I was watching a Veritasium video. It was about the misconception of energy flow in electricity. The main take away was that energy flows fields. Classically, this is the Poynting vector. The energy and all that is important in electro-magnetism is through the electro-magnetic fields. Clearly, in the video, Dereck, demostrates that the the light is turned on wirelessly. The initial turn of the switch causes a change in the electro-magnetic field in which propogates the energy to light, causing it to “turn on” 1. Dereck’s description is more correct in that the experiment conduct matches well with classical electro-magnetism vs an electrician’s version of the theory. His video is in the genre of edutainment where the viewer is enlightened in two ways. Either, their previous mental model of some physical phenomenon 2 is debunked or corrected or seemingly pardoxical physical phenomenon is explain in an easy to grasp manner. Let’s focus on the former.
It’s true that in the canonical physics class, the physics being taught is justified because the physics in the prerequisite class is not as correct in explaining some corner of nature. It’s true that nature is quantum, it’s not the classical world of Laplace. Nevertheless, countless engineers still use several hunderd year old principles of Newtonian mechanics. This is is my hill. Physics is useful as much as assumptions hold and any evetual discrepancies in description can be neglected. All physics is an effective theory.
In Dereck’s video, he uses classical electro-magnetism with electron and protons as points. The air is the same as a vacuum. He also assumes that the electro-magnetic disturbance can approximated by a plane Wave which can be time averaged. Essentially, he’s neglecting the oscilations of the electro-magnetic wave produced. So, he is saying the physics in this description is neglecful of phenomenon on the scale of light frequencies. Nevertheless, his time resolution is fine enough to measure the light traveling a meter. The answer to video’s posed question is correct. Nevertheless, as Newton’s mechanics is useful for engineers, electric engineers find use in circuit theory. If we take a more coarse grain view of Veritasium’s model, the “wrong answer” should be correct. To measurement devices of electrician, the light turns once a voltage is turned on and applied across it.
To an electrician, the light turns on once enough current propogates through the wire. The timescale is small, but compared to the aforementioned time resolution, is coarse grain indeed. According to his instruments, his theory of currents and voltage is sufficient to descrbe the electro-magnetic phenomenon in the circuits.
I would say that it’s important and useful, to pursue for fundemental and ever encompassing theories of nature. It’s nonetheless important to remember physics is something to descrbe to the world. Course graining our view usually is help since it gets rid of the noise an illumiantes the major factors of whatever we are aiming to describing.