Neutrino

The neutrino is the ghost of the Lepton family: no Electric charge, almost no mass, and so little appetite for interaction that trillions stream through your body every second without leaving a mark. It is NOT a small Neutron — the similar names are a historical accident (Fermi's Italian for "little neutral one").

The three flavours

flavour	partner lepton
electron neutrino (νₑ)	Electron
muon neutrino (ν_μ)	muon
tau neutrino (ν_τ)	tau

Where they come from

• Beta decay — every n → p + e⁻ conversion emits one (see Neutron).
• The Sun — fusion in the core floods space with them.
• Reactors, supernovae, and the Big Bang's leftover background.