This is a nit-pick, but the oscillation is not because there is any direct delay in the interaction between the electric and magnetic portions, it’s because the electric and magnetic portions effect each other through derivatives. This is similar to how the the acceleration (second time derivative of position) is directly related to position in any number of mechanical oscillators, such as springs, pendulums, and even circular orbits, when viewed right. For light, while there are still two time derivatives, they are coupled so that one time-derivative arises between magnetic and electric, and the other arises between electric and magnetic.
It’s OK—it’s a matter of language, and not being very precise. Very loosely, in the case of a pendulum, you could say that in the upswing of the pendulum, it takes finite time (a delay) for the pendulum to respond to the downward force of gravity and start moving to 0. By the time it gets to 0, it already has momentum in the other direction and overshoots the equilibrium again. I see how this is the result of the dynamics being described by changes in the derivative of the motion, rather than—say—in the direction of motion itself.
There is no delay for the pendulum to respond to gravity, it starts accelerating immediately. There could be a delay before it achieves a velocity large enough to be perceived.
This is a nit-pick, but the oscillation is not because there is any direct delay in the interaction between the electric and magnetic portions, it’s because the electric and magnetic portions effect each other through derivatives. This is similar to how the the acceleration (second time derivative of position) is directly related to position in any number of mechanical oscillators, such as springs, pendulums, and even circular orbits, when viewed right. For light, while there are still two time derivatives, they are coupled so that one time-derivative arises between magnetic and electric, and the other arises between electric and magnetic.
I don’t see where Byrnema claimed there was such a direct delay.
Ok, now I am wondering how I completely missed that last paragraph. I agree with your nit-pick.
It’s OK—it’s a matter of language, and not being very precise. Very loosely, in the case of a pendulum, you could say that in the upswing of the pendulum, it takes finite time (a delay) for the pendulum to respond to the downward force of gravity and start moving to 0. By the time it gets to 0, it already has momentum in the other direction and overshoots the equilibrium again. I see how this is the result of the dynamics being described by changes in the derivative of the motion, rather than—say—in the direction of motion itself.
Right. I’d describe that as a delay for gravity to finish overcoming the motion, rather than a delay in response.
There is no delay for the pendulum to respond to gravity, it starts accelerating immediately. There could be a delay before it achieves a velocity large enough to be perceived.