What Is Messaging to Extraterrestrial Intelligence, and Why Should You Be Worried About It?

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Key Takeaways

• METI transmits signals to space intentionally
• Debates focus on risks of contact
• Mathematics serves as the universal language

Introduction to Active Transmissions

Messaging to Extraterrestrial Intelligence, often abbreviated as METI, represents a proactive shift from the traditional search for extraterrestrial intelligence. While standard SETI efforts focus on listening for signals that might originate from distant civilizations, METI involves creating and transmitting messages from Earth with the specific intent of contacting intelligent life elsewhere in the universe. This distinction marks a significant change in how humanity interacts with the cosmos. The practice forces scientists, ethicists, and the general public to confront the implications of announcing our presence to the galaxy.

The concept relies on the assumption that other intelligent beings exist and possess the technology to receive and decode artificial signals. It also assumes that these beings might be monitoring the sky for anomalies just as astronomers on Earth do. The transmissions typically encode information about humanity, our biology, our location in the galaxy, and our understanding of mathematics and science. These messages serve as cosmic calling cards, traveling at the speed of light toward specific star systems or general regions of the Milky Way that show potential for habitability.

Discussions surrounding this endeavor are intense and multifaceted. Some argue that reaching out is a natural step in the evolution of a curious species. Others suggest it presents an existential risk, citing the possibility that extraterrestrial civilizations might be hostile. Despite these debates, various projects have sent messages over the last several decades, ranging from simple radio pulses to complex digital encyclopedias.

Historical Context of Interstellar Messaging

The history of sending messages into space dates back to the early days of radio technology, although many early attempts were largely symbolic or lacked the power to reach interstellar distances. The realization that radio waves could escape the ionosphere and travel through the vacuum of space opened the door to the possibility of communication with off-world intelligence.

The Morse Message

In 1962, Soviet scientists directed a radio signal at the planet Venus. This transmission, known as the Morse Message, contained the words “MIR” (meaning both “peace” and “world” in Russian), “LENIN,” and “SSSR” in Morse code. While the target was within our own solar system and the intent was largely to test planetary radar technology, it demonstrated the capability to send coherent information across the void. The signal reflected off Venus and returned to Earth, confirming the viability of planetary radar, but it also conceptually laid the groundwork for future interstellar attempts.

The Arecibo Message

The most famous early attempt at interstellar communication occurred on November 16, 1974. Astronomers used the Arecibo Observatory in Puerto Rico to transmit a powerful radio signal toward the globular star cluster M13, located approximately 25,000 light-years away. Designed by Frank Drake with assistance from Carl Sagan and others, the message consisted of 1,679 binary digits.

The number 1,679 was chosen because it is a semiprime number, divisible only by 1 and itself, or by the prime numbers 23 and 73. The expectation was that an intelligent recipient would realize the mathematical significance and arrange the bits into a grid of 23 columns and 73 rows. When arranged correctly, the resulting image depicted the numbers one through ten, the atomic numbers of the elements composing DNA, the formulas for the sugars and bases in DNA, a graphic of the DNA double helix, a figure of a human, the population of Earth at the time, a graphic of the Solar System, and a graphic of the Arecibo transmitter itself. This transmission was more of a demonstration of human technological achievement than a serious attempt at conversation, given the 50,000-year round-trip travel time.

The Voyager Golden Records

While not a radio transmission, the Voyager Golden Record represents a physical form of METI. Launched in 1977 aboard the Voyager 1 and Voyager 2 spacecraft, these phonograph records contain sounds and images selected to portray the diversity of life and culture on Earth. The contents include greetings in 55 ancient and modern languages, a variety of natural sounds like wind and thunder, and a musical selection featuring artists from Bach to Chuck Berry.

The records are encased in a protective aluminum jacket with instructions on how to play them, written in binary code and referenced against the transition time of hydrogen atoms. These spacecraft are currently traveling through interstellar space. While the likelihood of them being found is statistically minuscule, they serve as a time capsule for humanity, preserving a record of our existence long after the spacecraft cease to function.

The Science of Transmission

Sending a message across light-years requires overcoming significant physical challenges. The signal must be powerful enough to stand out against the cosmic background noise and directed precisely enough to reach a target. Two primary methods dominate the field: radio waves and optical lasers.

Radio Transmission

Radio waves have historically been the preferred medium for interstellar communication. They travel at the speed of light and are relatively easy to generate and detect. A key concept in radio SETI and METI is the “Water Hole,” a quiet band of the electromagnetic spectrum between 1,420 MHz (the frequency of neutral hydrogen) and 1,666 MHz (the frequency of the hydroxyl radical). Because hydrogen and hydroxyl combine to form water, a substance essential for life as we know it, scientists theorize that water-based life forms might choose this quiet band for communication.

