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A message just arrived from outer space. Can you decode it?

A revolutionary SETI experiment seeks to find out how earthlings might respond to a signal from aliens.

The Green Bank Telescope in West Virginia is the world’s largest fully steerable radio telescope.
Michael S. Williamson/Washington Post via Getty Images
Sigal Samuel is a senior reporter for Vox’s Future Perfect and co-host of the Future Perfect podcast. She writes primarily about the future of consciousness, tracking advances in artificial intelligence and neuroscience and their staggering ethical implications. Before joining Vox, Sigal was the religion editor at the Atlantic.

After decades of searching for extraterrestrial intelligence, humanity finally picked up a message from outer space today. Three of Earth’s top radio astronomy observatories detected the signal coming from somewhere near Mars. Its content has yet to be decoded.

Okay, okay, the message is not actually from aliens. Humans arranged for it to be transmitted to simulate receiving a signal from extraterrestrials. Consider it a dress rehearsal — a chance for us all to see how we’d respond if aliens really did transmit a message to Earth.

Would different nations cooperate to track and record the message? Would scientists and members of the public join forces to decode it? Who would get to decide if and how we reply to the aliens? Would we make decisions democratically, or would we fall into authoritarianism, distrust, and conspiracy theories?

This act of global theater is the brainchild of Daniela de Paulis, who serves as artist in residence at the Search for Extraterrestrial Intelligence (SETI), the premier research institute hunting for intelligent life in the universe. As part of a project she’s calling “A Sign in Space,” de Paulis devised the content of the encoded message together with a team of scientists.

She then directed the European Space Agency’s ExoMars Trace Gas Orbiter, a spacecraft in orbit around Mars, to transmit the signal to Earth. It was picked up today by SETI’s Allen Telescope Array in California, the Green Bank Observatory in West Virginia, and the Medicina Radio Astronomical Station observatory in Italy.

Now it’s up to the public to decode the radio message. Anyone working to interpret it can submit findings on the project’s Discord server and website. If you’ve ever dreamed of being Ellie Arroway from the movie Contact, now’s your chance. Have at it!

But as you do, be aware that you’re stepping into a minefield of controversy. Figures like Stephen Hawking and Elon Musk have warned that if we do actually communicate with extraterrestrials — regardless of who reaches out first — it could pose a huge risk to humanity. In fact, if less-than-friendly aliens one day become aware of us, that could pose an existential threat not only to the human species but to every species on Earth.

Is communicating with aliens a good idea?

In the 1997 movie Contact, radio astronomers passively listen for a message from outer space, turning their dishes up to the sky like giant upturned ears. But in the real world, scientists have sometimes been much more bold, actively shouting toward the stars in search of extraterrestrial life.

In 1974, astronomers sent out a signal using the Arecibo radio telescope in Puerto Rico. Frank Drake, who came up with the famous “Drake Equation” for estimating the odds that intelligent life exists in our galaxy, crafted the message with help from Carl Sagan, the astronomer who penned Contact and popularized SETI.

Written in binary code — a series of ones and zeros — the message was designed with the hope of being intelligible to any aliens who might be listening. It sought to give them some basic information about us, like the position of Earth in our solar system, the size of the human population, the shape of the human body, and the double helix structure of DNA.

After the Arecibo Message was transmitted, some scientists expressed concern that it had been broadcast without international consultation and buy-in. They argued that decisions with such profound implications for earthlings should be made more democratically. Even Drake reportedly said he regrets transmitting the message.

Since then, the critics of transmission have grown more strident.

In the late 1980s, scientists with SETI drafted a post-detection protocol, which listed best practices for what to do if and when we ever find aliens. One of its principles reads: “No response to a signal or other evidence of extraterrestrial intelligence should be sent until appropriate international consultations have taken place.” This protocol was put on file as a brief at the UN and it was endorsed by the International Academy of Astronautics and the International Institute for Space Law. But it has no binding regulatory force.

In 2010, physicist Stephen Hawking famously articulated the risk of advertising our existence to E.T.: “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans,” he said. Scientists in Hawking’s camp often argue that aliens don’t need to have violent intentions to do us harm; they might just view us the way we view, say, ants — they’d step on us on the way to something else and think nothing of it.

Scientists who favor transmitting messages to aliens, on the other hand, think that worry is unwarranted. Douglas Vakoch, an astrobiologist who spent many years at SETI, split off in 2015 to found his own organization, Messaging Extraterrestrial Intelligence (METI). Rather than just scanning the stars for signs of intelligent life like SETI does, METI proactively seeks to make contact with aliens by transmitting radio signals from powerful telescopes.

“With respect to Hawking,” Vakoch told me in 2019, “the key point he was missing was that any civilization that could do us harm would already know we’re here from our accidental TV and radio leakage.” He was referring to the fact that we’ve long been unintentionally sending out messages that aliens could detect because our TV shows and radio broadcasts constantly flow out from Earth into space.

But opponents of intentional broadcasts argue this is misleading. Yes, our signals have been floating out into space for decades, but they’re weak and not directed at anything in particular. A purposeful transmission from a radio telescope would be much more powerful and targeted, so it would be easier for aliens to detect — the difference between a whisper and a shout.

Statistically, an alien civilization capable of detecting and responding to our signals is very likely to be older and more technologically advanced than we are. We’ve only been transmitting radio signals for about 100 years, so the chances that they’d be picked up by a civilization that’s been using radio technology for less than a century are vanishingly tiny. Critics of transmission say this power differential makes seeking out the attention of alien civilizations a frightening prospect because we can’t assume they’ll put their power to altruistic uses.

The more you think about the scale of the risk involved, the more obvious it becomes that deciding whether and how we communicate with aliens should not be left up to one class of people. As Kathryn Denning, an anthropologist who studies the ethics of space exploration, put it in a 2017 interview with the New York Times, “Why should my opinion matter more than that of a 6-year-old girl in Namibia? We both have exactly the same amount at stake.”

A 2015 statement released by SETI researchers, Elon Musk, and others made the same critique: “We feel the decision whether or not to transmit must be based upon a worldwide consensus, and not a decision based upon the wishes of a few individuals with access to powerful communications equipment,” it said. “We strongly encourage vigorous international debate by a broadly representative body prior to engaging further in this activity.”

So far, there is still no “broadly representative body” regulating communication with aliens. But the message that just arrived from outer space will hopefully kick off an international debate. Though it’s unlikely to yield global consensus anytime soon, the responses could help inform an international protocol for responding to first contact.