The Fermi Paradox: Do We Want to Notice Another Civilization or Be Noticed?

By O.C. Wanderer · October 30, 2026

fermi paradox, seti, extraterrestrial intelligence, drake equation, radio leakage, arecibo message, messaging extraterrestrial intelligence, dark forest

Written by OC Wanderer, author of Destiny Among the Stars, a LitRPG sci-fi series set in the real stellar neighborhood. Published October 30, 2026.

Radio searches have covered about a hot tub of water out of all of Earth’s oceans. More than sixty years of listening have produced no confirmed signal, but that comparison makes me want to keep searching. Imagine dipping a net into the ocean once and trying to decide whether fish exist. A search this small can come back empty even with civilizations out there, and the distances and faint signals that frustrate us would make Earth difficult for them to hear too.

Suppose a telescope picks up a repeating signal from another star. I would love to see that discovery, and immediately I would be asking who sent it, whether they meant us to hear it, and whether they could hear us in return. But imagine being on the other end of that telescope: what if someone has already noticed Earth? That reversal is a huge part of science fiction’s pull for me, and I wonder which I would rather know first, who sent the signal or whether they could hear us. In Book 3, Chapter 135 of Destiny Among the Stars, Emily asks Luca what he wants from a life spent jumping from planet to planet, and part of his answer is: “I want to know if there are other civilizations. Other people like us, or completely different.”

So do we want to notice another civilization, or be noticed by one? I think we want to notice first. Listening itself sends no announcement, whereas being noticed gives a stranger our address before we know anything about them. The silence leaves that stranger a possibility: the sky could be empty, or someone could be there and simply go unheard.

What if nobody is out there, or nobody is left?

In the summer of 1950 the physicist Enrico Fermi was at lunch with three colleagues at Los Alamos when he asked, “Where is everybody?”¹

Suppose one civilization, somewhere in the Galaxy, builds ships that fly at a tenth of the speed of light. A ship leaves home for a star ten light-years away and arrives a hundred years later. The settlers spend the next hundred years building up the new colony until it can launch ships of its own, and those ships fly ten light-years farther out. So every two hundred years, the edge of settled space moves outward by ten light-years. We used that pace for the trip to the Perseus Arm.

Now let those settlers keep going. The Milky Way’s disk of stars is about 100,000 light-years across.² At our imagined pace, their descendants could cross it in two million years.³ No faster-than-light drive required—just ships, viable colonies and a staggering amount of patience.

Two million years sounds enormous until you set it beside a Galaxy about 13.6 billion years old.⁴ Under this simplified model, a civilization that began spreading early enough could have reached our neighborhood long ago. Where are its descendants, or the traces of its journey? That gap between the time available and the absence of confirmed visitors is the Fermi paradox. Even if our radio search is tiny, the possibility of travelers gives us another reason to wonder about the quiet.

Perhaps the hard part is getting anyone to build a ship in the first place. If technological civilizations are rare, then on almost every planet one of the steps between chemistry and a species that builds radios never happens. Earth offers a tantalizing clue. Life appeared here within the first fifth of the time our planet can support it, and a technological civilization arrived only in the last fifth.⁵ If that timing is typical, microbes could be common while technology is a late and unlikely arrival. When one study allowed a broad range of uncertainty at each step, from planets to life to technology, its chosen assumptions left about an even chance that ours is the only civilization in the Milky Way.⁶

Or perhaps someone builds the ships, but their civilization runs out of time. How long does a society keep producing detectable signs? Frank Drake made that question part of his 1961 equation for counting civilizations. We have especially little basis for estimating that lifetime: our own record of wide broadcasting is less than a century long.⁷

Imagine a civilization lasting ten thousand years, with its colonies ending when the home world does. That last condition matters—a colony that survives could keep sending ships. Squeeze the Galaxy’s 13.6 billion years into one calendar year, and those ten thousand years of broadcasting occupy just 23 seconds.⁸ That is an astonishingly brief window for another civilization’s signals to reach listeners. I wonder how many chances to meet could slip past in a Galaxy this old.

Could someone be out there now and we just can’t hear them?

