Projections of Earth's technosphere: Scenario modeling, worldbuilding, and overview of remotely detectable technosignatures (2409.00067v3)

Abstract: This study uses methods from futures studies to develop a set of ten self-consistent scenarios for Earth's 1000-year future, which can serve as examples for defining technosignature search strategies. We apply a novel worldbuilding pipeline that evaluates the dimensions of human needs in each scenario as a basis for defining the observable properties of the technosphere. Our scenarios include three with zero-growth stability, two that have collapsed into a stable state, one that oscillates between growth and collapse, and four that continue to grow. Only one scenario includes rapid growth that could lead to interstellar expansion. We examine absorption spectral features for a few scenarios to illustrate that nitrogen dioxide can serve as a technosignature to distinguish between present-day Earth, pre-agricultural Earth, and an industrial 1000-year future Earth. Three of our scenarios are spectrally indistinguishable from pre-agricultural Earth, even though these scenarios include expansive technospheres. Up to nine of these scenarios could represent steady-state examples that could persist for much longer timescales, and it remains possible that short-duration technospheres could be the most abundant. Our scenario set provides the basis for further systematic thinking about technosignature detection as well as for imagining a broad range of possibilities for Earth's future.

• The paper presents a systematic methodology using global and technology factors to create 10 self-consistent 1000-year projections of Earth’s technosphere.
• It employs morphological analysis and worldbuilding techniques, combining LLM-assisted narrative descriptions with human oversight.
• The study assesses potential technosignatures and challenges traditional views like the Kardashev scale by revealing that advanced civilizations may be spectrally indistinguishable.

This paper, "Projections of Earth's technosphere. I. Scenario modeling, worldbuilding, and overview of remotely detectable technosignatures" (2409.00067), presents a systematic methodology for developing self-consistent, long-term (1000-year) future scenarios for Earth's technosphere. The goal is to use these projections as templates for identifying potential extraterrestrial technosignatures, moving beyond informal or linear extrapolations common in SETI research.

The methodology is divided into three main parts:

1. Scenario Modeling

This phase aims to define a manageable set of plausible future scenarios from a vast possibility space. It employs a "^^^^1^^^^" (GMA):

• Global Factors (GF): The problem "What are the technological phenomena of the future anthroposphere and how can they be described?" is broken down using a PEST (Political, Economic, Social, Technological) framework. Initially, political, economic, and social factors are considered:
  • Economy (X): Scarcity (X1) vs. Non-scarcity (X2).
  • Politics (Y): Rule by one (Y1), few (Y2), all (Y3), or none (Y4).
  • Society (Z): Hierarchical (Z1) vs. Distributed (Z2).
  • This creates a 2x4x2 matrix of 16 initial global scenarios. A cross-consistency assessment, assisted by the LLM "Claude" and manually reviewed, eliminates inconsistent pairings (e.g., "rule by one" with "distributed social structures"). This results in three viable Global Factors scenarios:
  • GF1 (Philosopher-king): Scarcity, Rule by one, Hierarchical (Discipline/Collapse archetype).
  • GF2 (Survival of the Fittest): Scarcity, Rule by few, Hierarchical (Growth/Collapse archetype, similar to present-day Earth).
  • GF3 (Pure Democracy): Non-scarcity, Rule by all, Distributed (Transformation archetype).
• Technology Factors (TF): A second morphological matrix focuses on technology:
  • Relationship to Biosphere (A): 5 values (e.g., equivalent sets, biosphere subset of technosphere, technosphere subset of biosphere, some common elements, no common elements).
  • Spatial Distribution of Technomass (B): Unipolar, Bipolar, Multipolar, Non-polar.
  • Development Nature (C): Evolved and emergent vs. Designed and directed.
  • Highest Order of Technology (D): 1st-order (humans to nature), 2nd-order (humans to tech/symbolic), 3rd-order (tech to tech/realms).
  • Smallest Scale of Interconnected Systems (E): <1 nm, 1 nm - 1 µm, >1 µm.
  • This 5x4x2x3x3 matrix yields 360 initial technology scenarios. Another cross-consistency assessment reduces these to 11 viable TF scenarios. These are then manually clustered based on LLM-generated descriptions and underlying myths/metaphors into six clusters:
  • 1. Cluster 1 (Living Parallel to Machines): Designed technosphere, biology/technology separate, co-existing on Earth or with tech leaving Earth.
  • 2. Cluster 2 (Technology Flees Earth): Technology emigrates from Earth.
  • 3. Cluster 3 (Environmental Sustainability): Technosphere significantly engulfed by biosphere.
  • 4. Cluster 4 (Planetary Engineering): Technosphere transforms planetary systems.
  • 5. Cluster 5 (Simplicity): Much present-day technology lost.
  • 6. Cluster 6 (Earth 2024): Corresponds to present-day technosphere.
• Final Scenarios: The 3 GF scenarios and 11 TF scenarios (grouped into 6 clusters) initially suggest 33 (or 18 clustered) combinations. A final compatibility assessment, based on the "myths/metaphors" of the GF and TF clusters, further refines this. This step, also LLM-assisted and human-reviewed, ensures that the deepest cultural underpinnings of the combined scenarios are consistent. This results in 10 final, self-consistent 1000-year scenarios for Earth's future technosphere (S1-S10).

