The radiation strength is relative to the restmass and the energy of pa.
辐射强度与辐射粒子的能量、静质量、简并因子有关。
2
Evidently one of the main distinguishing characteristics of photon is just its zest restmass.
显然光子的一个主要区别于其它粒子的特征就在于它的静止质量为零。
3
A hypothetical particle postulated to be the quantum of gravitational interaction and presumed to have an indefinitely long lifetime, zero electric charge, and zero restmass.