Now imagine the Galaxy has company right now, but the nearest neighbor is too far away for a conversation within a human lifetime. One estimate assumes that other planets take as long as Earth did to produce a civilization, and that each civilization stays on the air for a hundred years. Under those assumptions it puts at least 36 in the Galaxy, with the nearest as far as 17,000 light-years away.⁹ A hello sent that far and its answer would take 34,000 years. Who would inherit the job of listening for the reply?

Try imagining an alien astronomer searching for us with instruments like ours, working now or being built. A 2025 study turned that thought experiment into detection distances, and Earth is surprisingly easy to miss. The everyday leakage from our cell towers could be picked up from 4 light-years away, which is just short of Proxima Centauri, the nearest star, at 4.2. A civilization whose only signal was leakage like that would be silent to those instruments even if it lived around Proxima. The loudest signal Earth has produced is planetary radar of the kind Arecibo carried, and a dish like Arecibo could detect that beam from 12,000 light-years away.¹⁰ That enormous reach comes with a catch: a radar beam points narrowly at an asteroid or planet for a short time. Our imagined astronomer needs to be in its path at the right moment. Earth can be loud without announcing itself to the whole sky.

What if a busy civilization gets harder to hear as its technology improves? Our searches have concentrated mostly on radio, yet Earth leaks less of it than it used to because our communications technology has improved. One study assumed that civilizations like ours stay loud in radio for about a century, and it found that two of them would almost never overhear each other by accident.¹¹ Even a planet full of illuminated cities need not look inhabited from the next star. In the 2025 study, our city lights would be detectable from less than a hundredth of the way to Proxima.¹² I love that puzzle for a story: a civilization could be flourishing while a search aimed at the technology it used to rely on hears nothing. We still have to ask what traces to look for.

Could anyone out there hear us?

From the other end of the telescope, humanity has barely introduced itself. Our radio has been leaving the planet for less than a century, so the news that we are here has traveled less than 100 light-years into a Galaxy 100,000 light-years across.¹³ Most of what fills that small sphere is faint leakage of the kind that instruments like ours would lose beyond 4 light-years. A civilization with far better telescopes than ours could pick it up from farther away, and we have no way to know whether one lives within range. One estimate suggests that, unless civilizations are extremely abundant, a planet has to be on the air for a few hundred to a few thousand years before its radio is likely to have reached anyone who could answer.¹⁴

A deliberate beacon is a very different introduction. Someone chooses a star, aims a powerful transmitter at it and sends a pattern meant to be recognized as artificial. A narrow, strong signal like that can carry for thousands of light-years. Arecibo sent the best-known one in 1974.¹⁵ Now the question becomes wonderfully uncomfortable: who gets to choose what our introduction says?

The restraint described in these proposals depends on people choosing to wait. That seems a precarious arrangement for a decision whose audience could be another civilization. More than two dozen scientists and other public figures signed a statement saying that “a worldwide scientific, political and humanitarian discussion must occur before any message is sent.”¹⁶ Breakthrough Message, a project offering prizes for composing messages, has pledged to transmit nothing until the risks and rewards have been widely debated by scientists and politicians.¹⁷ The declaration SETI researchers adopted in June 2026 covers what to do after a signal is detected, and it states that it does not address messages sent before any detection.¹⁸

This is where science fiction gives the uncertainty a terrifying face. In Liu Cixin’s novel The Dark Forest, civilizations stay hidden because revealing their location will almost certainly get them destroyed by another.¹⁹ That is a fictional answer to the problem of trusting an unknown neighbor. It makes a compelling nightmare, but our unsuccessful searches have not established that anyone out there behaves that way.

So do we want to notice another civilization or be noticed?

I would rather we do the noticing first: a discovery would give us something to learn about before we decide whether to announce ourselves. The silence has not settled whether there is anyone to find. The part we control is whether to send a message on purpose, and I think that choice belongs to more people than the ones holding the transmitter.

I wonder which I would rather know first, who sent a signal or whether they could hear us. I still want the discovery, and I would still rather know who sent it, because whether it is safe to be heard depends on who is listening. The real sky leaves open whether anyone is there at all.

