video to watch!

This was great and really helped break these misconceptions which I held. Another misconception break was discovering space time algebra and the idea that the electromagnetic field is a 4-D bivector field, and that itself a derivative of a potential field. I was immediately struck that the B field created by the angle between the electric field and the position vector is a wedge product…? Now how does this relate to how the EM field is perceived based on the motion of the observer? I wish I understood how to tie space-time algebra, the LW potential, Lorentz force, and relativity all into one coherent concept.

At 4:15, E and B are synchronous ONLY for perfect plane waves; these waves are essential for Fourier composition but are entirely unphysical since they extend infinitely in both space and time and thus require infinite energy to create. Don't take metaphors too far or you will be disappointed. At 5:00, though PHOTONS don't interact in VACUUM, EM fields do interact by adding to each other. But just like sound, water surfaces, and every other wave neither deflects the other. At 6:15, there ARE particle beams in electron microscopes, cathode ray tubes, and particle accelerators that do NOT have cancelling opposite charges, so once again I call B.S. Three is my limit...

You really took us behind the curtain. That was excellent and unlike anything else I’ve heard on youtube. I’d really like to see this in more mathematical depth. Can you do a second video where you demonstrate these ideas with some form of Maxwell’s equations (differential forms)? I know you weren’t saying that the distant detector is aware of the current position/velocity/acceleration of the charge (that would mean instantaneous transmission of information), so I believe you are saying the distant detector is comparing it’s last update with it’s current update - it is generating the magnetic field based on the local rate of change of the position-velocity-acceleration of the signal from the distant moving charge. Would a Lorentz transformation be involved here? Could you calculate some examples for us? I took electromagnetic theory some years ago but this explanation was never explicitly taught to me. Thank you. Subscribed!

I'm extremely confused, and Veritasium would argue that means I learned something. Cheers mate excellent discussion!

This seems insightful, and I'm still mulling it over, but I must admit I am disturbed by the sweeping statement "This is how all E&M works". Surely this only describes classical E&M at best, not quantum phenomena (where we can't consistently determine properties like position and velocity which are crucial to this video's perspective). And of course, in our deepest and most accurate theories of the universe, Quantum Electrodynamics and Quantum Field Theory, the fields themselves are considered to be the fundamental physical entities, and not the particles (which are merely excitations of the fields). This seems to be in contrast to the perspective of this video, which maintains that the particles (and their classical properties) and the fundamental objects, and the fields are merely a "mathematical bookkeeping device". So I must conclude this is just a other one of many mental models, which may prove useful in understanding nature in some cases, and will fail to predict her in others - just as all of our human models do.

Why is the 'magnetic field vector' perpendicular to both the 'electric field vector' and the 'time-delayed vector', instead of the difference between them?

You can't imagine how bothered I have been by this topic. Literally spend a good 20 hours a few months ago watching videos related to electricity and electrons just to understand this. Two days ago I decided to revisit and started to watch some more videos. Now i have a better grasp of electricity and electrons and with this video I finally feel like I understand the fields.

Before finding this video, I'd spent countless evenings worrying about this same topic, being incredibly discomforted with the mainstream way of illustrating "electro-magnetic waves" and "magnetic" fields. I initially figured that magnetism and electro-magnetism is actually caused by "time-delayed" feilds and the resultant "kink", and then tried working out the vector mathematics. I gave up, then got this video recommended. You've made my day - thank you so much, and God bless.

I think the traditional Maxwell's Equn's throw up red flags because they are Classical (non-relativistic) like Newton's Laws of Motion, but they break Classical physics as it produces a speed of light that is constant for all observers. So it is not a fully Classical theory, but it totally misses out on the Relativistic viewpoint where there is only one kind of field (not separate E and M) in 4-D spacetime. So, it works very well for many practical applications and allowed the understanding needed to invent radio, for example. But even when applied in situations where non-relativistic physics should be OK (i.e. participants are not moving quickly relative to each other), it doesn't _quite_ work out. Even at hand-held speeds, a moving magnet gives different physical effects than a moving coil, when Newton would have it that we can't really tell which one is moving and either viewpoint is correct and gives consistent answers. Remember, Einstein's famous paper introducing SR was called _On the Electrodynamics of Moving Bodies_ and solving this issue is what it was really about.

