Cryptonomicon

by Neal Stephenson

Long cables act as antennae, picking up all kinds of stray currents as the rotation of the Earth, and its revolution around the sun, sweep them across magnetic fields of terrestrial and celestial origin. At the Museum of Submarine Telegraphy in Porthcurno, Cornwall (which we’ll visit later), is a graph of the so-called Earth current measured in a cable that ran from there to Harbor Grace, Newfoundland, decades ago. Over a period of some 72 hours, the graph showed a variation in the range of 100 volts. Unfortunately, the amplitude of the telegraph signal was only 70 volts. So the weak, smeared-out pulses making their way down the cable would have been almost impossible to hear above the music of the spheres.