Long-term implications of observing an expanding cosmological civilization

Abstract

Suppose that advanced civilizations, separated by a cosmological distance and time, wish to maximize their access to cosmic resources by rapidly expanding into the universe. How does the presence of one limit the expansionistic ambitions of another, and what sort of boundary forms between their expanding domains? We describe a general scenario for any expansion speed, separation distance, and time. We then specialize to a question of particular interest: What are the future prospects for a young and ambitious civilization if they can observe the presence of another at a cosmological distance? We treat cases involving the observation of one or two expanding domains. In the single-observation case, we find that almost any plausible detection will limit one's future cosmic expansion to some extent. Also, practical technological limits to expansion speed (well below the speed of light) play an interesting role. If a domain is visible at the time one embarks on cosmic expansion, higher practical limits to expansion speed are beneficial only up to a certain point. Beyond this point, a higher speed limit means that gains in the ability to expand are more than offset by the first-mover advantage of the observed domain. In the case of two visible domains, it is possible to be "trapped" by them if the practical speed limit is high enough and their angular separation in the sky is large enough, i.e. one's expansion in any direction will terminate at a boundary with the two visible civilizations. Detection at an extreme cosmological distance has surprisingly little mitigating effect on our conclusions.

8 pages, 9 figures. Appendix added, discussing the plausibility of the homogeneous expansion model with a map of ~44,000 galaxies. Two figures added. Acknowledgements added. Accepted to International Journal of Astrobiology

References in corpus (6)

• The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. III. The Reddest Extended Sources in WISE
• The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. II. Framework, Strategy, and First Result
• Extragalactic SETI: The Tully-Fisher relation as a probe of Dysonian astroengineering in disk galaxies
• Homogeneous cosmology with aggressively expanding civilizations
• Our Sky now and then $-$ searches for lost stars and impossible effects as probes of advanced extra-terrestrial civilisations
• On the visible size and geometry of aggressively expanding civilizations at cosmological distances

Cited by in corpus (2)

• If Loud Aliens Explain Human Earliness, Quiet Aliens Are Also Rare
• Artificial versus Biological Intelligence in the Cosmos: Clues from a Stochastic Analysis of the Drake Equation