Things start off slow in the simulation, but the civilization’s rate of spread really picks up once the power of exponential growth kicks in. But that’s only part of the story; the expansion rate is heavily influenced by the increased density of stars near the galactic center and a patient policy, in which the settlers wait for the stars to come to them, a result of the galaxy spinning on its axis. The whole process, in which the entire inner galaxy is settled, takes one billion years. That sounds like a long time, but it’s only somewhere between 7 percent and 9 percent the total age of the Milky Way galaxy.