What Sparks Lightning Remains a Mystery

Lightning flashes through the sky millions of times a day, and humans have witnessed the spectacle repeatedly for tens of thousands of years. It was probably the spark for organic life, an idea tested in the lab back in 1952 when the chemist Harold Urey and his graduate student Stanley Miller exposed a simulation of the early atmosphere to artificial lightning. To their delight, they ended up with a primordial soup of amino acids – the building blocks of life. According to the sociobiologist Edward O Wilson, lightning even played a role in the evolution of the human mind. Wilson argues that pre-humans gained access to high-protein, brain-boosting meals when lightning burned big game on the African savanna, leaving entire carcasses cooked and ready to eat. That same lightning provided the flames that our ancestors captured to keep the home fires burning. It was around the campfire (enabled by lightning) that human philosophy and culture was spawned. 

Early humans who saw only lightning's immense power, with no inkling of its electrical nature or its influences on life and evolution, believed that it came direct from the gods – most famously, the chief Greek god Zeus, who hurled down lethal thunderbolts from Mount Olympus. Norse mythology had Thor, son of Odin, whose rumbling chariot wheels and magic hammer generated thunder and lightning. Other cultures, from the Japanese to the Slavic, have honoured similar deities.

These early associations might explain why lightning symbolises the awe-inspiring power of nature and the creation of life. We are still gripped by the scene in the classic film Frankenstein (1931), where intense lightning flashes amid the roar of thunder animate the monster (Boris Karloff) made of dead body parts. Lightning also represents overwhelming force delivered at blinding speed. Military insignia often feature lightning bolts, and heavily armed military aircraft have been named Lightning and Thunderbolt since the Second World War. In that war, the Nazis called their fast-moving attacks that overran Europe blitzkrieg, for ‘lightning warfare'; they took the symbolism still further by stylising the initials of their SS units as two lightning bolts.

‘High voltage' signs still display fearsome lightning bolts but lightning has also become the universal symbol of electricity as our benign servant. A digital device such as my smartphone uses only small, harmless voltages, but the phone displays a tiny lightning bolt while it is being charged. For decades, the electric power industry advertised itself with Reddy Kilowatt, a stick figure with limbs made of lightning and a lightbulb for a nose.

The widespread electrical phenomenon of lightning has existed for much of the Earth's lifetime, but its origin story remains a mystery to this day. ‘When we consider how much we know about complex and exotic astrophysical objects half way across the Universe, it is quite amazing that we do not understand the basics of how something as common as lightning gets started in clouds just a few miles above our heads,' wrote the physicists Joseph Dwyer and Martin Uman in a substantive review of the field in 2014. The irony is deepened by our urgent need to understand lightning, which has become more destructive around the globe, largely due to human activities and climate change.

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