To send a radio message, astronomers modulate a carrier wave to encode information. This modulation can be in amplitude, frequency, or phase. The signal is then amplified and transmitted via a large antenna. The effectiveness of a radio message depends on the power of the transmitter and the gain of the antenna. High-gain antennas focus the radio energy into a narrow beam, increasing the intensity of the signal in the direction of the target but requiring precise pointing.

Optical Communication

Optical SETI and METI utilize lasers to transmit signals. Lasers offer the advantage of higher bandwidth, allowing for the transmission of large amounts of data in a short time. A tightly focused laser beam can appear brighter than a star for a brief moment, making it detectable over vast distances.

Optical pulses can be extremely short, lasting only a fraction of a nanosecond. This distinctiveness helps distinguish artificial signals from natural astrophysical phenomena, which typically do not produce such rapid, high-intensity pulses. However, optical signals require the transmitter and receiver to be in a direct line of sight, and the narrowness of the beam means the sender must target specific stars with high accuracy. The atmosphere of a planet can also absorb or scatter optical light, although certain wavelengths can penetrate effectively.

Constructing a Cosmic Language

A major challenge in METI is creating a message that an alien intelligence can understand. Human languages are culturally bound and rely on shared context that an extraterrestrial civilization would not possess. Consequently, scientists and linguists turn to mathematics and physical constants as a universal foundation for communication.

Mathematics as a Bridge

Mathematics is generally considered to be universal. The properties of prime numbers, pi, and basic arithmetic operations remain true regardless of where one is in the universe. Messages often begin with simple counting schemes or pulses that establish a base system, such as binary.

The Cosmic Call messages, sent in 1999 and 2003 from the Yevpatoria Planetary Radar, utilized a custom-designed mathematical “lexicon.” The message started by defining numbers, then introduced basic arithmetic operations, and gradually built up to more complex concepts like variables and physical equations. By teaching the recipient the language within the message itself, the senders hoped to ensure decodability.

Pictorial Messages

Images offer a direct way to convey information. The Arecibo message used a bitmap grid to create crude images. The Cosmic Call and the Teen Age Message also employed bitmaps. These images rely on the recipient understanding how to assemble the stream of data into a two-dimensional array.

The challenge with images is that the interpretation of visual data might be specific to organisms with sight similar to humans. An extraterrestrial species that senses the world primarily through echolocation or electric fields might find a two-dimensional visual representation meaningless. However, the geometric patterns within the data might still convey an artificial origin.

Lincos

Hans Freudenthal, a mathematician, developed a constructed language called Lincos (Lingua Cosmica) in 1960 specifically for interstellar communication. Lincos uses radio signals to define mathematical concepts, then uses those concepts to define time, mass, and space, and eventually attempts to describe social interactions and abstract concepts. While no full-scale Lincos message has been transmitted, the logic behind it influences modern message construction. It prioritizes logical steps, ensuring that each new concept is defined using only previously established terms.

Target Selection Strategies

Choosing where to send a message is as important as the content of the message itself. The Milky Way contains billions of stars, but not all are suitable hosts for life. METI projects typically focus on stars that are stable, long-lived, and likely to possess rocky planets within the habitable zone.

The Habitable Zone

The habitable zone, often called the Goldilocks zone, is the region around a star where conditions are just right for liquid water to exist on the surface of a planet. If a planet is too close, water evaporates; if it is too far, water freezes. Astronomers identify exoplanets within these zones using data from missions like the Kepler space telescope and the Transiting Exoplanet Survey Satellite. Targets like Tau Ceti, Epsilon Eridani, and the planets orbiting TRAPPIST-1 are frequent candidates for study and potential messaging.

Proximity

Distance plays a major role in target selection. A message sent to a star 1,000 light-years away will take a millennium to arrive, and any reply would take another millennium to return. For communication to be meaningful on a human timescale, targets must be relatively close, within a few dozen light-years. The Alpha Centauri system, located just over four light-years away, is the nearest star system and a prime candidate for proximity-based messaging, although the habitability of its planets is still under investigation.

Star Type

Stars are classified by their spectral type. G-type stars, like the Sun, are stable and burn long enough for complex life to evolve. K-type stars (orange dwarfs) and M-type stars (red dwarfs) are also common targets. M-dwarfs are the most numerous stars in the galaxy and often host rocky planets, but they can be volatile with intense stellar flares that might strip planetary atmospheres. K-dwarfs offer a “sweet spot” of stability and longevity. Short-lived massive stars are generally avoided as they burn out before life can likely develop to an advanced stage.

