Sandia National Laboratories | 2017 Feb 17
When a meteor is about to conk your neighborhood and gives fair warning by emitting sizzling, rustling and hissing sounds as it descends, you might think that the universe is being sporting.
But these auditory warnings, which do occur, seem contrary to the laws of physics if they are caused by the friction of the fast-moving meteor or asteroid plunging into Earth’s atmosphere. Because sound travels far slower than light, the sounds should arrive several minutes after the meteor hits, rather than accompany or even precede it. ...
But what if the sounds are caused by the brilliant, pulsating light emitted by the asteroid as it burns up in Earth’s atmosphere?
... researcher Richard Spalding reasoned that such intense light could suddenly heat the surface of objects many miles away, which in turn heats the surrounding air. This could create sounds near the observer. Colleagues ... experimentally demonstrated and analyzed that effect.
They found that objects with low conductivity, such as leaves, grass, dark paint and even hair, could rapidly warm and transmit heat into nearby air and generate pressure waves by subtle oscillations that create a variety of sounds. The process is called photoacoustic coupling. ...
Photoacoustic Sounds from Meteors - Richard Spalding et al
- Scientific Reports 7:41251 (01 Feb 2017) DOI: 10.1038/srep41251
