For centuries, people have reported glowing balls of light during thunderstorms — spheres from pea-sized to several meters across that drift through the air for seconds at a time, far longer than a lightning flash, before vanishing or bursting with a bang and a whiff of sulfur. Ball lightning has been described passing through closed windows, moving along wire fences, and, in one 1963 account, floating down the aisle of an airliner past a startled passenger.
Some sightings turned deadly. In 1638 a fireball reportedly tore through a church in Devon, killing four people and hurling stones from the walls. In 1753 a Russian physicist named Georg Richmann, flying a kite to study storms as Benjamin Franklin had proposed, was killed when a glowing ball ran down the string and struck his forehead.
Scientists have struggled to pin it down, partly because almost all the evidence is eyewitness testimony. In 2014, researchers in China happened to have their instruments trained on ordinary lightning on the Tibetan Plateau when a ball formed, and caught the first optical spectrum of one. It showed silicon, iron, and calcium — the stuff of soil — which fits one leading idea: that a lightning strike vaporizes silicon out of the ground, and the glowing ball is that silicon slowly burning in the air.
Previously:
• Lightning strike survivors describe what 100 million volts feels like
• Slate: Surviving a lightning strike
