Coherer Effect [video]

This was amazing! Never knew of this. And Mehdi is great as always!

And this is certainly one of the few things on his channel that I can try at home!

The wikipedia article -

https://en.m.wikipedia.org/wiki/Coherer

This is fascinating, but what blows my mind even more is Bose's experiments with mmWave in the order of 60 GHz (!)

https://www.cv.nrao.edu/~demerson/bose/emerson_delhi.pdf

In old days there would be little vibrating hammers mounted to the side of them to 'unstick' them automatically. And that 'low power arc' is actually a few thousand volts across an airgap of a couple of millimeters, the EM from that is massive.

For an encore: you can pick up lightning strikes with a long piece of rebar overwound with insulated copper wire stuck into the ground (so it's vertical). Every 'click' you pick up is a lightning strike somewhere within a few thousand km from where you are, louder clicks are closer or more energetic discharges.

I built one of these when I was a kid with a piece of plastic tube, filled with filings from an iron pipe and two metal pushed into either side. I tested by clicking the electric started on the stove and flicking to reset, I was amazed when it actually worked.

also nicely covered in the Secret Life of Radio in context of the development of radio communication.

https://youtu.be/LMxate9gegg?si=Z5pANQTsQGIosIcU

Mehdi been explaining EE concepts since I was in school a decade ago. What a legend.

I was wondering when watching the video if Mehdi's supposition about an oxide layer is the only thing at play or whether there could be a layer of air instead / as well?

I've had cheap battery operated devices that react in the same way when a lighter clicks near them. Except they stay turned on because the first thing they do is latch their power on.

It takes a great teacher to make learning a technical subject seem like good dumb fun. What a guy!

tl;dr

strange device produces light in response to lighter

and the light ceases after you blow on it