What Actually Sparks Will-o’-the-Wisps? A New Study Traces the Science Behind the Mysterious, Wandering Lights

The ghostly phenomenon could be the product of a chemical reaction involving methane, researchers suggest

Sara Hashemi | Daily Correspondent

October 1, 2025

Share

Copy linkEmailSMSFacebookXRedditLinkedInBlueskyPrint

Add as preferred source

For centuries, stories about will-o’-the-wisps have captured the popular imagination. Countless tales have been told to explain the mysterious lights seen hovering above marshes, swamps and bogs, with folklore and myth insisting they’re caused by tricksters, ghosts or spirits.

Scientists have previously suggested that the flames come from decaying organic matter releasing flammable methane gas, but they didn’t know what sparked the reaction to start the fire.

Now, a new study offers an explanation for the mysterious phenomenon. In a series of lab experiments, researchers observed that water bubbles containing methane can spontaneously ignite, causing what they call “microlightning.” The findings were published in the journal Proceedings of the National Academy of Sciences on September 29.

“Your first reaction when you hear about this finding might be, ‘Okay, will-o’-the-wisps are these ghostly, spooky things, but so what?’” Richard Zare, a physical chemist at Stanford University and senior author of the study, tells Rachel Nuwer at Scientific American. “In fact, the phenomenon we found—related to how chemistry can be driven at interfaces—is profound.”

Zare and his team had previously observed that water droplets can generate electricity. But they didn’t know if tiny bubbles could do the same thing. To test that out, they used high-speed cameras to record what happened as a nozzle blew bubbles of methane and air into water. They also used a photon counter and a spectrometer to detect other evidence of microlightning.

Once the machine started bubbling the water with methane, the counter detected photons, or particles of light. Eventually, as they kept bubbling and the water heated up, the camera picked up microlightning. That was because droplets of different sizes took on opposite electric charges, and when they got too close to each other, they would release a spark.

“[The Italian physicist Alessandro] Volta first speculated that it was lightning causing these [will-o’-the-wisps], and in some sense he was right, but not for the reasons he thought,” Zare tells Alex Wilkins at New Scientist. “It’s not lightning in the air coming from the sky; it’s really from the droplets.”

Antônio Pavão, a chemist at the Federal University of Pernambuco in Brazil who was not involved in the research, tells Laura Allen at Science News that while the study clearly demonstrates that microbubbles can create electricity, it doesn’t necessarily explain will-o’-the-wisps. If microlightning does cause the phenomenon, he adds, then people should still report seeing the lights. But research has shown that there aren’t many modern-day sightings. Instead, Pavão suggests that will-o’-the-wisps were caused by past reactions between travelers’ lanterns and gas generated by wetlands.

Though the lack of modern lanterns may be the main reason behind the phenomenon’s strange disappearance, it could also be, in part, linked to a reduction in marshlands and similar ecosystems worldwide, as Pavão and other colleagues wrote in the Brazilian chemistry journal Química Nova in 2023. The world has lost 561 square miles of salt marshes between 2000 and 2019, and peat bogs—a staple of European will-o’-the-wisp lore—are also declining across Europe.

The recent findings may not explain what causes will-o’-the-wisps, but the microlightning discovery is still significant for chemistry. Graham Cooks, a chemist at Purdue University, tells Science’s Robert F. Service that chemical reactions initiated by the microbubbles are “going to turn out to be a much bigger and general phenomenon.” Both his and Zare’s teams have also shown that bubble-driven reactions can make some of the essential building blocks for life, reports the outlet.

Sara Hashemi | Read More

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.