The makers of these solar balloons love to inspect the devices Venus In future.
Researchers have sent Hot air balloons Microphones are highly sensitive to the stratosphere and have recorded sounds that have never been explained before.
As light in the infrared spectrum is invisible to the human eye, it is “infrasound,” inaudible to the human ear. Recorded with special equipment and sped up several thousand times, they sound like mumbled, steady whispers.
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“When we started flying balloons years ago, we didn’t know what we were going to hear,” says Daniel Bowman of Sandia National Laboratories in New Mexico. “We learned to recognize the sounds of explosions, meteor crashes, airplanes, electrical storms, and cities. But every time we send up the balloons, we find sounds we can’t identify.”
Bowman and his colleagues measured infrasound signals (sounds of a frequency too low for human ears) using solar-powered balloons floating at an altitude of 20 kilometers.
The researchers created balloons about 7 meters wide and made of thin plastic. They filled them with coal dust, which was heated by sunlight and made the balloon float. Unlike weather balloons, which rise until they explode, these solar-powered balloons float in the stratosphere for hours, carrying infrared sensors for hundreds of miles. Researchers have used more than 50 balloons over seven years, starting in 2016.
The data they collected shows that stratosphere It sounds completely different from the surface of the earth. On the ground, infrasound sensors pick up signals deflected by downwind winds, but balloons float above those winds and record signs of turbulence elsewhere in the atmosphere and infrared sounds from ocean storms. However, Bowman says many come from infrared signals stratosphere They have no apparent appearance. He presented the work at a meeting of the Acoustical Society of America in Chicago.
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These mysterious signals may be related to types of atmospheric turbulence that have not been recorded before, but the infrared stratosphere They’ve rarely been explored before, so it’s hard to predict, Bowman says.
Collaborates with Bowman NASA To create a similar balloon technology to an even less explored space: clouds Venus. He and his colleagues want to adapt their solar-powered balloons to record infrasound on the planet’s surface, which could help record seismic activity on the planet.