One Kink, Three Generations

Everything you can see and touch is made of just four particles. Protons and neutrons- the stuff inside atoms-are built from two types of quarks (called up and down), held together by the strong force. Orbiting outside the nucleus is the electron. And lurking in the background is the electron neutrino, a nearly invisible particle that appears in radioactive decay. Four particles, and you can build every atom in the periodic table. But nature didn't stop there. It made the same four particles two more times, each copy heavier than the last. The muon is a heavy electron. The charm quark is a heavy up quark. The tau is an even heavier electron. The top quark is the heaviest of all-86,500 times heavier than the up quark, even though it carries the same electric charge and feels the same forces. The three generations of matter Same pattern, three times - nobody knows why Generation 1 Everyday matter Generation 2 Heavier copies Generation 3 Heaviest copies Up quark 2 MeV Down quark 5 MeV Charm quark 1,300 MeV Strange quark 100 MeV Top quark 173,000 MeV Bottom quark 4,200 MeV Electron 0.5 MeV Electron neutrino ~0.000009 MeV Muon 106 MeV Muon neutrino ~0.009 MeV Tau 1,777 MeV Tau neutrino ~0.05 MeV Top quark is 86,500 times heavier than up quark Same electric charge, same forces - just heavier Why three copies? Why these masses? The Standard Model has no answer - it just accepts 22 numbers as inputs.