What Is Messaging Extraterrestrial Intelligence (METI)?

The Great Silence and the Human Urge to Answer

For as long as humanity has understood that the stars are suns, we have wrestled with a significant, unanswered question. Our galaxy, the Milky Way, contains hundreds of billions of stars. An increasing number of astronomical surveys suggest that planets are not the exception, but the rule, with billions of them orbiting in the “habitable zones” of their stars, where conditions might be right for liquid water and, just maybe, for life.

Given the sheer age of the universe – some 13.8 billion years – and the fact that our own solar system is a relative newcomer at 4.5 billion years, there should have been ample time for life to emerge, evolve, and perhaps develop intelligence and technology, not just once, but many times over.

This statistical likelihood clashes with a stark and unsettling reality: we see no one. The cosmos is quiet. We have found no artifacts, received no signals, and seen no evidence of any other technological civilization. This contradiction, the gap between the high probability of extraterrestrial intelligence and the total lack of evidence for it, is famously known as the Fermi Paradox.

Physicist Enrico Fermi is said to have first posed the question in 1950 during a casual lunchtime conversation: “Where is everybody?” This simple, four-word query has echoed through scientific and philosophical disciplines for decades. It implies a number of stark possibilities. Perhaps we are, against all statistical odds, truly alone in the galaxy. Perhaps civilizations are common, but they inevitably destroy themselves before they can cross the stars. Perhaps they are common, but we simply lack the technology or the perception to find them. Or perhaps, most chillingly, they are common, but they are all silent, and for a very good reason.

This lack of any contact, this significant celestial quiet, is often referred to as the “Great Silence.” It is the fundamental mystery, the central existential question, that drives the entire field of searching for life beyond Earth.

In response to this silence, humanity has developed two distinct strategies, born from the same family of science but possessing opposite philosophies. They are the yin and yang of our cosmic search: one of patience, the other of action. One is to listen. The other is to shout.

A Tale of Two Strategies: Defining SETI and METI

The human endeavor to find intelligent neighbors is not a single, unified field. It’s a discipline divided by a fundamental, philosophical bright line: should we passively search, or should we actively transmit?

SETI: The Listeners

The more famous, and far less controversial, of the two approaches is SETI, the Search for Extraterrestrial Intelligence. This is the passive endeavor. SETI researchers do not send signals; they listen.

The methodology of SETI involves using advanced technology, primarily massive radio telescopes and, more recently, specialized optical systems, to scan the stars. The goal is to detect signals that are unambiguously artificial. Nature produces a great deal of “noise” in the cosmos, from the steady hiss of the cosmic microwave background radiation to the rhythmic pulses of spinning neutron stars (pulsars). SETI scientists are looking for a signal that stands out from this natural background – for example, a powerful, narrow-band radio signal, or a rapid pulse of laser light, which cannot be easily explained by any known astrophysical phenomenon.

Modern SETI began in 1959, when physicists Giuseppe Cocconi and Philip Morrison published a paper suggesting that a radio search at the 21-centimeter wavelength (the frequency of neutral hydrogen) would be the most logical way for civilizations to communicate. Just one year later, in 1960, the astronomer Frank Drake launched “Project Ozma,” the first-ever radio SETI search, by pointing the Green Bank radio telescope at two nearby stars, Tau Ceti and Epsilon Eridani.

Since then, SETI projects have grown in scope and sophistication. In 1977, a SETI search run by Ohio State University’s “Big Ear” radio telescope detected a powerful, 72-second-long narrow-band signal. The astronomer who found it, Jerry Ehman, famously circled the data on a printout and wrote “Wow!” in the margin. The “Wow! signal” remains the most tantalizing, and enigmatic, potential signal ever detected; it was never seen again.

In recent decades, projects have become far more powerful, from the popular SETI@home distributed computing project that allowed millions of people to donate their home computers’ processing power, to the massive, privately-funded “Breakthrough Listen” initiative, a $100 million, 10-year project to conduct the most comprehensive SETI survey in history.

The core philosophy of SETI can be summed up with a popular analogy. SETI is like a submarine gliding silently through the ocean. Its engines are off, its crew is quiet, and its only mission is to listen with sensitive hydrophones for the ping of another vessel’s sonar or the churn of its propellers. It is an act of pure, patient, passive observation.

METI: The Messengers

If SETI is the listener, METI is the messenger.

METI stands for Messaging Extraterrestrial Intelligence. It is also known, particularly by its critics, as Active SETI. This is the deliberate, active attempt to send messages to potential extraterrestrial civilizations in the hope of eliciting a reply.

The methodology of METI is the inverse of SETI. Instead of just listening, METI projects use powerful transmitters – the same massive radio telescopes that SETI uses to receive, but reversed – to beam high-intensity, structured signals at specific targets. These targets are usually nearby, Sun-like stars or star systems thought to be promising candidates for harboring habitable planets. METI can also take the form of physical messages, artifacts sent into the void with no specific target, but on the infinitesimal chance they might one day be found.

To return to the submarine analogy, METI is not content to just listen. METI turns on its active sonar. It sends a loud, powerful, and intentional “ping” into the dark, cosmic ocean, hoping to hear an echo bounce back from a hidden, unknown object. And just like in submarine warfare, this act of “pinging” is seen by many as a significant, and potentially reckless, gamble. Active sonar immediately reveals your own position, and the assumption is that any submarine commander would only do it if they were either absolutely certain they were alone, or if they were prepared for the fight that might follow.

The very name “METI” is a statement of intent. The terms “Active SETI” and “METI” are often used interchangeably, but the distinction is subtle and important. The term METI was coined in 2006 by the Russian scientist Alexander Zaitsev, one of the field’s most prolific and vocal practitioners.

Zaitsev proposed a philosophical distinction. He argued that “Active SETI” was a term used by SETI (listening) scientists to debate a narrow, technical question: would transmitting a signal help their passive search?

