If someone is lost in the wilderness, they have two choices. They can search for civilization, or they could make themselves visible by building a fire or spelling HELP in large letters. For scientists exploring the possibility of intelligent alien life, the options are remarkably similar.
For over 70 years, astronomers have been scanning the skies for radio or optical signals from other civilizations in the search for extraterrestrial intelligence, known as SETI. Most scientists believe that life likely exists on many of the 300 million potentially habitable worlds in the Milky Way galaxy. They also think there’s a good chance some of these life forms have developed intelligence and technology. Yet, no signals from another civilization have ever been detected—a mystery often referred to as “The Great Silence.”
While SETI has long been part of mainstream science, METI—messaging extraterrestrial intelligence—has been less common. As an astronomy professor and advisor for a nonprofit designing messages for extraterrestrial civilizations, I’ve spent much of my career considering the implications of these efforts.
In the coming months, two teams of astronomers will send messages into space in hopes of contacting intelligent extraterrestrials.
These efforts are akin to lighting a large signal fire and hoping someone sees it. But the question of whether such actions are wise remains a matter of debate.
The History of METI
Early attempts to contact extraterrestrial life were akin to messages in bottles cast into the vast ocean of space.
In 1972, NASA launched the Pioneer 10 spacecraft, which carried a plaque featuring a line drawing of a man and a woman along with symbols indicating its origin. In 1977, NASA followed up with the iconic Golden Record aboard the Voyager 1 spacecraft. Both crafts, along with their twins, Pioneer 11 and Voyager 2, have now left the solar system. However, the likelihood that any of these physical objects will ever be found is astronomically low.
Electromagnetic waves, however, provide a more efficient means of communication.
In 1974, the Arecibo Observatory in Puerto Rico sent the first deliberate radio message designed for extraterrestrial ears. This signal, a binary-coded message, was aimed at the globular cluster M13, about 25,000 light-years away. Needless to say, any response will require patience.
Additionally, accidental transmissions from Earth—such as radio and television broadcasts—have been radiating into space for nearly a century. While these signals are expanding outwards, their diffuse nature means they become increasingly faint, blending into cosmic background noise relatively quickly.
New Messages on the Horizon
Nearly 50 years after the Arecibo message, two international teams are preparing to send new messages into space using advanced techniques.
One team plans to use the world’s largest radio telescope in China to send a message called “The Beacon in the Galaxy” in 2023. This message will include mathematical concepts, biochemistry, information about humanity, Earth’s location, and a timestamp. It will be aimed at a dense region of stars near the center of the Milky Way, about 10,000–20,000 light-years away. Any reply would take tens of thousands of years.
The second effort, set to launch from the Goonhilly Satellite Earth Station in England, will target TRAPPIST-1, a star system just 39 light-years away that hosts seven planets, three of which are Earth-like. If intelligent life exists there, a reply could reach Earth in as little as 78 years.
Ethical Concerns
The idea of contacting extraterrestrial civilizations raises profound ethical questions.
Who gets to speak for Earth? Currently, decisions about the content and recipients of these messages are made by small groups of scientists, without global consultation. More critically, is it even safe to broadcast our existence?
The late physicist Stephen Hawking warned that advanced alien civilizations could pose a threat to humanity. By revealing our location, he argued, we risk inviting disaster. Others contend the risk is negligible, as any advanced civilization likely already knows of Earth’s existence. Nonetheless, the debate continues, with some—like Russian-Israeli billionaire Yuri Milner—actively encouraging METI by offering substantial incentives for innovative message designs.
For now, there are no international regulations governing METI, allowing experiments to proceed despite the risks.
The Unknown Outcome
For now, intelligent alien life remains within the realm of speculation. Works like The Three-Body Problem by Cixin Liu explore the potential consequences of successful METI efforts, often painting a bleak picture. If humanity ever does make contact, one can only hope that any extraterrestrial visitors come in peace.