Awesome video! Thanks for making it. I am reading the blog post now. Can you please make a video explaining WHY the relative motion of a magnet and a conductor induces a current in the conductor?

Incredible video, I subscribed. You put a lot of time in effort into your work I can tell.

The best thing about this channel is that it's all I could hope in terms of the ability to conceive what's reallly going on from the POV of another person who hears things like "electric and magnetic fields create each other" somewhere else and go oh really? that seems like an important insight, ie we could invent things off of this, only to find out no, this was something someone who couldn't think properly heard or assumed and propagated. Same thing with the particles being waves that do normal wavey things. I hate all the "woooo it's so mysteeerious" aspect of everything. It's cool enough as it is, and we have these people in the field that have been told you just need to do your homework and you'll get to the top of the class, when really what we need is clean thinkers that cut through all the skaffolding our brain puts in to understand things functionally before we have a proper core-based intuition. Your work gets to to that "past the skaffolding" level, and so many of the top science youtubers have just become outlets of the textbook and the textbook's shitty examples and explanations. I hope you keep it up, I keep checking back for more!

Thank you very much Sir for this. I wish you grow more and more with this rich content of yours reaching more masses. I believe, David J. Griffiths would be pleased watching someone presenting this is such a nice manner. Regards

My understanding is if you move a charge around, a ripple in the EM field propagates outwards in all directions, and that's what an electromagnetic wave is, and that's what light is. Not sure where the particle view of light fits into this. Also not sure how photons fit in, and how atoms emitting or receiving photons alongside their electrons changing energy states fits in. Here is an incoherent jumbled mess of questions. I guess at some point the wave collapses into particle like behavior, but like, is that the thing that violates time? (I doubt that's the part that violates time as in the quantum eraser experiment, but how can a wave that's propagating outwards in all directions collapse into particle like behavior once it runs into something and act like it was a particle moving in that one direction the whole time? I guess that's the point.. light is weird). It's weird that a wave would propagate in all directions, but the particle view of light is only in one direction or something. Not sure how multiple devices can pick up on these WIFI waves too.. like the waves are continuously being generated. Not sure if any of these outwards rippling waves collapse into particle like behavior, etc, and if they do, how can devices that are further away receive any signal if the wave already collapsed into a particle when it hit the closer device? Also based on a stack exchange answer with 100+ upvotes, it seems the word photon is poorly defined and means different things based on context.

This is well articulated---really enjoyed it!

I find this video totally confusing. Please correct me if Icm wrong. Thinking in photons appears much more easy to me... In conductors a current flows when there is an imbalance between the poles' electron concentration as same charges repel each other to achieve a minimal energetic state see chaos theory and bring the understanding of that in line with entropy and resulting probabilities. When an electron approaches a proton, it emits a photon. This happens continuously while the electrons move to high entropy states say fixing the imbalance. When photons interact with electrons in the vicinity of protons they kind of move away the electron from the proton "farther" as they take up the energy of the photon and thus the attraction force of the protons becomes negliable in relation to the kinetic energy of the electron. As a current flowing as outlined above causes quite chaotic radiation of photons, those photons will effect other electrons which is being described as an electromagnetic field. This in turn causes the same effect over and over again... I don't know how they teach physics in the US, but here in Germany we were made aware of the differences of an electromagnetic and a static magnetic field. Maybe you should have done so, too, because I don't have a clue what you're talking about after watching this video...

