The Quiet Galaxy

Explanations · They are there and we cannot see them

They are already here: visitors or their machines have reached the solar system, now or long ago, and we have not recognised them

Proposed by Many; the sober form is one Michael Hart listed and rejected in 1975, and Robert Freitas and others turned it into searches of the solar system in the 1980s, 1975 fc left alone

The simplest answer to "where is everybody" is "here". It comes in several strengths. The weakest, and the one researchers take seriously, is that a probe sent long ago could be sitting quietly somewhere in the solar system, on the Moon, in one of the stable points where gravity holds objects in place, or among the asteroids, and that nobody has looked hard enough to find it. The middle version is that visitors came in the distant past and left traces we have misread or lost. The strongest, that they are visiting now and are the cause of unexplained sightings in the sky, has a long history of claims and no good evidence. The silence, on any of these, is a failure to notice rather than an absence.

Enrico Fermi's original question, asked over lunch in 1950, was prompted by a cartoon about flying saucers, and the idea that the visitors are already here has been attached to the problem ever since. Michael Hart, whose 1975 paper made the question scientific, listed it among the possible explanations and set it aside: if the galaxy had been settled, he argued, Earth would have been settled too, not merely visited, and there is no sign of that. The serious form of the idea has been narrower ever since. It asks whether an artefact, rather than a population, might be in the solar system now.

Robert Freitas and Francisco Valdes reported searches in 1980 and 1983 (the telescope work was done in 1979 and in 1981 and 1982) for objects at the points in the Earth-Moon system where an object can stay put without fuel, on the grounds that a probe meant to watch Earth for a long time would park there. They found nothing down to the size their telescopes could see, which left room for anything small. The idea has been revisited as instruments improved. In 2019 James Benford proposed searching the near-Earth asteroids that share Earth's orbit, which a long-term observer would find convenient, and coined the word lurkers for the probes such a search might find. The Galileo Project, begun in 2021, set out to look for artefacts in the solar system with purpose-built instruments. The passage through the solar system in 2017 of the first object known to have come from another star, named 'Oumuamua, with properties nobody fully explained, gave the question a brief public prominence, though most astronomers think it was a natural body.

The ancient-visitor version, that someone came in the geological or human past and left signs, has a worse record. Claims that monuments or myths record visits do not survive scrutiny, and a 2018 study by Gavin Schmidt and Adam Frank asked, as a thought experiment, whether an industrial civilisation on Earth millions of years ago would even be detectable in the rock record now. Their answer was that it would leave a trace, but one that does not differ greatly, in many respects, from natural events already in the record, so telling the two apart would be hard. That cuts both ways.

The strongest version, that unexplained objects in the sky are craft from elsewhere, has been investigated repeatedly, most recently by the United States government in a series of reports from 2021 onward. The first, in 2021, covered 144 reports made between 2004 and 2021, mostly by Navy personnel; it could explain only one of them (a deflating balloon), said the rest lacked enough data to judge, and did not claim a visitor. The Defense Department's office set up for the question, the All-domain Anomaly Resolution Office, reported in 2024 that it had found no evidence of extraterrestrial beings, activity or technology, while a small number of cases stay unexplained for want of good data. Researchers on the Fermi question keep their distance from this version, because the evidence is anecdotal, the claims are extraordinary, and the subject has a long history of hoaxes and wishful thinking.

The bearing on the Drake Equation is nil, which is why this explanation sits in the "unseen" family: it says the factors are whatever they are and the silence is a failure to notice what is near us. The honest statement of its standing is that the search of the solar system for artefacts is a legitimate and cheap scientific project with nothing to show yet, and that everything louder than that is unsupported.

What it says about the equation

Every explanation is a claim about one or more of the seven pieces that are multiplied to give the number of detectable civilisations. This one bears on 1 piece:

The test: what would strengthen or weaken it

Would strengthen it: Discovery of an artificial object in the solar system that could not have been made by humans; a clearly artificial feature on the Moon or an asteroid; an interstellar object whose behaviour cannot be explained by natural physics after close study.

