by Sam Kean
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If you were an English speaker, you might just recognize a greeting in that message, the word HI mapped out using only a binary language of on-and-off states.
Drake took the same approach, only using a much larger semiprime, which gave him a 23-by-73 grid to send a more complicated message. Because his imagined correspondents in M13 were not likely to understand any human language, he filled the grid with a mix of mathematical and visual referents. The top of the grid counted from 1 to 10 in binary code—effectively announcing to the aliens that numbers will be represented using these symbols.
Having established a way of counting, Drake then moved to connect the concept of numbers to some reference that the citizens of M13 would likely share with us. For this step, he encoded the atomic numbers for five elements: hydrogen, carbon, nitrogen, oxygen, and phosphorous, the building blocks of DNA. Other parts of the message were more visually oriented. Drake used the on-off pulses of the radio signal to “draw” a pixelated image of a human body. He also included a sketch of our solar system and of the Arecibo telescope itself. The message said, in effect: this is how we count; this is what we are made of; this is where we came from; this is what we look like; and this is the technology we are using to send this message to you.
As inventive as Drake’s exosemiotics were in 1974, the Arecibo message was ultimately more of a proof-of-concept than a genuine attempt to make contact, as Drake himself is the first to admit. For starters, the 25,000 light-years that separate us from M13 raise a legitimate question about whether humans will even be around—or recognizably human—by the time a message comes back. The choice of where to send it was almost entirely haphazard. The METI project intends to improve on the Arecibo model by directly targeting nearby Goldilocks-zone planets.
One of the most recent planets added to that list orbits the star Gliese 411, a red dwarf located eight light-years away from Earth. On a spring evening in the Oakland hills, our own sun putting on a spectacular display as it slowly set over the Golden Gate Bridge, Vakoch and I met at one of the observatories at the Chabot Space and Science Center to take a peek at Gliese 411. A half-moon overhead reduced our visibility but not so much that I couldn’t make out the faint tangerine glimmer of the star, a single blurred point of light that had traveled nearly 50 trillion miles across the universe to land on my retina. Even with the power of the Oakland telescope, there was no way to spot a planet orbiting the red dwarf. But in February of this year, a team of researchers using the Keck I telescope at the top of Mauna Kea in Hawaii announced that they had detected a “super-Earth” in orbit around Gliese, a rocky and hot planet larger than our own.
The METI group aims to improve on the Arecibo message not just by targeting specific planets, like that super-Earth orbiting Gliese, but also by rethinking the nature of the message itself. “Drake’s original design plays into the bias that vision is universal among intelligent life,” Vakoch told me. Visual diagrams—whether formed through semiprime grids or engraved on plaques—seem like a compelling way to encode information to us because humans happen to have evolved an unusually acute sense of vision. But perhaps the aliens followed a different evolutionary path and found their way to a technologically advanced civilization with an intelligence that was rooted in some other sense: hearing, for example, or some other way of perceiving the world around them for which there is no earthly equivalent.
Like so much of the SETI/METI debate, the question of visual messaging quickly spirals out into a deeper meditation, in this instance on the connection between intelligence and visual acuity. It is no accident that eyes developed independently so many times over the course of evolution on Earth, given the fact that light conveys information faster than any other conduit. That transmission-speed advantage would presumably apply on other planets in the Goldilocks zone, even if they happened to be on the other side of the Milky Way, and so it seems plausible that intelligent creatures would evolve some sort of visual system as well.
But even more universal than sight would be the experience of time. Hans Freudenthal’s Lincos: Design of a Language for Cosmic Intercourse, a seminal book of exosemiotics published more than a half century ago, relied heavily on temporal cues in its primer stage. Vakoch and his collaborators have been working with Freudenthal’s language in their early drafts for the message. In Lincos, duration is used as a key building block. A pulse that lasts for a certain stretch (say, in human terms, one second) is followed by a sequence of pulses that signify the “word” for one; a pulse that lasts for six seconds is followed by the word for six. The words for basic math properties can be conveyed by combining pulses of different lengths. You might demonstrate the property of addition by sending the words for three and six and then sending a pulse that lasts for nine seconds. “It’s a way of being able to point at objects when you don’t have anything right in front of you,” Vakoch explains.
Other messaging enthusiasts think we needn’t bother worrying about primers and common referents. “Forget about sending mathematical relationships, the value of pi, prime numbers or the Fibonacci series,” the senior SETI astronomer, Seth Shostak, argued in a 2009 book. “No, if we want to broadcast a message from Earth, I propose that we just feed the Google servers into the transmitter. Send the aliens the World Wide Web. It would take half a year or less to transmit this in the microwave; using infrared lasers shortens the transmit time to no more than two days.” Shostak believes that the sheer magnitude of the transmitted data would enable the aliens to decipher it. There is some precedent for this in the history of archeologists studying dead languages: the hardest code to crack is one with only a few fragments.
