Among the known elementary particles, neutrinos are the hardest to detect and study. But now there are plans to organise 'mass migration' of neutrinos to another detector many miles away. An experiment called NuMl being conducted at Fermilab, Illinois, US will send an intense beam of neutrinos some 1,000 km into the earth to a 10,000- tonne detector in a defunct iron mine (Science, Vol 269, September 29,1995).

What the researchers really wish to study are neutrino oscillations, which will provide dues to the nature of neutrinos and their mass.