Thank you! I’ve been trying to understand electromagnetism but the relationship between electric fields, magnetic fields and radiation didn’t make sense intuitively. Now it does. Please keep up the good work by illuminating misconceptions and limitations of conventional explanations.

Its fascinating science can be this simple yet complicated. After a long time I enjoyed electromagnetism. Thanks

When I was in school, I asked a lot of my professors about electromagnetic induction and never really got a straight answer. The response typically sounded something like this: "A changing electric field creates a magnetic field (Ampère's law) and a changing magnetic field creates an electric field (Faraday's law) , so electric and magnetic fields are the same; an elecro-magnetic field." I was never content with this "explanation". My questions were either being brushed off, or more likely, the professors didn't know the connection between electromagnetism and length contraction (relativity). It wasn't until I was taking a grad-level class on microwave circuit design that my professor tipped me off to the connection with relativity.

I have a bit of a problem with the way you described the electron sending out information about its velocity and acceleration. The electron has no way of 'knowing' its velocity, not to mention transmit that information. I think it would make much more sense to assume a resting electron and a moving point A. That way, you only need to know the magnitude and direction of the electric and the whole velocity/acceleration information is just stuff the point A experiences as it moves though the field. Or am I missing something here? Anyway, great video!

I just don't understand why the electric field doesn't point in the direction of the time delayed position in the first place. If the electric field is radially emanated outwards the charge, why it gets deflected when it reaches the point A. It should have a perpendicular angle with that yellow circle, shouldn't it?

Does it explains the lorentz force? field up for magnetic momentum in magnets far away ( N--> S) and close to current (S-->N) ? This is incredible,thanks.

I really like this explanation, am taking a course on electomagnetism at a community college right now and this video has a lot of the intuition I've been missing

Thank you so much for this video!! I love it when a video explains something I couldn't understand for so long. Before I had zero understanding now I have 1%. A big improvement for me. Now I have to work on learning the LW equations.

Question: How does this perspective relate to the impedance of free space, which establishes the ratio of E to H for electromagnetic radiation?

This video tried to correct the picture that one has when introduced about EM waves, the textbooks saying changing electric fields creating magnetic fields and so on sometimes paints a picture that is bit misleading and creates unnecessary struggle for the subject.

Visualisation of em vawe in most books is wrong. You are right, both E and B are shifted to each other.

All in line with Maxwell as I see. I just missed this part with acceleration. Moving charge with constant speed also make magnetic field. Can you explain bit more this part about magnetic field at distant point?

Really nice explanation. Very easy to follow, just the right pace, great graphics. But one thing you didn't mention is 'the photon', how does a photon fit into this understanding? thanks

Very interesting. I've also wondered a lot of the topics you mentioned such how two light beams can just pass through each other and not effect one another under the principle that changing field induce the other field

I like your videos. I hope your channel grows so that you can make more videos. Are your gradient symbols upside down? I am talking about the signs in 2:10 when you start talking about changing E and B.

The magnetic field is at a 90-degree angle because it is delayed by the speed of c. It would be in phase at zero degrees if it were in perfect unison.

