Overview
- At EPSC–DPS2025, Manuel Scherf and Helmut Lammer presented a framework indicating extraterrestrial technological civilizations in the Milky Way are likely uncommon.
- The analysis finds a concurrent neighbor would typically lie about 33,000 light-years away, implying any detected civilization is probably much older than ours.
- For planets with 10% carbon dioxide, a technological society would need to persist at least ~280,000 years for there to be even one other civilization alive at the same time.
- Their scenarios require plate tectonics to sustain the carbon–silicate cycle and at least ~18% atmospheric oxygen to permit open-air combustion needed for metal smelting.
- Modeled biosphere lifetimes vary with CO2 levels (~4.2 billion years at 10% CO2 versus ~3.1 billion years at 1% CO2), yet the authors stress large biological unknowns and urge continued SETI searches as the decisive test.