You’ve probably seen and heard at least one video of February’s fireball exploding over Cheylabinsk, Russia. The shock wave from entry and subsequent break up of the meteoroid blew out thousands of windows, caused part of a building to collapse and set off countless car alarms.
Scientists estimate the incoming object measured about 55 feet (17m) across – as big as a 5-story building – weighed 7,000 tons and blazed across the sky at over 40,000 mph (64,000 kph). The shock pressure and heat upon entry converted much of the mass into dust, seen as a smoky “contrail”, and the rest into thousands of small meteorites that pocked snow drifts in the surrounding countryside.
While the Chelyabinsk event was the most impressive witnessed meteor in more than 100 years, its effects were even more far-reaching. Almost 6,000 miles (9,600 km) away in Lilburn, Georgia a full 10 hours after the explosion, infrasound sensors recorded multiple rumbles from the object’s impact with the air.
Infrasound, a very low frequency sound wave that can travel long distances, can’t be heard by human ears but can be detected with sensors. When a large meteor enters the atmosphere it sends ripples of infrasound through the atmosphere and around the planet revealing information about its speed, direction of travel and how much energy it contains.
Lilburn is home to one of nearly 400 seismic/infrasound stations in use in the eastern United States. They are part of a large-scale project named Earthscope, an initiative funded by the National Science Foundation that studies the Earth’s interior beneath North America. Although the stations mostly record seismic waves from earthquakes, they also are sensitive to long-period waves of infrasound.
Georgia Tech faculty member Zhigang Peng took the Lilburn infrasound data, sped it up and amplified it so we can heard the reverberations created by the falling meteoroid as it plowed through the atmosphere.
“The sound started at about 10 hours after the explosion and lasted for another 10 hours in Georgia,” said Peng. Like a tsunami set in motion by an earthquake, the Chelyabinsk meteoroid created a series of tsunami-like waves in the atmosphere itself. Both travel at nearly the same speed.
Peng has used the same process to convert seismic waves and underground nuclear explosions into audible sound. Click above for a listen. Check out this site for more exploding Chelyabinsk videos.