Extraterrestrial: The First Sign of Intelligent Life Beyond Earth

The book describes the 2017 detection of ʻOumuamua, the first known interstellar object passing through the Solar System.[8] Loeb, an astronomer at Harvard University, speculates that the object might possibly be from an alien civilization in a far distant star system, a conclusion that is considerered unlikely by the scientific community.[9][10][11][12] Earlier, Loeb demonstrated that the interstellar object was not an asteroid, was moving too fast in a very unusual orbit and left no gas trail or debris in its path to be a comet.[13][14] Loeb believes, due to the observed acceleration of the object near the sun, that ʻOumuamua may be a very thin disk that acts as a solar sail of some sort.[2] Further, Loeb and colleagues demonstrated that the object was unlikely to be frozen hydrogen as proposed earlier by other researchers.[15][16]

Besides ʻOumuamua, another interstellar object, the comet 2I/Borisov, has been detected passing through the Solar System. In comparison, 2I/Borisov has been found to be clearly natural, whereas ʻOumuamua has not been so determined.[2] Accordingly, the possibility that ʻOumuamua may be alien technology has not been entirely ruled out, although such an explanation is considered very unlikely by most scientists.[8] Nonetheless, according to Loeb, "We should be open-minded and search for evidence rather than assume that everything we see in the sky must be rocks."[17][18]

According to Alan Lightman, American physicist and The New York Times best-selling author, the book is "provocative and thrilling," and Lightman commends Loeb for suggesting that readers "think big and to expect the unexpected."[1] Jeff Foust, editor and publisher of The Space Review, comments that Loeb "fails to close the case that the object must be artificial ... Just because something can’t be immediately explained by natural phenomena doesn't mean it’s not natural". Further, "Perhaps ʻOumuamua will turn out to be the first of many in a new class of interstellar objects with an unusual, but natural, origin. Or, maybe, it will be like the “Wow!” signal, which was never seen again and its source never identified; mysterious, but not necessarily alien".[19] Dennis Overbye. science writer for The New York Times, notes that the book is, "part graceful memoir and part plea for keeping an open mind about the possibilities of what is out there in the universe — in particular, life. Otherwise, he says, we might miss something amazing, like the church officials in the 17th century who refused to look through Galileo’s telescope."[20] Reviewing for The New Yorker, Elizabeth Kolbert, a Pulitzer-Prize winner, writes, "It seems a good deal more likely that [the book] will be ranked with von Däniken's work than with Galileo's," but concedes "it's thrilling to imagine the possibilities."[21]

• Popularizers of science, listing of notables – Interpretation of science intended for a general audience

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