What is Real?

Avi Loeb
5 min readAug 23, 2022


Webb telescope image of the gravitationally lensed star Earendel at z=6.2. (Credit: Welch et al. 2022)

In a recent podcast hosted by Lex Fridman, the clinical psychologist Jordan Peterson asked: “What is real?”

Jordan knocked on the table in front of him and confirmed: “matter is real.” He then continued: “What else? Pain is real, love is real.” As he described human feelings, I thought to myself: “Well, real things are associated with physical systems, and pain or love are just emergent phenomena in the complex human body.” The laws of physics describe all real entities.

This is not a philosophical argument, since it can be tested experimentally. By constructing sentient systems with artificial intelligence (AI), we will be able to reproduce emergent phenomena out of the matter that makes computers. In this way, we could test whether the pain associated with the loss of a friend from death caused by a stroke would resemble the pain of losing a friendly sentient AI system by the non-reversible damage inflicted on its operating system from an electric power outage.

Also, in finding what is real, we should look outwards and not just inwards. And by outwards, I mean into the Universe. There is much more out there than meets the eye here on Earth.

So far, the unambiguous signals we received from the Universe at large relate to physical matter, not sentient entities. Astronomers have imaged the matter in the Universe all the way back to 400,000 years after the Big Bang — in the form of brightness fluctuations of the cosmic microwave background, or hundreds of millions of years later — in the form of the deep images from the Webb telescope.

From these images, cosmologists infer that most of the matter in the universe is not of the type familiar from the Solar system. Our ignorance about its nature is encapsulated in its label: “dark matter”. Similarly, the first two interstellar objects do not resemble the familiar rocks in the Solar system. Perhaps they represent emergent phenomena of sentient beings, like a flat, lightsail-shaped leaflet that we labeled `Oumuamua, or a technological artifact tougher than iron that we labeled as the meteor CNEOS 2014–01–08, or AI systems in Earth’s atmosphere that are catalogued by the intelligence agencies as Unidentified Aerospace Phenomena (UAP). One thing is clear. We would appear intelligent if we were curious about these objects as much as we are curious about the nature of dark matter. To find what is real we must seek new evidence, as the Galileo Project aims to do.

The chance of identifying emergent phenomena of extraterrestrial intelligence scales with the probability of reproducing the conditions that led to our existence on Earth. This, in turn, depends on the fraction of Sun-like stars that host an Earth-size planet in their habitable zone, labeled in the astronomical literature by the parameter: eta_Earth. Over the past few years, there were multiple attempts to analyze the statistics of planets based on the Kepler satellite data. These studies resulted in a wide range of values for eta_Earth between a few percent and nearly a hundred percent.

While discussing the large uncertainty in the value of eta_Earth with the Galileo Project member, Ed Turner, he noted wisely that “the 800-lb gorilla in the room is really the far more difficult and unsettled question of what are the necessary and sufficient conditions to make a planet “Earth-like” in the context of life, intelligence and technology.” We both agreed that the best way to calibrate the abundance of extraterrestrial technological civilizations is through an observational search, such as the Galileo Project is pursuing.

And it is not just planets in the Milky-Way galaxy that might give rise to emergent phenomena of sentient beings, but also those in trillions of other galaxies within the observable volume of the Universe or beyond. Intelligence could have emerged as soon as the centers of galaxies were enriched with heavy elements in the first billion years of cosmic history.

The most remarkable data obtained by the Webb telescope from the first billion years after the Big Bang concerns a single star called Earendel, which was gravitationally lensed by a foreground cluster of galaxies WHL0137–08 and magnified by a factor between four thousand and several tens of thousands. Given that the Webb telescope is so sensitive to detect the light from a single star at a cosmological redshift of 6.2, it might also be able to detect emergent phenomena from sentient beings, like city lights on the night side of a habitable planet, as considered two years ago in a paper I wrote with the Stanford undergraduate student, Elisa Tabor.

But a message may arrive from cosmological distances in other forms. For example, one may wonder whether among the numerous fast radio bursts detected so far, there is one transmission from a powerful radio system operated by an extraterrestrial civilization, as considered in a paper I wrote with my former postdoc, Manasvi Lingam.

If we ever discover that there is a smarter kid out there, this will be part of what we regard as the reality of our cosmic neighborhood. Such a realization of what is real would be far more uplifting than any talk about the pain of human existence on Earth.


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.



Avi Loeb

Avi Loeb is the Baird Professor of Science and Institute director at Harvard University and the bestselling author of “Extraterrestrial” and "Interstellar".