Interesting. I'd be interested to see your analysis of the Aharonov-Bohm effect using this model. And then on another tangent, an analysis of the Tom Bearden MEG, which if you research it, he claims that it uses this effect entirely in its ability to operate as a "very efficient" transformer. It uses a Honeywell Metglas Amorphous C-core (AMCC-320, I believe). That laminated core has a very high magnetic permeability. If you put a permanent magnet into the center of this core (you'll have to check a video of the replication of the MEG and the diagrams since it is pointless to try to describe the geometry with words here), it will contain the entirety of the magnetic B-field, but the A-field (electromagnetic vector potential) is claimed to still exist in the space around the magnet that the B-field would be in if it was not contained with the Metglas core. This effectively "decouples" the E and B fields from each other (with the A-field being the electromagnetic four-potential which they are both derived from). Perturbing the A-field alone (which is in the space around the coil) will actually induce an E-field in coils wrapped around this transformer. Because the B-field is contained entirely in the core, it does not interact with the E-field and therefore does not have the usual losses associated with a typical transformer design (where the magnetic field works against (counter-balances) the induced electric field). This is a naive explanation of how it works. It is not meant to be rigorous here, because I am not a physicist. There is plenty of info out there on UKposts and in the US patent for this device (patent number US6362718B1) to build it and understand the inventor's explanation of how it works. He explains the observed effects as being related to the Aharonov-Bohm effect experiments. But an "infinitely long solenoid" is not necessary to isolate the B and A fields. Because the laminated metglas material and the geometry of this device does this for you. I am not a physicist, so I probably have terminology wrong here. The research on this device is properly rigorous, though. I think your model that you describe here will shed a new light on how this device works, and possibly be a more "acceptable" explanation to mainstream physicists. Thank you Paul PS: It would also be interesting to reconcile your model with general relativity given the time-delay aspect of your model. Or perhaps you have a different explanation for observed relativistic effects.

Excellent explanation. One doubt though ... You said that the time delay of information at a point is because the the information takes speed of light to reach that point. But while deriving the speed of light itself , in any books the it is seen that the two fields causes each other and then the derivation is proceeded. And we get a number which is th light speed. So can you tell how can you find the speed of light in the first place ?

Your theory is pure gold.

Very interesting arguments and ideas. But, I don't agree for the following reason: Electromagnetic waves are solutions to Maxwell's equations in the absence of electric charges and currents. Therefore, electromagnetic waves exist in the complete absence of electric charge.

I am an A-level physics student and I think i just had a stroke trying to watch this

You know, I'd love if you could make a follow up video to get better grasp on the math of the LW rulw.

Can you explain the significance of having the fields/force depend on acceleration when usually they depend only on position and velocity. Do you need 3 initial conditions( r0,v0 and a0) to solve a problem?

From your blog post linked in the description. "It turns out that in a radiating electromagnetic field the electric and magnetic fields are always perpendicular to each other and perpendicular to their direction of motion." By direction of motion, you're talking about the direction of motion of the EM disturbance, right?

Thank you for this video, you don't get many that get into knitty-gritty details while still being rather accessible (and entertaining). You mention early on that there is a misconception that the fields propogate each other - which is why they can continue for so long. Later you clarify that they have no effect on each other - but they still "radiate" together. Does this actually continue forever? Will light never slow down unobstructed - not even through something tiny that we cannot detect - just continuing forever? With sound, it's the movement of air particles that continues, with waves it's the water particles. With electromagnetism... it's moving through nothing at ridiculously fast speeds? Is it not something tiny that itself is being rippled after the initial acceleration? And if there is something tiny (tiny might not be the right word) - is that what causes the actual force of gravity - that tiny thing/lattice/field being "compressed" - or instead of a tiny thing - dimension(s) or intersecting parts of them? Thank you - Yasir. And also sorry in advance for, well, all of it.

Very interesting video! I do question one thing if these formulations give equivalent results why are you so sure that one is more fundamental in terms of physical nature. That is why are you certain that that E and B are just mathematical tools whereas Jefmenko's formulation tells us something more fundamental about the universe. Could it not be the otherway around? In fact historically before Maxwell E and B were thought of as nothing more than tools describing action and distance, before Maxwell "fixed" Ampere's law and saw them as a natural phenomenon rather than simply a tool.

Good video. There are a lot of subtle important pieces of information in this presentation. But I find the semantics difficult to follow. I am confused about your claim re: interaction of electric and magnetic fields as "they don't interact with each other". So for example, when a charge moves in a changing magnetic field, what then is mediating the motion of the charge?

So the magnetic field is basically the phase/time difference between the instantaneous wave function and the electric field traveling at the speed of light relative to the charge in motion? How then is the magnetic field weaker as we move away from the current? Is it perhaps then the inverse of the time difference? Then what about permanent magnets? What causes those materials to exhibit a magnetic field?

