Extraterrestrial: The First Sign of Intelligent Life Beyond Earth by Avi Loeb

This book is part auto-biography/memoir, part popular science. It relates two stories which are intersected, one Loeb’s and the other ‘Oumuamua’s. Loeb is a reputed astro-physicist from Harvard University. ‘Oumuamua is a space object identified in 2017 and which possessed qualities that did not follow patterns known to scientists. Although ‘Oumuamua was sighted on its way out of the solar system, scientists were able to collect some data from it. Anomalies were identified, and different hypotheses were considered to explain them. For example, its path and speed could not be explained by gravitational forces. Paper after paper, opinion after opinion, scientists tried to make the data collected match accepted theories, but they ended up with more questions. Loeb instead (being curious and out-of-the-box thinker) hypothesised that the data could not be explained by any known natural force/process and therefore ‘Oumuamua should be an alien artifact. This is only a hypothesis, mind you, but it grabbed the attention of academia, the media and everyone. 

In this book, Avi Loeb explains how his early life, studies and previous work have shaped the way he thinks. He provides a few examples of projects and papers he’s written with collaborators, in which he tackles exceptional, unconventional questions. Loeb argues for more unorthodox questions, which would allow us to arrive at unexpected findings. My favourite 2 chapters are Learning from Children and Vastness, in which he praises children’s innate curiosity and criticises stiff historical and current scientific patterns and ideologies, which hinder progress. He illustrates his ideas with several examples from his life and work. These are easy to read and understand.

All fine, except that I borrowed the book expecting to learn more about ‘Oumuamua the object and stronger justifications for the alien artifact hypothesis. Loeb presents the problem but does not give much more in this regard. I think he wrote the book to encourage other scientists—and especially the general public—to broaden their perspectives on the possibility of aliens and begin conducting serious research in that area. In this regard the following quote is one of my favourites: 

“One fact is clear. If we assign a zero probability for finding evidence of artificial objects, as some scientists did in the case of ‘Oumuamua, if human civilisation organises its efforts and its funding and its scholars by declaring, “It’s never the aliens,” then we guarantee that we will never find evidence of extraterrestrial civilisations. To move forward, we must think outside of the box and avoid prejudice about what we expect to find based on past experience.” 

1I/‘Oumuamua was sighted in Oct 2017 and has been classified as an interstellar object. A second object, 2I/Borisov, was sighted in Aug 2019. Unlike ‘Oumuamua, Borisov has been classified as a comet. A third interstellar object, 3I/ATLAS, was recently identified in July 2025. It remains under investigation, but current observations indicate it displays comet-like characteristics.