Zaitsev’s “METI,” in contrast, was a grander, more philosophical, and independent mission. He and other proponents viewed the transmission of information into the cosmos as a “pressing need of an advanced civilization.” The goal was not simply to get a reply. The goal was to overcome the Great Silence itself. It was a philosophical imperative to “bring to our extraterrestrial neighbors the long-expected annunciation: ‘You are not alone!'”

This reframes the entire endeavor. It’s not just an experiment. For its proponents, METI is a perceived moral duty, an act of cosmic altruism to end our isolation and, perhaps, the isolation of others.

The SETI Paradox

This philosophical justification for METI is rooted in a simple, but frustrating, logical trap: the SETI Paradox.

The paradox is this: if every civilization in the galaxy, for any number of reasons, comes to the same conclusion – that listening is safe and transmitting is dangerous – then everyone will listen and nobody will transmit. The galaxy could be teeming with intelligent, cautious civilizations, all with their radio telescopes pointed at the sky, but the “Great Silence” would be total and absolute, guaranteed by a universal, shared sense of prudence.

METI proponents point to this paradox as the core justification for their actions. The Great Silence, they argue, may not be a sign that we are alone, but a sign that everyone is shy. It’s a cosmic “wallflower” problem, with everyone at the dance waiting for someone else to be brave enough to ask for the first dance.

In this view, the failure of SETI to find anything is not evidence of absence, but evidence that a passive strategy is flawed. Someone must be the first to speak. Someone must be willing to take the (perceived) risk to break the silence and get the conversation started.

The proponents of METI have, in effect, decided that it may fall to humanity, one of the galaxy’s younger, newer species, to be that first, brave voice.

Bottles in the Cosmic Ocean: Humanity’s Physical Messages

Before humanity developed the power, or the audacity, to send targeted radio “shouts” at nearby stars, we first dipped our toes into the cosmic ocean. We sent “messages in a bottle” – intricate, physical artifacts of our existence, affixed to our first robotic explorers that were destined to leave the solar system forever.

These physical messages represent our earliest, and perhaps most poetic, METI attempts. The evolution of these artifacts, in the short five years between the first and the second, reveals a rapid and significant shift in how humanity’s scientific and cultural leaders thought about the challenge of representing our entire species. The first was a cold, brilliant, scientific diagram. The second was a rich, multi-layered work of art and anthropology.

The Pioneer Plaques (1972 & 1973)

The first of these messages were the Pioneer plaques. Two identical plaques, a pair, were affixed to the antenna struts of the Pioneer 10 and Pioneer 11 spacecraft, launched in 1972 and 1973, respectively. These were historic missions; Pioneer 10 was the first human-built object to fly through the asteroid belt and the first to make a direct observation of Jupiter. More importantly, both spacecraft were on trajectories that would, after their primary missions were complete, see them achieve “escape velocity,” leaving our solar system to coast silently, for millions or billions of years, through interstellar space.

The idea for a message was conceived just months before launch. The plaque was designed in a hurry by a small team, most notably the astronomers Carl Sagan and Frank Drake. The artwork itself was prepared by Sagan’s then-wife, the artist and writer Linda Salzman Sagan.

The artifact is a 6-by-9-inch (15 by 23 cm) gold-anodized aluminum plate. The material was chosen for its durability, with the hope that it could survive for eons in the void, resisting erosion from interstellar dust. The message itself is engraved into this golden plate, a dense pictogram designed to be deciphered by any civilization with a basic understanding of science.

To a non-technical audience, it looks like a complex and abstract line drawing. But to a scientist, it’s a “Rosetta Stone” of information.

• The “Universal Key”: At the very top left is a small, simple diagram depicting two circles connected by a line. This represents the hyperfine transition of a neutral hydrogen atom. Hydrogen is the most common element in the universe. When its electron flips its spin state, it emits a radio wave at a specific, universal frequency (1420 MHz) and wavelength (about 21 centimeters). This diagram is the key to all the other information on the plaque. It provides a universal unit of length (the 21-cm wavelength) and a universal unit of time (its frequency).
• The Human Figures: The plaque’s most famous, and at the time most controversial, feature is the line drawing of a nude human male and female, standing in front of an outline of the spacecraft. The man’s hand is raised in a gesture of peace or greeting. The nudity caused a minor scandal at NASA, but the designers insisted that it was the only way to show our fundamental biology, unadorned by any single, and potentially confusing, culture’s clothing.
• The Scale: The silhouette of the Pioneer spacecraft behind the figures is not just for decoration. A small binary marker on the side indicates the height of the woman, which can be compared to the spacecraft to give a sense of scale for both the humans and their creation.
• The “Return Address”: The large, star-like pattern radiating from a central point is the most complex piece of information. This is a pulsar map, a “return address” for Earth. The central point is our Sun. The 14 radiating lines point to the locations of 14 known pulsars. The long binary numbers on each line represent the unique “spin” frequency of that pulsar. Since pulsars’ spin rates slow down at a very predictable rate, a recipient civilization could use this “cosmic clock” to do two things. First, by triangulating the positions of these 14 pulsars, they could pinpoint the map’s origin: our Sun. Second, by comparing the plaque’s frequencies to the current frequencies of the pulsars, they could calculate precisely how long ago the spacecraft was launched.
• The Solar System: At the bottom of the plaque is a simple, schematic map of our Solar System, showing the Sun and its planets. A small icon of the spacecraft is shown with a trajectory originating from the third planet – Earth – and swinging past the fifth planet, Jupiter, on its way out.

The Pioneer plaque was a remarkable achievement, a scientific “hello” designed to be understood by a non-human mind. It was a message from scientists to scientists.

The Voyager Golden Records (1977)

Just five years later, humanity was preparing to launch its next, and most ambitious, robotic explorers of the outer solar system: the Voyager 1 and 2 spacecraft. Launched in 1977, both of these probes were also destined for interstellar space. Having learned from the Pioneer experience, NASA approved a far more ambitious “time capsule.”

Instead of a small, engraved plaque, the Voyagers would carry a 12-inch, gold-plated copper phonograph record. These were the “Voyager Golden Records,” and they were curated by a committee, again chaired by Carl Sagan. The records were designed not just to say “who we are” in biological terms, but to capture the full, rich, and complex tapestry of life and culture on Earth.

