eng Science and Education Publishing International Journal of Physics 2013-09-21 1 1 110 114 10.12691/ijp-1-5-3 IJP2013153 article Zhan Likui zlk@iim.ac.cn 1 Sun Yining 1 Chinese Academy of Science, HeFei, China 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. http://pubs.sciepub.com/ijp/1/5/3/ijp-1-5-3.pdf gravitational field mass energy covariance