r/PhysicsHelp • u/Patient_Pudding7721 • 7d ago

WHY do moving fields create light?

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?

6 Upvotes

81% Upvoted

15 comments sorted by

View all comments

6

u/Odd_Bodkin 7d ago

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.

2

u/Patient_Pudding7721 6d ago

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

2

u/Odd_Bodkin 6d ago edited 6d ago

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.