How light is a neutrino?

Physicists are closer than ever to nailing down the mass of the elusive neutrino. A team at the Karlsruhe Tritium Neutrino (KATRIN) experiment in Germany found that neutrinos have a maximum mass of 0.8 electron volts. Researchers have long had indirect evidence that these mysterious particles should be lighter than 1 eV, but this is the first time that this has been shown in a direct measurement. The experiment has so far been able to put only an upper bound on the mass. But researchers might be able to make a definite measurement once it finishes collecting data in 2024.