>>13873897Here's the comment I left on the subject:
But how does the energy field know *how* to propagate before the electric and magnetic fields aren't done doing their own propagation?
Thinking about it, this seems like a trick question: In the same way that accelerating _any_ charge emits photons (radio waves), the slightest induction of the magnetic field will emit miniscule (frankly, imperceptible) amounts of energy to the light bulb via radio transfer. You could probably achieve this just by shaking the battery with your bare hands, no wires required.
The light bulb turning on doesn't become _perceivable_ until the electric and magnetic fields orient themselves in a way that they *concentrate* the energy field at the bulb. This occurs in the wire. So It seems like a technicality that, yes, the very first photons emitted by the bulb occur in 1/c time, but you'd hardly be able to tell.
I suppose much of the confusion stems from the false premise that the light bulb discretely goes from a single "off" state to a single "on" state. When it actually continuously increases in brightness to a maximum. How _quickly_ and at what rate it brightens depends on the *shape* of the wire. For the full effects of this shape to be realized, the "light-cone" of the switch needs to encompass the whole circuit, which takes about 0.5s.
Consider a differently shaped circuit, a "T" shape instead of a rectangle, where two wires from the battery/switch (the "bottom" of the "T") go directly towards the bulb for 0.9 meters before jutting out at opposite right angles for 0.5 light seconds, turn, continue for the remaining 0.1 light seconds, and then travel 0.5 light seconds back directly to the bulb.
I wager, given the different shape, that the bulb would brighten much faster, perhaps ~10x faster.
