Meteors, and meteor showers in particular, are one of the most amazing sights that you can see when you look at the night sky. Those brief flares of light are a reminder that many small rocky objects and particles – most about the size of a grain of sand – enter Earth’s atmosphere every day and harmlessly burn up. Seeing this is cool enough, but is it possible to actually hear meteors as well?
People have reported hearing meteors as they disintegrated in the atmosphere after a meteor shower. A low hissing sound, similar to bacon sizzling, has been reported with some exceptionally bright meteors. But is that what is actually happening?
Astronomers now think it is.
For years, professional astronomers dismissed the idea of meteor sounds as a myth. What is the reason for this? A meteor usually burns up around 100 kilometers (60 miles) above the Earth’s surface. Because sound travels at a much slower rate than light, the rumblings of a particularly large meteor may not be heard for several minutes after the meteor’s sighting. Something like hearing thunder after the lightning flashes have already happened. A meteor 100 kilometers high would boom about five minutes after it appears. Such an object is called a “sonic” meteor. The noise it makes is related to the sonic boom caused by a faster-than-sound aircraft.
But sometimes, meteors seem to make a sound at the same time that they are being seen. These meteors would be seen and heard simultaneously. Is this possible? Yes, according to astronomers. There are what astronomers call “electrophonic meteors.”
Basically, the explanation is that these meteors give off very low frequency (VLF) radio waves, which travel at the speed of light. Even though you can’t directly hear radio waves, these waves can cause physical objects on the Earth’s surface to vibrate. The radio waves cause a sound, which our ears might interpret as the sizzle of a meteor shooting by.
One classic example of people hearing meteors, as recorded by Live Science in 2013, occurred in 817 A.D., when a meteor shower flew over China. According to a 1992 study by Colin Keay, a physicist at the University of Newcastle in Australia, several researchers reported hearing buzzing, sizzling, or hissing sounds. In England in 1719, something similar occurred.
According to astronomer Edmond Halley:
“Of several accidents that were reported to have attended its passage, many were the effect of pure fantasy, such as the hearing it hiss as it went along, as if it had been near at hand.”
These reports weren’t taken seriously until the 1970s and later. People who claimed to hear meteors were ignored as crackpots, according to Keay’s article in the journal Asteroids, Comets, Meteors.
The observation of a massive meteor over New South Wales in 1978, however, prompted hundreds of stories. Keay looked at 36 of them.
VLF waves travel at the speed of light, so observers would hear them the same time that they saw the meteors pass overhead. But those waves need something physical to act as a transducer and create the sound. Keay found that various objects such as aluminum foil, plant foliage like pine needles, thin wires, dry frizzy hair and wire-framed eyeglasses could all produce those kinds of sounds. That phenomenon is called electrophonics. According to one observer:
“When I was out [viewing the Leonid meteor showers in 1999], I had my head back on the ground and heard a sizzling sound. My head was close to grass and leaves and I wear wire-frame glasses as well. The sound was definitely simultaneous with the observation of a rather large streak.”
Keay’s hypothesis was further tested during the Leonid meteor shower of November 18, 1999. The researchers detected distinct VLF sounds, and also found that many of the meteors were not even visible by eye, but were heard. In fact, 50 times more meteors were detected by their VLF signatures than by sight alone. Dennis Gallagher, a space physicist at the NASA Marshall Space Flight Center, said:
“What makes this exciting is that we’re talking about a phenomenon that has been experienced by people for perhaps thousands of years. Even in modern times folks who reported hearing such sounds were ridiculed. It was only about 25 years ago that Keay was able to do the research and legitimize the experiences of all those generations of people. It shows there are still wonders in nature yet to be recognized and understood. We should take this experience with meteors as a reason to open our minds to what may yet be learned.”