Risks and Ethical Considerations

The decision to broadcast our existence to the universe is not universally accepted. A significant portion of the scientific community and the public raises concerns about the potential dangers of METI. These concerns revolve around the uncertainty of alien intentions and the potential consequences of contact.

The Dark Forest Theory

The Dark Forest theory, popularized by science fiction author Liu Cixin, presents a grim solution to the Fermi Paradox. It suggests that the universe is like a dark forest where every civilization is an armed hunter stalking through the trees. If a hunter finds another life form, the safest course of action is to eliminate it to ensure their own survival. In this view, broadcasting one’s location is a suicidal act that invites destruction. While this is a theoretical concept from fiction, it articulates a genuine fear: that silence is the norm in the universe for a reason, and breaking that silence carries existential risk.

The Hawking Warning

Physicist Stephen Hawking famously warned against trying to contact extraterrestrials. He compared the potential encounter to the arrival of Christopher Columbus in the Americas, which did not turn out well for the Native Americans. Hawking argued that an advanced civilization might view humanity as no more valuable than bacteria, or they might simply be looking for resources to plunder. His viewpoint emphasizes caution and suggests that humanity should prioritize listening over shouting.

The San Marino Index

To quantify the potential risk of transmissions, scientists developed the San Marino Scale. This scale assesses the significance of a transmission from Earth based on the intensity of the signal and the information content. A simple, low-power carrier wave directed at a random part of the sky ranks low on the scale. A high-power, information-rich message directed at a specific, nearby habitable planet ranks high. This index helps researchers and policymakers evaluate the potential impact of planned transmissions.

International Regulation

Currently, no legally binding international laws govern METI. The International Academy of Astronautics (IAA) has a set of protocols, but they are voluntary. These protocols suggest that no message should be sent without prior international consultation. However, enforcement is impossible, and private organizations or nations can theoretically transmit whatever they wish. This lack of regulation leads to debates about who has the authority to speak for Earth.

Notable METI Projects

Several projects have pushed the boundaries of interstellar messaging, experimenting with different coding schemes, targets, and technologies.

Cosmic Call 1 and 2

In 1999 and 2003, a team led by Alexander Zaitsev used the 70-meter planetary radar in Yevpatoria, Crimea, to send digital messages to nearby stars. The project was funded by a commercial startup, making it one of the first privately funded METI efforts. The messages included the “Interstellar Rosetta Stone,” a primer on math and science, along with names and messages from everyday people who paid to be included.

A Message from Earth

In 2008, the social networking site Bebo, in collaboration with other organizations, transmitted “A Message from Earth” to the planet Gliese 581c. The message consisted of 501 photographs, drawings, and text messages selected from user submissions. It was transmitted from the Yevpatoria telescope. This project highlighted the growing interest in crowdsourcing content for interstellar messages, moving away from purely scientific data to a more cultural representation.

Lone Signal

Lone Signal was a crowdfunded active SETI project that launched in 2013. It used the Jamesburg Earth Station in California to send a continuous wave signal to Gliese 526. The project allowed users to send text messages and photos. While the project eventually ceased operations due to funding issues, it demonstrated the potential for public engagement in METI.

Breakthrough Message

Breakthrough Initiatives, funded by Yuri Milner, includes a program called Breakthrough Message. This initiative sponsors an international competition to design a digital message representing Earth and humanity. Unlike other projects, Breakthrough Message pledged not to transmit the winning message until there has been a wide-ranging debate about the risks and benefits of doing so. The focus is on the intellectual challenge of message construction rather than the act of transmission itself.

The Problem of Interpretation

Even if a message reaches an extraterrestrial civilization, there is no guarantee they will interpret it as intended. This issue is known as the “decoding problem.” Anthropocentrism inevitably colors how humans construct messages. We assume that visual representations, binary logic, and certain mathematical sequences are universal, but they might be unique to human cognition.

Cultural Bias

When we include images of humans, we make choices about gender, race, and clothing (or lack thereof). The Voyager Golden Record, for instance, includes a line drawing of a male and female human. The decision to make the figures nude was controversial at the time, but clothing would have been even more confusing to an alien. Similarly, music selections reflect human aesthetic preferences. An alien species might perceive our music as chaotic noise or physically painful vibrations.

Incommensurability

The concept of incommensurability suggests that two sufficiently different conceptual schemes may be mutually unintelligible. If an alien civilization evolved in a fluid environment like the sub-surface ocean of Europa, their understanding of physics, geometry, and space might differ radically from ours. They might not use discrete numbers or linear logic. Overcoming this barrier requires finding the most fundamental common ground, which most researchers agree is the behavior of the physical universe – atoms, stars, and radiation.

