Extraterrestrial: The First Sign of Intelligent Life Beyond Earth

by Avi Loeb

Interstellar visitors are far rarer than asteroids or comets. In fact, at the time of ‘Oumuamua’s discovery, we had never seen an object that originated outside of our solar system pass through it.

a lesson I eventually learned myself and that I have since tried to teach my own students—wasn’t about whether you should or shouldn’t follow the crowd but rather that you should take time to figure things out before acting. In deliberation, there is the humility of uncertainty.

I have also found that staring out into the vastness of space, contemplating the start and end of everything, provides a framework for answering, “What is a life worth living?”

For starters, prior to ‘Oumuamua’s discovery, no confirmed interstellar object had ever been observed in our own solar system. That alone made ‘Oumuamua historic, and it was enough to draw many astronomers’ attention, which led to the gathering of more data, which was interpreted and found to reveal further anomalies, which drew more astronomers’ attention, and so on.

In the case of ‘Oumuamua, the object’s brightness varied tenfold every eight hours, which we deduced to be the amount of time that it took to complete one full rotation. This dramatic variability in its brightness told us that ‘Oumuamua’s shape was extreme, or at least five to ten times longer than it was wide.

We estimated its length at about a hundred yards, or around the size of a football field, and its width at less than ten yards.

Consider, for context, that all asteroids previously seen in the solar system had length-to-width ratios of, at most, three. ‘Oumuamua’s, as I have just noted, was somewhere between five and ten.

‘Oumuamua proved to be relatively bright, at least ten times more reflective than typical solar system asteroids or comets. If, as seems possible, ‘Oumuamua was a few times smaller than the upper limit of a few hundred yards that scientists presumed it to be, its reflectivity would approach unprecedented values—levels of brightness similar to a shiny metal.

Overall, about a quarter of our galaxy’s two hundred billion stars are orbited by planets that are habitable in the way Earth is, with surface conditions that allow liquid water and the chemistry of life as we know it. Given so many worlds—fifty billion in our own galaxy!—with similar life-friendly conditions, it’s very likely that intelligent organisms have evolved elsewhere. And that’s counting only habitable planets within the Milky Way. Adding all other galaxies in the observable volume of the universe increases the number of habitable planets to a zetta, or 1021—a figure greater than the number of grains of sand on all of the beaches on Earth.

Some of the resistance to the search for extraterrestrial intelligence boils down to conservatism, which many scientists adopt in order to minimize the number of mistakes they make during their careers. This is the path of least resistance, and it works; scientists who preserve their images in this way receive more honors, more awards, and more funding. Sadly, this also increases the force of their echo effect, for the funding establishes ever bigger research groups that parrot the same ideas. This can snowball; echo chambers amplify conservatism of thought, wringing the native curiosity out of young researchers, most of whom feel they must fall in line to secure a job. Unchecked, this trend could turn scientific consensus into a self-fulfilling prophecy.

Recall the clerics who refused to look through Galileo’s telescope. The scientific community’s prejudice or closed-mindedness—however you want to describe it—is particularly pervasive and powerful when it comes to the search for alien life, especially intelligent life. Many researchers refuse to even consider the possibility that a bizarre object or phenomenon might be evidence of an advanced civilization. Some of these scientists claim that they simply will not dignify such speculation with their attention. But as I’ve noted, other forms of speculation are enshrined in the scientific mainstream—the existence of multiple universes, for example, and the extra dimensions predicted by string theory, and this despite the fact that there is no observational evidence for either of these ideas and perhaps never will be.

These are certainties, and they allow us to declare confidently that the first three of ‘Oumuamua’s identified anomalies—its unusual orbit without a tail, its extreme shape, and its luminosity—make it statistically different, by a large margin, from all other objects cataloged by humanity. To put this distinctiveness in statistical terms, we can conservatively state that based on its extra push and its lack of a cometary tail, ‘Oumuamua is a one-in-a-few-hundred object. Based on its shape, it is, also conservatively, a one-in-a-few-hundred object. And based on its reflectivity, it is (again, conservatively) at least a one-in-ten object. When we multiply those three anomalous qualities, we can appreciate how much of an outlier ‘Oumuamua is. It is now a one-in-a-million object.

a quarter of all stars hosted habitable Earth-scale planets. Even if only a small fraction of all habitable Earths led to technological civilizations like our own during the lifetime of their stars, there might be plenty of relics out there in the Milky Way for us to explore.

even more intriguing was the possibility that we would find flying through our solar system technological relics with no detectable functionality—for example, pieces of equipment that had lost power over the millions of years of their travel and become space junk.

