DARPA accidentally detects SpaceX Falcon 9 rocket reentry by listening to Earth's atmosphere

Clouds can be seen beneath the curvature of earth under a dark blue sky at the edge of space.

Researchers with the U.S. military's Defense Advanced Research Projects Agency (DARPA) have successfully used Earth's atmosphere as a sensor to detect a distant disturbance.

DARPA's AtmoSense program aims to study how sound waves or electromagnetic frequencies travel through Earth's atmosphere, and to find ways to use these waves as a "global sensor" to detect and pinpoint disturbances such as earthquakes or volcanic eruptions.