I Always Wondered Whether Electro-Magnetic Fields are Even Real?!

[@dialectphilosophy]

This was a thought-provoking video -- and we're enjoying this new bent of yours towards electromagnetism, which, let's be honest, who really understands? Indeed asking what is "real" about electric and magnetic fields is a great question, however ambitious. Our take is that electromagnetism suffers from a lot of the same issues as our other modern theories, in that it possesses a solid mathematical formalism but lacks a clear accompanying theoretical model or picture by which such formalism can be understood. As such it is hard to pin a solid ontological status to any of its features. Measurement is part of the issue as well, as no quantity in physics -- not mass, charge, energy, etc. -- is ever measured directly, but rather inferred via spatiotemporal measurements and a-priori adopted mental models. This makes asking the question "what is real" somewhat of a rabbit hole, as you say. But anyhow, thanks for providing another informative video for our corner of the internet that informs as much as it encourages deeper questioning and reflection on the part of its viewer. Keep it up! (Also something nitpicky: a light beam wouldn't propagate forever once emitted, as its amplitude would experience fall-off and eventually sink below any detectable level.)

[@SchienexScience]

Hi Dialect :)

[@PWFSeattle]

For me, what convinced me the fields are real was when I learned that they contain energy and momentum in otherwise empty space - locally (that is, they impart momentum and energy to objects through local interaction, independent of their sources). Maybe that's the same thing as saying that photons are real in your argument?

[@jessstuart7495]

But you can't generate or interact with either the E or B fields unless there are charges present. Calculating the energy/momentum stored in a field is just a mathematically convenient way to add up the energy some charges will transfer to other (possibly very distant) charges; It's the photons that transfer the energy and momentum between charges.

[@threeMetreJim]

15:33 - Is it actually possible to observe a photon anywhere but along it's direction of travel? Like you cannot see a laser beam side on unless it interacts with something (dust, smoke, fog, etc...). I would guess that a single emitted photon could be detected at any point though (laser beam directional waves, actual wave/photon not). I find imagining a wave as a particle (photon) difficult at the best of times.

[@massimookissed1023]

Magnetic field lines are no more real than contour lines on a map or isobars on a weather chart. Magnetic field lines are drawn in line with the field gradient, whereas the others I mentioned are perpendicular to their gradients.

[@Juttutin]

Subscribed. You also sent me off on a tangent (lol) wondering about how 'circumference' works out for higher order n-spheres. Which got me wondering how they roll.

[@chrimony]

A video tying this in to quantum entanglement would be much appreciated.

[@dic3664]

Before watching, I must warn that the existence of fields as opposed to say particles is a missplaced question for fieldes as much as things, forces, energies, properties etc are CONCEPTS to capture our ideas about reality and the relations between conjectired things. Constructivism, in a word

[@darrennew8211]

Exactly. The fields represent the values you'd get if you evaluated the math we've constructed at those points. The field isn't "there" unless you're measuring it, at which point it isn't a field because you're measuring it at one time and one place.

[@copernicofelinis]

John Percy Hammond wrote a paper (or an essay) on the three ways to describe electromagnetism: through charges and currents, through electric and magnetic fields, and through potentials. I need to dig out the exact reference. The fourth way of using polarization is interesting but... What happens in the presence of sources? Are we not straying too far from the field of classical electragnetism?

[@kreynolds1123]

Position in a field represents potential energy. Fields are real and independent of our mathematical modeling. Field lines are our inventions to imagine field direction and intensity. I once wondered if magnetic fields were real because they don't exist in the charged parcle's inertial reference frame. But, realitivity forces us to unite electric fields and magnetic fields into a single electomagnetic field.

[@DrDeuteron]

or potential momentum

[@jessstuart7495]

Zangwill, A. (2012) Modern Electrodynamics. Cambridge University Press, Cambridge is the EM textbook I wish I had when I learned EM theory.

[@copernicofelinis]

In this era of maddening expensive textbooks, it is also still reasonably priced. I wish they had not printed it in miniscule characters, tho.

