Make ball lightning and instrument it

Why the library suggests it

A group at the Federal University of Pernambuco struck an electric arc on a wafer of pure silicon and produced orange-white glowing balls roughly golf-ball sized, spinning, bouncing and lasting seconds rather than the fraction of a second a hot spark manages — demonstrating the mechanism proposed in Nature in 2000, in which a strike reduces silica to silicon vapour that condenses into nanometre-scale particles which glow while burning back to oxide (Production of Ball-Lightning-Like Luminous Balls by Electrical Discharges in Silicon, 2007). The natural counterpart is a slitless-spectrograph capture on the Qinghai Plateau: a ball roughly five metres across, drifting at about 8.6 metres per second, lasting a little over a second and a half, its spectrum carrying silicon, iron and calcium emission lines — the soil the lightning had just struck — for the object's entire lifetime (Observation of the optical/spectral characteristics of ball lightning, 2014). And the observational channel now has a second, instrumented leg: structured public reports matched against a professional lightning-location network, with the network data substantiating the witness in all seven worked cases, and with a physical result falling out immediately — the ball does not necessarily form where the stroke hit the ground (First comparisons of ball-lightning report website data with lightning-location-network data, 2022). The field's own map of itself, separating natural events from deliberately made long-lived luminous formations, is Long-Lived Luminous Formations, Ball Lightning, and Their Researches (2022).

The experiment or build

Reproduce the silicon-arc recipe — it needs an arc supply, a silicon wafer and a camera — and then do the thing the natural measurement makes possible: put a slitless spectrograph on your own laboratory ball and compare its spectrum, line for line, with the natural one. The settling measurement is the emission spectrum and the lifetime of the laboratory ball against the published natural spectrum, with the composition of the substrate varied so that the lines move where the chemistry says they should. If the laboratory object reproduces the natural spectrum when you feed it the right elements, the mechanism is settled; if it does not, the residue is the interesting part and it is measured rather than argued.