There is enough energy in a lightning bolt to power about a billion homes. The snag is that the bolt lasts for only millionths of a second, lightning is sporadic and unpredictable, and power grids could not manage that surge.
This staggering estimate was made not by measuring a lightning bolt itself, but using an ingenious method based on “fossil lightning”. Lightning can heat the air to 30,000C (54,000F), almost six times hotter than the surface of the Sun. If a lightning bolt strikes sandy ground, that intense heat instantly melts the sand, which rapidly cools into a wonderful hollow glassy tube called a fulgurite. This strange phenomenon looks rather like a knobbly tree root and can reach up to 5m in length, tracing the path of the lightning bolt as it drilled down into the ground.
While fulgurites are fragile, they remain buried in the sand for thousands of years and give a fossil record of the original lightning strike’s path. The energy of that bolt can also be calculated from the thickness of fulgurites, which range from about the size of a baby’s little finger to the size of a man’s arm — the thicker they are, the more energy the lightning bolt had.
Scientists in Florida have found that it is the ideal place to study fulgurites. The state is frequently struck by lightning and there’s a lot of sand, which is quarried to supply the raw material for roads and cement. By trawling through commercial sand quarries, the scientists collected several hundred fulgurites dating back thousands of years. Writing in the journal Scientific Reports, they found that the most powerful lightning strikes, with thick fulgurites, were fairly uncommon, but were immensely energetic, being 20 times as great as the average lightning strike. That power highlights the immense damage that lightning can inflict on wood, electronics and vulnerable materials, as well as illustrating how resilient lightning protection systems need to be to manage strikes safely.
