Gerade eben hatte ich auf Vixra einen Gedankenblitz... open your mind:
Let me try an obscure assertion:
An EM wave traveling with "c" in a vacuum can only oscillate transversely because there is no contraction transverse to the direction of flight. Longitudinal EM waves in a vacuum, on the other hand, do not exist because the oscillation is completely squeezed in the direction of movement.
In a medium, on the other hand, the speed is lower. And that is the only reason why longitudinal oscillations are possible there.
Which experiment can disprove this assertion? I can't think of anything off the top of my head.
Let me try an obscure assertion:
An EM wave traveling with "c" in a vacuum can only oscillate transversely because there is no contraction transverse to the direction of flight. Longitudinal EM waves in a vacuum, on the other hand, do not exist because the oscillation is completely squeezed in the direction of movement.
In a medium, on the other hand, the speed is lower. And that is the only reason why longitudinal oscillations are possible there.
Which experiment can disprove this assertion? I can't think of anything off the top of my head.