Whistler (Radio)

en.wikipedia.org

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Just found this yt channel which has audio of whistlers from various space missions:

https://www.youtube.com/user/VoyagerPWS/

The British Antarctic Survey has collaborated with a musician to create a work incorporating these and other Sounds of Space:

https://www.bas.ac.uk/project/sounds-of-space/

So this is 1kHz radio wave (300km wave length), I didn't know they can get that low, what is theoretical limit? One of my favorite explanation of how the now-debunked em-drive supposed to work was that it produces radio waves with such a long wavelengths that it doesn't fit observable universe and that makes it push in one direction.

> So this is 1kHz radio wave (300km wave length), I didn't know they can get that low, what is theoretical limit?

The theoretical limit is the size of the universe. For practical purposes, this is about the lowest: https://en.m.wikipedia.org/wiki/Extremely_low_frequency

Interesting, clicked a bit further and found out that submarines use VLF communication, however it's one way only:

"Submarines carry only a VLF reception aerial and do not respond on such low frequencies, so a ground-to-submarine VLF broadcast is always a one-way broadcast, originating on the ground and received aboard the boat."

https://en.m.wikipedia.org/wiki/Communication_with_submarine...

Have a look at the photos of the Rugby VLF Transmitter to see why it is not practical to put one on a sub:

https://www.subbrit.org.uk/sites/rugby-radio/

How would the wave know how big the observable universe is?

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