Who Speaks for Earth?

The question of “Who speaks for Earth?” is central to the political and sociological aspect of METI. Past messages were crafted by small groups of scientists or commercial entities. Critics argue that sending a message is a planetary action with planetary consequences, and therefore requires a planetary consensus.

Achieving a global consensus is practically difficult. Different nations, cultures, and religions have varying views on the desirability of contact. Some might view aliens as potential saviors, others as demons, and others as resource competitors. A message that represents all of humanity would need to navigate these conflicting perspectives. Some proposals suggest an “open source” message where anyone can contribute, creating a chaotic but democratic representation of the species. Others advocate for a curated message crafted by a diverse international committee of experts in science, art, sociology, and ethics.

Future Technologies and Methods

As technology advances, new methods for METI become feasible. These future technologies could increase the range, data rate, and detectability of our signals.

Neutrino Communication

Neutrinos are nearly massless particles that interact very weakly with matter. They can pass through stars and planets unimpeded. This property makes them an ideal medium for communication across vast distances where dust and gas might block radio or optical signals. However, generating and detecting neutrino beams requires immense energy and massive detectors, far beyond current capabilities for interstellar communication purposes. If an advanced civilization uses neutrinos, we would need significantly more sensitive equipment to hear them.

Gravitational Waves

The detection of gravitational waves opened a new window into the universe. While currently we only detect massive events like black hole mergers, it is theoretically possible to modulate gravitational waves for communication. This method would require manipulating masses on an astronomical scale, placing it firmly in the realm of Type II or Type III civilizations on the Kardashev scale.

Artifacts and Probes

Sending physical probes, like the Voyager spacecraft but much faster, is another form of messaging. The Breakthrough Starshot initiative proposes sending a fleet of gram-scale spacecraft to Alpha Centauri at 20% the speed of light using powerful ground-based lasers. These probes could carry data and transmit back information upon arrival. Physical artifacts have the advantage of durability; a probe can wait in a target system for millions of years to be discovered.

<figure class=”wp-block-table”>

<table>

<thead>

<tr>

<th>Method</th>

<th>Current Status</th>

<th>Pros</th>

<th>Cons</th>

</tr>

</thead>

<tbody>

<tr>

<td>Radio</td>

<td>Active use</td>

<td> proven tech, speed of light</td>

<td>Signal decay, RFI</td>

</tr>

<tr>

<td>Optical/Laser</td>

<td>Experimental</td>

<td>High bandwidth, focused</td>

<td>Requires precise targeting</td>

</tr>

<tr>

<td>Neutrinos</td>

<td>Theoretical</td>

<td>Passes through matter</td>

<td>Hard to generate/detect</td>

</tr>

<tr>

<td>Physical Probes</td>

<td>Active (Voyager, etc.)</td>

<td>Tangible, durable</td>

<td>Extremely slow travel time</td>

</tr>

</tbody>

</table>

</figure>

To METI, or not to METI?

Despite the controversies, METI efforts continue. Organizations like METI International are dedicated to researching and conducting transmissions. They argue that we have been leaking radio and television signals for a century, so we are already visible to any sufficiently advanced observer. Intentional messaging simply improves the quality of the signal and demonstrates intelligence.

The debate between silence and transmission will likely persist until actual contact occurs. Until then, humanity stands on the shore of the cosmic ocean, debating whether to light a beacon or remain in the shadows. The messages we send, or choose not to send, define our collective identity and our hopes for the future of our species in the universe.

Summary

Messaging to Extraterrestrial Intelligence (METI) marks a bold step beyond passive listening, involving the active transmission of signals to potential alien civilizations. Throughout history, from the Morse Message to the Arecibo Message and the Voyager Golden Records, humanity has attempted to bridge the cosmic divide using radio waves and physical artifacts. Scientists employ radio and optical lasers to carry these messages, encoding them with mathematics and scientific constants to overcome linguistic barriers. Target selection focuses on stable stars within habitable zones, balancing proximity with the likelihood of life.

However, the endeavor is fraught with ethical and existential debates. Concepts like the Dark Forest theory and warnings from figures like Stephen Hawking highlight the potential risks of revealing Earth’s location to potentially hostile entities. The lack of international regulation raises questions about who has the authority to represent the planet. Despite these challenges, projects continue to evolve, exploring new technologies like neutrino communication and interstellar probes. METI remains a significant expression of human curiosity and the innate desire to connect with the cosmos.