Each record was sealed in a protective aluminum jacket. The cover of this jacket is, itself, part of the message. It’s a user’s manual for an alien. Etched onto the cover are instructions, in symbolic language, explaining that the record is a time capsule from a distant world. It shows a diagram of a stylus and a record, indicating how it is to be played. It specifies the correct playback speed using the same universal “hydrogen transition” time unit from the Pioneer plaque. It also includes instructions on how to decode the 116 images that are encoded as audio signals on the record, and it repeats the Pioneer plaque’s pulsar map, our “return address.”

The contents of the record are a staggering portrait of a planet.

• Spoken Greetings: The record begins with 55 spoken greetings in different languages. These range from ancient languages like Akkadian (spoken in Sumer 5,000 years ago) and Ancient Greek, to a wide swath of modern languages. The English greeting, recorded by Sagan’s son, says, “Hello from the children of planet Earth.” Another English message, from the U.S., states, “we step out of our solar system into the universe seeking only peace and friendship, to teach if we are called upon, to be taught if we are fortunate.”
• Sounds of Earth: The greetings are followed by a 12-minute audio collage of “The Sounds of Earth.” This is a sound-portrait of our planet, including natural sounds like wind, rain, thunder, surf, the songs of birds, and the calls of whales. It also includes human-made sounds: a train, a car, a steam engine, a rocket launch, and human sounds like footsteps, laughter, and the cry of a baby.
• Music: The vast majority of the record – nearly 90 minutes – is given over to music, a selection intended to showcase global cultural diversity and emotional depth. It is an eclectic and beautiful mix, including Bach’s “Brangdenburg Concerto No. 2,” Igor Stravinsky’s “Rite of Spring,” and “Melancholy Blues” by Louis Armstrong. Alongside these Western classics are traditional and folk pieces from around the world, including music from Peru, Senegal, China, and Azerbaijan.
• Images: As mentioned, the record also contains 116 images (some sources say 115), encoded in analog audio signals. The cover provides the key to re-assembling these signals into pictures. These images are a visual encyclopedia of our world. They include scientific diagrams of our solar system, our planet’s composition, and the structure of DNA. They show pictures of our architecture (the Taj Mahal, the Sydney Opera House), scenes of nature, and images of people from different cultures, eating, farming, and running.
• Printed Messages: Finally, the record’s “run-out groove” (the blank space in the center) contains an engraved message. It also contains the audio of printed messages from U.S. President Jimmy Carter and U.N. Secretary-General Kurt Waldheim. President Carter’s message captures the hopeful, and somewhat lonely, spirit of the entire project: “This is a present from a small, distant world, a token of our sounds, our science, our images, our music, our thoughts, and our feelings. We are attempting to survive our time so we may live into yours.”

The Voyager Golden Records, unlike their Pioneer predecessors, are not just messages. They are memorials. The designers were keenly aware that these records would likely survive for a billion years, long after our planet and our species might be gone. They are a time capsule, a final “message in a bottle” from a species that had learned to explore the cosmos and, in doing so, had learned to see itself as a single, complex, and beautiful whole.

Humanity’s Radio Calls: The Intentional Broadcasts

While the Pioneer and Voyager artifacts drift silently through the interstellar dark, with only the slimmest chance of ever being found, the true METI debate centers on a far more direct approach: the intentional, high-power radio broadcast. These are humanity’s “shouts,” aimed at specific star systems, designed to be detected, and sent in the explicit hope of a reply.

This effort began not as a hopeful call to the cosmos, but as a technological byproduct of the Cold War.

The Morse Message (1962): A Cold War Whisper

The very first intentional radio message sent into space by humans was the “Morse Message,” broadcast in November 1962. It was not a serious attempt to contact aliens.

The sender was the Soviet Union, using its powerful new Yevpatoria Planetary Radar (EPR) in Crimea. The target was the planet Venus. The content of the message was a simple series of radio pulses in Morse code, which, when translated, spelled out three words in Russian: “MIR” (a word which famously means both “Peace” and “World”), “LENIN,” and “USSR.” A few days later, a second transmission was sent.

The stated purpose of this transmission had nothing to do with extraterrestrials. It was, first and foremost, a technical test of the powerful new radar system. By bouncing a signal off the surface of Venus and timing its return (which it did, in about 4.5 minutes), Soviet engineers were demonstrating their radar’s capability and gathering data.

But its second purpose was pure propaganda. At the height of the Cold War, just after the Cuban Missile Crisis, this was a potent demonstration of the Soviet Union’s technological and scientific prowess, a clear signal to its rivals on Earth, not to any potential neighbors on Venus.

However, a radar-strength radio wave doesn’t just stop. After reflecting off Venus, the signal continued, traveling at the speed of light, out of our solar system and into deep space. In its current-day transit, it is on its way toward the star HD 131336. The Morse Message thus became the first accidental interstellar radio transmission, a broadcast of nationalist pride that became, by default, humanity’s first “hello” to the wider galaxy.

The Arecibo Message (1974): The First True Beacon

The most famous and widely recognized METI broadcast is, without question, the Arecibo Message. It was transmitted on a single day: November 16, 1974.

The sender was the 1,000-foot (305-meter) Arecibo Telescope in Puerto Rico, at the time the largest and most powerful radio telescope in the world. The occasion was a ceremony to celebrate a major upgrade and remodeling of the telescope, which had just been given a new, more accurate surface and a powerful transmitter for radar astronomy.

Much like the Morse Message, the Arecibo Message was not a serious attempt to start an interstellar conversation. Its designers, a team from Cornell University that included Frank Drake and Carl Sagan, conceived it as a “demonstration of human technological achievement.” It was a symbolic act, a dedication ceremony for a new scientific instrument, not the opening salvo of a diplomatic exchange.

This symbolic, rather than practical, nature is proven by its target: Messier 13, or M13. M13 is not a single star, but a globular cluster – a dense, spherical collection of several hundred thousand old stars. The choice was almost “photogenic.” M13 was a large, impressive-looking collection of stars that happened to be available in the sky at the time and place of the ceremony.

