Redshifted civilizations, galactic empires, and the Fermi paradox

Abstract: Given the vast distances between stars in the Milky way and the long timescales required for interstellar travel, we consider how a civilization might overcome the constraints arising from finite lifespans and the speed of light without invoking exotic or novel physics. We consider several scenarios in which a civilization can migrate to a time-dilated frame within the scope of classical general relativity and without incurring a biologically intolerable level of acceleration. Remarkably, the power requirements are lower than one might expect; biologically tolerable orbits near the photon radius of Sgr A* can be maintained by a civilization well below the Type II threshold, and a single Type II civilization can establish a galaxy-spanning civilization with a time dilation factor of $10^4$, enabling trips spanning the diameter of the Milky way within a human lifetime in the civilizational reference frame. We also find that isotropic monochromatic signals from orbits near the photon radius of a black hole exhibit a downward frequency drift. The vulnerability of ultrarelativistic vessels to destruction, combined with the relatively short timescales on which adversarial civilizations can arise, provides a strong motivating element for the ``dark forest'' hypothesis.

• The paper's main contribution is demonstrating that redshifted, time-dilated travel can enable civilizations to overcome lifespan limits while addressing the Fermi Paradox.
• It employs general relativity and time dilation models—examining orbits near supermassive black holes—to illustrate feasible interstellar migration scenarios.
• The study implies that synchronized relativistic acceleration networks could underpin galactic empires, offering a fresh perspective on cosmic invisibility.

"Redshifted Civilizations, Galactic Empires, and the Fermi Paradox": An In-Depth Analysis

Introduction

The paper by Chris Reiss and Justin C. Feng titled "Redshifted Civilizations, Galactic Empires, and the Fermi Paradox" (2510.00377), investigates the feasibility of space-faring civilizations overcoming the limitations imposed by finite lifespans and light speed constraints without resorting to theoretical physics beyond established principles. Within the framework of general relativity, the authors explore scenarios involving civilizations migrating to highly time-dilated frames, enabling interstellar travel on galactic scales within a single lifetime. The implications for the Fermi paradox are also discussed, introducing provocative considerations regarding the conspicuous absence of detectable extraterrestrial civilizations.

Time Dilation in Relativity

The authors provide a detailed review of time dilation phenomena in special and general relativity. Time dilation is a well-documented consequence of relativistic physics, enabling travelers to experience reduced proper time on high-speed voyages compared to stationary observers. This foundational principle is illustrated using the "twin paradox," where a traveling twin ages slower than a stationary one due to relativistic effects.

Figure 1: Spacetime diagram depicting the twin paradox, with trajectories marked by elapsed proper time and clock ticks.

The concept extends to gravitational time dilation, notably around massive objects like black holes, where observers experience significantly dilated time relative to distant observers. However, biological constraints limit the applicability of static positions near event horizons due to high intolerable acceleration forces.

Time-Dilated Civilizations Around Black Holes

A key scenario explored is the possibility of sustaining biologically tolerable time-dilated orbits around supermassive black holes like Sgr A* without invoking complex spin parameters. By considering artificial maintenance of orbits near the photon radius, a civilization might achieve notable time dilation factors without exceeding Type II civilization energy thresholds.

Figure 2: Time dilation factor for unstable circular orbits versus black hole mass for biologically tolerable tidal accelerations.

Observations suggest that maintaining such orbits in accreting plasma environments, akin to those around Sgr A*, can be energetically feasible given sufficient power capacity. Although challenging, these factors suggest potential for sustained galaxy exploration.

Galactic Confederations and Linear Motion

The scalability to a galactic confederation is conceptualized through networks of vessels undergoing uniform relativistic acceleration. This model enables rapid transit across significant galactic distances within practical lifetime segments, enabling coherent civilizational expansion even under current technological constraints.

Figure 3: Civilization network based on synchronized linear paths and nodes enabling coincident arrival timings.

Figure 4: Distance and time required to reach peak dilation factors for vessels under uniform acceleration.

Despite substantial power requirements, Type II civilizations could feasibly maintain tens of thousands of such vessels, leveraging existing astrophysical knowledge to craft a galaxy-wide presence.

Construction of Ringed Black Hole Structures

The paper posits constructing closed gravitational paths via a ring of black holes to support a centralized civilization. This theoretical structure circumvents continuous acceleration needs while offering immense energy extraction potential through processes like those pioneered by Penrose.

Figure 5: Proposed ring of black holes centered within the Milky Way.

While ambitious, the authors articulate practical constraints in terms of required mass transportation and energy expenditure, suggesting that existing astrophysical knowledge paired with future technosignatures could support such developments.

Implications for the Fermi Paradox

The discussion returns to the Fermi paradox, speculating that civilizations might select time dilated states for strategic invisibility—motivated both by existential threat mitigation and the limited communication frequencies due to relativistic effects. The paper advocates considering "Dark Forest" hypotheses, where advanced civilizations intentionally obscure their presence as a preventive measure.

Figure 6: Logarithmic representation of power requirements for executing large-scale astro-engineering akin to constructing a galactic ring of black holes.

The vulnerability of advanced civilizations to emergent threats compels a reevaluation of how extraterrestrial life might navigate or evade detection, reshaping perspectives on galactic expansion.

Conclusion

This paper offers an intricate exploration of advanced civilizational dynamics within the constraints of current physics, prompting reconsideration of how future societies might transcend conventional barriers to expand their territorial reach while addressing the implications of technological progression on existential risks. The proposed methodologies for achieving dilated frames, coupled with deep exploration into the Fermi paradox, present compelling scientific and speculative avenues for further research and debate.