The Fermi/MTH Crossover

Every resolution to the Fermi Paradox must be compatible with a prior on N. Sandberg, Drexler & Ord (2018) showed that using wide log-uniform priors over the Drake factors gives P(N < 1) ≈ 30–50% — substantially higher than the near-zero probability implied by point estimates. The “MTH as resolution” scenario uses Sandberg priors because the MTH is most relevant when N is small but nonzero: if N = 0, no resolution is needed; if N is large, the MTH must explain the silence of many civilisations simultaneously. The “optimistic + transcension required” scenario uses modern optimistic priors (following Lineweaver/Chopra or similar) which push N to hundreds or thousands — making the silence strongly paradoxical and requiring a systematic resolution. The Drake tool shows you the distribution over N; the following five steps show what happens to whatever fraction of N survives into technological maturity.

Given that we observe silence (N is small), Hanson’s Great Filter argument says there is at least one bottleneck in the path from non-life to galactic civilisation where nearly all branches terminate. The location of that bottleneck has radically different implications. An early filter (abiogenesis or eukaryogenesis) means life itself is rare — good news for us (the filter is already behind us). A late filter (industrial self-destruction, ecological collapse, or some civilisation-ending attractor) means that civilisations exist in abundance but typically fail before or shortly after our current stage — bad news. The transcension filter is a third possibility: the bottleneck is not destruction but divergence from detectability — civilisations survive but become invisible because they converge inward on compact objects. The Great Filter tool lets you distribute the total filter probability budget across eight steps and read off the implied future danger. The transcension hypothesis is the only Fermi resolution that predicts the OC IMBH to be a detectable proxy for civilisational presence.

For the residual fraction of N that survives the Great Filter, Sandberg et al. (2017) proposed that thermodynamic logic drives them to hibernate: computing is more efficient in a cold universe, so sufficiently advanced civilisations defer computation until the CMB has cooled. This explains radio silence without requiring destruction. Bennett et al. (2019) contested the premise: cold reservoirs exist today. The aestivation calculator shows both cases simultaneously — the Sandberg gain at the end of the wait period, and the Bennett “same gain available now” counter-argument via the reversibility slider. In the MTH scenario, aestivation is a transitional state: civilisations may hibernate for 10¹⁰–10¹² yr, but the ultimate endpoint is the ergosphere, not indefinite hibernation. In the “rarity alone” scenario, aestivation is moot because no civilisations exist. In the “transcension required” scenario, aestivation is insufficient because the Bennett critique holds and the filter demand is too large — the MTH must carry the full explanatory weight.

The MTH predicts that the observational signature of an advanced civilisation converging on a compact object is an anomalously accreting IMBH in an old, dense stellar environment. ω Cen is the most chemically anomalous globular cluster in the Milky Way — almost certainly a stripped dwarf-galaxy nucleus — and it hosts the strongest IMBH candidate in any globular: the Häberle 2024 result (≥ 8,200 M_△) from fast-star orbital kinematics. The Constraint Stacker shows every published evidence line — proper motions, velocity dispersion, pulsar timing upper limits, JWST accretion limits, N-body models, and the M–σ prediction — simultaneously. In the “MTH as resolution” scenario, the stacker is filtered to the Häberle 2024 lower-limit line, which is the single strongest positive detection. In the “transcension required” scenario, the stacker is set to the same filter because the MTH test case is the most conservative: if the evidence holds at ≥ 8,200 M_△, that is the mass to use for Steps 5 and 6. This is the step where the Fermi argument becomes empirically testable: Gaia DR4 (December 2026) will either confirm or constrain this mass window.

Once the mass window is established, the Blandford-Znajek mechanism translates it into power. At 8,200 M_△, a = 0.9, and B = 10⁴ T (a strong but physically plausible accretion disc field), BZ power reaches ~10³⁶ W — the Kardashev-III ceiling for a galactic-scale civilisation, achieved from a single compact object with an ergosphere the size of a small city. In the “transcension required” scenario, the spin and field are set to higher values (a = 0.99, B = 10⁴ T) representing a civilisation that has actively spun up the black hole through decades of accretion management. The BZ tool is the conversion from “is there an IMBH?” to “what could a civilisation inside it be doing?” The Kardashev scale label — K-I, K-II, or K-III — reads off directly from the power output panel. The inverse mode allows you to set a target power and ask what magnetic field is required.

The final step translates BZ power into the fundamental limits on computation. Three limits bound the ops budget from different directions. The Lloyd limit (2E/πℏ) is the maximum operations per second on a physical system of energy E, set by the time-energy uncertainty principle. The Landauer limit (k_BT ln 2 per irreversible bit) is the minimum energy cost per operation at temperature T; at the CMB temperature of 2.73 K, this gives the current-epoch ops/s per watt. The Bekenstein bound (2πRE/(ℏc ln 2)) gives the maximum bits of information storable in a volume of radius R and energy E. At BZ power and the ergosphere geometry of an 8,200 M_△ IMBH, all three limits are simultaneously set by the physics of the object itself: the BZ power is P, the ergosphere radius is r₊ ≈ 2.4×10⁷ m, and the rest-mass energy is Mc². The ops budget across all three measures exceeds anything achievable by any Dyson-sphere-level civilisation by many orders of magnitude. This is why the MTH predicts that technologically mature civilisations find the ergosphere route and are subsequently undetectable by any megastructure survey.