Every other Friday, the Outside/In team answers a listener question about science and the natural world.
This week's question comes from Meg in Gofftstown, N.H.
“I've heard a lot about the folklore of the will-o’-the wisp. What’s the science behind these ghostly lights?”
Producer Marina Henke looked into it.
This has been lightly edited for clarity.
Marina Henke: In 1783, Thomas Paine and George Washington dangled torches over a river, while a group of soldiers used long sticks to disturb the mucky riverbed. Pale blue flames erupted at the water’s surface. Honestly? Seems like some elaborate procrastination for two guys supposedly busy with founding the country.
But their defense would have been that this was an act of science! For centuries people had reported mysterious flames floating above wetlands, marshes, and cemeteries. They went by many names: swamp lights, will-o’-the wisps, even jack o’lanterns! The founding fathers’ theory was that will-o’-the wisps were caused by traveler’s torches igniting methane gas, which bubbled up from decomposing materials underground.
Richard Zare: I'm not telling you that there's nothing to what people say. I'm just telling you, it's not the whole truth!
Marina Henke: When I began my conversation with Stanford chemist Richard Zare, I realized I’d stumbled into a bit of a scientific debate. Richard doesn’t necessarily reject these founding fathers’ hypothesis. But he doesn’t think it’s an explanation for the majority of them. Because, for one, how could this hypothesis explain modern day sightings? I don’t know about you, but I’m not using torches in my day to day travel. Richard thinks that these lights could be sparked from a far more ubiquitous and, at first, seemingly unlikely source. Water.
Richard Zare: We generally think of water as being neutral and benign. And here I'm telling you a paradox, that you can actually make a fire with water.
Marina Henke: Without getting too lost in the finer details of chemistry, there’s something called the Lenard effect. The idea is that water droplets carry a charge. Smaller droplets are negative and larger ones are positive.
Richard Zare: And when they're close together… big electric field… electrons jump!
Marina Henke: The jumping of these electrons, between negative and positively charged droplets , creates a spark. Richard himself coined the term for this phenomenon...
Richard Zare: Microlightning!... It's enough to actually cause a fire, if you have a combustible gas around.
Marina Henke: Low and behold, the ground in swamps, wetlands, and cemeteries is constantly belching methane, a highly combustible gas.
Richard Zare: The gas bubble bubbles through, comes to the surface, bursts, and that gives droplets and you have sparks! And that spark sets off the gas.
Marina Henke: The significance of this microlightning theory goes way beyond creepy stories and possibly ill-advised late night experiments.
Richard Zare: This also explains all types of other phenomena that people wonder about.
Marina Henke: Think grain elevator explosions, and maybe even the origin of life itself. There’s no consensus yet on what triggered the formation of Earth’s first organic molecules. … but any guesses what Richard thinks might have been the spark?
If you’d like to submit a question to the Outside/In team, you can record it as a voice memo on your smartphone and send it to outsidein@nhpr.org. You can also leave a message on our hotline, 1-844-GO-OTTER.
