By now, I had written more than a thousand scientific papers, five hundred essays and eight books. In a conversation with graduate students of the Harvard Astronomy department, I explained that signs of gratitude are far more common regarding my writings for the public. Strangers routinely approach me in public places, ask for selfies and express gratitude for my work. This was not the case in preceding decades when I focused solely on writing scientific papers and textbooks. As of now, I am steadily invited to large-scale public events, where I meet and converse with the general public. When asked to autograph one of my books, I often write: “Keep your inspiration from the sky!”
Astronomy is different from the rest of science in that it engages with the reality that lies far from Earth. Because of that, most astronomical revelations — like the discovery of dark matter, dark energy or black holes, have little impact on our daily lives. But also because of that, some unexpected revelations carry the potential of changing everything for us.
For example, three quarters of plant and animal life on Earth including non-avian dinosaurs, were extinct as a result of an impact by a rock the size of Manhattan Island — the Chicxulub impactor, that fell unexpectedly from the sky sixty-six million years ago. According to a recent paper, its impact generated a plume of fine silicate dust that blocked sunlight and triggered a global winter with a decline of 15 degrees Celsius in the average surface temperature on Earth. This would have devastated our civilization as much as a global nuclear war.
Obviously, such “global cooling” events pose an existential threat to humanity. But like the dinosaurs, humans were not aware of the risk from rocks falling from the sky prior to the 18th Century. It was the testimonies from residents of the French town of L’Aigle who witnessed more than 3,000 stones falling from the sky on April 26th, 1803, which finally helped scientists confirm that meteorites came from space.
Just a decade before this event, a physicist named Ernst Chladni had published in 1794 a book suggesting that meteorites came from space. The historian Ursula Marvin writes that Chladni was hesitant to publish, because he knew that he was “gainsaying 2000 years of wisdom, inherited from Aristotle and confirmed by Isaac Newton, that no small bodies exist in space beyond the Moon.”
A few months after the meteorites fell in L’Aigle, the physicist Jean-Baptise Biot traveled there for nine days to analyze the event. Biot was a strong believer in the power of science communication, and his literary report on the L’Aigle meteor fall was echoed in popular media as well as in the scientific community, amplifying his conclusion that “stones fell around L’Aigle.” Because his report relied on evidence from many independent witnesses, it raised wide public interest.
The researcher Matthieu Gounelle notes that “Biot distinguished two kinds of evidence of an extraterrestrial origin of the stones.” First, the kind of stone that had fallen was totally different than anything else available locally — but it was similar to the stone from the Barbotan meteor fall in 1790. Biot wrote: “The foundries, the factories, the mines of the surroundings I have visited, have nothing in their products, nor in their slag that have with these substances any relation.”
Second, unlike earlier meteor falls, there were multiple witnesses “who saw ‘a rain of stones thrown by the meteor,’” Gounelle writes. The witnesses came from different backgrounds, and so Biot reasoned that it would be ridiculous to think they had all conspired to report on something that had not actually taken place.
Fast forward two centuries later, when the first interstellar objects were reported. The first was the meteor, IM1, identified by US Government satellites in 2014, which was faster and tougher than solar system rocks. The second was `Oumuamua in 2017, which exhibited an extreme shape and a non-gravitational acceleration without noticeable evaporation, unlike the familiar asteroids and comets of the solar system.
When I wrote scientific papers on a possible technological origin for one or both of these objects, followed by the bestselling book “Extraterrestrial” and more recently “Interstellar”, I was following the spirit of Ernst Chladni in gainsaying decades of wisdom, inherited from and confirmed by solar system experts, that all small bodies beyond the Solar system must be natural in origin.
The Galileo Project is currently engaged in the scientific search for extraterrestrial technological objects near Earth. The research team studies anomalies in the data flowing from our first observatory at Harvard University as well as the composition data on the “BeLaU”-type spherules retrieved from IM1’s site in the Pacific Ocean. In the future we hope to search for `Oumuamua-like objects in the LSST data stream from the Rubin Observatory in Chile. Here’s hoping that Project’s findings will play a similar role to Biot’s findings in demonstrating the reality of unexpected objects from outer space.
As Mark Twain noted: “a favorite theory of mine [is] that no occurrence is sole and solitary, but is merely a repetition of a thing which has happened before, and perhaps often.” Here’s hoping that history will repeat itself two centuries later, and we will be inspired once again by unexpected objects in our sky.
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.