Cast Your Craft Upon Interstellar Waters

Avi Loeb
5 min readDec 5, 2022
On Nov. 28, 2022, NASA’s Orion spacecraft reached its maximum distance from Earth during the Artemis I mission — 268,563 miles, farther than any spacecraft designed to send humans to space and back has gone before. Here, Orion captures a unique view of Earth and the Moon, from a camera mounted on one of the spacecraft’s solar arrays (Credit: NASA).

One of the wisest life lessons is given in Ecclesiastes 11:1: “Cast your bread upon the waters, for after many days you will find it again.”

This principle of taking a risk without expecting very much in return and finding it empowering after many days, reverberated in my life recently. When my literary agent, Leslie Meredith, called me twice in 2019 to suggest that I write a book about my risky research on `Oumuamua, I first declined her proposal since I preferred to focus on scientific research. Her persistence gave birth to my book “Extraterrestrial”, which has been translated to 25 languages. In this unexpected way, my bread was cast upon international waters. Consequently, when a young Iranian-born entrepreneur asked me for a selfie at a public forum last month, I did not expect that after posting the photo on Instagram — she would receive messages from hundreds of women scientists in Iran who texted her that they follow my research on interstellar objects. Yesterday, a young Israeli woman traveled to my home and volunteered to join the Galileo Project, after being inspired by the Hebrew translation of my book. The unexpected excitement of young followers from Israel to Iran implies that the search for extraterrestrials unites all humans without borders. Every day, I get half a dozen emails from Galileo Project volunteers in countries all over the world.

We are all equal members of the human species when viewed from the perspective of space. In the image of the blue Earth taken in recent weeks by NASA’s Orion spacecraft, the border between Ukraine and Russia is invisible. Yet, this border is featured far more prominently on the front page of our daily newspapers than Orion’s perspective.

Ecclesiastes’ lesson can be generalized to the relationship between humanity and space. So far, we cast our bread upon terrestrial waters located on the two-dimensional surface of our rock of residence, the Earth. But in the future, we should broaden our horizon along the third dimension of space and venture towards waters on other planets in the Solar system and beyond. This includes the Moon and Mars which possess polar ice caps, Venus — where droplets may exist in the clouds, and the moons Enceladus, Europa and Titan, where liquid water lies under the icy surface. Casting probes upon these waters will enable us to search for extraterrestrial life or to establish sustainable human bases that reduce the existential risk to humanity from a single-residence catastrophe on Earth. But the journey must go farther, following the dictum: “Cast your craft upon interstellar space, for after millions of years you will find it again.”

The wisdom encapsulated in Ecclesiastes 11:1 is that unexpected reciprocity could be remarkably rewarding. In the long run, humanity could benefit greatly by taking the risk of venturing into interstellar space. We might discover that other technological civilizations did the same before us and that we can learn from them.

In a Zoom meeting with a former executive of SpaceX last week, I noted that Elon Musk is probably not the most accomplished rocket builder who ever lived in the Universe over the past 13.8 billion years after the Big Bang. Most Sun-like stars formed 5 billion years before the Sun, and so interstellar probes from Musk-like engineers on exoplanets could have arrived into the Solar system long ago.

The trip across the Milky-Way galaxy takes less than a billion years with SpaceX-like chemical rockets. If probes with AI astronauts arrived at the Solar habitable zone a few billion years ago, they may have been disappointed to find that the Earth’s atmosphere had little oxygen and terrestrial life took the primitive form of microbes. At that time, Mars had an atmosphere, liquid water and the chemical foundation for similar forms of life. Coincidentally, Mars lost its atmosphere at around the same time as an unknown cause triggered cyanobacteria to elevate the oxygen level in the Earth’s atmosphere 2.4 billion years ago. Was an extraterrestrial visit responsible for terraforming these neighboring planets? If so, the return of humans to Mars would be a reversal of fortune for the Red Planet and a demonstration that humanity is also capable of engineering its cosmic neighborhood.

With five interstellar probes launched by NASA, the human journey is already destined to extend beyond the Solar system. In the process of casting probes upon interstellar waters, we might encounter traffic that we never imagined. A large abundance of interstellar crafts would echo the urgent exodus from exoplanets just before the death of their star, as well as self-replicating probes that were sent billions of years ago and by now multiplied exponentially.

In the meantime, the Galileo Project seeks evidence for any interstellar probes that arrive within the Earth’s orbit around the Sun. As I showed in a recent paper with my student Carson Ezell, functional craft that target the habitable zone around the Sun will be concentrated by a factor of ten quadrillion (10 to the power of 16) relative to defunct space trash which fills space uniformly.

As noted by Ecclesiastes, it takes many days to benefit from risk taking. But the new knowledge we might gain from venturing into space could help us resolve the most fundamental and challenging scientific questions. Instead of investing billions of dollars to answer them on our own based on experiments or computers in our laboratories, we could invest a small fraction of these funds in seeking what extraterrestrials already know.

In particular, consider the most fundamental question about our cosmic roots: “What happened before the Big Bang?” The prerequisite is a predictive theory that unifies quantum mechanics and gravity. Time will tell whether the answer will be revealed from the corridors of academia on Earth or from interstellar space.


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”, is scheduled for publication 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".