We Better Think Twice About What We Say to ET

Extraterrestrials could take our intergalactic message in entirely the wrong way.


Parents around the world tell their children to be careful about speaking to strangers. It’s good advice for our innocent offspring, because even if the risk of a dangerous interaction is very small, the consequences could be very great. Yet when it comes to the idea of sending unsolicited messages out into the cosmos to try to get a response from technological alien life, we seem to forget these sensible domestic rules. That goes for everything from the earliest messages beamed into space to one outlined last month by a group of researchers from the Jet Propulsion Laboratory at Caltech and several international organizations. Each could spark consequences beyond our control.

As a case in point, the first deliberate, high-powered radio message sent by humanity to another world lacked any semblance of careful thought, or any poetry. It consisted of the Morse code dots-and-dashes for three words: “MIR,” “LENIN,” and “USSR.” Mir means “peace” or “world,” the other two words need little explanation.

This cryptic transmission was beamed into the cosmos in November of 1962 from the Pluton Complex in Crimea by a planetary radar made from 16-meter-wide radio dishes mounted on a structure built out of railway bridge trusses and the hulls of a pair of repurposed Soviet submarines—a brutalist architect’s delight. The message was used to produce a radar echo from the planet Venus, but decades later scientists realized that the eventual lucky recipient of this pronouncement is a star some 2,100 light-years away, and therefore not yet aware of its role in human history.

A TETRIS-Y TRANSMISSION: The act of transmitting this message, in 1974, from the Arecibo radio observatory, was a bit of a throwaway stunt. Constructing the message, on the other hand, took some clever thinking. It’s a string of 1,679 bits of clearly non-random, attention-provoking data that could be displayed as an image (which wasn’t actually colorized) depicting items like the decimal number system, life’s elemental constituents, the shape of DNA, and a few other tidbits about the human form, and the architecture of our solar system. Credit: Arne Nordmann / Wikicommons

The oddly parochial nature of this first step in extraterrestrial messaging was not without precedent, or so very different from efforts that followed it. For instance, there’s a famous but probably apocryphal anecdote about how, in 1820, the physicist Carl Fredrich Gauss proposed sending signals to other worlds by creating a vast representation of the Pythagorean theorem of right-angled triangles, carved into the Siberian tundra and outlined with pine forest. Gauss may or may not have suggested this, but having invented the heliotrope for reflecting sunlight over great distances, he did write to the German astronomer Heinrich Olbers in 1822 about building a huge heliotrope array of hundreds of mirrors to message “our neighbors on the Moon.”

In the late 1800s, the French inventor Charles Cros also thought about mirrors for signaling Mars or Venus, except his idea was to use these to focus sunlight and to burn features onto the desert zones of those worlds, possibly the most aggressive notion of extraterrestrial messaging thus far envisioned. To be fair, Cros had a special kind of creative mind, as demonstrated by his proclivity for writing poems such as The Kippered Herring, presaging the absurdist antics of Monty Python by more than a half-century.1

Should any one group of humans be speaking on behalf of the entire species?

By the 1970s, our vastly improved knowledge about the universe and our increasingly complex technology led to more sophistication. Most famously, in 1974, the Arecibo radio observatory in Puerto Rico (that could also transmit as a planetary radar) sent a demonstration message toward a globular cluster of stars about 25,000 light-years away. The act of transmission itself was a bit of a throwaway stunt; the more interesting and rigorous work went into constructing the message: a string of 1,679 bits of clearly non-random, attention-provoking data that could be displayed as an image depicting items like the decimal number system, life’s elemental constituents, the shape of DNA, and a few other tidbits about the human form, and the architecture of our solar system. In this sense the Arecibo message was mostly a Gedankenexperiment, a thought experiment in how we might “ping” an alien species to get noticed.

Most recently, in April, physicist Jonathan Jiang and his colleagues published their idea of “A Beacon in the Galaxy”: an updated binary-code message that could be transmitted toward a star cluster nearer to the Milky Way’s center, to increase the “reach” of the signal to potentially habitable systems.2 The message uses images of 128 by 128 pixels—compact enough to transmit efficiently, but large enough to depict a wealth of information, from our location details to mathematical proofs, biological data, particle physics, and so on.

To fend off concerns about talking to strangers, these scientists suggest that it’s likely for long-lived, technological intelligences to have figured out how to be cooperative and peace-loving, or else they wouldn’t have survived. This rather hopeful sentiment echoes others across the years. However, it’s rooted in our experience as a parochial, planet-bound species. In our world of finite resources, the strategy of cooperation, and even altruism, is indeed often successful—and is seen across individual genetic lineages and between species. But it’s not at all clear that this can apply to life elsewhere.

In truth, all of these laissez-faire approaches to messaging extraterrestrial intelligence, or METI, minimize what could be serious risk factors. The first is whether any one group of humans should be speaking on behalf of the entire species, and the second is whether METI is actually fundamentally dangerous.

