2023-05-17 15:04:09
Hums, whispers and strange intermittent signals: scientists are trying to understand where the noises detected in the stratosphere come from. The experiment will also be used to discover new planets.
Strange things happen 21,000 meters above the earth’s surface. A group of researchers sent solar-powered balloons made of duct tape and plastic sheets to explore the stratosphere. When they listened to the recordings made there, they noticed a hidden acoustic world. This is infrasound, so it cannot be heard by the human ear, but with special instruments they were able to transform it and listen to it: murmuring, whispering, blowing, such as those we hear when we put an earpiece to our ears.
“And no, we don’t know what it is” said the Washington Postnak Daniel Bowman, a Sandia National Laboratory scientist who builds solar balloons. “I’ve been doing this for regarding 10 years, and you know, the fact that there are mysterious voices that I don’t understand is unsettling.”
The researchers explain that they have managed to understand the origin of some sounds. For example, the low hum is the waves of the sea as they crash once morest the shore, but there are other intermittent crackles that they cannot explain.
Exploring new worlds with balloons
In the stratosphere “there are mysterious infrasound signals that appear a few times per hour during flight, but their source is completely unknown” Dr. Bowman said. Studying stratospheric sounds is actually a larger project. Soviet scientists already used the instruments in the Vega 1 and Vega 2 missions in the 1980s to make atmospheric measurements on Venus. Now they want to use their previous knowledge to refine their research and understand whether there are active volcanoes on the planet.
“A new generation of Venus balloons are being designed that can last more than 100 days and can change their altitude to navigate the different layers of the Venusian atmosphere” the scientists write in the study.
Volcanic activity on Venus is central to understanding why, despite its Earth-like appearance, it became an uninhabitable planet. Balloons might be just that, as Bowman says they’ve already been used to measure volcanic eruptions. When hovering over earthquake-prone areas, they can detect their sounds in advance. Seismic waves caused by earthquakes are detected by the devices as they spread through the area.
Despite the ambitious plans, floating balloons in the Earth’s stratosphere is considered a low-tech enterprise. In fact, only ordinary materials like plastic sheets, duct tape and carbon powder are needed to build them, Bowman explained. The sun heats the air inside, so the balloon rises into the stratosphere, then returns to Earth when the sun sets and the temperature drops. It doesn’t follow a set route, but flies according to the direction of the wind, as researchers said, as one balloon traveled from the launch center in New Mexico to the suburbs of Houston.
“Our balloons are basically giant plastic bags with a bit of coal dust in them. When the sun hits the balloons, the air inside them warms up and becomes animated. This passive solar energy is enough to propel the balloons from the surface to more than 20 kilometers into the sky” Bowman explained.
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