In electron spin resonance (ESR), a chemical sample is placed in a strong magnetic field and irradiated with microwaves. Unpaired electrons in the sample reveal themselves by resonating. Daedalus has been musing on interstellar space, and its content of hydrogen atoms. Each has an unpaired electron (indeed, it is the only one it has). In the low magnetic field of space, each electron should resonate feebly at some audio frequency. Yet the total signal might be quite strong: there are cubic light-years of this specimen. Indeed, the distribution of monatomic hydrogen, and the range and intensity of the interstellar magnetic field itself, are all hot astronomical topics. Daedalus reckons that audio frequencies from space are well worth looking for.

An audio signal would have a very long wavelength — 200 km or thereabouts. A directional parabolic aerial, which must be many wavelengths across, could never be made big enough. Even a conventionally resonant quarter-wave aerial of 50 km would be hard to build. But Daedalus recalls that power-lines and telegraph cables, thousands of kilometres long, already span the globe. Furthermore they are liable to dangerous surges when solar magnetic effects induce big voltages in them. This astrophysical phenomenon suggests to him that a careful search should be made on these conductors, looking for another astrophysical effect: small but detectable audio frequencies from space.

Of course 50 Hz and 60 Hz, the main human power frequencies, will contribute hugely, and will have to be well filtered out. These, however, will have their own human rhythm, caused by the known changing load. The audio spectrum to be studied is wide, too. Furthermore, the system as a whole will be steadily scanned in longitude by the rotation of the Earth, and in latitude by choosing the right conductors to listen to. Circumpolar ones, for example, should discriminate rather well against equatorial signals or ones from the wrong hemisphere.

Here, says Daedalus, is a new way of testing the theory of 'steady-state continuous creation'. It holds that monatomic hydrogen is appearing steadily throughout space, at just the rate needed to compensate for spatial expansion. The Universe has no beginning and no end. If the Earth is indeed receiving a steady ESR hydrogen signal from every point in space, the implications would be cosmologically profound indeed.