The Quiet Galaxy

Explanations · They are there and we cannot see them

We have not looked long enough: all the searching ever done amounts to a glass of water dipped from the ocean

Proposed by Jill Tarter gave the image; Jason Wright, Shubham Kanodia and Emily Lubar put a number on it, 2010 fc left alone

The search for signals from other civilisations has been going for about sixty years, but for most of that time it looked at a few hundred stars, at a few frequencies, for a few minutes each. A proper search has to cover the whole sky, every frequency a signal could use, every moment a signal might arrive, every kind of signal, and every level of faintness. Measured against that, the astronomer Jill Tarter compared everything done so far to scooping one glass of water from the ocean and concluding there were no fish. A careful count in 2018 made it a large hot tub or a small swimming pool instead of a glass, which does not change the point. The silence may simply mean we have hardly started listening.

The first search for radio signals from another civilisation was Frank Drake's Project Ozma in 1960: two stars, one frequency, six hours a day from April to July 1960. The searches since have been larger, and the Breakthrough Listen programme that began in 2016 is larger than all its predecessors together, but the space to be searched is enormous in a way that is easy to underestimate. A signal could come from any direction, on any of billions of possible frequencies, at any time, with any pattern, and at any strength down to the limit of the telescope. A search covers a tiny box in that space, and a signal outside the box is invisible no matter how strong it is. The galaxy could contain a thousand civilisations transmitting steadily and the searches so far could easily have missed every one.

Jill Tarter, who led the search for decades, made the comparison that stuck: all the searching ever done is a single glass of water from the ocean. In 2018 Jason Wright and two colleagues set out to check it. They defined the volume of the search space along eight dimensions (a refinement of an earlier nine-dimensional description by Tarter and colleagues), worked out how much of it every published search had covered, and compared the total with the whole. Their answer, depending on the assumptions, was somewhere between a large hot tub and a small swimming pool against the volume of Earth's oceans. The comparison is not a figure of speech: it is the fraction of the possible signals that could have been found if they existed.

The bearing on the Drake Equation is that there is none. This explanation says the equation's factors may be anything, that the observation of silence is far weaker than it feels, and that the honest state of knowledge is "not yet searched". For the catalogue it leaves every factor unchanged and puts the silence down to our effort so far.

The objections come from the strong form of the Fermi question. Even a weak search should have found something if the galaxy were settled on the scale Hart imagined, because a settled galaxy would look different as a whole, not just transmit. Wright and his colleagues agreed and noted that their count applies to signals, not to large-scale engineering, which other surveys have begun to rule out. A second objection is that the argument never ends: no finite search covers the ocean, so there is always room to say we have not looked enough. The reply is that this is a fact about the problem and not a flaw in the argument, and that the right response is to keep enlarging the pool. The searches now under way will multiply the fraction searched many times over in the next decade, and this explanation will weaken as they do, if nothing turns up.

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: Nothing can strengthen it except the passage of time without a comprehensive search; a demonstration that past searches had systematic gaps, such as missing the most likely frequencies or signal types, would show how far from complete they were.

Would weaken it: A comprehensive all-sky, all-frequency search over years with no detection, which is what the current generation of instruments is beginning to make possible; conversely, a detection would end it, since it would show the galaxy was never as silent as it seemed.

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

    No comprehensive all-sky, all-frequency search is complete; the COSMIC survey on the Very Large Array had passed 950,000 pointings by September 2024 with no detection. Mason, Garrett and Siemion (2025-11-25) show past surveys covered far more stars than their target lists suggest, which shrinks the glass-of-water argument a little; Crawford (2026-05-30) argues for artefact searches that probe accumulated time; Vidal and others (2026-05-20) map what has and has not been searched. Logged three.

    Mason, 2025Crawford, 2026Vidal, 2026 source 1source 2source 3

How seriously it is taken

The standard position of the researchers who run the searches, and uncontroversial as a statement about radio signals; it is not an explanation of why a settled galaxy would show no large-scale traces, and is usually paired with one.

The papers that bear on it

Books, films and other work that take it up

Read next

Notes

Corrected 2026-10-16. (1) Project Ozma: the text said it lasted 'a few weeks' (and the check note said about six weeks). The SETI Institute gives observations from April to July 1960, six hours a day, at the 21-centimetre hydrogen-line frequency (https://seti.org/project-ozma), and Britannica gives about 150 hours over four months (https://www.britannica.com/event/Project-Ozma); the two stars, Tau Ceti and Epsilon Eridani, were right. (2) Dimensions: Wright, Kanodia and Lubar's abstract describes an eight-dimensional model, which refines the nine-dimensional description of Tarter and colleagues; the text said 'eight or nine'. Their result is 'a large hot tub or small swimming pool' compared with Earth's oceans (The Astronomical Journal 156, 260 (2018), https://arxiv.org/abs/1809.07252; the volume, article number and year are confirmed). (3) The glass-of-water comparison: the earliest documented use found is Tarter and others, Proceedings of SPIE 7819 (2010), which Wright, Kanodia and Lubar cite for it (section 1), and Tarter's own 2010 commentary on CNN (search listing only; the page itself could not be opened). So proposed_in stays 2010, but no earlier use was ruled out.

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/not-looked-long-enough.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.