the cursed riddle of ball lightning – Palatinate
By Leo Li
Science is the ultimate demystifier. Nevertheless, the mystery of ball lightning still remains unsolved.
This almost millennial enigma confounds Gervais of Canterbury in the 12th century. Recent interdisciplinary research by physicist Professor Emeritus Brian Tanner and historian Professor Giles Gasper of Durham University has revealed this first eyewitness account of ball lightning. Quoting their translation of the Chronicle of Gervase: “A marvelous sign has descended near London. For the densest and darkest cloud appeared in the growing air […] in a spherical shape […] a kind of fiery globe threw itself into the river.
It’s hard not to idealize a phenomenon as spellbinding as Zeus’ Brimstone. Imagine: an electrifying, white-hot orb brighter than daylight, catapulting and hissing through the air, finally exploding into a fiery, sulfurous mist. The mythical charisma of ball lightning extends beyond the scientific community, even inspiring Nobel Prize winner in Literature Mo Yan to symbolize it, in one of his short stories, as an ominous phantasmagoria.
This time around, some scientists have complied with the antiromantic empiricists they are often misinterpreted with. Through laboratory recreations and direct detections, several theories to unravel the physical nature of ball lightning have been proposed.
One of the simplest theories is the vaporized silicon model. It is believed that the immense heat of a lightning flash vaporizes silicon oxides in the ground it strikes. The oxide binds to carbon in the soil and leaves pure silicon vapor suspended in the air. Chemical reactions between vaporized silica and atmospheric oxygen release energy through rebonding, producing the quintessential flicker of ball lightning. A direct measurement of ball lightning emission spectra by a group of Chinese scientists shows significant peaks at the characteristic wavelengths of silicon and oxygen, proving that the theory is successful in predicting the composition of lightning in Bowl. Brazilian scientists have even managed to reproduce small semi-permanent orbs using silicon slices subjected to electric shocks.
The Solid Electron Core Model rectifies the “fluid” nature proposed by the Vaporized Silicon Model. He envisions ball lightning as a concentrically layered sphere with a solid core. A lightning strike induces an outward force that pulls electrons away from a positively charged solid nucleus; balanced by Coulomb attraction, the electrons form a layer around the positive nucleus, enclosing a vacuum impregnated with electromagnetic radiation. The outermost core is what infuses ball lightning with its essence – a plasma envelope. This envelope is a pool of dissociated ions induced by the electron shell. This model trumps the vaporized silicon model because it also explains why ball lightning could shoot out sparks and float in rapid motion – the former due to fragmentation and scattering of the positively charged core; the latter due to buoyancy, gravitational and electrostatic forces acting simultaneously on the semi-rigid conductive sphere.
However, the model neglects wave interferences and resonances due to higher electromagnetic modes. The inability to experimentally reproduce ball lightning of greater complexity has blocked the model’s potential to capture the uncompromising and complicated interior of ball lightning – despite some noteworthy recreations using low complexity systems with high current and low voltage discharges.
The resonant microwave cavity model, however, fills in the gaps in the solid electron core model. He assumes that ball lightning is a maser-soliton, which is simply a self-sustaining wave packet or bubble in which microwaves are constantly emitted by stimulations. The physics behind the stimulations is similar to that of the Solid Electron Core model, but with an additional boundary condition limiting the size of the ball of lightning at which it facilitates resonances at microwave wavelengths. These kinds of plasma balls are reproducible even with home microwave ovens, though they are far from the intensity and spatial extent with which nature shines with exultation.
There are many other hypotheses, all no less spellbinding; they are also no longer plausible experimentally or observationally, for now. In the days of Gervase’s divine superstition, fear made his contemporaries think that ball lightning – as natural as lightning from a storm, though more exotic – is a manifestation of God’s wrath. In our age of reason, however, scientists are pushing the boundaries of ball lightning research, using nanotechnology and advanced plasma physics, to reveal its physical nature – less than mythical, therefore all the more beautiful. Just one day, our astute scientific investigation will turn this age-old mystery into a blessing.
Illustration: Verity Laycock