That latter risk is the most difficult to assess, in the same way that the possibility of any kind of extraterrestrial communication is incredibly difficult to evaluate because of the array of assumptions that have to be made. Will, for example, intelligences across the universe have any properties in common? Will the pieces of information that we think are universal and recognizable mean anything at all to aliens? We might imagine, like with Pythagoras’ Theorem or Arecibo’s list of atoms and DNA, that some qualities of the world will be discovered by all species technologically capable of hearing our messages. But it’s hardly a given, and what appear to us as dry facts about the natural world could represent wholly different things to an alien, for whom a geometric rule might connote an act of aggression, or a molecular structure might represent a holy relic.

The late Stephen Hawking felt that the biggest concern is not in appearing aggressive, but in attracting aggression. He questioned whether making our presence known isn’t just an invitation for any roaming interstellar species on the lookout for resources to show up ready to consume and conquer. A 2017 paper by Peter Todd and Geoffrey Miller analyzed the possible evolution of extraterrestrial psychologies and concluded3 that sending out hopeful messages to ETs is basically announcing that you live somewhere without competition, in effect saying, “Here is a delectable treat—a home-world with valuable and easy-to-acquire resources, lightly guarded by a gullible young species.”

Ideas can be dangerous, especially meme-like ideas that spread contagiously.

That sentiment can seem a little off-base though. After all, resources like water and metals are abundant in the cosmos. You’d hardly need to raid an inconvenient little planet for any of these things. Maybe though there are more precious, but harder to quantify resources in planetary habitability, and in the wealth of novelty produced by billions of years of natural selection and evolution—these things could be worth traipsing between the stars for.

For others, like the science-fiction author Liu Cixin writing in his trilogy The Three-Body Problem, the danger comes from the “Dark Forest Hypothesis.” This posits that all species want to survive, and if they succeed, they will continuously expand. But our galaxy has finite usable spaces and resources, and it is impossible to obtain real-time knowledge about other species due to the limits of the speed of light. Everyone is intent on their own survival and must assume that by the time they learn of aliens, those aliens may have already developed more capable technology, and greater ambitions. Consequently, the most logical and prudent course of action is to remain silent and try to eliminate any other species that you learn of, before they eliminate you, or before they evolve to a level where they can eliminate you. In other words, keep your head down in the forest, or else.

These are all pretty grim assessments. But there are also hazards from the mere act of communication. In 2014 I wrote in Nautilus about the potential for transmitted information to destabilize and perhaps even destroy a civilization—whether intentionally or unintentionally. Ideas can be dangerous, especially meme-like ideas that spread contagiously and could, in principle, be “weaponized” to destroy just as effectively as a massive fleet of spacecraft.

Nonetheless, the astronomer and SETI expert Jason Wright has pointed out that we tend to fall prey to a “monocultural fallacy” in thinking about alien civilizations when we assume that decisions and actions will be made as one. Clearly that is not true for humans, and messages have gone barreling out into the cosmos because a few people have decided to send them and the rest of our species simply hasn’t cared to notice. If there is any characteristic that is most likely to apply to alien species it may well be this same one; whoever messages us, or hears us, could easily be a few specialists, or obsessives, who may or may not have influence over their civilization.

Perhaps though, in the end, the most decisive factor lies in the stratification of time due to light’s finite speed. This means that all decisions to do with ETs (whoever’s ETs those are) will be based on extrapolation from information that gets more and more outdated with distance. You may have just picked up the “Hello World” (or “MIR”) signal from a distant star, but by now that species could be a bomb-wielding interstellar terror or have been rendered harmless by extinction. If you return a message you simply don’t know what state the recipient will be in when it receives that signal, or what state you will be in if you get a conversational reply. That isn’t just a problem for distances of hundreds of light-years, even a few light-years makes a difference—just consider our own changing conditions between the middle of 2019 and 2022, or between 1938 and 1945.Just like our parental admonition to never talk to strangers, we should think carefully about talking to species when we can’t talk to them in any temporally fixed way, or know how our future selves will deal with this. The Soviet researchers who sent “MIR,” “LENIN,” and “USSR” off into the galaxy couldn’t have known what was coming down the line for their way of life. Perhaps the real risk of messaging extraterrestrials is that no one will ever get to have the conversation they’d like.

Caleb Scharf is the director of astrobiology at Columbia University. His latest book is The Ascent of Information: Books, Bits, Genes, Machines, and Life’s Unending Algorithm. Follow him on Twitter @caleb_scharf.

Lead image: Rytis Bernotas / Shutterstock


1. Bates, S. Revolutionary nonsense: Charles Cros’s Kippered Herring. The French Review 57, 601-606 (1984).

2. Jiang, J.H., et al. A beacon in the galaxy: Updated Arecibo message for potential FAST and SETI projects. arXiv (2022). Retrieved from DOI: 2203.0428

3. Todd, P.M. & Miller, G.F. The evolutionary psychology of extraterrestrial intelligence: Are there universal adaptations in search, aversion, and signaling? Biological Theory 13, 131-141 (2018).