Question: 1. A gravitational interaction causes two energy densities to accelerate towards each other. 2. This increases their relative velocity. 3. By special relativity, increasing relative velocity increases (relativistic) mass. Even if the energy involved is small, the energy still must be accounted for. 4. By general relativity, energy densities travel along geodesics. Why would traveling along a geodesic increase the energy of an energy density? In other words, assuming energy is conserved, where does the energy come from to increase the relativistic mass of the accelerating energy density?