One solution to Fermi’s paradox: “where is everybody?” contends that technological civilizations are short lived because of self-inflicted wounds. This tendency shortens the lifespan of detectable civilizations in the Drake equation and limits their ability to venture into interstellar space.
Our own emerging technologies opened three concurrent wounds: the biological impact of processed food on human health, the influence of energy production on climate change, and the bruising effect of artificial intelligence (AI) algorithms in social media on political polarization and mental health.
But what if extraterrestrial civilizations found the recipe for overcoming self-destruction? Are we ready to accept an extraterrestrial technological package carrying this uplifting message in our sky? And if so, what could we learn from this interstellar package?
The opportunities for identifying extraterrestrial technologies near Earth is discussed in a new scientific paper that I wrote with Dr. Sean Kirkpatrick who serves as director of the All-domain Anomaly Resolution Office which was established by the National Defense Authorization Act for fiscal year 2022 at the Pentagon on July 2022, in coordination with the Director of National Intelligence.
Our paper, which is still under review, describes the physical constraints that can be set on objects moving through the Earth’s atmosphere or oceans based on radar and infrared data. These constraints could guide the interpretation of Unidentified Aerial Phenomena (UAP) based on standard physics and known forms of matter and radiation. We show that the friction of UAP with the surrounding air or water is expected to generate a bright optical fireball as well as an ionization tail with associated radio signatures. The fireball luminosity scales with inferred distance to the 5th power. The radar cross-section of the resulting ionization tail scales in proportion to the radius and length of the ionization cylinder. A lack of all these observable signatures could imply inaccurate distance and velocity measurements for single site sensors without a reliable gauge of range.
In 2005, the US Congress tasked NASA to find 90% of all Near Earth Objects (NEOs) that are larger than 140 meters. The Congressional task resulted in the construction of the Pan-STARRS telescopes in Hawaii. On October 19, 2017, the Pan-STARRS sky survey flagged an unusual NEO, the interstellar object `Oumuamua. Unlike Solar system asteroids or comets, `Oumuamua appeared to have an extreme flat shape and was pushed away from the Sun without showing a cometary tail of gas and dust, raising the possibility that it was thin and artificial in origin. Three years later, Pan-STARRS discovered a definitely artificial object, namely NASA’s rocket booster 2020 SO, which exhibited a similar behavior involving an extreme shape, a push by the Solar radiation pressure and no cometary tail because its thin walls were made of stainless steel.
On March 9, 2017, seven months before `Oumuamua’s closest approach to Earth, a meter-size interstellar meteor, IM2, collided with Earth, based on a recent paper I published with my student Amir Siraj. Surprisingly, IM2 had an identical speed relative to the Sun at large distances and an identical heliocentric semimajor axis as `Oumuamua had. But the inclination of IM2’s orbital plane around the Sun was completely different from `Oumuamua’s, implying that the two objects are unrelated.
Nevertheless, the coincidences between some orbital parameters of `Oumuamua and IM2 raises the possibility that an artificial interstellar object could potentially be a parent craft that releases many small probes during its close passage to Earth. These “dandelion seeds”, mentioned in my book Extraterrestrial, could be separated from the parent craft by the tidal gravitational force of the Sun or by a maneuvering capability. A small ejection speed at a large distance could lead to a large deviation from the trajectory of the parent craft near the Sun. The changes would manifest themselves both in arrival time and distance of closest approach to Earth. With proper design, these tiny probes would reach Solar system planets for exploration, as the parent craft passes by within a fraction of the Earth-Sun separation just like `Oumuamua. Astronomers would not be able to notice the spray of mini-probes because they do not reflect enough sunlight for existing survey telescopes to notice them if they are on the 10-centimeter scale of CubeSats or smaller. Objects of this size that reflect a tenth of the sunlight impinging on their surface from a distance comparable to the Earth-Sun separation, would yield a flux that is several orders of magnitude too faint to be detected by the Webb Space Telescope. In contrast, the radar signatures of a meter class object like IM2 would be detectable with deep space radars up to an altitude above 36,000 kilometers, beyond the scale of geosynchronous orbits. Such objects could also become optically detectable as they get close to Earth, especially if they heat up as a result of their friction with air. With a large surface-to-mass ratio of a parachute, technological “dandelion seeds” could slow down in the Earth’s atmosphere to avoid burnup and then pursue their objectives wherever they land.
Within a close range to a star, extraterrestrial technological probes could use starlight to charge their batteries and liquid water as their fuel. This would explain why they might target the habitable region around stars, where liquid water may exist on the surface of rocky planets with an atmosphere — like the Earth. Habitable planets would be particularly appealing to trans-medium probes, capable of moving between space, air and water. From a large distance, Venus, Earth or Mars would be equally attractive. But upon closer inspection, Earth would show spectral signatures of liquid water (through reflection of blue light) and vegetation (through its red edge) that might attract more attention.
What would be the purpose of an interstellar journey? In analogy with actual dandelion seeds, the probes could propagate the blueprint of their senders. As with biological seeds, the raw materials on the planet’s surface could also be used as nutrients for self-replication or scientific exploration. Interstellar travel from the edge of the Milky-Way disk of stars takes 50,000 years at the speed of light, and half a billion years at the speed of chemical rockets. Therefore, it is presumptuous to imagine that the original intent of interstellar probes launched long before we became distinguishable from nature, had anything to do with us as a technological civilization.
Based on the detection rate of interstellar objects, I estimated in a paper with my student Amir Siraj that for every interstellar NEO there are a thousand Solar system NEOs of the same size. Searching for interstellar meteorites among the many more meteorites from the Solar system without information about their impact velocity, is like searching for a needle in a haystack.
This is why the first interstellar meteor (IM1), confirmed by velocity measurement of the US Space Command, is the target of a fully-funded ocean expedition by the Galileo Project. Hopefully, by retrieving IM1’s fragments within the coming year we will know whether its extraordinary material strength resulted from it being made out of an artificial alloy, like stainless steel or other composite materials not yet developed by humans.
Are there any functioning extraterrestrial probes near Earth? We do not know as of yet. But the Galileo Project that I have the privilege of leading, intends to use the scientific method in exploring this possibility, following the 2021 UAP report from the Office of the Director of National Intelligence to the US Congress. The state-of-the-art suite of instruments and computer algorithms of the Galileo Project will be able to study new data in the near future.
My paper with Sean constrains the physical properties of UAP with parameters that govern their movement and interaction with the atmosphere and oceans on Earth. Existing UAP data is limited by uncertainties, allowing a wide range of possible interpretations. This inevitably leaves open the debate on whether some objects exhibit truly anomalous behavior.
When faced with the unknown, it is easy to adopt the prejudice of a believer or a skeptic but it is much more challenging to assemble reliable evidence that will guide us to the correct answer. To paraphrase John F. Kennedy’s Moon speech delivered on my birth year of 1962, I say: “The Galileo Project members choose to collect UAP data and do other things, not because they are easy but because they are hard.”
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”, is scheduled for publication in August 2023.