The important fact is its distance. M13 is approximately 25,000 light-years away. This means the Arecibo Message, traveling at the speed of light, will take 25,000 years just to arrive. If any civilization there detects it, decodes it, and sends a reply, that reply will take another 25,000 years to get back to us. The total round-trip time is 50,000 years. The designers knew, of course, that no one involved in the project, nor their children, nor their civilization in its current form, would be around to hear the answer. It was a gesture.

The technology of the message was simple but powerful. It was broadcast a single time via frequency-modulated radio waves at a frequency of 2,380 MHz. The entire transmission, which contained the most complex message ever designed by humans for an extraterrestrial audience, lasted less than three minutes.

The message itself consisted of 1,679 binary digits, or “bits” (1s and 0s). This number was chosen with great care. 1,679 is a “semiprime” – a number that is the product of only two prime numbers, in this case, 23 and 73. This was the puzzle key. The designers reasoned that any intelligent civilization would recognize this and deduce that the 1,679 bits were not meant to be read as a single stream, but should be arranged in a rectangular grid. The only options are 23 rows by 73 columns, or 73 rows by 23 columns. One arrangement (73×23) produces meaningless static. The other (23×73) forms a simple pictogram.

The pictogram, when decoded, is a story of humanity, told from the top down:

1. Numbers: The first section, at the very top, is a binary representation of the numbers one through ten. This is a primer, establishing a basic counting system.
2. The Elements of Life: The next block depicts the atomic numbers for five elements, again in binary: Hydrogen (1), Carbon (6), Nitrogen (7), Oxygen (8), and Phosphorus (15). These are the five key chemical components of Deoxyribonucleic Acid (DNA).
3. DNA Nucleotides: The third section is a more complex block of chemical formulas, representing the sugars and bases that make up the nucleotides of DNA.
4. The Double Helix: Below the formulas is a simple, blocky graphic of the DNA double helix structure. In the center of the helix is a binary number (around 4.3 billion, the 1974 estimate) representing the number of base pairs in the human genome.
5. Humanity: The central and most prominent part of the message is a simple stick-figure graphic of a human. To its left, a binary number indicates the average male height. To its right, a binary number indicates the human population of Earth at the time (approximately 4 billion).
6. The Solar System: Below the human is a graphic of our Solar System, with the Sun on the left and the planets in order, (including Pluto, which was considered a planet at the time). To indicate our home, the third planet, Earth, is raised slightly out of line, sitting directly beneath the human figure.
7. The Sender: The final, bottom-most section is a graphic of the Arecibo radio telescope itself, with a binary number indicating its diameter.

The Arecibo Message was a brilliant, self-contained summary of our science, our biology, and our location.

The Yevpatoria Transmissions: Russia’s Cosmic Calls

If the Morse and Arecibo messages were symbolic acts, the series of transmissions that began in 1999 from the same Yevpatoria RT-70 radio telescope in Crimea were something new. These were the first sustained, serious METI projects, explicitly designed to get a reply.

After the fall of the Soviet Union, the Yevpatoria facility, now under Ukrainian control but operated with Russian collaboration, became the workhorse for METI. It was one of only two telescopes in the world with a transmitter powerful enough for the task. The projects were largely spearheaded by Russian radio astronomer Alexander Zaitsev, the man who coined the term “METI.”

These transmissions trace a fascinating evolution: from a message designed by scientists, to one designed by children, to one designed by a social media company.

• Cosmic Call 1 (1999): In May and June of 1999, Zaitsev and his team sent the first “Cosmic Call.” It was a multi-part, high-information-density message, transmitted over several days to four nearby, Sun-like stars, including 16 Cygni A, which is about 69 light-Cyears away. The message content included a highly robust, noise-resistant “Rosetta Stone” (known as the Dutil-Dumas Message) designed to teach basic math and physics, a copy of the Arecibo Message, and a variety of text, images, and other data.
• Teen Age Message (2001): This was perhaps the most unique transmission. Sent in August and September 2001, it was targeted at six Sun-like stars, including 47 Ursae Majoris (about 46 light-years away). The message had three parts. The first was a scientific “Rosetta Stone.” The second was a “logotype” of the message. The third, and largest, part was composed by teens from different parts of Russia. This was also the first musical interstellar radio message, as it included a digital recording of the “First Theremin Concert for Extraterrestrials,” performed on the eerie, wave-form-based electronic instrument. This marked a clear shift from sending only “science” to sending “culture” and “art.”
• Cosmic Call 2 (2003): In July 2003, a second, upgraded Cosmic Call was sent. This was targeted at five nearby stars, including 55 Cancri (about 41 light-years away). The message was an update of the first. It featured a modernized, corrected version of the scientific “Rosetta Stone,” another copy of the Arecibo Message, a “Bilingual Image Glossary,” and a large section (220 megabytes) for public messages from anyone who had contributed to the project.
• A Message from Earth (AMFE) (2008): This 2008 project completed the evolution from scientific to commercial. Sent on October 9, 2008, AMFE was aimed at the Gliese 581 system, a red dwarf star (about 20.4 light-years away) known to host exoplanets. The content of this message was a “digital time capsule” containing 501 messages. These messages were not chosen by scientists; they were the winners of a competition on the social networking site Bebo.

In the 2010s and 2020s, the METI debate has become formalized, with dedicated organizations, ambitious new project proposals, and high-profile commercial ventures that have tested the public’s appetite for interstellar communication.

METI International and the “Active” Proponents

For many years, METI was a scattered effort conducted by a few individuals. This changed in July 2015 with the founding of METI International, a non-profit research and educational organization based in San Francisco.

Its founder is Dr. Douglas Vakoch, an astrobiologist, psychologist, and one of the world’s most prominent and steadfast proponents of METI. Vakoch was formerly a director at the SETI Institute, but he parted ways to create an organization that would be dedicated to the “active” side of the search.

