Science and Education Publishing International Journal of Physics 1 1 2013 09 21 Discussion on Mass in a Gravitational Field 110 114 EN Zhan Likui Chinese Academy of Science, HeFei, China Sun Yining IJP2013153 10.12691/ijp-1-5-3 2013 08 21 2013 09 14 2013 09 21 In a black hole, no force can prevent matter from collapsing into a point, a gravitational singularity. The problem of the singularity is always a difficult one. We attempt to discuss gravitation from another angle in this work. Based on experimental analysis and theoretical verification, a hypothesis regarding mass in gravitational fields is presented. It can avoid the problem of singularity, and the meaning of gravitation is simple to determine.