Blink and you'll miss it -- How Technological Acceleration Shrinks SETI's Narrow Detection Window

The search for extraterrestrial intelligence (SETI) has historically focused on detecting electromagnetic technosignatures, implicitly assuming that alien civilisations are biological and technologically analogous to ourselves. This paper challenges that paradigm, arguing that highly advanced, potentially post-biological civilisations may undergo rapid technological acceleration, quickly progressing beyond recognisable or detectable phases. We introduce a simple model showing that the technological acceleration rate of such civilisations can compress their detectable phase to mere decades, dramatically narrowing the temporal "detection window" in which their technosignatures overlap with our current capabilities. This framework offers a plausible resolution to the "Great Silence": advanced civilisations may be abundant and long-lived, but effectively invisible to present-day SETI methods. Consequently, our efforts must include but also evolve beyond the search for narrow-band communication signals in the radio and optical domains. Instead, we require an expanded, technology-agnostic strategy focused on persistent, large-scale manifestations of intelligence, such as broadband electromagnetic leakage, waste heat from megastructures, and multi-dimensional anomaly detection across extensive, multi-wavelength and multi-messenger datasets. Leveraging advanced artificial intelligence for unsupervised anomaly discovery, recursive algorithm optimisation, and predictive modelling will be essential to uncover the subtle, non-anthropocentric traces of advanced civilisations whose technosignatures lie beyond our current technological and cognitive frameworks.