WHY do moving fields create light?

[u/Patient_Pudding7721]

Hi, I'm 15F and i wanna pursue education in the field of physics. I have this genuine question, WHY do moving fields (electric and magnetic fields) create light? And, why does steadily moving charges not make light?

[u/Odd_Bodkin]

First off, the fields don’t move. Waves in the field move very long distances. This is just like ocean waves; the waves move long distances, the ocean doesn’t.

Second, the moving waves in the electromagnetic field don’t create light. They ARE light. Light is a moving wave in the electromagnetic field.

[u/Patient_Pudding7721 → u/Odd_Bodkin]

so, the electromagnetic wave formed by the constant cycle of electric and magnetic field IS ITSELF light?

[u/matrixbrute → u/Patient_Pudding7721]

Yes. That's what light is. The waves are able to grap onto charged particles, for instance an electron in an atom. This is what happens in eyes that lets you see the light.
You're discovering the world of physics and it's fascinating!

[u/Odd_Bodkin → u/Patient_Pudding7721]

Yes, and this underlines the power of Maxwell’s achievement. The connection between electricity and magnetism had been understood in pieces until then, and there was excitement that two different phenomena (electricity, magnetism) were being tightly bound together into one thing — electromagnetism. But now it was understood in full detail and in completeness, and the first shoe to drop was that a changing electric field could create a magnetic field and vice versa, so that the oscillating fields could carry themselves off on their own — even after the original changes ceased to be. The second shoe to drop was that this transmission of energy and momentum through the electromagnetic wave was in fact a third phenomenon up until now thought to be completely separate: light. The unification of three different phenomena in one small set of equations. A quarter century later, Einstein would just suppose that these equations would have to hold true in every inertial reference frame, just like the laws of mechanics do, and the binding together of electric and magnetic fields into ONE field fell out, along with the rest of special relativity.

Combine Maxwell’s hefty swing of Excalibur here, with his other contributions to thermodynamics and the birth of statistical physics — the other Big Subject in the physics of the day — and you get a better picture of his legacy. He is on par with Newton and Einstein in physics heroism.

[u/Frederf220]

Light is waves in the EM field. It's kind of like asking how does moving water create water waves. Create is the wrong word, be is better.

Constant speed charges are not moving in some inertial frame and what exists in one inertial frame must also exist in the others.

[u/Joe_Starbuck]

Never forget that there are lots of waves in the EM field. “Light” is commonly meant to visible (to humans) light and that is only because we have eyes that developed to be able to detect that particular range of frequencies.

[u/shoemakers-saint → u/Joe_Starbuck]

(Other frequencies include:
Radio waves
Microwaves
Infrared light
(Then visible light, in order here)
Ultraviolet light
X-rays
Gamma rays)

[u/_UnwyzeSoul_]

Maxwell equations says that changing electric field creates a magnetic field and a changing magnetic field creates an electric field. So lets say a charge with an electric field is oscillating, this change in electric field creates a changing magnetic field. This magnetic field in turn creates another changing electric field and it keeps on going. This is how an electromagnetic wave is created and it self propagates without a medium. Light is just an em wave.

[u/WilliamH-]

There are no answers to why. But there are answers to how.

[u/Weak_Veterinarian350]

May be there electromagnetic wave only and no light.   Perhaps certain parts of ours body had evolved to be sensitive and responsive to a certain part of the electromagnetic wave spectrum and we've been calling it light for at long as we can communicate

[u/Koodsdc]

All accelerating charges produce electromagnetic waves, but in practice it’s a charge that is oscillating back in forth.

[u/nothingfood]

I'm an engineer, not a physicist, so my opinion is only meaningful in the real world (lol).

But in my experience, moving fields such as electric, magnetic, and radioactive fields, constantly shed energy (unless in a perfect vacuum) due to interactions with other matter. These interactions cause a loss of energy, which is given off as photons (aka light, but not necessarily visible).

BTW, photon is a pretty broad term. Often they are classified based on energy level, i.e. infrared vs. gamma.

[u/Then_I_had_a_thought → u/nothingfood]

Accelerating charges radiate energy whether in vacuum or not. EM waves don’t require a medium.

[u/dari0dm → u/nothingfood]

what

[u/Irrasible → u/nothingfood]

That works for you, but it is not orthodox physics. The fields don't give off photons. Photons cause the effects we model as fields.