Extraordinary claims. Ordinary investigations.

Heat Screams: the Rijke Tube Spirits

Have you ever heard the sound of heat? In a way that’s what you can hear with the curious Rijke Tube, an effect discovered by Dutch physicist P.L. Rijke in 1859.

Consisting of nothing more than a long tube open at both ends in which a red hot wire gauze is introduced, the sound is very loud: in the demonstration above by Yoshiaki Watanabe of Doshisha University, Japan, they got 160dB, “equivalent to the sound coming from 100 aircraft engines”, he says. From a simple red hot wire gauze.

The sound comes from a self-amplifying standing wave formed by the interaction of the air heated by the gauze and the fundamental frequency of the tube. It was first explained by Lord Rayleigh in 1879, and the understanding means the Rijke tube can produce a continuous deafening sound by heating the gauze with an electrical resistance.

You can also change its frequency by adjusting the tube’s length, and I wonder if a Rijke tube organ was ever made – a Google search sadly didn’t turn anything like it. The principle also has more practical applications in combustors that can burn more efficiently – and yes, they hum too.

But did I just write that the Rijke tube was discovered by Rijke in 1859? Because actually the effect is being reproduced for quite a long time in the Japanese Narukama Shiji ritual. In this old tradition, the priests heat a bamboo rice pot and when they remove the top, something quite extraordinary happens.


Well, not that extraordinary if you already know the Rijke tube without all the ritual. Fact is, the rice pot “sings”, and a strong and long sound is interpreted as a good sign (more details, in Japanese, here). Certainly a rice pot shouting “Ooooo…” must be good.

kamai The priests, unsurprisingly, didn’t speak of self-amplifying standing sound waves, but rather attributed the sound to the spirits and gods. If you look at how the rice pot is made, however, you will see all the elements of the Rijke tube. Lord Rayleigh didn’t know that he wasn’t only explaining the effect described by his Dutch fellow twenty years before, he was also shedding light into an age-old ritual practiced thousands of miles away and which people interpreted as divine voices. How else would they explain it?

But this is not only the story of science clarifying mysteries and bringing knowledge to the world. One must credit these priests who managed to notice the effect long ago and even turned it into a ritual, without understanding exactly how or why it worked.

We already blogged about the Mpemba effect, described by Aristotle (!), then Francis Bacon (!) and even René Descartes (!), but ignored by science until it was rediscovered in 1963 by Tanzanian high-schooler (!!!) Erasto Mpemba. But we don’t even have to go to these varied phenomena, we can stay with sound, because the Ancient Greeks did a magnificent work in the Epidaurus theater. And is there a better way to show how amazing it is that 14,000 spectators could hear the play in this +2,300 years old theater than Rickrolling?

See how distant the Rickrollers are. The acoustics is amazing, and all sorts of explanations were given throughout history, from the shape of the theater to the winds or maybe even… spirits. It was only recently, very recently, though, that it was understood by a team of the Georgia Institute of Technology that the secret is in the seats. The limestone seats act as an acoustics filter that eliminates the low-frequency background noises while also reflecting the high-frequency noises of the actors towards the spectators.

Alas, the Ancient Greeks didn’t get what was happening and were unable to reproduce the Epidaurus acoustics elsewhere. The fact they did it by accident is amazing by itself. Thousands of years without science didn’t stop people from accidentally stumbling upon complex effects that science itself would take a long time to catch up with. Forteans already know this, and well, it is very true.

It’s highly improbable that an integrated circuit, or even a transistor, would emerge by accident without science. There’s only so much you can go blindfolded, even if you can go somewhere. And even if science takes a long time to catch up, when it does it usually goes way beyond the mere puzzled contemplation of the effect or the association with unpredictable (and inexistent) gods and spirits. The effect is reproduced, understood and applied.

As scientists should perhaps look more seriously to anecdotal stories and old superstitions for the possibility they still hide unusual and perhaps complex effects so far ignored, Fort should not have been so dismissive of established science. Fortunately, most of the contemporary Forteans embrace the scientific method with more enthusiasm.

Cumulative knowledge may advance more slowly, but it’s cumulative, and after a few centuries we have actually reached far beyond the wildest powers of ancient gods. You can reproduce the Rijke tube with rice or metal pellets and three tin cans. A strong and long sound will be the sign you reproduced an interesting physical effect, and understanding it, a prediction that you are on your way to better appreciating the world around you for all the beautiful and unexpected complexities it has.

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