Our current understanding of observed physical phenomena is through theories based on a framework that incorporates quantum mechanics and special relativity. We have successfully tested this framework with observations involving all the non-gravitational interactions. In particular, gauge theories play a central role in the description of such interactions. Taming gravity, though, has turned out to be a particularly complex adventure. Even at the classical level, the theory of gravity, though well understood and tested, is highly non-linear and difficult to work with.
Recently, a correspondence has emerged between gravitational theories and (two copies of) gauge theories, dubbed the double copy. Given our extensive understanding of non-gravitational theories, the double copy simplifies gravitational calculations, and might even provide a new approach to understand gravitational theories. Furthermore, peculiar theories, such as that of the bi-adjoint scalar, also make an appearance, offering the potential to streamline both gauge and gravity theories.