[@Merilix2]

I really like the way you address fundamental questions about those topics. I myself tend to belive the electric field is more fundamental and real than the magnetic field for some reasons. (yes, I quantify reality) 1) electric field has a source, the charge, which can be localized to some degree. 2) we measure both, electric field as well as magnetic fields by how they affect charges. 3) magnetic field depend on velocity of a moving charge, therefore it's existence depend on the frame of reference you are looking at. 4) magnetic fields create momentum to a moving charge perpendicular to its momentum and the direction of "field lines". Where does this momentum came from? 4a) Right hand rule / cross product. This "rule" is pure convention. To me, It only makes sense if the convention cancels out somehow. If the magnetic field created by an moving charge is by convention "right-handed" AND the force on 2nd charge affected by this field also, the same convention got applied in reverse and disappear. To me it looks like magnetic fields are just intermediate quantity that mediates forces between electrical charges. An of course quite usefull artifact of the math we use to describe the behavior of electric charges. Einstein in his publication 1905 named the "electromotive force an auxiliary variable". I'm not sure if he meant exactly the same. Quite interesting questions. What is real and what just model artifacts. Are we able to recognize what is really real?

[@briandwi2504]

Deeply interesting.

[@xooberant]

The field does not have lines. The measuring device has lines. Lines of magnetized iron filings are formed in the uniform field, IMHO.

[@Daniel_Zhu_a6f]

it's real enough to make radiotelescopes, electron microscopes and MRI machines. like the term doesn't even make sense for a scientific model such as a force field, it's not "real" or "unreal" it's just accurate or inaccurate for solving a particular set of problems.

[@iurikroth2281]

i have this crazy theory that a electron and other tinny particle are 4 dimentional entitys. maybe the atomic orbitals could be better represented with more dimentions

[@baldurstudios5637]

a theory based on a hunch isent science it's just a hunch, what do you mean with a 4 dimentional enity. We have not seen anything that is proven to have 4 spacial dimension's, so what do you even mean with a 4 dimentional entity?

[@Akio-fy7ep]

"Measure the force on a charged particle"... but how do we measure force? You cannot experience force. We can watch a charged object accelerate, if it's big enough, bouncing light off of it and timing its visible motion; or we can measure stress in something preventing its motion, maybe via a string around our finger; or note when it arrives at a target and delivers its charge, triggering a flash of light.

[@CouchExpert-007]

Wait, the magnetic field is just a relativistic manifestation of the electric field, right?

[@mishakorshkov7677]

Right.

[@TheLostDarkly]

I enjoy these chats. When I think about whether electromagnetic fields are real or not, I think back to the example given in Griffiths' intro to electrodynamics in which: "A line charge λ is glued onto the rim of a wheel of radius b, which is then suspended horizontally, so that it is free to rotate (the spokes are made of some nonconducting material-wood, maybe). In the central region, out to radius a, there is a uniform magnetic field B0, pointing up. Now someone turns the field off. What happens? The changing magnetic field will induce an electric field, curling around the axis of the wheel. This electric field exerts a force on the charges at the rim, and the wheel starts to turn. According to Lenz’s law, it will rotate in such a direction that its field tends to restore the upward flux. The motion, then, is counterclockwise, as viewed from above... There is a torque on the wheel and there is a certain amount of angular momentum imparted to it... It doesn’t matter how quickly or slowly you turn off the field; the resulting angular velocity of the wheel is the same regardless... Note that it’s the electric field that did the rotating... To convince you of this, I deliberately set things up so that the magnetic field is zero at the location of the charge. The experimenter may tell you she never put in any electric field-all she did was switch off the magnetic field. But when she did that, an electric field automatically appeared, and it’s this electric field that turned the wheel." I also think about the Feynman disk paradox. Where does the angular momentum come from!? It can be shown that the angular momentum lost by the fields is precisely equal to the angular momentum gained by the apparatus, and the total angular momentum (fields plus matter) is conserved. Yes. The fields are real.

[@darrennew8211]

It wasn't the electric field that did the rotating. It was the change in velocity of the charge. The "field" that wasn't near the charge had no effect on the charge.

[@TheLostDarkly]

​@@darrennew8211 A change in velocity is an acceleration. F=ma. Where should we say F came from?

[@pyrokinethic]

Luckily I am going through Feynman's volume on electrodynamics right now, otherwise I'd have been lost somewhere along the middle of this video.

