Psst! Sounds like a meteor: in the debate about whether or not meteors make noise, skeptics have had the upper hand until now

Natural History, July-August, 2002 by Alan Burdick

In 1998 Dejan Vinkovic joined a team of scientists led by Slaven Garaj, a physicist at the Swiss Federal Institute of Technology in Lausanne, Switzerland, in an effort to test Keay's theory in the field. They journeyed to Mongolia--remote, quiet, albeit a little cold in November--to observe and record what was expected to be a major Leonid shower. The team set up a video camera, a radio antenna, and two sets of microphones: one open to the voices of the scientists as they watched the sky; the other isolated in boxes containing paper and aluminum foil, which would function as transducers. To count as electrophonic, the researchers agreed, a sound would have to be heard by two viewers and be recorded on all the devices, and the devices would have to synchronize within .04 second. With those restrictions, and many controls, they recorded the sounds (and sights) of not one but two separate meteors--two ghostly but unambiguous "pops" at about 250 Hz. "We concluded that electrophonic sounds are really a real phenomenon," Garaj says, "not a psychological phenomenon."

The recordings have quieted many long-standing skeptics. Jeremy Tatum, a physicist/astronomer--and the self-described "Unbeliever-in-Chief" of electrophonics--wrote an open letter to the Canadian Space Agency's Meteorites and Impacts Advisory Committee, of which he is a member. "Their paper does supply convincing evidence of the reality of simultaneous sound and its instrumental detection under carefully controlled and designed scientific experiment," he declared. "This has come far closer to convincing me than anything to date."

Still, a question remained: How does a meteor generate radio waves in the first place? Keay proposed that in the turbulent wake of a meteor, Earth's magnetic field lines become twisted and trapped, forming "magnetic spaghetti" that produces radio waves in the course of untangling itself. Another group of scientists has proposed that a meteor builds up an electrical charge as it plummets. Whenever the charge reaches a critical maximum, the meteor releases electrical energy, shedding electrons, and the process begins once more, creating pulse after pulse of radio waves as the meteor moves along.

The 1998 recordings suggest to Garaj that neither explanation suffices. The mathematics of both theories require that a meteor be at least ten inches wide (enormous, as meteors go) to be able to produce radio waves energetic enough to vibrate eyeglasses and pine needles. But a Leonid meteor is tiny, a supersonic mote of dust. And the radio frequencies detected from the meteors in Mongolia were far lower than those predicted by current theories. "There's something else beyond these theories that is responsible for electrophonic sounds," Garaj says.

As for Vinkovic, he hopes the Global Electrophonic Fireball Survey will shed some light, and sound, on the matter. Anyone who has heard a meteor can go to his Web site and fill out a standardized response form. When a hundred or so have come in, Vinkovic hopes to conduct the types of statistical analyses that will prove far more convincing than randomly gathered anecdotes. He is, in effect, catching stars with the Internet; last November's Leonid shower netted him twenty responses.