India, Oct. 6 -- Somewhere deep in space, a violent event takes place, perhaps a supernova exploding, or perhaps a supermassive black hole devouring matter at the centre of a galaxy. The cosmic event sends radiation of various forms scattering into space. Some of the radiation reaches Earth in the form of particles, where scientists note their uncharacteristically high energy and know they could not have originated on the planet. But they cannot pinpoint the cosmic source, because the particles reached Earth after an untraceably haphazard path, deflected at various points by their interactions with light and matter.

One form of radiation could provide more useful information, but it is not of the kind scientists usually detect. Neutrinos...