Appendix: Top 10 Questions Answered in This Article

What is the difference between SETI and METI?

SETI (Search for Extraterrestrial Intelligence) focuses on listening for signals from space. METI (Messaging to Extraterrestrial Intelligence) involves actively creating and transmitting messages from Earth to target stars.

What was the Arecibo Message?

The Arecibo Message was a radio signal sent in 1974 toward the globular cluster M13. It contained 1,679 bits of data that, when arranged in a grid, formed images of DNA, a human figure, and the solar system.

Why is mathematics used in interstellar messages?

Mathematics is considered a universal language that remains true throughout the universe. Scientists assume that any intelligent civilization will understand basic arithmetic, prime numbers, and physical constants, providing a common ground for communication.

What is the “Water Hole” in radio astronomy?

The Water Hole is a quiet band of the electromagnetic spectrum between 1,420 MHz and 1,666 MHz. It is bounded by the frequencies of hydrogen and hydroxyl, which form water, making it a symbolic and practical frequency range for interstellar communication.

What are the Voyager Golden Records?

These are phonograph records attached to the Voyager 1 and 2 spacecraft containing sounds, music, and images from Earth. They serve as time capsules intended to communicate the diversity of life on Earth to any extraterrestrial finders.

What is the Dark Forest theory?

The Dark Forest theory suggests that the universe is a hostile environment where civilizations destroy others to ensure their own survival. It argues that broadcasting one’s location is dangerous because it invites attack from aggressive alien civilizations.

Who was Frank Drake?

Frank Drake was a radio astronomer who pioneered the search for extraterrestrial intelligence. He designed the Arecibo Message and formulated the Drake Equation, which estimates the number of active, communicative extraterrestrial civilizations in the Milky Way.

What is the San Marino Scale?

The San Marino Scale is a tool used to assess the risk of transmissions from Earth. It quantifies the potential impact based on the signal’s intensity and the nature of the information being sent.

Can lasers be used for interstellar communication?

Yes, optical SETI uses lasers to transmit signals. Lasers offer higher bandwidth and can be tightly focused, making them detectable over vast distances, though they require precise targeting and a direct line of sight.

What is Lincos?

Lincos, or Lingua Cosmica, is a constructed language developed by Hans Freudenthal for interstellar communication. It uses radio signals to define mathematical and logical concepts first, gradually building up to more abstract ideas.

Appendix: Top 10 Frequently Searched Questions Answered in This Article

Is it dangerous to send messages to aliens?

Many scientists and thinkers, including Stephen Hawking, have argued that it poses a risk. The concern is that an advanced civilization might be hostile or view humanity as a resource, leading to potential destruction or exploitation.

How long does it take for a message to reach a star?

The time depends on the distance to the star; a message to Alpha Centauri takes just over four years, while a message to M13 takes 25,000 years. Radio waves and laser signals travel at the speed of light, so the travel time in years equals the distance in light-years.

Has anyone ever replied to a message from Earth?

No, humanity has not received a confirmed reply to any message sent. Given the vast distances and the relatively recent start of our transmissions, any potential reply would likely take decades or centuries to arrive.

What kind of information is sent in these messages?

Messages typically include mathematical principles, scientific constants, and biological information about humans. They may also contain images of the solar system, DNA structures, and cultural artifacts like music or photographs.

Can I send a message to space?

Some private projects and commercial ventures have allowed the public to include names or text messages in their transmissions. However, significant high-power transmissions are typically managed by scientific organizations or large-scale initiatives.

What is the best language to speak to aliens?

There is no single “best” language, but mathematics is widely regarded as the most effective starting point. Because mathematical truths are universal, they provide a logical foundation that does not rely on human culture or biology.

Are there laws against sending messages to aliens?

There are currently no binding international laws that prohibit sending messages to space. While organizations like the IAA have voluntary protocols suggesting consultation, individuals and nations are technically free to transmit.

What is the “Wow!” signal?

The “Wow!” signal was a strong narrowband radio signal detected in 1977 that appeared to come from the direction of the constellation Sagittarius. While it bore hallmarks of an artificial origin, it has not been detected again, and it was a received signal, not a sent message.

How far have our radio signals traveled?

Humanity has been leaking radio waves for over a century, creating a “radio bubble” that extends about 100 light-years in all directions. However, these unintended leakage signals become very weak over distance compared to focused METI transmissions.

What is the difference between active and passive SETI?

Passive SETI involves using telescopes to listen for signals that might already be out there. Active SETI, or METI, involves intentionally generating and directing high-power signals toward specific targets to initiate contact.