By Sidney Perkowitz

Lightning illuminates the sky millions of times daily, a phenomenon witnessed by humanity for millennia. This powerful spectacle may have sparked the beginnings of life on Earth, a notion first examined in 1952 when chemist Harold Urey and his student Stanley Miller simulated the early atmosphere and introduced artificial lightning. Their experiment yielded a primordial mix of amino acids, essential for life. Sociobiologist Edward O. Wilson posits that lightning influenced human evolution by providing access to high-protein meals, as it cooked game on the African savanna. The flames from lightning not only facilitated cooking but also ignited the development of human culture around the campfire.

In ancient times, humans attributed lightning's immense power to divine sources, notably Zeus in Greek mythology, who unleashed thunderbolts, and Thor in Norse tales, who wielded thunder and lightning. Other cultures around the globe recognized similar deities, reflecting the awe-inspiring nature of lightning and its connection to life. This symbolism persists today, as seen in the iconic scene from the film Frankenstein (1931), where lightning breathes life into a creature. Lightning also embodies ferocity and swiftness, evident in military insignias and aircraft named after it, such as Lightning and Thunderbolt, dating back to World War II. The term "blitzkrieg," meaning lightning warfare, also underscores its connotations of speed and power.

Despite its historical significance, the origins of lightning remain largely uncharted. As physicists Joseph Dwyer and Martin Uman noted in a comprehensive 2014 review, it is remarkable that despite our understanding of distant cosmic phenomena, the basic mechanisms of lightning generation in clouds remain elusive. The urgency to grasp this phenomenon has increased, as lightning-related destruction escalates due to human activity and climate change.

Scientific inquiry into lightning dates back to the 6th century BCE when Greek philosopher Anaximander attributed it to natural phenomena. Aristotle expanded on this in the 4th century BCE, suggesting that a "dry exhalation" from the Earth caused thunder and subsequently lightning. The true nature of lightning was only revealed in the 18th century when scientists began experimenting with electric sparks, demonstrating that lightning was an enormous electric discharge. Benjamin Franklin famously tested this hypothesis in 1752 by flying a kite in a storm, drawing electricity from a key attached to the string—a pivotal moment in lightning research.

However, it wasn't until 1960 that the German-American physicist Heinz-Wolfram Kasemir proposed a more nuanced understanding, suggesting that lightning begins with leaders—electrically charged channels forming between regions of positive and negative charge within clouds. This complex process, confirmed by research in the 1980s, shifted our understanding from a simple spark to a more intricate series of events leading to visible lightning.

Further investigations into lightning revealed that it can reach millions of volts and thousands of amperes, far exceeding household electrical systems. The rapid flow of electrons in lightning heats the air to around 30,000°C, creating the thunderous sound we hear. Researchers have advanced our understanding of lightning's development using high-speed cameras and artificial triggers, examining how ice crystals in thunderclouds interact with super-cooled water and graupel, generating positive and negative charges that lead to lightning formation.

Despite significant progress, many questions remain. The exact mechanisms behind the charge separation in clouds and the conditions necessary for leaders to form remain unclear. Dwyer and Uman emphasize that understanding lightning's origins is one of atmospheric science's greatest mysteries.

As lightning's destructiveness grows, largely due to climate change, practical solutions are increasingly necessary. Franklin’s invention of the lightning rod has mitigated some risks, but the potential for lightning to cause fatalities, disrupt transportation, and ignite fires has intensified. Urbanization and climate change contribute to increased thunderstorms, creating a greater likelihood of lightning strikes in densely populated areas.

Tracking lightning has become a response to these dangers. Lightning flashes emit electromagnetic radiation that can be detected by specialized sensors, allowing for the triangulation of strikes. The World Wide Lightning Location Network (WWLLN) utilizes a global array of devices to monitor lightning activity. Research has shown that shipping lanes in the Indian Ocean and South China Sea experience twice as many lightning strikes as less-trafficked areas, likely due to pollution from ships.

Additionally, lightning emits infrared radiation, detectable by NASA satellites, which have identified active lightning regions globally. For instance, Lake Maracaibo in Venezuela boasts the highest lightning activity, producing over 233 strikes per square kilometer annually.

Understanding the energy of lightning is crucial. Estimates suggest that a typical bolt can unleash 1 to 10 gigawatts of power, with some bolts reaching 13 million horsepower. Research into fulgurites—glass formations created by lightning striking sand—has provided insights into the energy transfer of lightning strikes, revealing that the power delivered depends on the material struck.

Scientists are also exploring the potential for lightning as a renewable energy source, considering the high power it generates. Yet, capturing this energy remains a significant engineering challenge.

In addition to conventional lightning, the phenomenon of ball lightning, a glowing sphere associated with storms, remains enigmatic. Despite numerous eyewitness accounts, including historical incidents of destruction, a definitive explanation for ball lightning has not yet been established. Recent observations by Chinese scientists have suggested a connection between lightning and silicon compounds, supporting theories about its formation.

Despite the mysteries surrounding lightning, our understanding has facilitated studies of other planets. Jupiter exhibits extensive lightning activity, detected by the Juno spacecraft, revealing insights into the planet's atmospheric dynamics. Saturn also shows signs of lightning, while Mars experiences "dry lightning," resulting from friction among dust particles during storms.

The discovery of perchlorates on Mars, potentially formed by lightning, raises intriguing questions about past life on the planet. As researchers investigate these phenomena, they are reminded of humanity's evolution from mythological explanations to scientific understanding, with many mysteries about lightning still awaiting resolution.

Sidney Perkowitz is a science writer and emeritus professor of physics at Emory University, author of *Hollywood Science: Movies, Science, and the End of the World (2007), and his latest works include Physics: A Very Short Introduction (2019) and Real Scientists Don’t Wear Ties (forthcoming, 2019). He resides in Atlanta.*

Edited by Pam Weintraub