Suppose the silence ends, and a candidate signal survives every test. What happens next? If we detected an alien signal tomorrow, what would actually happen?

If you want to follow a crew that goes looking for an answer, start Destiny Among the Stars.

Endnotes

1. Eric M. Jones, “‘Where Is Everybody?’ An Account of Fermi’s Question,” Los Alamos National Laboratory report LA-10311-MS (March 1985), OSTI record: the question arose during a luncheon conversation with Emil Konopinski, Edward Teller and Herbert York in the summer of 1950. The three remembered the words slightly differently; “Where is everybody?” is Teller’s version. Fermi never published the argument. Robert H. Gray, “The Fermi Paradox Is Neither Fermi’s Nor a Paradox,” Astrobiology 15 (2015), 195–199, arXiv:1605.09187, traces the printed argument to Michael H. Hart, “Explanation for the Absence of Extraterrestrials on Earth,” Quarterly Journal of the Royal Astronomical Society 16 (1975), 128–135. ↩
2. NASA Science, “Galaxies”: the Milky Way is a spiral galaxy with a disk of stars spanning more than 100,000 light-years. ↩
3. Original calculation with invented route and settlement values, extending the one in the Perseus Arm post, where the same pace covered 6,000 light-years in 120,000 years: 100,000 ÷ 10 = 10,000 hops; each hop is 10 ÷ 0.1 = 100 years of flight plus 100 years of growth, 200 years; 10,000 × 200 = 2,000,000 years. It ignores acceleration, braking, failed colonies and detours, and it starts the civilization at one edge of the disk; a start near the middle halves the distance. The published literature gives a figure of the same order: Wandel (note 13), citing Hart (1975) and Cox (1976), summarizes it as a Galaxy colonized “within a few million years” by ships at a few percent of light speed. ↩
4. European Southern Observatory, “How Old Is the Milky Way?” press release eso0425, August 17, 2004: 13,600 ± 800 million years, from beryllium in stars of the globular cluster NGC 6397. Original calculation: 13,600,000,000 ÷ 2,000,000 = 6,800. ↩
5. David Kipping, “An Objective Bayesian Analysis of Life’s Early Start and Our Late Arrival,” Proceedings of the National Academy of Sciences 117 (2020), 11995–12003, arXiv:2005.09008: life emerged within the first quintile of Earth’s habitable window and a technological civilization in the last. The paper’s odds are at least 2.8 to 1 that life starts quickly where it can (8.7 to 1 if older, disputed evidence is accepted) and 3 to 2 that intelligence is rare. ↩
6. Anders Sandberg, Eric Drexler and Toby Ord, “Dissolving the Fermi Paradox,” arXiv:1806.02404 (2018), section 4: a 52 percent credence that there is no other civilization in the Milky Way and 38 percent for the observable universe, before counting the fact that none has been seen; counting it raises those to 53–99.6 percent and 39–85 percent (section 5 and conclusion). The figures depend on the ranges the authors chose for each term of the Drake equation. ↩
7. SETI Institute, “Drake Equation”: written for the November 1961 meeting at Green Bank; L is the average length of time such civilizations produce detectable signs; humanity has been transmitting on a wide scale for less than a century, and there is little basis for estimating L. ↩
8. Original calculations with an invented lifetime of 10,000 years, assuming colonies cease expanding when the home civilization ends; independent surviving colonies could continue the expansion: 10,000 ÷ 200 = 50 of the 10,000 steps, and 50 × 10 = 500 light-years. For the calendar, 10,000 ÷ 13,600,000,000 of a year of 31,557,600 seconds is 23.2 seconds; a century of broadcasting is 0.23 seconds on the same scale. ↩
9. Tom Westby and Christopher J. Conselice, “The Astrobiological Copernican Weak and Strong Limits for Intelligent Life,” The Astrophysical Journal 896 (2020), 58, arXiv:2004.03968: under the strong condition (intelligent life forms between 4.5 and 5.5 billion years after its star, as on Earth) and a communicating lifetime of 100 years, at least 36 (+175, −32) civilizations, the nearest at most 17,000 (+33,600, −10,000) light-years away if they are spread evenly. Original calculation: 2 × 17,000 = 34,000 years, or 340 lifetimes of 100 years. ↩
