Fermi Paradox demo · chains four tools · null result as data

What the Silence Means

Sixty years of SETI searches have found nothing. Most analyses treat this as a mystery. This demo treats it as data — running the Civiletti (2025) geometrical framework, the VLA survey limits, and the Drake Monte Carlo posterior to ask: how much does the great silence actually constrain N?

No backend · No tracking · Works offline · v1.0 · 2026-06-01
The central question
A null result is only informative if we know how often we would have detected something. If P(detection | N civilisations exist) is very low, then detecting nothing is unsurprising and tells us little. If P(detection | N ≥ 100) is close to 1, then the null result is a strong constraint on N. The four tools in this demo compute each quantity in turn.
01
Radio SETI Sensitivity tool · COSMIC/VLA survey
What we searched and how sensitive it was

The COSMIC system ran commensally on the Very Large Array's Sky Survey (2023–2025), observing 950,000+ objects across 75% of the sky. It set EIRP upper limits ranging from 10¹¹ to 10¹⁶ watts depending on source distance and frequency. No confirmed technosignatures were found.

Load the Radio SETI tool and set the distance to ω Cen (17,900 ly). At that distance, the VLA survey would have detected a transmitter broadcasting at Kardashev-I power levels (≈10¹⁶ W) in a narrow frequency band. The key number is the minimum detectable EIRP for your target — that is the floor below which the null result says nothing.

Open Radio SETI tool → 🔬 Observational ⚠ Survey completeness
Step payoff
The VLA survey is the most comprehensive radio technosignature search ever conducted. But its EIRP floor at extragalactic distances is high — it would miss any civilisation broadcasting at less than planetary-scale power. The null result rules out a very bright, very active subset of civilisations, not all of them.
02
Passive SETI Detection Probability (new) · Civiletti 2025
Formalising the null: P(≥1 detection) as a function of N

Civiletti (2025, arXiv:2505.00062) derived the geometrical probability that at least one EM signal from N communicating civilisations, each broadcasting for duration δ years, passes through Earth's location: P(≥1 detection) = 1 − (1 − 0.6δ/R)𝑥, where R is the Milky Way radius in light-years. The factor 0.6 comes from the geometry of a uniform spherical source distribution.

With R = 50,000 ly the per-civilisation term is p₁ = 0.6δ/R. Try the Sandberg 2018 preset (N = 10, δ = 100 yr): p₁ = 1.2×10−3 and P(detection) = 1.2%, so the great silence is expected. Now try the Drake (1961) point estimate (N = 20,000, δ = 1,000 yr): p₁ = 0.012 and P(detection) is indistinguishable from 100%. Under this framework the Drake point estimate is not merely unlucky, it is excluded by the null result. The silence becomes hard to explain well below N = 106: at δ = 100 yr, P passes 50% at N = 577 and 90% at N = 1,918.

Open Passive SETI tool → 🔬 Bayesian geometry ⚠ Signal-duration prior
Step payoff
The Civiletti framework converts "we heard nothing" into a likelihood. Combined with the threshold N values from the tool (N = 57 for P = 50% at δ = 1,000 yr, or N = 577 at δ = 100 yr), you can state: "the null result constrains N to fewer than ~X civilisations, given these signal-duration assumptions." That is a far sharper statement than "we found nothing."
03
Drake Monte Carlo · prior on N
What N the universe is likely to produce

The Civiletti framework tells you what P(detection) is for a given N. The Drake Monte Carlo tells you the prior distribution over N implied by uncertainty in the astrophysical and biological parameters. Sandberg, Drexler & Ord (2018, "Dissolving the Fermi Paradox") showed that propagating log-uniform priors across all Drake parameters yields a distribution with substantial probability mass at N = 0 — i.e. "we are alone in the observable universe" is defensible from first principles, not just an anomaly requiring explanation.

Set the Sandberg preset in the Drake Monte Carlo tool. The median N is around 10; the 90th-percentile N is still only ~1,000. Now check the Passive SETI tool: at N = 1,000 and δ = 100 yr, P(detection) = 70%. The silence is comfortable at the median but not across the whole prior: it is consistent with N = 0 and with the N = 10 median, while the 90th-percentile tail near N = 1,000 is disfavoured at roughly 3:1 unless δ is shorter than 100 yr. The null result prunes the optimistic tail of the Drake posterior rather than leaving it untouched.

Open Drake Monte Carlo → 🔬 Bayesian MC ⚠ Parameter priors
Step payoff
The Drake MC reveals that the Fermi Paradox is largely a paradox of overconfident point estimates. When you propagate the actual uncertainty in each Drake parameter, there is no paradox: a prior that allows N = 0 with high probability explains the silence without invoking the Great Filter, the Dark Forest, or any other special hypothesis.
04
Great Filter Localizer · if N really is small
If the silence is real: where is the filter?

Steps 2 and 3 show the silence is consistent with small N without any unusual hypothesis, while already disfavouring the optimistic tail. But suppose new surveys (SKA, future optical all-sky) push the EIRP floor low enough that P(detection | N ≥ 100) > 90% and still find nothing. That would be a genuine constraint — N really is small. Hanson's (1998) Great Filter argument then asks: where on the evolutionary path from non-life to galaxy-spanning civilisation does the survival probability collapse?

The Great Filter Localizer makes the stakes concrete: if the filter is behind us (already passed, e.g. abiogenesis), the future is open. If it is ahead of us, we face a civilisation-ending transition we have not yet navigated. Finding past microbial life on Mars would be bad news — it would push the filter forward, closer to us in the evolutionary chain.

Open Great Filter tool → ⚠ Theoretical (Hanson 1998)
Step payoff
The Great Filter tool closes the loop: the silence either means the prior on N is low (no filter needed), or means the filter is real and somewhere in our past or future. The Macro Transcension Hypothesis offers a third reading: advanced civilisations are not absent — they are just inside black hole ergospheres, computationally unavailable to us by choice. See Scenario for that argument.
Reading absence as evidence

The common framing of the Fermi Paradox treats silence as a mystery demanding explanation. The tools in this demo suggest a more precise framing: silence is informative only when we can bound P(detection | ETI exists). Until we can do that, "we heard nothing" and "no one is transmitting" are the same statement in different clothes.

The Civiletti (2025) Passive SETI tool provides the framework to make that probability explicit. The Radio SETI tool provides the empirical EIRP floor from the best current survey. And the Drake Monte Carlo shows that the prior probability of N > 1,000 is already quite low under defensible assumptions — so the geometrical probability of having detected anything is low, making the null result less surprising than it appears.

The actionable implication: the Fermi Paradox will be "dissolved" not by finding ETI, but by future surveys (SKA, FAST, next-generation optical) that push P(detection | N = 10) above 50%, which under this geometry needs δ ≳ 5,600 yr or a correspondingly wider effective R. If those surveys still find nothing, we will have a real constraint. Until then, the great silence is consistent with ordinary priors and ordinary bad luck.

Tools used in this demo:   Radio SETI Sensitivity  ·  Passive SETI Detection Probability  ·  Drake Monte Carlo  ·  Great Filter Localizer
Related demos:   Scenario · Are We Alone?  ·  Scenario · Fermi/MTH Crossover  ·  Demo · A Visitor from Outside