Do you know what a lepton is? A muon? A quark? A boson? Bob can’t even grasp the Facebook terms of service, but he found a particle physicist who both understands the nature of matter and was willing to explain it to him. Or try, anyway. Joining Bob for the first of a two-part conversation is Steven Goldfarb, a physicist at the University of Melbourne working on the ATLAS Experiment at CERN — the European particle physics consortium that operates the world’s biggest particle accelerator near Geneva, Switzerland.