Neutrino
An extremely light, electrically neutral spin-1/2 elementary lepton that interacts almost exclusively via the weak nuclear force.
Governing formula
m_ν < 0.1 eV/c², Spin = ½, Charge = 0
SI unit
eV/c² (Mass Limit)
In depth
Produced abundantly in nuclear fusion, fission, and beta decay. Because neutrinos lack electric and color charge, they travel vast cosmic distances through solid matter without scattering.
Examples in the real world
Trillions of solar neutrinos passing harmlessly through every square centimeter of human skin every second.