# "Strange contradiction" that Maxwell found and resolved

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• Swamp Thing
Swamp Thing
In "The Strange Story of the Quantum", Banesh Hoffmann writes:

Not content with translating Faraday’s ideas into mathematical form. Maxwell went on to develop the mathematical consequences of the theory and to extend its realm. Soon he came to a contradiction. Evidently all was not well with the theory, but what the remedy might be was not easy to determine. Various scientists sought for a cure, among them Maxwell himself. So refined and mathematical had the theory of electricity and magnetism become by now that when Max well arrived at a cure by sheer intuition based upon most unreliable analogies, he produced a group of equations differing but slightly in external form from the old equations. But not only did the new equations remove the contradiction, they also carried a significant new implication. They required that there should exist such, things as electromagnetic waves, that these waves should move with the speed of light, and that they should have all the other major known physical properties of light.

What was that contradiction?

Swamp Thing said:
What was that contradiction?
I would guess it had to do with Newtons hypothetical aether, and free space having an intrinsic impedance. That concept was needed before EM wave propagation could be considered.

Wikipedia suggests that what he did was add the dependence of the magnetic field on the time variation of the electric field, which is definitely a necessary component of the derivation of the EM wave equation.

I'm not sure what the contradiction would be from leaving that term out.

Perhaps the "contradiction" is what is explained here in the section "Maxwell’s Correction to the Laws of Electricity and Magnetism":

PeroK, Swamp Thing and Ibix
The Feynman lectures also explain it quite well. Without the term that Maxwell added (called Maxwell's displacement current), the equations are not self consistent.

dextercioby and Swamp Thing
The equation,
$$\nabla\times{\bf H}=4\pi{\bf j}/c$$,
contradicts the continuity equation because,
$$\nabla\cdot(\nabla\times{\bf H})=(4\pi/c)\nabla\cdot{\bf j}=-4(\pi/c)\partial_t\rho\neq 0$$.

Last edited:
Spinnor and Ibix

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