How heavy is a neutrino?

Physicists gathered this week to compare notes on how to weigh neutrinos, one of the most mysterious of the elementary particles. Currently, only one experiment in the world has a shot at making such a measurement — the massive, Zeppelin-shaped Karlsruhe Tritium Neutrino (KATRIN) detector in Germany. The researchers hope to build scaled-up versions of alternative experimental techniques that could eventually compete with KATRIN, or even improve on it.