This was amazing! Never knew of this. And Mehdi is great as always!<p>And this is certainly one of the few things on his channel that I can try at home!<p>The wikipedia article -<p><a href="https://en.m.wikipedia.org/wiki/Coherer" rel="nofollow noreferrer">https://en.m.wikipedia.org/wiki/Coherer</a>
This is fascinating, but what blows my mind even more is Bose's experiments with mmWave in the order of 60 GHz (!)<p><a href="https://www.cv.nrao.edu/~demerson/bose/emerson_delhi.pdf" rel="nofollow noreferrer">https://www.cv.nrao.edu/~demerson/bose/emerson_delhi.pdf</a>
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 <i>thousand</i> volts across an airgap of a couple of millimeters, the EM from that is massive.<p>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.<p><a href="https://youtu.be/LMxate9gegg?si=Z5pANQTsQGIosIcU" rel="nofollow noreferrer">https://youtu.be/LMxate9gegg?si=Z5pANQTsQGIosIcU</a>
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.