Where is Everybody? The Causal Disconnect and the Limits of Interstellar Detectability

The Fermi Paradox (“Where is everybody?”) refers to the apparent contradiction between the visualisable abundance of extraterrestrial civilizations and the continued absence of confirmed detections. This work explores whether finite communicative lifetimes, combined with Galactic distance scales and the finite speed of light, can substantially suppress the probability of causal overlap between technological civilizations. Using a simplified stationary Galactic model (v = 0) within a Minkowski spacetime framework, technological civilizations are represented as finite world-line segments generating expanding “Information Shells” through electromagnetic signal propagation. Within this interpretation, successful detectability requires overlap between the communicative intervals of different civilizations in both space and time. For representative communicative lifetimes of order L ~ 10³ years, the effective causal reach of detectable signals remains small compared with typical interstellar separations expected in sparse-civilization scenarios. Using a heuristic overlap model, we estimate that for N = 100 contemporaneous civilizations distributed throughout the Milky Way, the effective causal-overlap probability remains below 1% . The analysis further considers long-term engineering limitations on autonomous probes and persistent signalling systems, including radiation damage, impact erosion, and power degradation, collectively described here as a “Hardware Filter.” In addition, the work distinguishes between the total biological lifetime of a civilization and its externally detectable communicative phase, suggesting that advanced civilizations may evolve toward increasingly low-leakage or radio-quiet technological states. Within this framework, the apparent “Great Silence” may emerge naturally from finite communicative windows, spacetime separation, and engineering constraints even if intelligent life itself is not intrinsically rare.