Extraterrestrial: The First Sign of Intelligent Life Beyond Earth

by Avi Loeb

A better, more precise framing of the question would be this: Throughout the expanse of space and over the lifetime of the universe, are there now or have there ever been other sentient civilizations that, like ours, explored the stars and left evidence of their efforts? I believe that in 2017, evidence passed through our solar system that supports the hypothesis that the answer to the last question is yes.

Over the years, I have come to believe that the laws of physics cease to apply in only two places: singularities and Hollywood.

Measured by all dimensions, each human life is infinitesimal; our individual accomplishments are visible only in the aggregate of many generations of effort. We all stand on the shoulders of our predecessors—and our own shoulders must support the endeavors of those who will follow. We forget that at our peril, and theirs.

It is commonly thought that life is a collection of the places you visit. But this is an illusion. Life is a collection of events, and these are the results of choices, only some of which are ours to make.

Long before I confronted the evidence presented by ‘Oumuamua, I had learned that across all facets of life, taking the evidence presented to you and pursuing it with wonder, humility, and determination can change everything—if, that is, you are open to the possibilities contained in the data.

Sometimes, by near accident, something exceptionally rare and special crosses your path. Life turns on your seeing clearly what’s in front of you.

In addition to being small and oddly shaped, ‘Oumuamua was strangely luminous. Despite its diminutive size, as it passed the Sun and reflected the Sun’s light, ‘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.

As I have mentioned, when ‘Oumuamua sped part of the way around the Sun, its trajectory deviated from what was expected based on the Sun’s gravitational force alone. There was no obvious explanation for why.

Ultimately, all of these mysteries can be traced back to one: ‘Oumuamua’s deviation from its expected path. All hypotheses as to what ‘Oumuamua is have to account for that deviation, and that means explaining the force that acted on it while respecting the fact that if there was any cometary tail of gas and dust behind it, that tail was slight enough to go undetected by our equipment.

The implication of this was obvious: Nature had shown no ability to produce anything like the size and composition of what our assumptions suggested, so something or someone must have built such a lightsail. ‘Oumuamua must have been designed, built, and launched by an extraterrestrial intelligence. It is an exotic hypothesis, without question. But it is no less exotic than other hypotheses that have been proposed to explain the outlier characteristics of ‘Oumuamua. Nature has shown no propensity to produce pure-hydrogen comets or fluffy clouds of materials that are both more rarefied than air and structurally cohesive.

As I stood at my front door, the reporter asked, “Do you believe there are alien civilizations out there?” “A quarter of all stars host a planet the size and surface temperature of the Earth,” I said into the camera. “It would be arrogant to think we are alone.”

‘Oumuamua, a small interstellar object first discovered by humans on October 19, 2017, that was highly luminous, oddly tumbling, and most likely disk-shaped, deviated from a path explicable by the Sun’s gravity alone without any visible outgassing.

Throughout the media storm that descended on me as a result of my most public work (yet) on SETI, I was often animated by a simple thought: If I attract one child somewhere in the world into science as a result of my answering the demands of the media, I will be satisfied. And if I make the public and, perhaps, even my profession more willing to entertain my unusual hypothesis, so much the better.