THANK YOU! You're confirming several of the conclusions I had already come to (no help from standard E&M textbooks, or so many other physics videos).

When discussing the radiating/non-radiating parts, did you mean intensity? Because wouldn't summing the energy around radiation spheres be constant?

Your video is counter educational, and will confuse people learning E&M for the first time. You show a far field conclusion, but discuss near field theory. If you started at Maxwell's equations, and set charges to zero, the equations still allow for fields. As to the tone of this video, it sounds like the old debates were people are trying to eliminate fields and have charge only E&M, which Wheeler I believe succeed with a cumbersome theory. But, it is possible as Dirac showed to cast the theory with fields only. Finally, your disregard of sine waves is bizarre: Have you not heard of Fourier analysis?

Is magnetism the result that occurs when multiple eclectic fields collide (meaning the fields move)?

this is different than how I was taught physics! it'll take a while to digest. Thank you.

Sandy Check: LW RULE CANT ONLY APPLY to one light wave affecting itself later in time. However, to do so means electric fields INTERACT ( even if only with identical wave formations). When interacting they can produce a magnetic wave (the LW Rule invalidates your claim the ligh is not able to interact with light. And electric fields (moving or accelerating) do not create magnetic fields. Experience with linear accelerators indicate the electric fields must be aligned to produce measurable magnetic fields. Possibly also the same waveform. Magnetism may be required to have a limited angle of separation of the electric fields.

Yep. Lots of issues in there. Plane waves (infinite extent) don't exist in a 3d world because they can't have started anywhere. Spherical waves fail the hairy ball test. Plane waves ('horizontal and vertical' somehow measure gravity) fail the 'countable' quantum test as there are 3.14.. irrational orientations (radians;-). Finally you can have circular polarised light, which does at least have a countable number of 'orientations' (just need to add in wavelet packets to get energy quanta but that's not within present school maths..)

Where do photons fit into all of this? Atoms can accept or release photons at the same time as their elctrons move into different energy levels, etc.

Great video. Thanks for creating it. I have a somewhat related question. Why does changing magnetic field give rise to electrical current? I know it has to be so, it has been proven experimentally, and Maxwell's equations describe it. However, what is happing in the conductor at the atomic level to make the electrons move in response to the conductor's relative motion to the magnet? I have scoured the internet for a while but haven't found a satisfactory answer, except that it is just so. I will appreciate any help in understanding this phenomenon. Thanks.

This a brilliant and absolutely much-needed video. Can’t believe it’s been around for over four years and I just came across it! Don’t get down from what your criticizers say - there’s an extraordinarily large segment of science UKposts viewers out there who have a very poor grasp and the distinction between correlations and causations.

What happens if a electromagnetic field overlap? Does this quantify the electricity? Im asking in regards to rTMS. I moved my head during treatment and i wonder if i got double electricity

17:45 In your blog post, you mention that the EM field strength due an accelerating or decelerating charge decrease at 1/r (this in contrast to the 1/r^2 decrease of field strength due to a non-accelerating charge). Is this also the case for the "canonical" sinusoidal EM field which we've seen many times? Does the strength of a propagating sinusoidal EM field also die down? Such a field has been described as self sustaining, so that suggests that it maintains its strength forever. Is this true? And if so, it makes a sinusoidal EM field somewhat special. Or do they also die down?

Thank you for this! You amuse me, delight and entertain me, while also being informative. That's quite a gift.

This is called "Philosophy of Science".

Thanks for the very interesting explanation! Is this using special relativistic EM interpretation or just rely on the original Maxwell's equations? And what about QED? I thought E and B are just apparent measurables of the same thing, so they are just emergent properties of the underlying changing quantum fields.