2. Worldbuilding

This phase systematically constructs detailed, coherent descriptions for each of the 10 scenarios to define their observable properties. A novel "worldbuilding pipeline" is introduced:

1. Inputs: Each scenario's unique Global Factors (GF) and Technology Factors (TF) cluster, plus basic assumptions common to all (e.g., humans not extinct, no ET interference, 1000-year future).
2. Scenario Description: An LLM (Claude) generates a ~300-500 word narrative description, critically evaluated and iterated by humans for consistency.
3. Additional Narrative & Planetary Bodies: Human experts add details to explain the trajectory from present-day to the future scenario. Key planetary bodies (Earth, Moon, Mars, etc.) are identified, detailing their role in the biosphere/technosphere, population, and purpose.
4. Human Needs Assessment: Based on Max-Neef's Human Scale Development framework (9 needs: Subsistence, Protection, Affection, Understanding, Participation, Leisure, Creation, Identity, Freedom). This step describes how needs are met/unmet on each relevant planetary body, considering both planetary and regional scales. This informs:
   • Land Use and Human Biomes: Fraction of surface area for agriculture, urban use, other structures, and wilderness on each body.
5. Describing the Technosphere: The human needs assessment informs the physical components of the technosphere (urban, rural, subterranean, marine, aerial, orbital, deep space) for each planetary body.
6. Technosignatures: Based on the technosphere's description, potential remotely detectable technosignatures are identified across categories: Optical/UV, Infrared, Radio, Artifact, Quantum, Gravitational Wave, Other.
7. Recommendations for Technosignature Detection: Summarizes the most salient detection prospects for each scenario, highlighting different necessary search strategies.

Ten scenarios (S1-S10) are fully developed using this pipeline, each with a distinct narrative, myth/metaphor, and spatial distribution of its technosphere and biosphere (e.g., S1 "Big Brother is Watching," S4 "Living with the Land," S9 "Deus Ex Machina").

3. Technosignatures Overview

This section analyzes the remotely detectable technosignatures emerging from the 10 scenarios.

