Upon discovering the existence of intelligent life beyond Earth, the first question we are most likely to ask is “How can we communicate?” As we approach the 50th anniversary of the 1974 Arecibo message—humanity’s first attempt to send out a missive capable of being understood by extraterrestrial intelligence—the question feels more urgent than ever. Advances in remote sensing technologies have revealed that the vast majority of stars in our galaxy host planets and that many of these exoplanets appear capable of hosting liquid water on their surface—a prerequisite for life as we know it. The odds that at least one of these billions of planets has produced intelligent life seem favorable enough to spend some time figuring out how to say “hello.”
In early March an international team of researchers led by Jonathan Jiang of NASA’s Jet Propulsion Laboratory posted a paper on the preprint server arXiv.org that detailed a new design for a message intended for extraterrestrial recipients. The 13-page epistle, referred to as the “Beacon in the Galaxy,” is meant to be a basic introduction to mathematics, chemistry and biology that draws heavily on the design of the Arecibo message and other past attempts at contacting extraterrestrials. The researchers included a detailed plan for the best time of year to broadcast the message and proposed a dense ring of stars near the center of our galaxy as a promising destination. Importantly, the transmission also features a freshly designed return address that will help any alien listeners pinpoint our location in the galaxy so they can—hopefully—kick off an interstellar conversation.
“The motivation for the design was to deliver the maximum amount of information about our society and the human species in the minimal amount of message,” Jiang says. “With improvements in digital technology, we can do much better than the [Arecibo message] in 1974.”
Every interstellar message must address two fundamental questions: what to say and how to say it. Nearly all the messages that humans have broadcast into space so far start by establishing common ground with a basic lesson in science and mathematics, two topics that are presumably familiar to both ourselves and extraterrestrials. If a civilization beyond our planet is capable of building a radio telescope to receive our message, it probably knows a thing or two about physics. A far messier question is how to encode these concepts into the communiqué. Human languages are out of the question for obvious reasons, but so are our numeral systems. Though the concept of numbers is nearly universal, the way we depict them as numerals is entirely arbitrary. This is why many attempts, including “Beacon in the Galaxy,” opt to design their letter as a bitmap, a way to use binary code to create a pixelated image.
The bitmap design philosophy for interstellar communication stretches back to the Arecibo message. It is a logical approach—the on/off, present/absent nature of a binary seems like it would be recognized by any intelligent species. But the strategy is not without its shortcomings. When pioneering search for extraterrestrial intelligence (SETI) scientist Frank Drake designed a prototype of the Arecibo message, he sent the binary message by post to some colleagues, including several Nobel laureates. None of them were able to understand its contents, and only one figured out that the binary was meant to be a bitmap. If some of the smartest humans struggle to understand this form of encoding a message, it seems unlikely that an extraterrestrial would fare any better. Furthermore, it is not even clear that space aliens will be able to see the images contained within the message if they do receive it.
“One of the key ideas is that, because vision has evolved independently many times on Earth, that means aliens will have it, too,” says Douglas Vakoch, president of METI (Messaging Extraterrestrial Intelligence) International, a nonprofit devoted to researching how to communicate with other life-forms. “But that’s a big ‘if,’ and even if they can see, there is so much culture embedded in the way we represent objects. Does that mean we should rule out pictures? Absolutely not. It means we should not naively assume that our representations are going to be intelligible.”
In 2017 Vakoch and his colleagues sent the first interstellar message transmitting scientific information since 2003 to a nearby star. It, too, was coded in binary, but it eschewed bitmaps for a message design that explored the concepts of time and radio waves by referring back to the radio wave carrying the message. Jiang and his colleagues chose another path. They based much of their design on the 2003 Cosmic Call broadcast from the Yevpatoriaradio telescope in the region of Crimea. This message featured a custom bitmap “alphabet” created by physicists Yvan Dutil and Stéphane Dumas as a protoalien language that was designed to be robust against transmission errors.
After an initial transmission of a prime number to mark the message as artificial, Jiang’s message uses the same alien alphabet to introduce our base-10 numeral system and basic mathematics. With this foundation in place, the message uses the spin-flip transition of a hydrogen atom to explain the idea of time and mark when the transmission was sent from Earth, introduce common elements from the periodic table, and reveal the structure and chemistry of DNA. The final pages are probably the most interesting to extraterrestrials but also the least likely to be understood because they assume that the recipient represents objects in the same way that humans do. These pages feature a sketch of a male and female human, a map of Earth’s surface, a diagram of our solar system, the radio frequency that the extraterrestrials should use to respond to the message and the coordinates of our solar system in the galaxy referenced to the location of globular clusters—stable and tightly packed groups of thousands of stars that would likely be familiar to an extraterrestrial anywhere in the galaxy.
“We know the location of more than 50 globular clusters,” Jiang says. “If there’s an advanced civilization, we bet that, if they know astrophysics, they know the globular cluster locations as well, so we can use this as a coordinate to pinpoint the location of our solar system.”
To Send or Not?
Jiang and his colleagues propose sending their message from either the Allen Telescope Array in northern California or the Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) in China. Since the recent destruction of the Arecibo telescope in Puerto Rico, these two radio telescopes are the only ones in the world that are actively courting SETI researchers. At the moment, though, both telescopes are only capable of listening to the cosmos, not talking to it. Jiang acknowledges that outfitting either telescope with the equipment required to transmit the message will not be trivial. But doing so is possible, and he says he and his co-authors are discussing ways to work with researchers at FAST to make it happen.*
If Jiang and his colleagues get a chance to transmit their message, they calculated that it would be best to do so sometime in March or October, when Earth is at a 90-degree angle between the sun and its target at the center of the Milky Way. This would maximize the chance that the missive would not get lost in the background noise of our host star. But a far deeper question is whether we should be sending a message at all.
Messaging extraterrestrials has always occupied a controversial position in the broader SETI community, which is mostly focused on listening for alien transmissions rather than sending out our own. To detractors of “active SETI,” the practice is a waste of time at best and an existentially dangerous gamble at worst. There are billions of targets to choose from, and the odds that we send a message to the right planet at the right time are dismally low. Plus, we have no idea who may be listening. What if we give our address to an alien species that lives on a diet of bipedal hominins?
“I don’t live in fear of an invading horde, but other people do. And just because I don’t share their fear doesn’t make their concerns irrelevant,” says Sheri Wells-Jensen, an associate professor of English at Bowling Green State University and an expert on the linguistic and cultural issues associated with interstellar message design. “Just because it would be difficult to achieve global consensus on what to send or whether we should send doesn’t mean we shouldn’t do it. It is our responsibility to struggle with this and include as many people as possible.”
Despite the pitfalls, many insist that the potential rewards of active SETI far outweigh the risks. First contact would be one of the most momentous occasions in the history of our species, the argument goes, and if we just wait around for someone to call us, it may never happen. As for the risk of annihilation by a malevolent space alien: We blew our cover long ago. Any extraterrestrial capable of traveling to Earth would be more than capable of detecting evidence of life in the chemical signatures of our atmosphere or the electromagnetic radiation that has been leaking from our radios, televisions and radar systems for the past century. “This is an invitation to all people on Earth to participate in a discussion about sending out this message,” Jiang says. “We hope, by publishing this paper, we can encourage people to think about this.”
*Editor’s Note (4/11/22): This sentence was edited after posting to indicate that the authors of the new paper are discussing how they might be able to use the FAST telescope but are not in direct contact with researchers there.
A version of this article with the title “Long-Distance Call” was adapted for inclusion in the June 2022 issue of Scientific American.