Sending all of Google would be a logical continuation of Drake’s 1974 message, in terms of content if not encoding. “The thing about the Arecibo message is that, in a sense, it’s brief but its intent is encyclopedic,” Vakoch told me as we waited for the sky to darken in the Oakland hills. “One of the things that we are exploring for our transmission is the opposite extreme. Rather than being encyclopedic, being selective. Instead of this huge digital data dive, trying to do something elegant. Part of that is thinking about what are the most fundamental concepts we need.” There is something provocative about the question Vakoch is wrestling with here: of all the many manifestations of our achievements as a species, what’s the simplest message we can create that will signal that we’re interesting, worthy of an interstellar reply?
But to METI’s critics, what he should be worrying about instead is the form that the reply might take: a death ray, or an occupying army.
Before Doug Vakoch had even filed the papers to form the METI nonprofit organization in July 2015, a dozen or so science-and-tech luminaries, including SpaceX’s Elon Musk, signed a statement categorically opposing the project, at least without extensive further discussion, on a planetary scale. “Intentionally signaling other civilizations in the Milky Way Galaxy,” the statement argued, “raises concerns from all the people of Earth, about both the message and the consequences of contact. A worldwide scientific, political and humanitarian discussion must occur before any message is sent.”
One signatory to that statement was the astronomer and science-fiction author David Brin, who has been carrying on a spirited but collegial series of debates with Vakoch over the wisdom of his project. “I just don’t think anybody should give our children a fait accompli based on blithe assumptions and assertions that have been untested and not subjected to critical peer review,” he told me over a Skype call from his home office in Southern California. “If you are going to do something that is going to change some of the fundamental observable parameters of our solar system, then how about an environmental-impact statement?”
The anti-METI movement is predicated on a grim statistical likelihood: if we do ever manage to make contact
with another intelligent life-form, then almost by definition, our new pen pals will be far more advanced than we are. The best way to understand this is to consider, on a percentage basis, just how young our own high-tech civilization actually is. We have been sending structured radio signals from Earth for only the last 100 years. If the universe were exactly 14 billion years old, then it would have taken 13,999,999,900 years for radio communication to be harnessed on our planet. The odds that our message would reach a society that had been tinkering with radio for a shorter, or even similar, period of time would be staggeringly long. Imagine another planet that deviates from our timetable by just a tenth of 1 percent: if they are more advanced than us, then they will have been using radio (and successor technologies) for 14 million years. Of course, depending on where they live in the universe, their signals might take millions of years to reach us. But even if you factor in that transmission lag, if we pick up a signal from another galaxy, we will almost certainly find ourselves in conversation with a more advanced civilization.
It is this asymmetry that has convinced so many future-minded thinkers that METI is a bad idea. The history of colonialism here on Earth weighs particularly heavy on the imaginations of the METI critics. Stephen Hawking, for instance, made this observation in a 2010 documentary series: “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.” David Brin echoes the Hawking critique: “Every single case we know of a more technologically advanced culture contacting a less technologically advanced culture resulted at least in pain.”
METI proponents counter the critics with two main arguments. The first is essentially that the horse has already left the barn: given that we have been “leaking” radio waves in the form of Leave It to Beaver and the nightly news for decades, and given that other civilizations are likely to be far more advanced than we are, and thus capable of detecting even weak signals, then it seems likely that we are already visible to extraterrestrials. In other words, they know we’re here, but they haven’t considered us to be worthy of conversation yet. “Maybe in fact there are a lot more civilizations out there, and even nearby planets are populated, but they’re simply observing us,” Vakoch argues. “It’s as if we are in some galactic zoo, and if they’ve been watching us, it’s like watching zebras talking to one another. But what if one of those zebras suddenly turns toward you and with its hooves starts scratching out the prime numbers. You’d relate to that zebra differently!”
Brin thinks that argument dangerously underestimates the difference between a high-power, targeted METI transmission and the passive leakage of media signals, which are far more difficult to detect. “Think about it this way: If you want to communicate with a Boy Scout camp on the other side of the lake, you could kneel down at the end of the lake and slap the water in Morse code,” he says. “And if they are spectacularly technologically advanced Boy Scouts who happened also to be looking your way, they might build instruments that would be able to parse out your Morse code. But then you whip out your laser pointer and point it at their dock. That is exactly the order of magnitude difference between picking up [reruns of] I Love Lucy from the 1980s, when we were at our noisiest, and what these guys want to do.”
METI defenders also argue that the threat of some Klingon-style invasion is implausible, given the distances involved. If, in fact, advanced civilizations were capable of zipping around the galaxy at the speed of light, we would have already encountered them. The much more likely situation is that only communications can travel that fast, and so a malevolent presence on some distant planet will only be able to send us hate mail. But critics think that sense of security is unwarranted. Writing in Scientific American, the former chairman of SETI, John Gertz, argued that “a civilization with malign intent that is only modestly more advanced than we are might be able to annihilate Earth with ease by means of a small projectile filled with a self-replicating toxin or nano gray goo; a kinetic missile traveling at an appreciable percentage of the speed of light; or weaponry beyond our imagination.”