I have a question. I well understood how the waves are produced, and how the change in electric/magnetic fields aren't the main reason for it. But there are still expressions in Maxwell's equations implying these changes should have some effect on another, so even though those effects won't appear instantly (like you have shown as first suspicious notion), shouldn't they still have an effect on the wave in some way?

What carries the signal or information? It sounds like each electron (or charged particle for that matter) continuously broadcasts its position, velocity, and acceleration in all directions forever. Do they? Or is it more like each charged particle perturbs the field? And if we could isolate a charged particle's contribution to the electric and magnetic field at a point, then we could figure out that charged particle's past position, velocity, and acceleration?

I really enjoyed the video. But how do we know that the velocity and charge information travels at the velocity c?

I'm confused by what's happening. How does the time delayed position information differ from the LW predicted field? Why would this create a perpendicular magnetic field. I'm just not seeing the cause and effect of this reaction. Can anyone clarify?

CORRECTION --> While every thing displayed on the video is exactly accurate except the shape of 'light' at the very end. For a very specific case when the charge moves in a periodic oscillatory closed path (i.e. having periodic acceleration) the electric and magnetic fields indeed become sinusoidal [see Ref]. At a large enough distance from such a charged particle (called its 'wave-zone') the EM radiation acts nothing but a plane wave spreading radially outwards. The frequency of its oscillation is same as the frequency of the sinusoidal EM waves. If light would not have sinusoidal shapes there would not be an electromagnetic spectrum with different types of radiation with their specific range of frequency (i.e. we could not distinguish Radio waves and ultraviolet rays without the information of a proper frequency/wavelength of them). Ref -- 1. Chapter 9, Classical theory of fields by Landau & Lifshitz 2. Chapter 29 Feynmann lectures Vol. 1 I really enjoy all the quality videos of this channel. Especially this one made me go through the basics of electromagnetism again after a long time. Kudos!

When people say a changing magnetic field "causes" an electric field and vice versa, I don't think they really mean "cause". That word shouldn't be taken too seriously there; people are just giving a rough summary of Maxwell's equations. (I would not use such phrasing myself, though.)

Wow. Excellent, thankyou. Should be in every High School syllabus! 👍

are they in step ? what if the time diff is too small for us laymen to measure?

Thank you so much for making this. I love the way you shoot for conceptual clarity and intuition. This is the heart of good science and physics teaching.

After studying electrodynamics I also started questioning why people represent waves as sine curves. One reason may be the way we use light in our everyday lives. Radio stations and wifi use frequency bands of quasi-monochromatic radiation. But yeah I fully agree with you. The solution to 2nd order wave equations is any distribution f(r-ct) moving at the speed of light.

You're getting confused between near and far field EM waves along with electrostatic fields. There is no coupling between electrostatic fields, but there is always a coupling between time varying E and H fields according to Maxwells equations. In the far field plane waves they are related by the characteristic impedance. In the near-field the relation is complicated by the geometry and can be very high order.

Excellent tutorial. I'll have to listen to this a couple of times but I find it amazing that it can even be figured out at all. If time dilation is included then I'd require additional time to let it sink in!

I do find this inconclusive and I don't get the point of this clip. firstly at 5:00: electromagnetic waves do not interact, because they are but photons. Though photons are bosons and bosons don't correspond to the Pauli-Principle so it is possible for a system of two bosons or more to be in the same quantum state, since the wavefunction does not change the signs, what is called symmetrics ( by the way a system of two isolated electrons out of an atom can add up their spin to 1, thus becoming bosons, which would therefore account for the interferences with the double-slit-experiment...)... and secondly: the time delay of the em-wave-message is expressed by the sinusoidal shape of the waves, cause if there wasn't a delay it would be a flat line and no wave... The causation between electric and magnetic fields can be found in the equations Maxwell came up with and there is non argumentation in here, why they could be wrong. It is just claimed that they are wrong indeed without even mentioning them! The second equation stipulates that there is no geometrical source in any given point ( therefore the 0 at one side in this equation... ) but a source for there emergence there must be nonetheless. The fourth equation stipulates unanimously and unequivocally the causation of an magnetic field by an electrical field if it experiences any class of differenciation and in the clip this is turned down suggesting a mere coincidence between both fields but it is refused to explain for the source that as a consequence one need to account for. Le p'tit Daniel🐕🏒🍔🍟

