(SOUNDBITE OF BACON SIZZLING)
SCOTT SIMON, HOST:
The crackle and pop of bacon frying in a pan. Or is it a meteor? Well, that last sound really was bacon. But the sizzle is how people have often described the sound they hear when meteors pass overhead. And for a long time, scientists doubted these accounts. Now, a group of researchers thinks they have an explanation for the snap, crackle and pop some people hear from meteors. Bill Sweatt of the Sandia National Laboratories joins us from Albuquerque. Thanks very much for being with us.
BILL SWEATT: Happy to be here.
SIMON: Now, first, is is this real or in people's minds, hearing bacon?
SWEATT: It's real. There are other experiments that people have run. Alexander Graham Bell was the first one to recognize the fact that by illuminating materials with sunlight and then having a chopper wheel in front it - right? - to make - to turn it on and off at a really high frequency, they actually could hear a sound. Of course, it took them a while to figure out what they were hearing, but indeed, that was what it was.
SIMON: Now, and this would be a little unusual, isn't it? Because the meteors we're seeing are a distance away. And one would think the sound that we would hear would be delayed.
SWEATT: There is the sonic boom, which you will hear later if the meteor's big enough. So what you say is absolutely correct. What this is - basically the light is actually flickering at a very high frequency. So it's flickering at a few hundred hertz or something like that, so that actually it comes out in the same range as sound. And the reason it flickers is because, of course, as the meteor's coming into the atmosphere, it's having its very worst day possible. And it's being destroyed by the heat.
What happens then is the flickering light warms materials near the human that's listening to this. Hair is one particularly good material. Another might be black clothing. The surface of the material is being heated. And what that does, it heats the air in contact with it. You heat the air, and of course it's going to change volume - right? - causing little pressure waves. And that's the source of the sound.
SIMON: That's amazing.
SWEATT: Kind of fun, huh?
SIMON: Yeah. And this is called the photoacoustic effect?
SIMON: What does this tell us that we didn't quite understand before? What are some of the implications that must run through your mind?
SWEATT: Well, mostly it's just interesting, at least that was our perspective. We tried to see if we could turn it into a program of some sort at Sandia, but that wasn't possible. So finally, we just pursued it because it was intriguing.
SIMON: So if you feel the hair stand up on the back of your neck and think you're dreaming about bacon, it could be that a meteor is passing overhead?
SWEATT: Yes. Yeah.
SIMON: (Laughter) Well, Dr. Sweatt, this has been fascinating. Glad we could talk to you.
SWEATT: It's a pleasure.
SIMON: Bill Sweatt is a researcher at the Sandia National Laboratories in New Mexico. His team's research has just appeared in the British journal "Scientific Reports." Good stargazing to you.
SWEATT: Thank you very much, likewise.
(SOUNDBITE OF KOLOTO'S "FOX TALES")
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