Touch the glass and the lightning follows your finger. A plasma tube looks like captured weather, but every tendril is a controlled avalanche of ionized gas obeying the same rules that govern neon signs and the sun’s corona. Inside sits a partial vacuum, usually a noble gas blend of neon, argon, xenon, and helium at a few percent of atmospheric pressure. A central electrode driven by a high-voltage, high-frequency oscillator (often 20-30 kV at tens of kilohertz) does the rest. The mechanism: • The oscillating field strips electrons from gas atoms, seeding a conductive plasma channel • Freed electrons collide with neutral atoms, knocking loose more electrons in a self-sustaining cascade • Excited atoms relax and dump that energy as photons, with color set by the gas (neon glows red-orange, xenon blue-white) • Low pressure lengthens the mean free path, so electrons gain enough energy between collisions to ionize rather than merely heat the gas The filaments are not random. They s...