Alien Earths: The New Science of Planet Hunting in the Cosmos by Lisa KalteneggerAlien Earths: The New Science of Planet Hunting in the Cosmos by Lisa Kaltenegger

Alien Earths: The New Science of Planet Hunting in the Cosmos by Lisa KalteneggerAlien Earths: The New Science of Planet Hunting in the Cosmos, by Lisa Kaltenegger is at times a fascinating book, is at times an inspiring book, is often an informative book, but also, unfortunately, is often a frustrating book. Or at least it was for me. It’s a worthy read, but one that feels like it could have been much more.

Kaltenegger is director of the Carl Sagan Institute to Search for Life in the Cosmos at Cornell University and as such is one of the best candidates for writing a book on exoplanets (those planets outside our own solar system), especially as her career has spanned the entire existence of exoplanets themselves (well, our awareness of their existence, they’ve existed for billions of years, and I’m pretty sure Kaltenegger is not that old). The details of that career, or at least some of them, are interwoven throughout the book, adding a welcome personal touch amidst the more removed science.

Kaltenegger opens by setting the stage for why we need to know more about exoplanets and why some think their existence makes the case for life beyond ourselves in the universe. Basically, it’s a numbers game, as she points out that “since the first extrasolar planets was discovered in 1995, astronomers have found more than five thousand others . . . One new world discovered for ever day sine we built the first instruments sensitive enough to detect them.” She goes to note that we’ve learned that planets are shockingly common, and given that the Milky Way has about 200 billion stars, we’re talking about (in true Sagan-speak) “billions and billons of new worlds to explore in our galaxy alone. Multiply by that by the number of galaxies (and our is hardly the largest), and, well, the point is self-evident.

From the introduction, the book moves on to various sections detailing the search for both exoplanets and life, exploring topics such as the various methods of detecting exoplanets, the telescopes and probes involved in the process both in the past and (hopefully) the future, the ways in which we might try to detect signs of life (which necessitates the surprisingly difficult task of defining life) from so far away, how we might use Earth and its signs of life as a guide, the possibility of communicating with other life if it exists, and more.

The science is all explaining quite clearly with mostly a lack of technical jargon and any that is required is just as clearly explained. If anything, I’d say the book is simpler than most popular science books I’ve read on this topic or similarly difficult ones (such as physics or biology). More than once, I found myself a little surprised at the choice to stop and explain what I would consider a relatively basic concept. That’s not a complaint, merely an observation, one based I’m sure more on my frequent reading of popular science books/magazines than on any “dumbing down” by the author.

Lisa Kaltenegger

Lisa Kaltenegger

Her descriptions of specific exoplanets we’ve already learned some details about, meanwhile, often border on the lyrical and are wonderfully vivid and compelling as she describes a water world (with reference to the famous/notorious Costner film), or one that rains lava or other equally exotic ones. I actually found myself wishing both she had spent more time giving us more full descriptions of those particular planets and gave us more total descriptions of other one as well.

Similarly, I felt the same way about the more personal stories she offered up, such as the nerve-wracking experience of watching one of your projects being launched (fingers crossed) into space, and then the the several hundred steps she had to wait patiently through, knowing failure at any one would doom the mission. Or, on a less positive note, the experiences she had in facing sexism, ranging from an early school person telling her girls don’t really do very well in the math/science area or a pair of colleagues discussing how she only achieved the position she held at the time because she was a woman. We get these sorts of vignettes sprinkled throughout, but I would have been happy to have had the book balanced more equally between the science and the personal (and really, it’s hard to separate the two), more of a 50-50 split. That’s one reason I felt the book didn’t reach its full potential.

The other is that overall, it felt somewhat disjointed, a bit scattered and at times a bit too much like it was skimming the surface of things. It’s not that the personal touches interrupted things—those elements actually were almost always seamlessly integrated. It was in the organization of explanations and the movement from one concept or mission to the other. In fact, by the end of the book I had started to wonder if the book was actually based on a series of columns she had written and then strung together in more narrative form. It isn’t, but the fact I wondered about that gives you a sense of how disjointed it felt to me. It’s also probably true that the book suffered somewhat from my having read two similar books, each of which was quite strong (The Sirens of Mars: Searching for Life on Another World by Sarah Stewart Johnson and The Possibility of Life: Science, Imagination, and Our Quest for Kinship in the Cosmos by Jaime Green) and both of which appeared on my Best of the Year lists for their respective publication years.

I’m certainly glad I read Alien Earths, particularly for the lively descriptions of those dozen exoplanets, but I couldn’t help feeling tantalized by what the book could have been. Recommended with caveats.

Published in April 2024. For thousands of years, humans have wondered whether we’re alone in the cosmos. Now, for the first time, we have the technology to investigate. But once you look for life elsewhere, you realize it is not so simple. How do you find it over cosmic distances? What actually is life?

As founding director of Cornell University’s Carl Sagan Institute, astrophysicist Lisa Kaltenegger has built a team of tenacious scientists from many disciplines to create a specialized toolkit to find life on faraway worlds. In Alien Earths, she demonstrates how we can use our homeworld as a Rosetta Stone, creatively analyzing Earth’s history and its astonishing biosphere to inform this search. With infectious enthusiasm, she takes us on an eye-opening journey to the most unusual exoplanets that have shaken our worldview – planets covered in oceans of lava, lonely wanderers lost in space, and others with more than one sun in their sky! And the best contenders for Alien Earths. We also see the imagined worlds of science fiction and how close they come to reality.

With the James Webb Space Telescope and Dr. Kaltenegger’s pioneering work, she shows that we live in an incredible new epoch of exploration. As our witty and knowledgeable tour guide, Dr. Kaltenegger shows how we discover not merely new continents, like the explorers of old, but whole new worlds circling other stars and how we could spot life there. Worlds from where aliens may even be gazing back at us. What if we’re not alone?


  • Bill Capossere

    BILL CAPOSSERE, who's been with us since June 2007, lives in Rochester NY, where he is an English adjunct by day and a writer by night. His essays and stories have appeared in Colorado Review, Rosebud, Alaska Quarterly, and other literary journals, along with a few anthologies, and been recognized in the "Notable Essays" section of Best American Essays. His children's work has appeared in several magazines, while his plays have been given stage readings at GEVA Theatre and Bristol Valley Playhouse. When he's not writing, reading, reviewing, or teaching, he can usually be found with his wife and son on the frisbee golf course or the ultimate frisbee field.

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