LOST IN SPACE
FOR DECADES, WE’VE SEARCHED FOR SIGNS THAT WE’RE NOT ALONE IN THE UNIVERSE. WE’VE FOUND NOTHING. NOW A RADICAL NEW THEORY SUGGESTS THE SEARCH FOR EXTRATERRESTRIAL INTELLIGENCE HAS BEEN DOING IT ALL WRONG.
NASA does not often crack jokes about aliens, but its recent announcement that a satellite camera had found “Martian Morse code” in the shape of sand dunes on the Red Planet’s surface inspired much mirth among space scientists.
Nathalie Cabrol, director of the Carl Sagan Center at the SETI (Search for Extraterrestrial Intelligence) Institute, which searches for alien messages, laughed out loud at the thought.
“Tell me about it,” she said sarcastically.
If only contact with aliens, if they exist, were so simple. This was just dirt shaped by wind, as NASA itself eventually conceded. Just as the wealthy American polymath astronomer Percival Lowell did not actually see canals on Mars in 1906, so too is this latest bit of Martian clickbait a figment of a rich human imagination, reflecting our desire to find patterns in chaos. But it is also revealing of a deep philosophical problem in the search for extraterrestrial intelligence, an all-or-nothing scientific gamble that is now at a crisis point.
The problem, as Cabrol describes it in a provocative new research paper, is that human scientists have only ever looked for other versions of themselves.
By scanning the heavens for the same sort of messages we ourselves sent out in the 1970s — from the Arecibo radio transmission with encoded details of arithmetic and chemistry to the engraved plaques launched on Pioneer with rudimentary sketches of a man and woman, and the Voyager golden record with music by Mozart and Chuck Berry — we have, basically, been searching blind.
Despite a century of major scientific progress in everything from biology and evolution to physics and planet formation, we still imagine extraterrestrial life forms as H.G. Wells did at the turn of the 20th century, as quaint foreigners, either friendly or threatening, but fundamentally similar.
“It is not a mistake. This is where we had to start,” said Cabrol, an astrobiologist and planetary geologist with a background in environmental science and the development of Mars rovers. “But we should not stay constrained or confined to that.”
“To find aliens, we must become the aliens,” she said. To that end, she described the tactical change she wants to make to the basic approach of research at SETI, which applies scientific rigour to a question — the possibility of life on other planets — that is more commonly associated with sweaty conspiracy theorists and flaky fantasists.
She described SETI’s current main strategy of looking for non-natural patterns in electromagnetic signals from other Earth-like planets as a “shot in the dark.”
“You don’t know exactly what you are looking for, or even if you found something, because you cannot recognize it,” she said.
Her solution is to take “a step upstream,” to broaden the perspective on what it might mean for intelligent life to have arisen somewhere else, and to unite the various scientific disciplines that might contribute, from mathematics and evolution to neuroscience and geology.
She said the response has been enthusiastic. One criticism has come from intelligent design theorists, who believe humans were created supernaturally, not by natural physical and evolutionary processes. They conclude from this that we are probably unique in the universe.
An editorial by the Discovery Institute on Cabrol’s idea, for example, compares SETI researchers to cultish fanatics searching for ghosts, who “refuse to take non-detection as an answer ... Despite continued failures, SETI is unlikely to cave anytime soon. Its motivations are too deeply grounded in evolutionary ideology. The believers think it too incredible to imagine humans as unique or exceptional in such a vast universe. To be sure, this ‘gut feeling’ extends outside evolutionary circles. But where is the evidence?”
The positive responses have generated the most excitement. For example Rene Heller, an astrophysicist at the Max Planck Institute for Solar System Research in Germany, recently of McMaster University, has proposed a strategy in line with Cabrol’s interdisciplinary thinking. His idea is that, because we often detect Earthlike planets by observing them pass in front of their own stars, we should assume aliens would find us in the same way. For SETI, that means looking for signals in the thin band of the cosmos called Earth’s Transit Zone, the area from which Earth can be seen passing in front of the Sun, which is only about one-thousandth of the entire sky.
