-A big, electron-counting machine has indirectly turned up a measurement of the slipperiest known particle in physics — and added to the evidence for dark matter. That measurement is the first result from an international effort to measure the mass of neutrinos — particles that fill our universe and determine its structure, but which we're barely able to detect at all. Neutrinos, according to the German-based Karlsruhe Tritium Neutrino experiment (KATRIN), have no more than 0.0002% the mass of an electron. That number is so low that even if we tallied up all of the neutrinos in the universe, they couldn’t explain its missing mass. And that fact adds to the pile of evidence for dark matter's existence.