Would weaken it: Thorough surveys of the Earth-Moon stable points, the asteroids that share Earth's orbit and the surface of the Moon finding nothing artificial; natural explanations for the interstellar visitors and for the remaining unexplained sightings; the continued absence of any physical evidence after decades of looking.

These two lines are what the record is read against when a new paper or discovery is logged. A result of the kind named here, published with its evidence, is what would settle it; a press claim on its own settles nothing.

The last reading

Once a week the records are read against the news, each against the test above. Open a line to see what that week held. Every reading ever made of this record is on the reading page.

  • 2026-10-16 Logged, no change By hand

    The third interstellar object, 3I/ATLAS (Seligman and others, 2025-07-03, found 2025-07-01), is a natural comet on every measurement, with a minority arguing otherwise and no evidence for it: a natural explanation for an interstellar visitor, which is on the weakening side. Crawford (2026-05-30) proposes looking for microscopic technological debris in lunar soil, a search that has not been done. No artificial object found. Logged both.

    Seligman, 2025Crawford, 2026 source 1source 2

How seriously it is taken

The search for artefacts in the solar system is respectable, inexpensive and ongoing, and has found nothing. The claims of past or present visitation are not taken seriously by researchers on the question, for want of evidence that survives examination.

The papers that bear on it

Books, films and other work that take it up

Nothing in the library illustrates this explanation yet.

Read next

Notes

Checked against sources on 2026-10-16. Corrected: (1) Schmidt and Frank, 'The Silurian hypothesis', International Journal of Astrobiology 18, 142-150 (online 2018, doi 10.1017/S1473550418000095, https://arxiv.org/abs/1804.03748): the authors say the geological signature of an industrial civilisation 'will not differ greatly in many respects from other known events in the geological record'; the text had said the answer was 'barely' detectable, and now says the trace would be hard to tell from natural events. (2) The United States government reports: the 2021 preliminary assessment (https://www.intelligence.gov/assets/documents/702%20Documents/declassified/Prelimary-Assessment-UAP-20210625.pdf) explained one report with high confidence (a deflating balloon), left the rest unexplained for lack of data, and did not address visitors; the 'no evidence of extraterrestrial beings, activity or technology' finding comes from the Defense Department's All-domain Anomaly Resolution Office in 2024 (historical report of 2024-03, reported at https://digital-release.thehill.com/policy/defense/4519018-pentagon-report-ufos-alien-visits/; annual report of 2024-11, reported at https://abc7news.com/post/pentagon-ufo-report/15546396/). The text had said all the reports found none that required a visitor; it now says what each report said. The 2023 annual report was not read directly. (3) Freitas and Valdes: the papers are Icarus 42, 442-447 (1980) and Icarus 53, 453-457 (1983) (http://rfreitas.com/Astro/SearchIcarus1980.htm and https://www.rfreitas.com/Astro/SearchIcarus1983.htm); the telescope work was done in 1979 and in 1981 and 1982, so the text now says they reported searches in those years. Confirmed with no change: Hart, Quarterly Journal of the Royal Astronomical Society 16, 128-135 (1975), sorts the ways out into four kinds including that visitors came and were missed, and rejects them (listed in the SciSpace record and surveyed on https://en.wikipedia.org/wiki/Fermi_paradox; Hart's own text was not reachable tonight); Benford, 'Looking for Lurkers: Co-orbiters as SETI Observables', The Astronomical Journal 158, 150 (2019-09-20) (Crossref, doi 10.3847/1538-3881/ab3e35); the Galileo Project was announced in July 2021 (https://arxiv.org/abs/2209.02479, Harvard Center for Astrophysics project page).

Think this page gets the explanation wrong, or misses an objection? Say so, or read how disagreement gets folded in. The record itself is data/explanations/they-are-already-here.toml in the public repository. This page's address will never change; if the explanation is ever retired, the address will say what replaced it.