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

Bubbles merging in water can spontaneously generate electrical sparks highly effective sufficient to ignite methane, which may clarify mysterious flashes of sunshine referred to as will-o’-the-wisps.

In bogs, swamps and marshes, folks often see mysterious blue-tinged flashes of sunshine above water, which have generally been related to ghosts or spirits. A extra seemingly rationalization for these will-o’-the-wisps, or ignis fatuus, is that the flashes come from the combustion of gases, like methane and phosphine, produced by decaying natural matter within the murky water beneath. But it’s unclear what would make the gases ignite, with proposed causes comparable to static electrical energy or lightning remaining unproven.

Now, Richard Zare at Stanford University in California and his colleagues have noticed spontaneous electrical sparks between bubbles of methane and air in water within the laboratory, which they name microlightning. They say such occasions may simply have sufficient power to ignite methane gasoline.

“We continue to discover things about water that, once you understand them, they’re obvious, but before then, they seem completely bizarre,” says Zare. “No one thinks of water related to fire. They think water puts out fire. They’re not telling you with water, I can get a spark and set something on fire. This is new.”

Zare and his colleagues had already seen water droplets, the dimensions of a grain of salt, increase cost and spontaneously creating sparks, so that they thought the same impact would possibly happen between methane bubbles in water. They used a nozzle to ship microbubbles of methane blended with air via water and noticed the place the bubbles would collide utilizing a high-speed digicam, in addition to a photon counter and spectrometer.

As the bubbles rose via the water, they modified form and collected cost. When two bubbles met, the distinction in cost between them would trigger a spark, producing a flash that Zare and his crew recorded with each the digicam and photon counter.

They additionally measured the frequencies of sunshine within the flash, and located they matched the signature of particular compounds that had been chemically excited. This suggests the sparks can be highly effective sufficient to set off the ignition of a gasoline like methane.

“[The Italian physicist Alessandro] Volta first speculated that it was lightning causing these ignis fatuus, and in some sense he was right, but not for the reasons he thought,” says Zare. “It’s not lightning in the air coming from the sky; it’s really from the droplets.”

“It clearly looks very interesting,” says Detlef Lohse on the University of Twente within the Netherlands. While it isn’t a definitive interpretation of what is inflicting will-o’-the-wisps, it’s a believable risk, says Lohse, and the outcomes are more likely to spark additional investigation.