Space races: settling the universe fast

This report examines the issue of the resource demands and constraints for very fast large-scale settlement by technologically mature civilizations. I derive various bounds due to the energy and matter requirements for relativistic probes, and compare with bounds due to the need to avoid collisions with interstellar dust. When two groups of the same species race for the universe, the group with the biggest resources completely preempts the other group under conditions of transparency. Expanding nearby at a lower speed in order to gain resources to expand far at a high speed is effective. If alien competitors are expected this sets a distance scale affecting the desired probe distribution. This report examines the issue of the resource demands and constraints for very fast large-scale settlement. If a technologically mature species wishes to settle as much of the universe as possible as fast as possible, what should they do? If they seek to preempt other species in colonizing the universe, what is the optimal strategy? What if the competitor is another fraction of their own civilization? 1 Motivation and earlier work In an earlier paper [2] we outlined how a civilization could use a small fraction of a solar system to send replicating probes to all reachable galaxies, and then repeat the process to colonize all stars inside them. The model was not optimized for speed but rather intended as an existence proof that it is physically feasible to colonize on vast scales, even beyond the discussions of galactic colonization found in the SETI literature. A key question is whether it is rational to use up much of the available resources for this expansion, or if even very aggressively expanding species would leave significant resources behind for consumption. Hanson has argued that a species expanding outwards would have economic/evolutionary pressures to use more and more of resources for settlement, ”burning the cosmic commons” [1]. In this model the settlement distances are small, so there are numerous generations and hence evolutionary pressures could exert much influence. In contrast, our model of long-range colonization [2] uses limited resources and has