(None of my points below say the graviton <i>is</i> massless, just that it&#x27;s not crazy. As another post says, this new observation probably confines the graviton mass to be less than 10^-55 grams)<p>&gt; If the massive gravitron was leaving a black hole it would be slowed by the black hole&#x27;s gravity.<p>A graviton wouldn&#x27;t be able to escape a black hole. A photon can&#x27;t, and it&#x27;s massless. The gravity of a black hole is actually a self-sustaining effect of the curvature of the spacetime <i>around</i> the black hole.<p>&gt; (1) We should see this as some inconsistency in how gravity scales with the mass of a black hole. The larger ones would have proportionately greater &#x27;drag&#x27; on leaving gravitrons.<p>We don&#x27;t know details of the gravitational field around black holes and the mass that created it, because none have been observed close up. To an extent, the mass of a black hole is <i>defined</i> by its gravity.<p>&gt; (2) If they are massive, and therefore subject to slowing, shouldn&#x27;t gravity waves leaving a black hole be subject to some sort of doppler effect? Should we be looking for red&#x2F;blueshifts in these waves?<p>Again, photons are massless and subject to the doppler effect. Gravitons, massless or not, will be too.<p>&gt; (3) If gravitrons have mass and are subject to gravity, what brings that gravity? What sub-gravitron particle regulates gravity going in&#x2F;to&#x2F;out of the gravitron? This would require a new set of particles be created by non-gravitron massive objects (ie black holes) alongside the gravitrons. Like I said, too strange to exist.<p>Force carying particles can interact with themselves, c.f. gluons in QCD. In fact, GR is a non-linear theory so there will be non-linear interactions (as far as you can describe them in the weak limit).