We may finally know what causes will-o’-the-wisps

The enigmatic blue flashes of light seen in swamps, bogs, and marshes, often attributed to ghostly phenomena, may actually be related to the combustion of gases such as methane. This gas, produced by decaying organic matter beneath the water’s surface, might ignite due to sparks generated between rising bubbles, according to new research.

Richard Zare and his team from Stanford University have conducted laboratory experiments revealing that spontaneous electric sparks, termed microlightning, can occur between bubbles of methane and air in water. These electric sparks possess sufficient energy to potentially ignite methane gas.

“Water isn’t just a fire extinguisher; it can also generate sparks that ignite gases,” Zare remarks, highlighting the unexpected relationship between water and fire.

The researchers initially observed that minuscule water droplets could accumulate charge leading to spark formation. They hypothesized that a similar mechanism could occur with bubbles of methane in water. By sending microbubbles of methane mixed with air through water, they meticulously documented interactions using high-speed cameras, photon counters, and spectrometers.

As the bubbles ascend, they alter shape and gather charge. The contact between two oppositely charged bubbles triggers a spark that the scientists captured on film, revealing flashes that correspond to the chemical excitation of specific compounds—indicating a spark powerful enough to ignite methane.

“Alessandro Volta’s early speculations about lightning as the cause of these phenomena weren’t completely off; he simply misattributed its source,” Zare reflects. “It’s fundamentally different from celestial lightning; here, the sparks stem from the bubbles themselves.”

Detlef Lohse, a physicist at the University of Twente, remarked, “This study presents a very intriguing idea. While it doesn’t definitively explain will-o’-the-wisps, it offers a plausible possibility that merits further exploration.”