Enrico Fermi famously asked: “where is everybody?” and Elon Musk echoed the same frustration last month: “I have not seen aliens yet.” But as with any relationship, we have to ask ourselves: “what have we done to deserve a cosmic partner?”
A few days ago, I delivered a keynote lecture in a public celebration at the city of Toruń in Poland, the birthplace of Nicolaus Copernicus 550 years earlier, on the subject of “The Next Copernican Revolution.” Copernicus inferred from data that we are not located at the center of the Universe because the Earth moves around the Sun. In other words, he realized that we occupy an unprivileged cosmic status, which was problematic given his role as a priest. The church adopted his heliocentric model because it allowed to accurately predict the time of Easter, but the theologians insisted that the model is a purely theoretical concept that does not represent reality and so they listed his De revolutionibus as a forbidden book until the 19th Century. Ironically, the agreement of a theoretical model with data is the only way to assess its realism in modern science, as pioneered by Galileo Galilei — who discovered the Moons of Jupiter a century later as confirmation of the heliocentric model of Copernicus. In 1992, the Vatican admitted that Galileo Galilei was right, but this came a bit late — 23 years after Apollo 11 that first landed humans on the Moon.
Applying the Copernican principle that we are not privileged to the search for cosmic partners, would naturally suggest that Sun-Earth analogs must have given rise to other technological civilizations like ours. Moreover, if extraterrestrials resembled us right now, then they are unlikely to notice us and we are unlikely to notice them. This would account for the frustration expressed by Fermi and Musk. Let me explain.
Earth had been transmitting city lights and radio signals to space for just over a century, which is merely one part in a 100 million of the life-span of Sun-like stars. If all Sun-like stars had a transmission episode that long at random times, there would have been only a thousand out of a hundred billion doing that at any particular time. The average separation between synchronized civilizations would have been about a thousand light years. But given that our transmission was recent, only aliens within a distance of about a hundred light years would be able to notice our technological advance and may not be that close if the average distance is ten times larger. But even at closer distances, the task requires better telescopes than we currently possess. As I showed in a paper with Elisa Tabor, our city lights cannot be noticed by the Webb telescope even at the distance of the nearest star, Proxima Centauri. Moreover, as I showed in another paper with Matias Zaldarriaga, our current radio transmissions are only detectable out to a hundred light years with our best radio telescopes.
Altogether, the chances are small that anyone would notice our electromagnetic transmissions if they resemble us right now. And even if they do notice us from a distance of a hundred light years, it would take another century before we will hear back from them. One reason for why they may not evolve beyond our current phase is that we reached the phase when self-destruction is easy so we might not survive much longer.
What about the detection of physical objects, like technological trash, instead of electromagnetic signals? Indeed, we launched 5 interstellar probes and they will leave the solar system while being gravitationally-bound to the Milky-Way galaxy. It will take them tens of thousands of years before they enter the territorial space of other stars. At that future time, they will be defunct, essentially space trash. Hence, our remaining hope is to find the space trash of those who preceded us by more than a billion years, the time that it will take our technological trash to fill the volume of the Milky-Way galaxy.
Unfortunately, our best survey telescopes, like the Zwicky Transient Facility or Pan-STARRS, can only notice the level of sunlight reflected from objects bigger than a football field at the Earth-Sun distance. Our civilization has not launched any spacecraft of that size so far. By the Copernican principle, it is therefore not surprising that it is challenging to find trash from similar polluters. Starting in 2025, the new Rubin Observatory will employ a 3.2-billion-pixel camera to survey the southern sky every 4 days. It might find new interstellar objects from other technological polluters that launched junk like Musk’s Tesla Roadster, the dummy payload on the 2018 test launch of the Heavy Falcon. Objects as small as the Tesla Roadster can be detected as technological meteors.
In my lecture at Toruń, I provided details about our findings from the Pacific Ocean expedition to recover materials from the first recognized interstellar meteor. The analysis results were reported in an extensive paper last week, suggesting that the recovered materials originated from outside the solar system based on their anomalous chemical composition.
In summary, the Copernican principle explains why we feel lonely in the Universe at this time. We have not made ourselves noticeable sufficiently far throughout the Milky-Way galaxy, and we cannot identify civilizations like ours at the distances that most of them reside. We better put some effort into a more thorough search rather than complain “where is everybody?” It is up to us to find our partners instead of waiting for them to find us. Rather than complain about being single and lonely, let’s get into action and seek relationships. This will constitute our next Copernican awakening.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, was published in August 2023.
