[magicalhippo]

The extreme lower edge could be said to fall around 7 Hz, where the wavelength of a radio signal matches the circumference of the earth.

Those are rookie numbers. Ok so not the same, but headline made me think of NANOGrav first, which uses minute shifts in pulsar timings to detect gravitational waves in the nano-Hz range[1].

The submission was about subs rather, and quite interesting as such.

The ELF system was found to cause problems ranging from flickering light bulbs to phantom telephone ringing, and the Navy installed additional grounding and filtering on public utilities throughout the area at its own expense—even reimbursing the utilities for administrative costs related to customer complaints.

Yea that surely helped drive some ghost stories and paranoid delusions.

[1]: https://arxiv.org/abs/2306.16218 (figure 9)