Likewise, Seth Shostak, a senior astronomer with SETI, has proposed using telescopes to look for “biosignatures,” such as oxygen, in the atmospheres of distant Earth-like planets, by analyzing the light they reflect. On this theory, the oxygen content of Earth has been advertising the presence of life here for millions of years. Oxygen is simply a byproduct of photosynthesis, not a sign of intelligent life, but as he put it, “if other worlds can spawn lettuce or maybe just algae, there’s at least some chance that they could also grow something a little more interesting.”
Cabrol’s key point is that Earth bears the cumulative physical effects of all life that ever existed here, and so would any life-bearing alien planet. As she sees it, the only way to investigate that properly is to imagine all the other kinds of ways life might disrupt a planet and its atmosphere. And that takes more kinds of scientists than just radio astronomers and satellite technicians.
“I’m going to go back to my French background here,” Cabrol said. “We had many different Gaul villages all over the place, and the only time we beat Caesar is when they all came together ... In the 15 years that I’ve been doing this, I saw how powerful synergies and bridges between disciplines are.”
This proposal is comparable to the dynamic in other scientific fields probing major mysteries, such as climate change or consciousness. After decades of ever greater specialization, the leaders in the diverse strands of these inquiries are finding it harder to talk to each other, and so the intellectual energy — not to mention the funding — has shifted to the synergistic integration of disciplines, in projects such as Barack Obama’s BRAIN Initiative. That collaborative research project is pursing technologies to further understanding of brain function.
For SETI, part of the problem is radio astronomers who do not know much about the origins of life, or astrobiologists who do not understand general relativity. If there are messages out there, the fear is we are failing to recognize them, either because we cannot recognize them, or we are not looking in the right way.
Part of the solution is, like in brain science, major funding pushes. Earlier this year, the Russian venture capitalist Yuri Milner announced a doubling of his $100-million contribution to SETI projects.
The other part is philosophical, a return to first principles. Like the best science, the search for alien life eventually runs up against a deep philosophical question — what is life in the first place? Answering that question involves considering whether it began anywhere else but on Earth. That question remains in the realm of speculative research and science fiction, but as best science can tell, the answer is “almost certainly.” From a purely statistical point of view, it would be far stranger to imagine Earth is the only one of billions of similar planets to have developed life.
This insight, which has inspired SETI since its origins half a century ago, was famously broken down by the pioneering astronomer Frank Drake in his Drake Equation. It states that the number of civilizations in our Milky Way galaxy whose electromagnetic transmissions are detectable is equal to: (the average rate of star formation) x (the fraction of stars with planet systems) x (the number of planets per solar system capable of sustaining life) x (the fraction of those that actually develop life) x (the fraction of planets with life that develop intelligent life) x (the fraction of civilizations that develop technology signalling their presence into space) x (the length of time they actually release such signals).
This equation has been criticized in many ways. For example, life does not inevitably lead to intelligence, and intelligence does not inevitably lead to technology, and technology does not inevitably lead to the broadcasting of messages.
If you do the math, and consider how many Earthlike planets we now know there are, it seems hard to imagine Earth is the only one to host life. The odds, overwhelmingly, say we are not. But as far as we know, we are.
This is known as the Fermi Paradox, best articulated by the physicist Enrico Fermi, who famously wondered: “Where is everybody?” (This prompted one of the funnier moments in astrobiological history, when his lunchmate at the Los Alamos National Laboratory, Leo Szilard, replied: “They are among us, and they call themselves Hungarians.”)
There are many other serious answers to this paradox. The Zoo hypothesis, for example, is that they are out there, but choosing not to make contact, at least for now, for our well-being or theirs. Another is that they are signalling in a way we cannot hear, or maybe they are listening, too, but not transmitting.
Or maybe they have transmitted in the past, but not anymore, or they will in the future, but have not yet. There may also be a generational aspect to the creation of life across the universe, driven by the elements released by dying stars, of which all life on Earth is composed. On this view, Earth might be either much younger than other life-sustaining planets or much older.
“Advanced, intelligent life beyond Earth is most likely plentiful, but we have not yet opened ourselves to the full potential of its diversity,” Cabrol writes in the journal Astrobiology. “With the vision presented here, we offer a unified and universal approach for the search for extraterrestrial life — one that is measurable and searches for ET at the crossroads of scientific and technological innovation, and imagination.”