Is the electromagnetic propagation time asymmetrical?

[calinvass]

For a point in space if we have the values of E and H fields at a certain instant of time, we can tell the direction of the propagation of these values, which is the direction of the cross product vector E x H. Is this phenomenon time asymmetric or not ?

 

[Dale]

The phenomenon is time symmetric. Don't forget that H changes sign under time reversal.

 

[calinvass]

If we change the arrow of time the propagation direction will be given by H x E, but basically the waves will propagate the same way. Is that what you meant? A world where S=H x E would be indistinguishable our world.
However, this doesn't mean that if we know the values of the fields at an instant, we can't predict the future propagation of the wave.

It seems that the apparent arrow of time at a macroscopic level can be simulated using time symmetrical laws.

 

[Dale]

If we change the arrow of time the propagation direction will be given by H x E, but basically the waves will propagate the same way. Is that what you meant?

No, under time reversal the direction of energy flow is still given by E x H, but H changes sign so the direction of energy propagation changes sign.

 

[calinvass]

Why doesn't E change direction ?

 

[Dale]

Charge does not change sign under time reversal, but current does. Then Maxwell's equations dictate the sign of the fields from that (consider Coulomb's law and the Biot Savart law respectively to see it in the simplest cases)

 

[calinvass]

Alright, Thanks.
That reminds me of Feynman diagrams.