Expanding cosmological civilizations on the back of an envelope

Abstract

We present a simplified description of expansionistic life in the standard relativistic cosmology. The resulting model is exactly integrable, yielding a simple set of predictive formulas. This allows one to quickly propose new scenarios for the life appearance rate and the dominant expansion speed and evaluate the observable consequences. These include the expected number and angular size of visible expanding domains, the total eclipsed fraction of the sky, and the life-saturated fraction of the universe. We also propose a simple anthropic bound on observable quantities, as a function of the dominant expansion velocity alone. The goal is to create a simple and intuition-building tool for use in the context of cosmology, extragalactic SETI, and futures studies. We discuss the general predictions of this framework, including conditions giving rise to an "extragalactic Fermi paradox," in which zero civilizations are visible beyond the Milky Way. This can occur even if a substantial fraction of the universe is already saturated with ambitious life.

7 pages, 3 figures

References in corpus (4)

• Homogeneous cosmology with aggressively expanding civilizations
• On the visible size and geometry of aggressively expanding civilizations at cosmological distances
• The Log Log Prior for the Frequency of Extraterrestrial Intelligences
• Life-hostile conditions in the early universe can increase the present-day odds of observing extragalactic life

Cited by in corpus (3)

• If Loud Aliens Explain Human Earliness, Quiet Aliens Are Also Rare
• On the Likelihood of Observing Extragalactic Civilizations: Predictions from the Self-Indication Assumption
• Implications of a search for intergalactic civilizations on prior estimates of human survival and travel speed