Something that probably unites many Hackaday readers is an idle pursuit of browsing AliExpress for new pieces of tech. Perhaps it’s something akin to social media doomscrolling without the induced anger, and it’s certainly entertaining to see some of the weird and wonderful products that can be had for a few dollars and a couple of weeks wait. Every now and then something pops up that deserves a second look, and it’s one of those that has caught my attention today. Why am I being offered planar PCB coils with some electronics, described as “Schumann resonators”? What on earth is Schumann resonance, anyway?
Atmospheric Physics Meets Cheap Junk
The second question is easy enough to answer, the Schumann resonances occur in the electromagnetic spectrum of the earth, and are the result of resonances in the waveguide created between the electrically charged and thus radio-reflective ionosphere and the planet’s surface. Just as a small section of microwave waveguide on your bench can have an electromagnetic resonant frequency, so can this huge planet-sized space.
The waveguide on your desk will probably resonate in the thousands of megahertz, while the atmospheric waveguide has its resonance in the very low frequencies, in the order of hertz with a fundamental frequency around 7.8 Hz and a series of harmonic frequencies
The story of the Schumann resonances is interesting in itself, because rather than being discovered through observation they were predicted in 1952 in a mathematical study of the ionosphere by a German physicist, Winfried Otto Schumann. He originally calculated a frequency of around 10 Hz. A decade later their existence was proved, and studies have shown them to be excited by lightning strikes. Their resonant frequency is lower than Schumann predicted because of the slower-than-light transmission speed in the earth’s atmosphere, and they are part of the field of climate and atmospheric science, and as an example their activity has been used as a marker of global temperature. Indeed, the frequency varies over the course of a day as different parts of the earth are exposed to the sun — the oft-cited 7.83 Hz value actually wanders around 7.5 Hz to 8.3 Hz.
All this is fascinating stuff, but what’s the connection between a global scale electromagnetic resonance requiring all those (naturally, 1.21 jiggawatt) lightning strikes to excite and which is of great interest to climate scientists, and a little AC magnetic field generator on a PCB from China? The answer took a bit of web searching to find out, and sadly it’s not the scientific breakthrough we might have hoped for.
Does It Work? It’s All In Your Head
A natural resonant frequency on a planetary scale is for engineers and physicists an interesting and entirely explainable physical phenomenon. It’s got a clear derivation and a mathematical proof that works, and it’s even got a few useful applications for climate scientists. But of course, not everyone who happens upon Schumann resonance has that background or training, and among those are a section who perhaps read a little bit more into it than they should.
My web search took me into people who believe that Schumann resonance is a “heartbeat” for a somehow sentient planet, something with which we have somehow lost touch, and turn the coincidence that some human brainwaves are around the same frequency into a vital connection. It seems that the Schumann resonators aren’t there for the planet but instead for us, they’re intended to stimulate the “right” brain waves which have somehow been lost due to our modern high-tech lifestyles. That they’re also claimed to improve the sound from HiFi systems and reduce pollutants in the air is the cherry on the cake.
So sadly the Schumann resonators have nothing to do with the ionosphere, and who knows, might just even be completely useless in themselves. In the past I’ve bought a few similarly pseudoscience devices for a teardown and investigation, but this time I somehow can’t find it within me to shell out twenty dollars or so on this one. Still, it’s been interesting to learn about the ionospheric resonance.
Can any of you think of a use for a ELF oscillator and planar coil that doesn’t involve pseudoscience? The comments await.