The Anatomy of Black Swans

Avi Loeb
5 min readJun 17, 2024


The Australian black swan (Cygnus atratus). (Image credit: Wikimedia)

What do events like the burst of the dot-com bubble in 2000, the terrorist attacks of September 11, 2001 or October 7, 2023, and the global financial crisis in 2008, have in common with the search for aliens?

This is the topic I addressed today at a fascinating summit of technology professionals. A first hunch for the common denominator of these events is that they all pose serious threats. After all, aliens could put humans on their dinner menu. But there is a far more substantive thread than that. As much as this deeper thread has important consequences for national security, it also carries crucial implications for innovation in science.

Who would have thought that the first recognized interstellar object, named `Oumuamua, would be nearly flat, exhibit non-gravitational acceleration without a cometary tail and change its brightness by a factor of ten as it tumbles, or that the first recognized interstellar meteor, named IM1, would move faster than 95% of the nearby stars and be tougher than all Solar system meteorites, or that Musk’s Tesla Roadster car might fall as a human-made meteor from the sky within 20 million years, or that animals could have walked between Europe, America, Asia, Africa, Antarctica, India and Australia 200 million years ago when these continents were all part of the Pangaea supercontinent, or that measuring reality is fundamentally uncertain according to quantum mechanics, or that the vacuum can accelerate cosmic expansion or that … perhaps we are not alone?

These are all `Black Swans,’ a metaphor used to describe major occurrences that appear as a surprise and are rationalized retroactively with the benefit of hindsight. Actual biological black swans were presumed not to exist until 1697 when Dutch explorers first discovered them in Australia. In 2007, Nassim Taleb described insightfully the response of experts to so-called `Black Swan events’: “First, it is an outlier, as it lies outside the realm of regular expectations, because nothing in the past can convincingly point to its possibility. Second, it carries an extreme impact. Third, in spite of its outlier status, human nature makes us concoct explanations for its occurrence after the fact, making it explainable and predictable… Our inability to predict in environments subjected to the Black Swan, coupled with a general lack of the awareness of this state of affairs, means that certain professionals, while believing they are experts, are in fact not based on their empirical record, they do not know more about their subject matter than the general population, but they are much better at narrating-or, worse, at smoking you with complicated mathematical models.” This was certainly the case for `Oumuamua which was argued to be a water-hydrogen or nitrogen iceberg of a type never seen before, even though each of these explanations suffers from fatal flaws that rule it out quantitatively. Some self-proclaimed experts claimed that this football-field size object is a `dark comet’, without checking that the evaporation rate in that case would be too small to explain `Oumuamua’s anomalous non-gravitational acceleration, which requires shedding a tenth of the object’s mass during its passage near the Sun. So much so for “experts smoking you with complicated mathematical models,” in line with Taleb’s insight.

Today, I was invited to speak at a summit of experts on cybersecurity, data science, artificial intelligence (AI), financial technology and digital health. I presented the case that `Black Swan events’ trigger breakthroughs in science but are not expected because of our limited imagination. In some scientific subfields, like the nature of dark matter, imagining `black swans’ is encouraged. But in others, like the study of near-Earth objects, a paper showing material evidence that an interstellar meteor was detected by U.S. Government was met with denial by solar system experts, who published a paper in The Astrophysical Journal insisting that the data must be wrong, even though in retrospect a more recent paper showed evidence that the Government data is likely correct.

During the past forty years, I worked on a broad range of topics in theoretical astrophysics, ranging from the Big Bang, dark matter and dark energy to the formation of the first stars and black holes to the emergence of life in the cosmos and the future of the Universe. Witnessing different scientific cultures of experts in the various disciplines gave me immunity to unsubstantiated criticism. Why would it be legitimate to speculate about extra dimensions and not about a possible technological origin for the anomalies of `Oumuamua or IM1?

The emotional response of experts reflects how invested they are in past knowledge. In fields where little is known empirically, theoretical speculations thrive, whereas in phenomenological fields with complex experimental input, imagination is suppressed.

The number of people increased by a factor of 4 since quantum mechanics was discovered a century ago. Regression to the mean according to the central limit theorem in statistics may explain why scientific papers are becoming less disruptive today than they were a century ago.

What do all `Black Swan events’ have in common? Their anatomy reveals a lack of imagined possibilities and the dismissal of first evidence that counteracts commonly adopted prejudice. Based on the number of selfies requested after my talk, it was apparent that the summit attendees resonated with my message.

If trained properly, AI systems can process large data sets and identify subtle early signatures of a `black swan’ before humans flag them. Our ability to anticipate `Black Swan’ occurrences in science would benefit from welcoming originality of thought and diversity of opinions with the help of human intelligence. My rule is to always encourage at least one dissenting view in my research team at any given time.

The swans swimming in interstellar space could be very different from the familiar `white swans’ of the Solar system. This is already evident from the fact that we did not witness dark matter or dark energy in the Solar system. But it may also be the case that common rocks ejected by planetary systems around dwarf stars are different from solar system rocks. We should allow for the possibility that Elon Musk was not the most accomplished space entrepreneur since the Big Bang, and so interstellar cars might collide with Earth long before Musk’s Tesla Roadster does it. They might appear as meteors of a type that we had not seen before, and their surviving engines might have piled up over the centuries at the bottom of our oceans.


(Image credit: Chris Michel, October 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 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".