"Changing Electric Fields DON'T Cause Magnetic Field" - there is nothing wrong with saying that changing electric fields cause changing magnetic fields, and calling this statement a simplified model of emf wave propogation. In alternating current used for utility electricity distribution it is clearly evident there are fluctuating magnetic fields. if we oscillate this alternating current close to the speed of light (if that makes sense) then you will get an emf wave , or a photon (again, depends on the model you use, that is, models which serve different purposes).

at 17:00, do these electric and magnetic fields oscillate in any way as the ripple propagates outwards? Like, doe the direction of these fields change or anything, or why is light normally conceived of as having oscillating fields?

In your example it doesn't look like a single sinusoid because the "flick" of the charged particle results in a multitude of superimposed sinusoids. This is physical and not just a mathematical concept; if you wanted to, you could isolate the sinusoids using a filter.

Please clarify how your ideas relate to: (1) linear differential equations and the superposition principle for solutions; (2) Fourier analysis. I think this should make clear the role of sinusoidal waves.

Well, you're right in pointing out that it's no surprise that light travels at the speed of light, since... it's light. But that is really missing the whole point. What *is* surprising is that this speed exists as a "special speed" in nature. What's significant about that *speed* (nothing to do with light here) is that if I measure something fly by me at that speed, then you will also measure it flying by you at that same speed, *regardless* of how we are moving with respect to one another. I might see the thing fly by me at speed c, and then see you fly by me at 0.99*c in the same direction. Naive thinking would lead to us assuming you would see the thing flying along at 0.01*c. But that's not how it works - you *also* see it flying along at speed c. And *that* is surprising - it's highly counterintuitive. The muddle of how we talk about this is just a semantic shortcoming in how we choose our words. It turns out that if you want the laws of physics to be invariant for all observers regardless of them moving at constant speed with respect to one another, then a speed that behaves in this special way *must* exist. That reasoning does not tell us, however, the numerical value of that speed. We know that because we have looked around us at the universe and seen how things behave - we *measured* the speed, and it just happens to turn out to be c. That's an observational fact. Then light *must* travel at that speed because light has no mass. Anything that has no mass must travel at that speed (in a vacuum). I agree with you, at least, that the standard presentation of EM theory isn't the simplest, cleanest presentation. It's much more clean to regard the electric and magnetic field as parts of a single unified entity - a "second rank tensor" field usually denoted as F. Also, you said something in there about the conventional theory claiming that EM waves "self-create." I don't think you literally meant that the claim is that EM waves can "pop out of nothing," but it almost sounded like that. That's not so of course - the energy housed in the field has to originate at some point. The fact that the wave can then travel through empty space, after it already exists, is then a fine claim - it's really no different from a wave move back and forth on a guitar string or a water wave moving across the surface of a lake. EM waves aren't really "special" in the sense of being some "additional kind of thing" - they're no different from any other EM field. It's just that if you create some arbitrary field configuration, the only part of it that's able to move through space is the part that has perpendicular electric and magnetic fields; any portions of your original configuration that deviated from that pattern just won't propagate. All in all, your video has a tone that seems to imply that the standard presentation of EM theory is "wrong," and that's not so. It's not the "best" presentation, but it's usually done that way to avoid having the student need to wade into the mathematics of tensors. If the student *can* get to the point where they can do a tensor based analysis, then he or she can have a much cleaner, more straightforward view of the whole business.

Is frequency the rate at which the electric and magnetic field oscillate at a given point? And this is determined by I guess how fast a charge particle oscillated or whatever in the past?

