In the Fermi weak interaction theory and even in the electro-weak unification theory, the neutrino is looked as the masslessparticle.
在费米弱作用理论乃至弱电统一理论中,都是把中微子当作无静止质量的粒子来处理的。
2
SA (spectral acceleration) is approximately what is experienced by a building, as modeled by a particle on a massless vertical rod having the same natural frequency of vibration as the building.