Long-term implications of observing an expanding cosmological civilization

TL;DR

This paper models the long-term effects of observing expanding civilizations in the universe, analyzing how such observations influence a civilization's expansion prospects and boundary formation, considering practical expansion speed limits and multiple observed domains.

Contribution

It introduces a general framework for understanding the impact of observing other expanding civilizations on future cosmic expansion, including the effects of multiple observations and practical speed constraints.

Findings

Observation limits future expansion prospects.

Higher practical expansion speeds can be both beneficial and detrimental.

Multiple observed domains can trap a civilization at boundary regions.

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.