The neutrino telescope, essentially 100,000 gallons of cleaning fluid at the bottom of a gold mine, arouses Daedalus's strong admiration: he would so like to have invented something like that himself. He now wants to make it directional, like a normal telescope. He plans a tube many metres long, underground as before, and full of dry-cleaning fluid, or another particle-detecting liquid. Only in the direction of the steerable tube, when neutrinos traverse it from end to end, is it at all sensitive. Several parallel tubes even permit energy-dispersion studies.

Solar neutrinos do not quite ignore the Sun and planets. Unlike photons, they are now known to have mass. They must be slowed by solid objects, perhaps even down to Solar or planetary orbital speeds. They could even be deviated by asymmetric encounters with matter, and so enter orbit. There could be quite a lot of neutrinos in nearby space, slowed by deep encounters with Mercury, Venus, the Sun, Earth and the Moon. They will be orbiting these solid bodies, entering them with little loss per orbit, and be topped up by new arrivals. Their equilibrium concentration will reflect the deep neutrino absorption of these objects.

Neutrinos slowed and deviated by the Moon, for example, should enter an Earth orbit from which a few of them would penetrate below the surface once per orbit, and traverse the telescope. Neutrinos slowed by the nearer planets but little deviated by them should enter a narrow elliptical Solar orbit. Some of them should traverse the telescope twice per orbit. At the other extreme, they would swing round the outer layers of the Sun, sampling its own neutrino-absorbing and -deviating properties. Daedalus's new telescope will look for these wayward particles. He hopes to calculate those orbits best configured to encounter new orbital neutrinos.

Of course, the neutrino flux of any orbit must carry the 'signature' of the whole of that orbit. Neutrinos deviated by the Moon, and passing through it once per orbit, will have an orbital equilibrium concentration reflecting its deep neutrino-absorbing and -deviating properties. These could be calculated, and would slowly give reliable information about the deep geology of the Moon. Similarly, the deep geology of the planets, and even of the Sun, would gradually become clear. It should reveal how opaque, or how deviating, these bodies are to entering neutrinos.