One of the most significant discoveries in cosmology is the cosmic microwave background, or 'relic radiation' as the Russians call it. Originally, in the early Universe, it was visible light. But the Universe has expanded so much since then that its frequency has been shifted down all the way to the microwave band, a frequency drop of perhaps 105 or so.

Last week Daedalus proposed a directional neutrino telescope, underground as usual to filter out competing particles, but consisting of a tube many metres long. It would be filled with a liquid such as dry-cleaning fluid or heavy water, as used in dedicated neutrino detectors. For some liquids it would be covered with photomultipliers. There would be several telescopes. Giving each some spectroscopic resolution, they could even estimate neutrino energies. Each tube would be sensitive to neutrinos mainly in its long direction, in which they would traverse it from end to end, and so had the best chance of interacting with its contents.

Seeking new uses for his device, Daedalus now reckons that the early Universe should also have created plentiful neutrinos, by the combination of protons or the commonest helium nuclei. As the Universe expanded, these 'relic neutrinos' will have lost energy. By now they should have formed a fairly uniform cosmic background. His directional neutrino telescope will therefore slowly establish that background, and distinguish it from that of the Sun.

It will take many years to sample this very weak neutrino background. But there are very few pieces of information in cosmology (the microwave background is one of them), so the slow effort seems worthwhile. It might even identify a neutrino flux from the nearer stars — Sirius is perhaps the best bet, although Alpha Centauri is nearer. But Daedalus will aim his device in the stellar gaps, especially out of the galactic plane, so as to acquire a true background. There might be surprises, of course. All previous neutrino astronomy has used detectors with no directionality, so it would be intriguing to discover that many neutrinos were coming from some concentrated source.

Indeed, Daedalus would like his telescope to found a whole new branch of astronomy. But he freely admits that the very low rate of data acquisition will greatly restrict the rate at which DREADCO can transform cosmology.