Electromagnetism Is the Weirdest Force

For a long time, physicists only knew about two fundamental forces: electromagnetism, and gravity. Physics students follow the same path, studying Newtonian gravity, then E&M, and only later learning about the other fundamental forces. If you’ve just recently heard about the weak nuclear force and the strong nuclear force, it can be tempting to think of them as just slight tweaks on electromagnetism. But while that can be a helpful way to start, in a way it’s precisely backwards. Electromagnetism is simpler than the other forces, that’s true. But because of that simplicity, it’s actually pretty weird as a force.

The weirdness of electromagnetism boils down to one key reason: the electromagnetic field has no charge.

Maybe that sounds weird to you: if you’ve done anything with electromagnetism, you’ve certainly seen charges. But while you’ve calculated the field produced by a charge, the field itself has no charge. You can specify the positions of some electrons and not have to worry that the electric field will introduce new charges you didn’t plan. Mathematically, this means your equations are linear in the field, and thus not all that hard to solve.

The other forces are different. The strong nuclear force has three types of charge, dubbed red, green, and blue. Not just quarks, but the field itself has charges under this system, making the equations that describe it non-linear.

Those properties mean that you can’t just think of the strong force as a push or pull between charges, like you could with electromagnetism. The strong force doesn’t just move quarks around, it can change their color, exchanging charge between the quark and the field. That’s one reason why when we’re more careful we refer to it as not the strong force, but the strong interaction.

The weak force also makes more sense when thought of as an interaction. It can change even more properties of particles, turning different flavors of quarks and leptons into each other, resulting in among other phenomena nuclear beta decay. It would be even more like the strong force, but the Higgs field screws that up, stirring together two more fundamental forces and spitting out the weak force and electromagnetism. The result ties them together in weird ways: for example, it means that the weak field can actually have an electric charge.

Interactions like the strong and weak forces are much more “normal” for particle physicists: if you ask us to picture a random fundamental force, chances are it will look like them. It won’t typically look like electromagnetism, the weird “degenerate” case with a field that doesn’t even have a charge. So despite how familiar electromagnetism may be to you, don’t take it as your model of what a fundamental force should look like: of all the forces, it’s the simplest and weirdest.

13 thoughts on “Electromagnetism Is the Weirdest Force”

1. Ian

Is gravity also similar like that? I know that gravity is non-linear but does it have it’s own charge that we know of?

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1. 4gravitons Post author

Gravity is quite different from the other forces mathematically speaking (I talk a bit about it here). It is like the other forces in that way though: gravitational fields carry energy, and energy gravitates.

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2. J Mark Morris

Hi. I’m not sure my ideas are welcome here, but I think if you zoom back to 1870 or so and pick up classical point charges from the physics discard pile and then give them immutability at a radius of Planck length divided by 2*pi with a field effect then you can start with a solution that physicists missed. If you start with a Euclidean space, and two types of these immutable point charges (I call them the electrino and positrino with charge magnitude |e/6|), and the energy carried by those point charges, then the universe will emerge, including all the mathematics of GR and QM. In fact the quantum is simply the energy increment required to take the most basic emergent structure, simple electrino-positrino dipole and increment the frequency by 1/2. That little dipole has amazing properties — think through the force of attraction, the centripetal force, the travel time of the electromagnetic field between each point charge, the B-fields generated and how they contribute to dipole dynamics, and we need to put in our immutability field effect which likely ties into permittivity and permeability. All told, an electrino-positrino dipole is a stretchy ruler and a variable clock. I can find no due diligence from the field of physics on this simple solution to nature, yet I can see how it ties to everything in physics and cosmology and solves all the open problems. I also have a blog at jmarkmorris.com where I have written hundreds of short posts about this, with no woo.

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1. 4gravitons Post author

Since you’re not being confrontational, I’ll just let you off with a warning this time, but to be clear, comments like this are spam. The only link to the post topic is that both the post and you mention E&M, and you’re using that as an excuse to link readers to an otherwise totally unrelated physics proposal, basically using this post as free advertising for yourself. I appreciate that you feel like you have found something that deserves more attention, but commenting on tangentially related educational blogs isn’t an appropriate way to get that attention, and my general policy is to delete off-topic comments like this.

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1. J Mark Morris

Well your response is both confrontational and incorrect and bullying. Shame on you! My intent was in direct response to your post and attempting to guide you back in time to understand the mistakes that threw physics so far off track. Attitudes like yours only serve to delay the next era and perpetuate the tragic mistakes. I’m saddened that you and your colleagues are so lost. The solution is so simple it’s obvious once you remap your narrative. Example: the quantum is emergent and not fundamental. The quantum is simply the angular momentum required to change an orbiting point charge dipole frequency by 1/2. Oh well, I tried. Sigh.

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3. Andrew Oh-Willeke

I would assume that the notion of gravity as QCD squared ties into the fact that the field itself is charged under the interaction in question?

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4. Jacques Distler

And …

The weak force is the weirdest, as it’s the only one that is spontaneously-broken (and hence very short-range).

The strong force is the weirdest, as it’s the only one that’s confining (so that no physical particles (asymptotic states, to be pedantic) are charged under it).

And gravity … well, gravity ….

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1. 4gravitons Post author

On the surface, a very strange paper. It’s in a journal that publishes proceedings of conferences, but it doesn’t say what conference it’s from. I didn’t know you could do that.

Anyway, the core of their proposal seems to be identifying the metric with two copies of the electrodynamic vector potential. This is something people in my field have been doing for years under the name “double-copy”, specifically the so-called “classical double-copy” which typically involves E&M rather than the more general Yang-Mills forces I compared it to in this post (and typically only on a classical, that is non-quantum, level). This only works in specific contexts though…you can’t get every metric from some combination of solutions of Maxwell’s equations, and you can’t square just any solution of Maxwell’s equations and get a metric that satisfies Einstein’s equations. There are known counterexamples. So right off the bat they’ve got to be doing something wrong.

Even if what they were doing worked mathematically, it has none of the implications they seem to want it to have. If you have gravity and E&M as literally the same field (not just convenient ways to calculate solutions for each other), then you’d have a clean relationship between mass and charge. But there is no such relationship: particles with very different masses have the same charge, and charge is quantized while mass is not. So none of this makes any sense.

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1. James Cross

Well, the math and much of what you wrote is beyond me, but I’m not sure they are saying they are literally the same field. I think it is more like they affect space time in a similar (same?) way.

“In particular, our research shows how electromagnetism is an inherent property of spacetime itself. In a way, spacetime itself is therefore the aether. Electric and magnetic fields represent certain local tensions or twists in the spacetime fabric.”

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1. 4gravitons Post author

That quote certainly makes it look like they’re saying it’s literally a property of spacetime. I think the confusion you might be having is that the gravitational field is space-time, it’s just two different ways to refer to it. They’re saying that E&M fields are twists in the spacetime fabric, and thus that they are a property of the gravitational field. And that claim is one I don’t think their math justifies at all.

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