Today, a young theoretical astrophysicist is more likely to get a tenure-track job by pondering multiverses than by seeking evidence of extraterrestrial intelligence. This is a shame, especially because budding scientists are often at their most imaginative during the early phases of their careers. During this fertile period, they encounter a profession that implicitly and explicitly reins in their interests by stoking their fear of standing outside the mainstream of science. An earlier generation of theoretical physicists was open to the humility of seeing their theories proven wrong by experimental data. But a new culture, one that thrives in its own theoretical sauce and exercises influence over award committees and funding agencies, is populated by advocates of popular yet unproven paradigms. When scientists double down on supersymmetry despite the Large Hadron Collider finding no evidence for it or when they insist that the multiverse must exist despite there being no data to support the theory, they are wasting precious time and money and talent. And we have not only finite funds to spend, but finite time.

As it happens, the Sun-Earth system is anomalous in two clear respects. First, the Sun’s mass—330,000 times that of Earth—makes it more massive than 95 percent of all known stars. And while this does not rule out our interest in searching for life on planets orbiting more statistically average stars, given that we have limited resources of time and money, it encourages us to look for stars that are especially massive, like the one that sustains us.

What is more, we now know that about a quarter of all stars are orbited by planets of Earth’s size and surface temperature, planets that might have liquid water—and the building blocks of the chemistry of life—on their surfaces.

Evidence is omnipresent for the real probability that humanity has not set the intelligence bar particularly high and that other civilizations have likely cleared it. It is as close as your newspaper, your nearest screen, and your endlessly refreshing newsfeed. The true marker of intelligence is the promotion of one’s own well-being, but too often our behavior does the opposite. I have found that paying close attention to the world’s most pressing news stories provides ample evidence that we cannot be the smartest species out there.

Humanity has rarely focused on its collective well-being, not over the preceding centuries and not today. Among our current bad habits, we repeatedly opt for short-term benefits over long-term benefits in matters as complex as carbon-neutral energy, as fraught as vaccines, and as obvious as shopping with reusable bags. And for over a century we have been broadcasting our existence to the entire Milky Way in radio waves without pausing to worry if any other civilizations out there might be both smarter than us and more predatory.

I have often used the analogy of cave dwellers discovering a modern cell phone. It aptly applies to the possibility that soon humanity may discover a piece of advanced technological equipment developed by an extraterrestrial intelligence. If we do not prepare ourselves, if we have not allowed for the science of space archaeology, we could act much as these cave dwellers would, imagining the phone to be nothing more than an exotic, shiny rock. And with that shortsightedness, those dwellers would miss the chance to take that million-year leap forward. One fact is clear. If we assign a zero probability for finding evidence of artificial objects, as some scientists did in the case of ‘Oumuamua, if human civilization organizes its efforts and its funding and its scholars by declaring, “It’s never aliens,” then we guarantee that we will never find evidence of extraterrestrial civilizations. To move forward, we must think outside of the box and avoid prejudice about what we expect to find based on past experience.

Youth is a matter not of biological age but of attitude. It is what makes one person willing to open up new frontiers of scientific discovery while others try to stay within the traditional borders. Becoming a scientist offers the great privilege of maintaining our childhood curiosity and questioning unjustified notions. But this opportunity does nothing for anyone unless people seize it.

The Myth of Sisyphus. According to Greek mythology, Sisyphus was punished by the gods and forced for all eternity to roll a heavy boulder up a hill only for it to roll back down once he managed to get it nearly to the top.

during the Second World War, Japanese soldiers were willing to sacrifice their lives for the sake of their emperor, Hirohito. But in view of our recent realization that there are approximately a zetta (or 1,000,000,000,000,000,000,000) of habitable planets in the observable universe, the emperor’s status cannot be more significant than that of an ant hugging a single grain of sand on a huge beach. And what is true of an emperor is no less true for a soldier or anyone else on Earth. We would do well to look up and look beyond that grain of sand. Perhaps, rather than behaving like outsize actors in puny roles, we should adopt the perspective of spectators and simply enjoy the dazzling show all around us. And in the broad spirit of stopping to smell the roses (or inspect the seashells), there is much for the spectator to enjoy, both on Earth and off it. If the rich spectacle of events on our planet is insufficiently inspiring, we can use our telescopes to witness an even wider variety of dramas.

Many scientists argue that we should communicate information to the public only once our collective detective work has produced a nearly unanimous conclusion. These colleagues of mine believe that discretion is necessary to preserve our good image. Otherwise, they reason, the public could come to doubt scientists and the scientific process. Indeed, this occurs even when there is near unanimous conclusion among scientists. Consider, they often point out, the minority of the public who still question climate change. Stepping into controversy that could erode the stature of science, they worry, is too great a risk. But my view is different. I think that in order to be credible, we need to show that scientific inquiry is a process that is more common and familiar than much of the public presumes. Too often, the approach taken by my colleagues contributes to the populist view of science as an occupation of the elite and fosters a sense of alienation between scientists and the public. But science is not some ivory-tower affair that, through inaccessible means, yields ironclad truths that can be dispensed only by sages. The scientific method is, in fact, closer to the commonsense approach to problem solving that a plumber adopts when trying to fix a leaking pipe.