The stated mission of METI International is to conduct scientific research into both METI and SETI, to promote international cooperation, and to “foster multidisciplinary research on the design and transmission of interstellar messages,” bringing together scientists, social scientists, humanities scholars, and artists. The organization also runs a passive optical SETI search, looking for laser pulses from an observatory in Panama.

METI International is one of the few groups in the world actively conducting transmissions. In 2018, in collaboration with the Sónar music festival, the organization sent a message called “Sónar Calling.” The transmission, which included music and scientific tutorials, was beamed from an antenna in Norway toward GJ 273b, a potentially habitable “super-Earth” exoplanet orbiting a nearby red dwarf star. The organization has also announced future plans to transmit a message to the famous TRAPPIST-1 system, which is home to seven Earth-sized planets.

The Rise and Fall of Lone Signal (2013)

Before METI International was founded, a high-profile commercial venture sought to bring METI to the masses – and turn it into a business. This was the “Lone Signal” project, which launched with a great deal of media fanfare in June 2013.

The project was founded by businessman Pierre Fabre and a team of entrepreneurs. They leased time on the historic Jamesburg Earth Station, a massive 30-meter radio dish in Carmel, California. The plan was to create the first continuous METI signal, a persistent beacon that would be “always on.”

The target was the red dwarf star Gliese 526, located 17.6 light-years away. The model was “freemium.” The transmission beam was composed of two parts. The first was a “hailing message,” a “Rosetta Stone” designed by scientists on the team to teach a potential recipient about our math and physics. The second, and much larger, part was a “user stream.”

This user stream was crowdfunded. Anyone on Earth could go to the Lone Signal website and send one 144-character text message to Gliese 526 for free. Subsequent messages, or the ability to send photos, would cost a fee, starting at 25 cents. The project was, in effect, a “Twitter-to-the-stars” service.

The project was a complete failure. Despite its media launch, it failed to secure the necessary funding. It began operations on June 17, 2013, and ceased transmissions just a few months later, in August 2013.

Lone Signal stands as a important cautionary tale. It demonstrates that while there is a flicker of public curiosity, a for-profit, commercial model is likely unsustainable for an endeavor that has no hope of a tangible return on investment for decades, or even centuries. It also pushed the “Who Speaks for Earth?” debate to its logical, and perhaps absurd, extreme: for a few months in 2013, anyone with an internet connection and a quarter could, in theory, speak for all of humanity.

Breakthrough Message: A Competition, Not a Transmission

A project that is frequently confused with METI, but is in fact its philosophical opposite, is the “Breakthrough Message.”

This is one component of the “Breakthrough Initiatives,” a $100 million suite of astronomical research programs launched in 2015 by philanthropist Yuri Milner and, in its initial announcement, physicist Stephen Hawking. The “Breakthrough Listen” component is the massive SETI search. “Breakthrough Starshot” is a research program to develop “nanocraft” for interstellar travel.

The “Breakthrough Message” component is a $1 million competition. It is not a transmission. The initiative created a prize pool to design a digital message that would be “representative of humanity and planet Earth.”

This project is a brilliant and strategic move, a direct response to the METI controversy. The program includes an explicit and important pledge: “not to transmit any message until there has been a wide-ranging debate at high levels of science and politics on the risks and rewards of contacting advanced civilizations.”

Breakthrough Message is not METI. It is a prompt for the very global conversation about METI that critics had been demanding for years. It turns the act of message design into the experiment itself, sparking public debate and scholarly thought without taking on any of the perceived risks of actually pressing “send.”

As of 2025, no competition winner has been announced and no message has been sent, in keeping with this pledge. A related project, Breakthrough Starshot, was reported in September 2025 to be on hold indefinitely, having spent only a fraction of its proposed budget.

Beacon in the Galaxy (BITG): A Proposed Successor to Arecibo

Another modern METI project is the “Beacon in the Galaxy” (BITG). It is important to be clear: this is a proposal, not a funded or executed project. It was published in 2022 as a non-peer-reviewed academic paper by a team of scientists led by Jonathan Jiang of NASA’s Jet Propulsion Laboratory (JPL).

This is not an official NASA project. The researchers designed the message and published their paper to propose it to the scientific community, but the message has not been transmitted.

The BITG is designed to be a successor to the 1974 Arecibo Message. It is a far more advanced, high-density binary message, created with 50 years of new knowledge. Its contents include:

• Basic mathematical and physical concepts to establish a common language.
• The biochemical composition of life on Earth.
• More detailed, digitized images of a male and female human figure (this time, both waving).
• A map of Earth’s surface, showing the continents and oceans.
• A “timestamp” of when the message was sent. This is a clever piece of science, measuring the time elapsed since the Big Bang in terms of the universal “hydrogen spin-flip” clock, to give the message a cosmic context.
• A direct invitation to reply.

The authors proposed a different targeting strategy. Instead of a single cluster like M13, they suggested aiming the message at a “concentric ring” in the Milky Way, about 13,000 light-years from the galactic center, a region they calculated as a high-probability zone for the emergence of intelligent life.

To send this powerful new message, they proposed using one of the new generation of massive telescopes, such as China’s 500-meter Aperture Spherical Telescope (FAST) or the SETI Institute’s Allen Telescope Array in California.

The Fates of the Great Transmitters

The modern METI debate is, for the moment, partially muted by a stark and poignant reality: its most important historical tools have been lost, silenced not by cosmic forces, but by terrestrial ones.

The Arecibo Telescope, the iconic instrument that sent the 1974 message and served as a premier tool for astronomy and planetary defense for over 50 years, is gone. After suffering a series of structural failures, the 900-ton instrument platform suspended above the 1,000-foot dish collapsed catastrophically on December 1, 2020, completely destroying the telescope. Its loss was due to the simple, relentless pull of gravity on a decaying structure.

The Yevpatoria RT-70 radio telescope, the workhorse of the Morse Message, the Cosmic Calls, the Teen Age Message, and A Message from Earth, is also gone. Its fate is a significant and tragic irony. After Russia’s 2014 annexation of Crimea, the scientific facility was seized and “modernized for military use.” It was integrated into Russia’s GLONASS satellite navigation system, its powerful transmitter repurposed to improve the accuracy of the military’s global positioning network.

