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Airdate: Aug 14, 2019
Scientist: Douglas O. Revelle

A Subtle, Distant Boom

A Subtle, Distant Boom
Scientists are tracking meteor impacts by listening for them.

A Subtle, Distant Boom(In Memory of Meteorologist Douglas Revelle)Here's a program from our archives.ambience: timelapse recordings of meteorites explodingScientists have recently discovered that the Earth is being bombarded with meteors, much more frequently than was previously thought. Now, researcher are monitoring those impacts, by listening for them. I'm Jim Metzner, and this is the Pulse of the Planet.In October of 1996, a large meteor entered the earth's atmosphere and exploded over Los Angeles. Douglas Revelle is a meteorologist with Los Alamos National Laboratory. Revelle: These are subaudible or infrasonic signals from the event over Los Angeles on October 4, 1996, and these signals were recorded in Nevada and Pinedale, Wyoming. And we have increased the rate at which we play them 200 times so we can make them audible.According to Dr. Revelle, when meteors enter the atmosphere, they'll often generate an explosion. Those explosions send out sub-audible sound waves, called infrasound, which travels for miles. Now, Dr. Revelle is tracking meteor impacts, by using sensors that detect those low frequency sounds.Revelle: We have a number of stations on the ground in the western United States. We refer to these stations as arrays. They are ground based pressure sensors that respond to very low frequency pressure waves. The arrays will be triangular in shape, with one kilometer between the various points of the triangle, and then an additional sensor in the middle. And by knowing the positions of the sensors, we know for example that if a wave is coming from the northwest, it will hit the north sensor first, and then as it exits the array, it will hit the sensor that's on the eastern side. And as a result of that information, we can actually go back and find out where the meteorite was that generated these signals.We'll hear more about meteors in future programs. I'm Jim Metzner, and this is the Pulse of the Planet.