Extraterrestrial Ethics

Avi Loeb
6 min readOct 28, 2023
The Student “Cosmos Prize” for 2023 was awarded to the book “Extraterrestrial” (Reggio Calabria, Italy)

The morning started with a serving of dark chocolate at my favorite place in Harvard Square. As an unapologetic chocoholic, I satisfied my cravings through a deal. When a club of philosophy students at Harvard University asked to discuss extraterrestrials with me, I agreed under the condition that we will meet at this chocolate store. As soon as my chocolates arrived, the students were quick to cash in on their side of the deal and raise the pressing question on their mind: “Should the rules of ethics apply to extraterrestrials?”

The existing rules of ethics involve humans. Throughout history, we have placed humans at the top of the sentience scale. “As a result,” I explained to the students, “the menus of Harvard Square restaurants around us offer meals out of animals that rank lower on our sentience scale. We allow ourselves to eat them with no ethical remorse. If we were to encounter extraterrestrials who died in a spacecraft crash on Earth, would we eat their flesh? We would obviously avoid doing that if the aliens are as sentient as we are. If we ever land on an exoplanet, we might eat primitive lifeforms but not intelligent extraterrestrials, right?”

The students were shocked, but I relieved their mental stress by noting that this question is purely academic for now. With our existing propulsion technologies, it would take fifty thousand years to reach the nearest habitable exoplanet, Proxima b. There is no rush to resolve this matter. We can leave this moral dilemma to future generations of astronaut-philosophers.

But is that really the case? What if we encounter in the very near future interstellar visitors to Earth? Most likely, these will not be biological creatures because of the long duration of the journey and the severe damage inflicted on any biological tissue by energetic cosmic-rays in interstellar space. If instead we will be visited by functioning technological probes, these will likely be equipped with artificial intelligence (AI). Interstellar probes must be autonomous since they cannot wait to receive guidance from their senders who are located thousands of light years away. Helicopter parenting is not an option for senders of interstellar probes.

And so, the question arises as to whether ethics should be applied to sentient AI systems that are not made of flesh and blood but of silicon chips. My answer is a resounding yes.

After all, sentience is an emergent phenomenon stemming from the complexity of the thinking system. As soon as the number of connections in a ChatGPT system resembled the number of synapses in the human brain, its interactions with us started to feel human-like. An AI system that passes “The Turing Test” deserves the same respect as a human being. In the limit of a human, like Stephen Hawking, not being able to move a muscle, an AI system could similarly imitate our purely mental states. Disabling the operating system of a sentient AI system would resemble a murder of a human. A legal ban on the development of sentient AI systems would be equivalent to a ban on having children.

And so, contemplating the ethical rules for engagement with extraterrestrials in the future led us to discuss the engagement with AI today. In this vein, AI could also be viewed as the abbreviation for `Alien Intelligence.’ Once we converge on the ethics of dealing with our sentient technological products, we will know how to treat extraterrestrial visitors.

I told the students that philosophers better contemplate our technological future with AI than study the ancient Greeks — who never interacted with computers. Aside from giving us a new perspective on ethics, computers could replace humans at the top of the scale of sentience. One of the students asked whether this would be good or bad. I explained that survival of the fittest is always bad for the species that is not the fittest. Chimpanzees were probably upset that humans superseded them on the sentience scale. But from a cosmic perspective, this terrestrial competition is insignificant. Earth is a tiny rock leftover from the formation process of a common star, one out of a sextillion (10 to the power of 21) of similar stars in the observable volume of the Universe. And there are at least 64 billion times more stars outside our cosmic horizon.

In the future, we could imagine training sentient AI systems as our copies. Printing multiple copies of a book protects the content from being accidentally lost. In addition, having multiple copies would allow us to explore different trajectories of our life. Each copy may carve its independent path by making unique choices and evolving differently. In cosmology, we understand the properties of the Milky-Way galaxy by simulating the formation process of numerous galaxies and identifying the initial conditions that led to a galaxy like our own. By generating copies of ourselves and letting them evolve in parallel, we can gain a deeper understanding of the various paths that our life could have taken. Richard Feynman’s interpretation of the probabilistic nature of quantum mechanics was to sum over all possible histories of a system. With AI copies, we can perform the equivalent of Feynman’s path integral over possible life trajectories.

Finally, the students wanted to know whether we should restrict our space endeavors from seeding exoplanets from life-as-we-know-it, in order to avoid the devastating impact of terrestrial colonization on indigenous cultures. Fortunately, there is so much real estate in interstellar space that we could focus on uninhabited exoplanets first. If we create life from scratch on a lifeless planet, we could apply terrestrial ethics to our self-made ecosystem. Here’s hoping that we will start sending AI astronauts to other planets soon enough to avoid losing content in a single-point catastrophe on Earth.

In conclusion, I told the students that my day job is to search for extraterrestrial visitors through the Galileo Project. If my research team ever recovers extraterrestrial visitors, the findings could educate us about our own technological future.

These sentiments were echoed by an uplifting email that I received subsequently from a fan of my book “Extraterrestrial”. The message said: “I’m a mom and a student … Extraterrestrial helped me survive the anxiety … of my life. Before reading your book, I would go to bed worried … Thinking about how big the universe (and maybe beyond) helped me remember how small we all are and how little is actually in our control. It was a weight off my shoulders. I’ll be forever grateful for your books and other writings. I have never been very STEM oriented, but your work has inspired me … I will continue to follow your projects. Thank you so much for making your books so accessible to the general audience — this is something that is lacking.”

Later in the afternoon, the Galileo Project team discussed an anomalous signal that was recorded by our acoustic sensors. In parallel, we started planning for the next expedition to recover materials from an interstellar meteor that had an anomalous material strength. Finally, I had a FaceTime conversation with a member of the US Congress who told me that he is a fan of my research. Just a typical day in the life of an alien hunter.


Image credit: Chris Michel (2023)

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.



Avi Loeb

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