In August 2025, during the Russo-Ukrainian War, the telescope was targeted by a Ukrainian drone. The facility, once a symbol of humanity’s outward, peaceful, and scientific gaze toward other worlds, had been turned into a military asset. It became a legitimate target in a terrestrial conflict. The destruction of the Yevpatoria radar silenced one of humanity’s loudest voices, not by an alien threat, but by our own, all-too-human capacity for conflict.

The Case for Contact: Arguments for METI

The decision to transmit is not taken lightly. Proponents of METI offer a range of powerful arguments, from the highly technical and practical to the deeply philosophical, to justify their belief that shouting at the stars is not only a reasonable, but a necessary, next step for our species.

“It’s Too Late to Hide”

This is the most common and, for many, the most compelling argument in favor of METI. It is championed by figures like Douglas Vakoch, and its logic is simple: we can’t hide, so we shouldn’t try.

The argument states that humanity has been unintentionally and unavoidably broadcasting its presence into the cosmos for over a century. Ever since the advent of powerful radio and, later, television broadcast transmitters in the early 20th century, a “bubble” of signals has been expanding from Earth at the speed of light.

These “accidental” signals, often called “leakage radiation,” have been streaming out into space. Proponents argue that any civilization with technology even slightly more advanced than our own could easily detect this. They paint a vivid picture of alien receivers picking up broadcasts of I Love Lucy, the 1936 Berlin Olympics, or the static from countless military and civilian radio communications.

From this perspective, any civilization advanced enough to pose an interstellar threat – one capable of crossing the vast distances between stars to do us harm – is already advanced enough to have detected this leakage. They already know we are here.

Furthermore, this leakage isn’t our only “technosignature.” An advanced civilization wouldn’t even need to detect our radio signals. They could infer our presence by other means. They could, for instance, analyze the chemical composition of our atmosphere from a great distance. The presence of pollutants like nitrogen dioxide, or the specific combination of gases like oxygen and methane, would be a strong tell-tale sign of an industrial, and possibly biological, civilization. They might even be able to detect the faint, artificial glow of our city lights on the night side of the planet.

The conclusion is that “the cat is already out of the bag.” We cannot put this genie back in the bottle; our presence is already known.

Given this, proponents argue, our best strategy is to engage. Hiding in our corner of the universe is a futile gesture. Instead, we should take control of the conversation. A deliberate, powerful, information-rich METI message is not a reckless shout; it’s a sign of confidence and maturity. It’s an attempt to manage first contact on our own terms, to introduce ourselves properly. As Vakoch has put it, if a potentially hostile civilization is already on its way, “it’s to our advantage to engage them and show them that we make better conversational partners than lunch.”

The Great “Leakage” Debate

The “it’s too late to hide” argument is powerful, but it rests on a massive, and highly debatable, technical assumption: that our leakage is actually detectable. Many scientists, including many who oppose METI, argue that this assumption is deeply flawed.

This is the “Great Leakage Debate.” The rebuttal states that proponents of METI overestimate the detectability of our accidental signals. Early, high-power television and radio broadcasts were “loud,” but modern communications have become quieter and more efficient. Much of our data now travels through fiber-optic cables, which leak no signals at all. Our digital and mobile phone transmissions are high-frequency but relatively low-power and diffuse.

The key scientific argument is that these jumbled, incoherent signals become indistinguishable from the natural cosmic background “noise” at a surprisingly short distance. A signal’s strength decreases by the square of the distance it travels. This means that a broadcast that is perfectly clear on Earth becomes an impossibly faint whisper just a few light-years away.

Critics have done the math. For an alien civilization to detect a signal like I Love Lucy from a star system a few hundred light-years away, they would need to build a radio telescope “antenna array the size of Chicago” or “Nebraska.” While not impossible, it suggests they would have to be looking for us specifically, and with an enormous investment of resources.

The only accidental leakage that is likely detectable at significant interstellar distances is not our TV shows, but our most powerful, narrow-band transmissions. These are, almost exclusively, military and planetary radar systems. Powerful ballistic missile early-warning systems, for example, sweep the skies with focused beams that are, for an instant, brighter than the Sun at their specific frequency.

This technical nuance changes the entire debate. Critics of METI argue that the “barn door” is not wide open; it’s barely ajar. Our general, incoherent leakage is like a faint, jumbled murmur in a crowded stadium. An intentional METI broadcast, by contrast, is a focused, high-power, narrow-band signal specifically designed to be detected.

It is the difference between being an anonymous face in a crowd and standing up on a chair and firing a flare gun into the air. One might be noticed; the other will be.

The Altruism Argument and the “SETI Paradox”

The “leakage debate” is technical. The other main arguments for METI are deeply philosophical.

The first is the direct assault on the SETI Paradox. As previously mentioned, this is the idea that if everyone just listens, the silence is guaranteed. METI proponents argue that this is a “cosmic tragedy of the commons.” They ask, what if we want to find other civilizations? What if they want to be found? We cannot, in good conscience, rely on a strategy (passive SETI) that would fail if everyone else adopted it too.

This position assumes that other advanced civilizations may also be listening, patiently waiting for new, young species like ours to “pass the test” and signal their existence, thereby showing they have achieved a certain level of technological and, perhaps, social maturity.

This leads to the second, more significant philosophical argument: the “moral imperative.” Proponents like Alexander Zaitsev have argued that transmission is a “pressing need,” a duty of an advanced civilization. It is an act of cosmic altruism. If we believe that knowledge, art, and connection are good, then sharing our existence with the cosmos is a moral positive. We are, in this view, breaking the silence not just for ourselves, but for the benefit of all other lonely species who may be out there, listening and wondering if they, too, are alone.

Douglas Vakoch adds a final, pragmatic twist to this. He argues that passive SETI is active METI in disguise, whether we admit it or not. He asks us to imagine a future where the SETI search succeeds. What happens, he asks, the day after the New York Times runs the headline, “We Are Not Alone: Confirmed Signal Received from Gliese 581”?