Brin looks to our own technological progress as a sign of where a more advanced civilization might be in terms of interstellar combat: “It is possible that within just 50 years, we could create an antimatter rocket that could propel a substantial pellet of several kilograms, at half the speed of light at times to intersect with the orbit of a planet within 10 light-years of us.” Even a few kilograms colliding at that speed would produce an explosion much greater than the Hiroshima and Nagasaki detonations combined. “And if we could do that in 50 years, imagine what anybody else could do, completely obeying Einstein and the laws of physics.”
Interestingly, Frank Drake himself is not a supporter of the METI efforts, though he does not share Hawking’s and Musk’s fear of interstellar conquistadors. “We send messages all the time, free of charge,” he says. “There’s a big shell out there now 80 light-years around us. A civilization only a little more advanced than we are can pick those things up. So the point is we are already sending copious amounts of information.” Drake believes that any other advanced civilization out there must be doing the same, so scientists like Vakoch should devote themselves to picking up on that chatter instead of trying to talk back. METI will consume resources, Drake says, that would be “better spent listening and not sending.”
METI critics, of course, might be right about the frightening sophistication of these other, presumably older civilizations but wrong about the likely nature of their response. Yes, they could be capable of sending projectiles across the galaxy at a quarter of the speed of light. But their longevity would also suggest that they have figured out how to avoid self-destruction on a planetary scale. As Steven Pinker has argued, human beings have become steadily less violent over the last 500 years; per capita deaths from military conflict are most likely at an all-time low. Could this be a recurring pattern throughout the universe, played out on much longer timescales: the older a civilization gets, the less warlike it becomes? In which case, if we do get a message to extraterrestrials, then perhaps they really will come in peace.
These sorts of questions inevitably circle back to the two foundational thought experiments that SETI and METI are predicated upon: the Fermi Paradox and the Drake Equation. The paradox, first formulated by the Italian physicist and Nobel laureate Enrico Fermi, begins with the assumption that the universe contains an unthinkably large number of stars, with a significant percentage of them orbited by planets in the Goldilocks zone. If intelligent life arises on even a small fraction of those planets, then the universe should be teeming with advanced civilizations. And yet to date, we have seen no evidence of those civilizations, even after several decades of scanning the skies through SETI searches. Fermi’s question, apparently raised during a lunch conversation at Los Alamos in the early 1950s, was a simple one: “Where is everybody?”
The Drake Equation is an attempt to answer that question. The equation dates back to one of the great academic retreats in the history of scholarship: a 1961 meeting at the Green Bank observatory in West Virginia, which included Frank Drake, a twenty-six-year-old Carl Sagan, and the dolphin researcher (and later psychedelic explorer) John Lilly. During the session, Drake shared his musings on the Fermi Paradox, formulated as an equation. If we start scanning the cosmos for signs of intelligent life, Drake asked, how likely are we to actually detect something? The equation didn’t generate a clear answer, because almost all the variables were unknown at the time and continue to be largely unknown a half century later. But the equation had a clarifying effect, nonetheless. In mathematical form, it looks like this:
N= R* x ƒp x ne x ƒl x ƒi x ƒc x L
N represents the number of extant, communicative civilizations in the Milky Way. The initial variable R* corresponds to the rate of star formation in the galaxy, effectively giving you the total number of potential suns that could support life. The remaining variables then serve as a kind of nested sequence of filte
rs: Given the number of stars in the Milky Way, what fraction of those have planets, and how many of those have an environment that can support life? On those potentially hospitable planets, how often does life itself actually emerge, and what fraction of that life evolves into intelligent life, and what fraction of that life eventually leads to a civilization’s transmitting detectable signals into space? At the end of his equation, Drake placed the crucial variable L, which is the average length of time during which those civilizations emit those signals.
What makes the Drake Equation so mesmerizing is in part the way it forces the mind to yoke together so many different intellectual disciplines in a single framework. As you move from left to right in the equation, you shift from astrophysics, to the biochemistry of life, to evolutionary theory, to cognitive science, all the way to theories of technological development. Your guess about each value in the Drake Equation winds up revealing a whole worldview: perhaps you think life is rare, but when it does emerge, intelligent life usually follows; or perhaps you think microbial life is ubiquitous throughout the cosmos, but more complex organisms almost never form. The equation is notoriously vulnerable to very different outcomes, depending on the numbers you assign to each variable.
The most provocative value is the last one: L, the average life span of a signal-transmitting civilization. You don’t have to be a Pollyanna to defend a relatively high L value. All you need is to believe that it is possible for civilizations to become fundamentally self-sustaining and survive for millions of years. Even if one in a thousand intelligent life-forms in space generates a million-year civilization, the value of L increases meaningfully. But if your L-value is low, that implies a further question: What is keeping it low? Do technological civilizations keep flickering on and off in the Milky Way, like so many fireflies in space? Do they run out of resources? Do they blow themselves up?