Awesome

[steuard]

Me: Great! I'm all ready for class: time to introduce magnetic fields and forces.

My Bored Brain: Wow, this looks dull.

Me: Look, it's the first day on a new subject, of course it's a bit dry. But there's some cool stuff in there.

MBB: Important, yes. But seriously: dull. I'm not gonna do it.

Me: We have to do it! I'm already behind what I'd aimed for on the syllabus.

MBB: Not gonna happen. Let's derive magnetism from scratch using electrostatics and relativity instead.

Me: Are you crazy? These guys are bound to be rusty on relativity; they may never have learned it well at all. And we don't have time for long digressions: I've dropped enough material as is.

MBB: Exactly! As the schedule stands, they're going to leave junior/senior E&M without ever hearing that electric and magnetic fields are secretly the same thing. I won't let that happen to any student of mine!

Me: Look, I just can't afford to... hold on... I can't afford... to bore them. How 'bout that.

Me, writing on board at start of class: "Today's plan: Screw it - we're doing something awesome."



Addendum: ukelele points out that by an awesome coincidence, today is The International Day of Awesomeness. Awesome.

Comments

[nemene.livejournal.com]

let see how you reac to this, I actually got mostly confused looks when I tried saying this in the Mudd Physics departmant.

I suggest that magnetic fields do not exist, magnetism does not exist. Wha we observe as magnitism is the simple fact that charged particles are effected by the electric field as observed in their own rest frame. The magnetic field is simply a mathematic artifact of this relativistic effect.

Not quite sure how to handle the whole radiation thing, being an EM wave, can it be described without the M? not sure.

[steuard.livejournal.com]

When I really think about electromagnetism, it's within a relativistic formalism based on 4-vectors (and 4-tensors). In fact, the 4-vector potential is the natural object to talk about in quantum electrodynamics, too.

From that perspective, claiming "there's no such thing as magnetism" feels a lot like claiming "there's no such thing as momentum". After all, in its own rest frame a particle's momentum is always zero! Who needs it?

So while I agree that it's possible (at least classically) to write down rules for computing electromagnetic forces on particles that never require a magnetic force to exist, those are truly terrible rules. You lose everything that makes sophisticated problem solving in physics possible, up to and including conservation of energy and momentum. And at the quantum level I don't think it's possible at all: intrinsic spin means that particles can feel magnetic forces in their own reference frames anyway.

As for radiation, I'm not as certain. You'd need to abandon all of Maxwell's equations except Gauss's law for E anyway (since the others all involve B), so conceptually there's room to simply impose the wave equation for E as an independent physical law to explain radiation. But there would be issues about frame-dependence there... still, I think you could pull it off just by defining the appropriate retarded potential. So my guess is that you'd have a working formalism, but one that felt very ad hoc and unmotivated.