Listening to Leonids?

ke4pjw writes "According to this article over at NASA, you may have actually heard a meteor as it zoomed overhead. How is it possible to hear it real time? Read the article and find out! HINT: Think VLF"



For editorial explanation and comments, continue to read:


Thank you KE4PJW for a very interesting and thought provoking post.



The "hearing" of VLF frequencies is hypothesized to occur as a
result of the fact that the "VLF" region of the electromagnetic spectrum covers from 3 kHz to 30 kHz. Note that the acoustic
receptive sensibility of the human ear falls within this range!!
There remains a critical question of whether the human ear is able to receive "electromagnetic waves" between 20 Hz and 20 kHz; yet there is certainly no remaining question of whether the the human ear is able to receive "acoustic waves" between those self-same frequencies between 20 Hz and 20 kHz. The question of whether comets and méteors can be heard at the same time that they can be seen was addressed by Edmund Halley in 1682 when "Halley's Comet" was first discovered. (cf. Encyclopedique LaRousse Universel). And Edmund Halley noted that one could hear méteors "hiss" as they passed. This point was made again by Halley in 1718. Now there exists one particularly notable difference between "acoustic waves" which travel at the speed of sound on the one hand-- and "electromagnetic waves" which travel at the speed of light on the other! The Leonids meteor showers typically encounter the atmosphere at an altitude of ~60 nautical miles (or ~110 km). This means that the "acoustic wave" from that event will reach your ear after about 6 minutes (assuming the speed of SOUND to be 600 kts). But this also means that the "electromagnetic wave" in the "VLF" spectrum will reach your ear within about 367 microseconds (assuming the speed of LIGHT to be 162,000 nautical miles per second [186,000 statute miles/sec and 300,000 kilometres/sec]. Therefore the preponderance of available anecdotal evidence appears to indicate that the human ear can indeed be expected to hear the Leonids meteor shower "in real time" by receiving "electromagnetic waves" traveling at the speed of light! ---Ed.