Undergrad Fastest Cause & Effect: Electric Field & Magnetic Field

[Jaysal]

Since the EM wave travels at the fastest speed could we say the fastest cause and effect interaction could be the change in electric field generating the magnetic field ?

 

[BvU]

That doesn't travel. It's local. And it's also (in the sense of: too) the other way around

 

[Jaysal]

How could it be the other way around its it the electric field that gets disturbed first.

 

[BvU]

No. It's simultaneous

 

[Dale]

How could it be the other way around its it the electric field that gets disturbed first.

Look at Maxwell’s equations, they do not say that the electric field gets disturbed first.

There is no cause and effect in Maxwell’s equations. If you want a cause and effect formulation of electromagnetism then you need to look at Jefimenko’s equations

 

[vanhees71]

Indeed, and Jefimenko's equations tell you that the causes of the electromagnetic field are not parts of the electromagnetic field but the charge-current distribution. There's no such thing as an electric and a magnetic field. There's only one electromagnetic field which can be decomposed in electric and magnetic components depending on the frame of reference, where you define these components.

 

[FactChecker]

Is it correct to say that the speed of light gives the limit that a cause-effect relationship can exist and that this is the reason that, although there can be disagreement about simultaneity, the simultaneity disagreement will never be great enough to cause a disagreement regarding cause-effect?

 

[Ibix]

Is it correct to say that the speed of light gives the limit that a cause-effect relationship can exist and that this is the reason that, although there can be disagreement about simultaneity, the simultaneity disagreement will never be great enough to cause a disagreement regarding cause-effect?

Yes. Two events where the second is on or inside the future light cone of the first can be causally related, and the time order is fixed. That is, there is an unambiguous "first event" and "second event", and all observers will agree which is which. Events that are outside each others' light cones cannot be causally related and their ordering is frame-dependent. But it doesn't matter, as you say.

However, I don't think the OP was asking about this. They were asking something along the lines of "if, in an EM wave, the E-field causes the B-field and the EM wave is the fastest thing, is the B-field's reaction to the E-field the fastest cause-and-effect". Which is based on a false premise, that the E-field causes the B-field rather than the two being parts of a more general thing, the EM field.