This manga, kudos on the author that truly know old communication technology via radio waves (radio communication was a thing even 1000+ years ago along electricity), but of course he can't directly speak about it since who own the world today forbid it since 1900 when wired electricity was created to replace the wireless free one, so he wisely mask it as "magic". Also the same author mention in the previous chapters what the Earth is supposed to be, indeed not a spinning ball in the space but a huge motionless electromagnetic energy collector device (all living beings are energy in a a perpetual cycle, aka law of conservation of energy).