To give some context for the general reader, the naive expectation for asymptotically flat spacetime symmetries, i.e., symmetries of spacetime seen by observers located far away from all sources of the gravitational field, would be to extend and reproduce the symmetries of flat spacetime of special relativity, viz., the Poincaré group, also called the inhomogeneous Lorentz group, which is a ten-dimensional group of three Lorentz boosts, three rotations, and four spacetime translations. In short, expectation was that in the limit of weak fields and long distances, general relativity would reduce to special relativity.