In theoretical physics, the graviton is a hypothetical elementary particle that mediates the force of gravitation in the framework of quantum field theory. https://en.wikipedia.org/wiki/Graviton So lets imagine, that we have two big black holes merging. As they merge, it creates huge gravitational waves, which can detected by aLIGO in distances more than billion light years. Gravitational waves are ripples in spacetime, which are mediated via massless gravitons. But here comes the catch. The hypothetical graviton is massless spin -2 boson, but all bosons, like for example photon should have curved trajectories around objects with mass and generally cant escape black hole. How is it possible that boson like graviton can escape black hole? Seems to be in direct conflict with General relativity.