Abstract: While there is a well-accepted notion of total energy and linear momentum of gravitational fields, finding a suitable definition of angular momentum is more challenging. The main difficulty is the presence of supertranslations. We discuss how a new definition proposed by Po-Ning Chen, Mu-Tao Wang, and Shing-Tung Yau provides a total flux of angular momentum that is supertranslation invariant. The talk is based on joint work with Po-Ning Chen, Jordan Keller, Mu-Tao Wang, and Shing-Tung Yau.