At the very beginning of your video you state that, "Changing Magnetic Fields DON"T Cause Electric Fields". Within this Charge-centric formulation of Maxwell's Equations, what is the mechanism for the induced current in a wire loop when a permanent magnetic is in motion near the wire loop?

i can't tell you how glad i am to see something like this...

The paradigm of field dynamics has its justifications, and you too have some misconceptions: - Talking about the fields as independently evolving entities allows us to ignore the history of the entire universe on our past light cone so we get purely local dynamics - Your paradigm presupposes the speed of light. Maxwell's equations were able to predict it. From a philosophy-of-science point of view, that's gotta count for something. - The misconception that "changing electric fields cause magnetic fields and vice versa" is just poorly worded. Actually, it is the spatial change (curl) of one field that causes the temporal change of the other, in so far as the right hand side of am explicit differential equation can be said to cause the left hand side. In that sense, the (spatial) change of the E-field causes the B-field (to change with time) and vice versa. The reason beams of light don't interact is that's a *linear* differential equation, so the superposition principle applies. - It's not true that EM waves only arise from accelerating charges. Or where are the accelerating charges when a positronium annihilates or a Higgs boson decays?

what application do you use to make these awesome videos?

So EMF perturbations ripple out in all directions like a wave if I'm understanding correctly.. where does the particle view of light fit into all of this?

So how does this look where an electron jumps from one energy level to another to release a photon?

I have heard in the past that the magnetic field is the relativistic correction to the electric field. Does this sound correct?

Nice work!

This (9:00) means that any charge traveling at less than the speed of light will encounter its own magnetic & electric fields as created in the past. Doesn't this field alter the trajectory of the charge?

The problem I've always had with moving point charge retarded potentials is that it's very intuitive, but as soon as you try to express even the basics in maths it becomes a nightmare, unless you've come across otherwise? A bit like the magnetic field associated with a circular loop of constant current - it sounds like it should be an easy calculation, but in reality it's a whole MSc programme.

So if fields themselves don’t exist, what is the means by which the forces between charges are communicated?

I think Maxwell would disagree with you, for him light was a real physical phenomenon, not a mathematical "information" apparatus made up of equations. That's why he introduced the concept of displacement current.

∇×E=-dB/dt and ∇×B=μ0ε0 dE/dt are the Maxwell's two laws in question (excluding the current term for the last equation). If we think about curl, if two nearby vectors are pretty much the same as each other, then there is small curl. If the two nearby vectors are very different from each other, we get larger curl. In the commonly taught version of EM waves where they create each other, here's the reasoning for them causing each other: As the B field goes from positive to negative, there is a larger curl because the vectors has a large change in magnitude. When the B field is maximum, there is low change in magnitude so the curl is smaller. There is basically a 90 degree shift between the B field and the curl of the B field. Since the rate of change of electric field is proportional to the curl of the magnetic field, the rate of change would be a scaled version of the curl but have similar form. If we integrate again, using the sine wave pattern, we get another 90 degree shift. Therefore, B and E are 180 deg shift. The same can be shown in the other equation.

At 1:55 you say that "it's often said" that EM waves cause themselves. Can you point me to *any* reputable source that makes this claim? I've taken a LOT of physics classes and read a lot of physics books and I've never heard this claim for electromagnetic waves. It's immediately obvious from the phase relation you pointed out that this isn't what's going on in EM radiation, so I find it hard to believe it's something that's "often said". I really appreciate your out-of-the-box approach but think there a few things missing for a complete picture (or maybe I'm still missing a few things 😉). I'd love to get in on the discussion so I'll check out your blog as soon as I get a chance. Thanks!

👏thank👏you👏 ... That is the first "honest" explantation I've heard that explains why how electric and magnetic fields for into electromagnetic radiation. It seems like the more easily digestible concept of fields is easier to teach but it is confusing in the long run! Thank you