[y04nn]

The first signal is a close RF transmission, billions of people rely on it everyday, a current disturbs the electromagnetic field and and an antenna, sometimes thousands of kilometers away, detects a very small variation in the field (-120dbm @ 50Ω = 0.2μV). This is how our cellphones, wifi, GPS, RFID works. So, even if you disconnect the bulb and the switch you can create a current in the bulb by turning on and off the switch.

[01100011]

I feel like RF is the wrong term. RF is short for radio frequency. That implies an oscillating EM field at a frequency which is practically useful for radio transmissions. This is a transient EM field disturbance. Same mechanism more or less, but it's not really 'radio'. I'm sure many will disagree but that's my opinion on it.

[y04nn]

Yes I agree with you, RF is not the good term in this case. I wanted to compare it to RF transmissions which are oscillations in the EM field.

[dehrmann]

Ignoring how accurate calling it RF is, so the experiment showed that electrons travel faster through air than through copper, you can see that, and the two delays are what you'd expect them to be?

[y04nn]

The transmission speed in air would be very close to a vacuum, so the speed of light (c). This depends on the velocity factor [1], for pure copper it's 0.95 c, so 95% the speed of light.

Actually for air, according to this source [2], the velocity factor is 0.999707085823853610892 c.

[1] https://lowpowerlab.com/guide/rf-best-practices/velocity-fac...

[2] https://www.qsl.net/ac5jw/isbp/vf.html

[userbinator]

I think the important point to note about that is it doesn't necessarily have to be a purpose-built "radio transmitter" to emit RF energy; everything which involves moving charges will radiate an EM field. This becomes especially apparent when you read the century-old books on early experiments with radio, and see the extremely crude circuitry they used to generate those waves.

[y04nn]

Absolutely, if you turn on and off a light switch while listening an AM radio (even static) you would hear it through your speaker, as in this demonstration [1] (it worth watching the whole video if you are interested).

[1] https://youtu.be/LMxate9gegg?t=104