By Ashley Strickland, CNN
Giant solar balloons were sent 70,000 feet up in the air to record sounds of Earth’s stratosphere — and the microphones picked up some unexpected sounds.
The stratosphere is the second layer of Earth’s atmosphere, and its lower level contains the ozone layer that absorbs and scatters the sun’s ultraviolet radiation, according to NASA. The thin, dry air of the stratosphere is where jet aircraft and weather balloons reach their maximum altitude, and the relatively calm atmospheric layer is rarely disturbed by turbulence.
Daniel Bowman, principal scientist at Sandia National Laboratories in New Mexico, was inspired in graduate school to explore the soundscape of the stratosphere after being introduced to the low-frequency sounds that are generated by volcanoes. Known as infrasound, the phenomenon is inaudible to the human ear.
Bowman and his friends had previously flown cameras on weather balloons “to take pictures of the black sky above and the Earth far below” and successfully built their own solar balloon.