Vakoch argues that “there’s no way to prevent a cacophony of responses from Earth.” Every person, every nation, every corporation with a transmitter would be scrambling to send a reply. The result would be a chaotic, uncontrolled, and contradictory flood of signals.

In this view, it is far better to plan for and manage that “reply” now, with a coordinated, thoughtful, and globally-endorsed message before we are under the pressure of a confirmed detection. Conducting METI now is, in effect, a responsible first step in a process that is, perhaps, inevitable.

The Case for Silence: Arguments Against METI

The opposition to METI is not born from a lack of curiosity. It is born from a objective assessment of risk, a deep skepticism of altruism, and a significant respect for the unknown. The arguments against “shouting” are not just scientific; they are rooted in game theory, evolutionary biology, human history, and pure, unadulterated ethics.

The Dark Forest Hypothesis

This is, by far, the most compelling and chilling argument against METI. It’s an idea that, once heard, is difficult to forget. The “Dark Forest hypothesis” is one of the most powerful proposed solutions to the Fermi Paradox, and it frames METI not as a hopeful act, but as an act of existential suicide.

The name comes from a 2008 science fiction novel, The Dark Forest, by Chinese author Liu Cixin. But the concept is taken very seriously in scientific and policy debates.

The hypothesis states that the universe is a “dark forest.” Every civilization is an “armed hunter,” stalking silently through the trees. Each hunter is doing their best to stay alive, and they are all, by necessity, paranoid.

This paranoia is built on a few, simple, terrifyingly logical axioms:

1. The Primary Goal is Survival: The first and most important goal of any civilization is to ensure its own survival.
2. Intentions are Unknowable: It is impossible to know, with 100% certainty, the intentions of another civilization. They may be peaceful, or they may be predatory. And even if they are peaceful now, it is impossible to know if they will remain peaceful.
3. Resources are Finite: Any civilization that wishes to expand will eventually require more resources, putting it in direct competition with other expanding civilizations.
4. Technology is Exponential: A species that is 100 years behind you today could, through a single breakthrough, be 1,000 years ahead of you tomorrow. You cannot gauge a species’ threat level by its current state; you must assume it is a potential future threat.
5. Distance is a Barrier: The vast distances of interstellar space, and the limitation of the speed of light, make real-time communication, negotiation, or de-escalation impossible. A “hello” message from a star 50 light-years away means that, by the time you receive it, the senders are already 50 years more advanced than when they sent it.

Given these axioms, there is only one logically safe-guarded action. If you, a silent hunter in the dark forest, detect another civilization – another hunter that has just stumbled and made a noise – you must preemptively destroy it. You cannot wait to find out its intentions. You cannot risk it becoming more powerful than you. You must eliminate the potential threat while you still can, to guarantee your own survival.

Any civilization that is foolish, naive, or arrogant enough to reveal its location is, by definition, a civilization that does not understand the rules of the forest. And it will be quickly silenced by the “hunters” who do.

The “Great Silence” of the Fermi Paradox, in this model, is not because we are alone. It’s because the “forest” is full of silent, paranoid, and highly competent hunters, and all the “loud” civilizations have been eliminated, one by one.

The implication for METI is stark. It is not a flare gun in the dark. It is a naive and suicidal scream that says, “I’m here, I’m a potential future threat, and I don’t know the rules!” This is why prominent scientists, including the late Stephen Hawking, have strongly and publicly criticized METI as significantly unwise, comparing it to the first contact between indigenous populations and more technologically advanced European explorers – an encounter that was, almost universally, a catastrophe for the less advanced culture.

The Berserker Hypothesis

A related, but distinct, risk scenario is the “Berserker” or “deadly probes” hypothesis. This, too, is a proposed solution to the Fermi Paradox.

The “Great Silence” exists, this hypothesis suggests, because the galaxy has already been “sterilized,” or is in the process of being sterilized, by an ancient, automated, and malevolent system.

The concept is based on the idea of “Von Neumann probes” – self-replicating, autonomous machines. A civilization could, in theory, build a “seeder” probe and launch it at a nearby star. When it arrives, it uses the raw materials of that system (asteroids, moons) to build copies of itself, which then launch to other stars. In a relatively short time (on a cosmic scale), the entire galaxy could be populated by these probes.

The Berserker hypothesis argues that an advanced civilization, perhaps one that is now long-dead, did exactly this. But for some reason – either by malicious design, or by a “coding” error that caused them to “go berserk” – these self-replicating probes are programmed with one, simple command: seek out any emerging technological civilization and destroy it.

This hypothesis is, as astronomer David Brin summarized in 1983, “entirely compatible with all the facts.” It explains the Fermi Paradox perfectly. The reason we haven’t heard any radio traffic from other civilizations is because “all were killed shortly after discovering radio.”

In this scenario, a powerful, intentional METI broadcast is not just a flare gun. It’s a beacon. It’s an automated trip-wire that will actively summon a pre-programmed, galaxy-wide sterilization system to our doorstep, a system that has been patiently waiting for a new civilization to get “loud” enough to detect.

The Asymmetry of Risk

The Dark Forest and Berserker hypotheses are speculative, though logical. The final, and most practical, argument against METI is not speculative at all. It is a simple, cold, ethical calculation based on risk management.

The METI debate, critics argue, is defined by a significant and dangerous “asymmetry of risk.”

The potential benefit of METI is finite. If we make contact with a friendly, advanced civilization, the upside is enormous. We might gain new knowledge – solutions to disease, new physics, new energy sources. We might gain a new philosophical perspective. We might end our cosmic loneliness. These are all tremendous, but ultimately finite, benefits.

The potential risk of METI is absolute. If we make contact with a hostile, or even just indifferent and careless, civilization, the downside is the total, irreversible extinction of our species. It could also mean colonization, enslavement, or the introduction of a pathogen (biological or digital) that wipes out our biosphere. The risk is, in a word, existential.

Because the potential risk is absolute and the potential benefit is finite, critics argue that no one – no individual scientist, no non-profit organization, no single corporation, no one nation – has the ethical right to take that gamble on behalf of all 8 billion people on the planet, let alone all future, unborn generations.

