Record-energy neutrino may have begun its journey in blazars

Three years ago, in the waters of the Mediterranean Sea, the passage of an "ultra-energetic" cosmic neutrino was observed—the most energetic ever detected. The event drew international attention from the scientific community as well as from the media and the public, not least because the origin of this particle—whose energy exceeded that of previously observed neutrinos by more than an order of magnitude—is unknown.