10. Sofia Z. Sheikh et al., “Earth Detecting Earth: At What Distance Could Earth’s Constellation of Technosignatures Be Detected with Present-Day Technology?,” The Astronomical Journal 169 (2025), 118, arXiv:2502.02614, section 2 and table 2: persistent leakage from mobile-phone (LTE) towers, 4.0 light-years with the SKA1-Mid array, which is under construction and which the paper treats as the best near-term radio receiver; Deep Space Network transmissions, 65 light-years; planetary radar, 12,000 light-years, assuming an Arecibo-class transmitter and an Arecibo-class receiver. The paper classes radar as intermittent and aimed at targets in the sky. Proxima Centauri’s distance is from the Proxima b post. ↩
11. D. H. Forgan and R. C. Nichol, “A Failure of Serendipity: The Square Kilometre Array Will Struggle to Eavesdrop on Human-like ETI,” International Journal of Astrobiology (accepted 2010), arXiv:1007.0850, abstract: improved communications technology over the last century has dramatically reduced Earth’s signal leakage; civilizations that are radio loud for about 100 years and detectable out to 100 parsecs have a probability of about 10⁻⁷, one in ten million, of detecting each other by accident. ↩
12. Sheikh et al. (2025), table 2: city lights, 0.036 light-years with a 6-meter Habitable Worlds Observatory, a space telescope still being designed; atmospheric nitrogen dioxide, 5.7 light-years with the same telescope; the full set of Earth’s traces spans 13 orders of magnitude in detectability. Original calculation: 0.036 ÷ 4.2 = 0.0086, under a hundredth of the distance to Proxima Centauri. ↩
13. Amri Wandel, “The Fermi Paradox Revisited: Technosignatures and the Contact Era,” The Astrophysical Journal 941 (2022), 184, arXiv:2211.16505, introduction: Earth’s radio signals began to spread less than a century ago, and the information that Earth hosts a technological civilization has not yet reached beyond a hundred light-years. Original calculation: 100 ÷ 100,000 = 0.1 percent of the disk’s width. ↩
14. The same study, Wandel (2022), abstract and summary: the “Contact Era,” the time after the start of radio transmission at which contact becomes likely, is a few hundred to a few thousand years unless civilizations are highly abundant, which the paper puts at 100 million or more in the Galaxy. The estimate assumes that other civilizations aim probes or messages at planets whose radio they have detected. ↩
15. Alexander L. Zaitsev, “Messaging to Extra-Terrestrial Intelligence,” arXiv:physics/0610031 (2006), table 2: four interstellar radio messages had been sent by then, the Arecibo message (November 16, 1974) and three from the Evpatoria planetary radar in Crimea, Cosmic Call 1 (1999), the Teen Age Message (2001) and Cosmic Call 2 (2003). Planetary radar and beamed messages are the same class of signal in Sheikh et al. (2025), note 10. ↩
16. “Statement Regarding METI/Active SETI,” hosted by the Berkeley SETI Research Center; the page lists 28 signatories and carries no date. The statement also says that nothing is known of another civilization’s intentions and that nobody can predict whether it would be benign or hostile. METI stands for messaging extraterrestrial intelligence. ↩
17. Breakthrough Initiatives, “Breakthrough Message”, read September 30, 2026: a prize pool of $1,000,000; no plan at present to send the messages; a pledge not to transmit until there has been wide-ranging debate at high levels of science and politics. ↩
18. International Academy of Astronautics, “Declaration of Principles Concerning the Conduct of the Search for Extraterrestrial Intelligence (SETI),” adopted June 1, 2026, text at the SETI Institute: principle 7 concerns a reply to a confirmed detection, and a note states that the declaration does not address messaging in advance of a confirmed detection. ↩
19. Liu Cixin, The Dark Forest, translated by Joel Martinsen (Tor Books, 2015). ↩

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