This is a thought experiment that I've done many times over the years. I like to create a nice and simple cosmos that allows me to select the variables I choose to particapate in my experiment. I always start out with a solar mass of some size. The first time I did this experiment, I just imagined a system of about 10 solar masses. I didn't include anything else at the start. step 1 - Turn on the light? At first I wasn't sure if I wanted a star or just a ball of hydrogen gas. I decided a ball of hydrogen gas would force me to address the issue of starting a fire, keeping in mine that at least in my model, the cosmos and the universe are one and the same before I light the fire. step 2 - Energy Propagation - push or pull? I decided my cosmos would not be a perpetual motion machine. So I choose to "pull" on the system to start the process of producing the radiating energy. The external pull would separate the force from the system. Due to the fundamental forces in nature, this external force would not be able to pull the system apart, but extract some of the energy contained in the hydrogen gas and convert it to a radiating light. The radiation increased the volume of the cosmos, at least in my system. If we relate this thought experiment to our own solar system and our solar system is five(5) billion years old, then this cosmos would have a diameter of about 10 billion light years. I would like to know if any of you like doing thought experiments of this type? I think as long as these types of experiments are done using sound physics guidelines and paramenters, much insight can be gained in relating to many complex configurations. I realize this example is an over simplication, but you gotta start somewhere.