Georg Christoph Lichtenberg was chasing static electricity in 1777. He charged an insulating plate with a large electrophorus, then dusted the surface with a mixture of sulphur and red lead. The powder did not scatter. It settled into branching, root-like figures tracing exactly where the charge had gone. Those figures carry his name, and they appear wherever an insulator loses. A Lichtenberg figure is a map of dielectric breakdown. Apply a potential difference across an insulator and nothing happens until the field exceeds what the material can withstand. At that threshold the insulator stops insulating. A conductive filament punches forward, and because the tip of that filament concentrates the field ahead of it, growth becomes self-reinforcing. The channel advances, splits, splits again, and leaves a permanent record of its own panic. The branching is not decorative. It is the geometry of a discharge hunting least resistance through a medium that is nowhere uniform: - Wood condu...