• Planetary Technosignatures:
  • Industrial Pollution: Estimated relative to present-day Earth based on population and industrial land use, modified by scenario-specific factors (e.g., terraforming, atmospheric remediation). Future Earth values range from 0 to 210 times present-day. Terraforming Mars (S5, S6) shows even higher values.
  • Agricultural Pollution: Estimated based on population and agricultural land use. Future Earth values range from 0 to 15 times present-day.
  • Artificial Illumination: Calculated from luminous surface area relative to present-day urban coverage, modified by light suppression policies. Future Earth values range from 0 to 450 times present-day.
  • Surface Modification: Fraction of planetary surface technologically modified. Future Earth ranges from 0 to 90%. Some scenarios show extensive modification of Moon, Mars, or Venus.
  • Satellite Belt Density: Relative to present-day Earth, including debris. Future Earth ranges from 0.015 to 10⁶ times present-day.
  • Contaminated Aerosol: From deorbited satellites, generally proportional to satellite belt density, but modified by remediation. Future Earth ranges from 0 to 10⁶ times present-day.
  • No single scenario is "most detectable" across all these signatures, and some scenarios feature more prominent technosignatures on other bodies than on Earth.
• Spectral Signatures (Preliminary Example):

  Atmospheric mixing ratios for pollutants (CO₂, NOₓ, CH₄, NH₃, CFCs, etc.) are estimated for Earth in each scenario by scaling the technological contribution relative to pre-agricultural (R0) and present-day (R1) Earth. Three scenarios (S5 "Transhumanism", S9 "Deus Ex Machina", S10 "Out of Eden") result in Earth's atmosphere returning to a pre-agricultural state (identical to R0) due to remediation or separation of technosphere from Earth's biosphere. Example absorption spectra (UV/visible and infrared) are calculated using the Planetary Spectrum Generator (PSG) for R0, R1, and S3 ("Golden Age"). Notably, NO₂ features can distinguish between these three cases. Industrial pollutants like CFCs show features in the mid-infrared for S3.

• System Technosignatures:
  • Common: Radio leakage (9/10 scenarios), optical communication (7/10), planetary defense radar, asteroid mining, fusion propulsion.
  • Less Common: Outer planet/Kuiper Belt activities, interplanetary quantum communication.
  • Rare/Exotic (appearing in specific scenarios like S9): Radio/optical/quantum beacons, laser propulsion, gravitational waves from superluminal travel, Dyson sphere elements.

Discussion and Conclusion

• Kardashev Scale Revisited: The paper critiques the assumption of continuous exponential growth underlying the Kardashev scale. The developed scenarios, rooted in co-evolving human needs and societal structures, mostly show stable (zero-growth) or slow-growth trajectories. Only one scenario (S9, driven by posthuman AI) approaches the 1% growth rate assumed by Kardashev and achieves Type I energy consumption levels after 1000 years. This suggests that rapid, continuous expansion is not an inevitable feature of human futures, and different "myths/metaphors" drive diverse outcomes.
• Degenerate Observations: A key finding is that three advanced technological scenarios (S5, S9, S10) result in Earth's atmosphere being spectrally indistinguishable from a pre-agricultural, pre-technological state (R0). Detecting these advanced technospheres would require searching for other signs, such as artificial illumination on Earth (S5), extensive surface modifications on other solar system bodies (S9, S10), or system-wide technosignatures, which might be difficult. This highlights the risk of missing advanced civilizations if searches are too narrowly focused on Earth-like atmospheric pollution.
• Longevity of Technological Civilizations: The scenarios present a range of longevities: some achieve long-term stability (S3, S5, S10), some collapse and rebuild sustainably with minimal detectable signatures (S4, S7), one oscillates (S8), and others are on growth trajectories with uncertain long-term stability (S1, S2, S6, S9). The 1000-year timeframe is long for futures studies but short astronomically. The paper briefly considers extending the methodology but notes its limitations for vastly longer timescales where human needs themselves might change. It also acknowledges that short-lived technosignatures might be more abundant or the first to be detected.
• Conclusion: The paper provides a novel, systematic approach to generating diverse, self-consistent 1000-year projections of Earth's technosphere, offering a rich set of possibilities to inform technosignature search strategies. It emphasizes that Earth's future is open, with optimistic, sustainable outcomes being plausible. The spectral similarity of some advanced scenarios to pre-industrial Earth poses a challenge for SETI.

The paper serves as a foundation for future quantitative detectability assessments and encourages a broader conceptualization of what advanced technological life might look like and how it might be found.