In the Fermi weak interaction theory and even in the electro-weak unification theory, the neutrino is looked as the massless particle.

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。

youdao

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.

而光谱加速度大致上是一座建筑物承受的加速度，科学家把一颗与目标建筑物具有相同自然频率的粒子放在一个近似无质量的垂直控制棒上进行模拟得出此数据。

youdao

Take the recent question of whether neutrinos, a type of near-massless subatomic particle, can travel faster than light.

请看最近的一个热点问题：中微子的传播速度能否超过光速？ 中微子是种亚原子粒子，几乎没有质量。

youdao