Imagine yourself outside of and apart from the spherical mass of the universe. From your position, there is a specific direction from which all the light is emanating. No other direction would be valid. The light that leaves this spherical universe will in effect be traveling at light speed but in all cases would be traveling directly away from the mass of the universe. This light, if it did have mass, would gradually decrease in velocity, with respect to its distance traveled, as it is traveling away from the mass of the universe. This should create a second sphere around the first. The diameter of the second is where the light velocity starts to decrease to sub-light speed. If this concept were to be extended further, it would have a light quanta eventually reach a point where it momentarily stops and then begins its tremendous journey back to the main mass of our universe. The innermost shell could be called the atomic shell because it alone is where atoms can be found. The middle shell only contains light; still traveling at light speed. The outermost shell also contains light particles; having sub-light velocities and either traveling directly to, or away from the central mass of the universe according to Newtonian physics.
Beyond this final region, Universe (using Fuller's definiton: all of the known and unknown), would become undetectable ( either through light observance or mass measurement) from within the atomic shell of this universe. We would enter a great void. Mass wise, it is difficult for me to imagine a black hole within the possible various universe of Universe. Our universe could be one of many, many such universes hiding in the great void. It is reasonable conjecture that, from the viewpoint outside of, and apart from these spherical universes, that each would have its own unique mass and location. Each would in turn move in accordance with the dynamics established through the Newtonian laws of motion.