[@sonofasalesman]

I love EM field study, and I instantly remembered this video, it's quite insightful kzbin.info/www/bejne/q4vRiZuInN-ne8k edit: if you also want to get VERY technical, the reality is that the electromagnetic force is propagated through virtual photons... I wish I understood more but that's all I can write here

[@LowellBoggs]

Excellent presentation. Thanks. It seems to me that there's another conundrum. I read some where that the vector cross product does not exist in any randomly chosen number of dimensions. It does exist in 3 dimensions and in 7 dimensions. This means that you can't imagine that there are 4 dimensions of space because maxwell's equations would not work. But you can imagine that there are 7. The conundrum will be, however, if the 7 dimensional meaning of cross product is the same as the 3+1d version if we are trapped in a 3+1d brane in 7+1d space. But it's it the same? If not, that could eliminate the possibility that we live in universe with a higher number of dimensions - wouldn't it?

[@loppy1243]

This just seems like an issue of formalism, not anything significant. Maxwell's equations in terms of the 4-potential are trivially extended to arbitrarily many spatial dimensions, and similarly for the differential forms formulation and the closely related geometric algebra formulation which only use the fields and not the potential.

[@Kraflyn]

counterexample: a static electric charge on a static elongated spring in a static electric field. No real photons.

[@Fixundfertig1]

The most unrealistic real thing

[@aniksamiurrahman6365]

But, aren't electro-magnetic waves are just oscillation in electro-magnetic field? I dunno how to comprehend the situation. The only real thing here are the electro-magnetic waves, but what they are oscillation of is, kinda unknowable?

[@antonk.653]

Well, as far as I know, we still haven't been able to "see" (measure) this momentary oscillation of the electromagnetic field, only its time average or interference effects from it. That's why we only see intensity in practice, and never the complete wave information.

[@philoso377]

Page 2:30 can we wave “an aluminum tunnel” along the polar axis to feel the existence of magnetic line of force with/without the magnet?

[@JackPullen-Paradox]

Third? I don't have time to watch at the moment, but I'll be back....Got to know your take on this.

[@pluto9000]

23rd but already watching

[@ExistenceUniversity]

Lol scooped @Inductica

[@gabrielmendez999]

The only things capably to produce mag field are moving electrons..period. Any common magnet natural or artificial having electron circulating in a ambient temp cluster of superconductors

[@darrennew8211]

Does electron quantum spin contribute to that?

[@Akio-fy7ep]

Protons, positrons, anti-protons in motion can also produce a magnetic field, and a passing photon can produce a transient magnetic field.

[@michaelbarker6460]

Your definition of existence is good enough for physics but for philosophy we might point out that different ontological layers of existence require different contexts. We can measure all kinds of things about the effects of money for instance but money doesn't exist as an inherent physical substance or process of reality. There's just nothing there except for shared narrative. The same is true for many things including government, rights, marriage, corporations, property, the self, etc. But this is also why no one likes philosophers 😅

[@Merilix2]

Money not real? I don't want to let a Rai stone roll over my feet ;)

[@philoso377]

I hear you. No those lines of force representing a visualization to a collective view of what magnetic force-vector may be if otherwise plot by a 3D compass around it.

[@philoso377]

Pressure, force? one magnitude and one vector, 2D. Field ? M magnitudes and V vectors in 2 and 3D In association with static parameters, we have induced : pressure / forces.

[@joshualeopior9019]

This video is cancer for my understanding I regret watching it.

[@darrennew8211]

Wow. There seems to be a lot wrong with this analysis. First, you can't measure force. You can only measure acceleration. You can't measure acceleration, but only a change in two velocities. You can't measure velocity at a single point in time - it's the change in distance between two times. So even measuring the force takes four measurements, assuming you know the mass, which is just as arguably only-mathematical as force and fields. Time doesn't pass the same for all of us, or a moving charge wouldn't create a magnetic field - relativity makes a neutral wire manifest a magnetic field when the charges are moving. Not only may the field be changing over time, but it may be changing over space, and if you're measuring velocity, you're measuring the field at two different places. I.e., you're not measuring the fields. You're measuring the change in velocity of charged particles. But the particle you measure only measures the field at a single place. So the field is actually a mathematical abstraction of what you *would* measure *were* a particle actually there. You can't measure the field. You can make a bunch of measurements, then deduce what you would have had you measured something else, and represent those measurements as a field.

[@climbeverest]

extremely difficult to understand your complex logic

[@macfrankist]

You know their net effect is real so why doubt?

[@darrennew8211]

It's arguing over whether "three" is a real thing. Fields are a description of what we would measure were we to measure it. Saying "the existence of the field causes the acceleration of a charge" is getting it backwards.

[@paulflocken2730]

Not first

[@adlerbrietzke]

First

[@briandwi2504]

Deeply interesting.