Before we “shout,” they argue, we must have a global consensus. And given the stakes, the only responsible action is silence.

Who Speaks for Earth? The Governance Vacuum

The METI debate is not just scientific (is it safe?) or philosophical (should we do it?). It is, perhaps most urgently, political: who gets to decide?

The answer, disturbingly, is no one. And everyone.

A Planet of Uncoordinated Voices

The central problem of METI is that there is no international body with the mandate or authority to regulate it. There are no legally binding international agreements that specifically address the sending of messages to other worlds.

The 1967 Outer Space Treaty, the foundational document for all space law, is the closest thing we have. It mandates that space exploration should be for the benefit of all countries and requires “international cooperation.” But it is completely silent on the issue of interstellar transmissions. It was written in an era when this was pure science fiction.

This “regulatory vacuum” creates a “Wild West” reality. Any individual, any private corporation, or any nation with access to a sufficiently powerful transmitter can, unilaterally, decide to send any message they want. The team behind the Bebo social network, when they sent their “A Message from Earth,” did not hold a global referendum. The commercial venture Doritos, which once broadcast an advertisement toward a star system, did not ask for permission.

This is the “Who Speaks for Earth?” problem. And right now, the answer is: whoever has the money and the technology.

The 2015 Statement: A Call for Debate

This long-simmering academic debate “went public” and became a true schism in 2015.

The schism was catalyzed by a key event. As internal reports suggest, when Douglas Vakoch proposed that the SETI Institute should begin high-power, active transmissions, the institute (which is dedicated to listening) rejected the proposal. In response, Vakoch left and founded METI International, a new organization explicitly created to do the very thing the SETI Institute had refused.

This “going rogue” by a new, active organization “fearing a gathering storm,” as one paper put it, forced the scientific community to respond. At a meeting of the American Association for the Advancement of Science (AAAS) in 2015, a group of prominent scientists and thinkers (including SETI scientists and astronomers) signed a public statement.

This statement was not a call for a ban. It was a call for a pause. It explicitly recommended that a “worldwide scientific, political and humanitarian discussion… [be held] before any message is sent.” It was a public plea to the new METI organizations to stop, to think, and to wait for a global consensus before “shouting” on behalf of a planet that had not consented.

Protocols for Receiving, Not for Sending

The true absurdity of the regulatory gap is illustrated by one simple fact: we have detailed, internationally-debated protocols for receiving signals, but absolutely none for sending them.

The scientific community, particularly the International Academy of Astronautics (IAA), has for decades maintained a “Post-Detection Protocol” (PDP). This is a detailed set of guidelines and principles for what to do if we receive a confirmed signal from an extraterrestrial intelligence.

The PDP is a objective, thoughtful document. It outlines a process for:

1. Verifying the signal (is it really alien?).
2. Announcing the discovery to the public, the scientific community, and the United Nations in atransparent and open manner.
3. Protecting the radio frequencies of the signal.
4. Consulting internationally before sending any reply.

But this protocol has a giant, glaring loophole: it only applies to passive SETI, not to METI. It outlines the rules for what to do when we hear a signal, but it is explicitly silent on the act of transmitting.

This is the core governance failure, what one sociologist has called “organized irresponsibility.”

Humanity has, in effect, a detailed, internationally-agreed-upon fire drill for what to do when we hear the smoke alarm. We have procedures. We have scientific scales to rate the fire’s importance (like the Rio and San Marino scales). We have a plan to call the “fire department” (the U.N.).

But we have no rules whatsoever about who is allowed to play with matches. The very act of starting the “fire” that would trigger all these protocols – the act of sending the first message – is completely, and dangerously, unregulated.

Summary

The act of Messaging Extraterrestrial Intelligence is one of humanity’s most ambitious, provocative, and controversial undertakings. It is born from a significant, perhaps uniquely human, desire to connect, to end our cosmic isolation, and to “overcome the Great Silence” that echoes from the stars.

The history of METI is a story of this desire. It is a story told through the physical artifacts we have sent, “bottles” drifting in the cosmic ocean, which themselves show an evolution from a cold, scientific diagram (the Pioneer plaques) to a rich, multi-cultural tapestry of art, music, and biology (the Voyager records).

It’s a story of radio “shouts” that evolved from a whisper of Cold War propaganda (the Morse Message), to a powerful symbolic demonstration (the Arecibo Message), and finally to a sustained, public, and even commercial enterprise, with messages crafted by scientists, by teenagers, and by users of a social media site (the Yevpatoria transmissions, Lone Signal).

But this desire to be heard is shadowed by an equally significant and unquantifiable risk. The METI debate pits two irreconcilable worldviews against each other.

On one side are the proponents, who argue that it’s already “too late to hide,” that our century of accidental radio leakage has already given us away. They believe an intentional, thoughtful message is our best chance to manage a first contact that is already inevitable. Or, they argue, we must be the ones to break the “SETI Paradox,” lest the entire galaxy remain silent forever.

On the other side are the critics, who warn that we are firing a flare gun in a “dark forest” we do not understand. They caution that in a universe where the only goal is survival, and the intentions of others can never be known, the only safe move is silence. They point to chilling scenarios like the “Berserker” hypothesis, where a message might not summon a friend, but an ancient, automated sterilization system. For them, the potential risk – absolute extinction – is so great that no one has the ethical right to take that gamble on behalf of the entire planet.

This debate, for decades a quiet academic disagreement, now rages in a dangerous vacuum. There is no law, no treaty, and no international body that governs this activity. We have detailed protocols for what to do if we are contacted, but none for the act of contacting. Today, any individual or organization with a powerful transmitter can choose to speak for Earth.

The question of whether we should “shout at the stars” remains one of the most significant and unresolved questions of our time. And for now, with the tragic, physical collapse of the Arecibo telescope and the wartime destruction of the Yevpatoria radar, the two loudest voices in this debate have been silenced – not by any cosmic entity, but by the relentless, terrestrial forces of gravity and human conflict.