Where are all the aliens? A new book explores possible answers
Seven Rasmussen, an astrobiologist and author of the new book Cloudy with a Chance of Starships, gives readers a tour of the astonishing science behind modern searches for alien life
We’ve been looking for aliens for as long as we’ve been looking up at the starry night sky. Wondering, “What’s up there?” quickly leads to asking, “Who’s up there—and why won’t they come down here and say hi?!”
Astrobiology—the study of life in the universe, from how it began and evolved to how it might take shape elsewhere—is the catch-all scientific field in which researchers grapple with such weighty questions about what’s out there. And, at least when we contemplate the existence of little green men rather than little green microbes, one of astrobiology’s cornerstones is the Drake equation, a seven-factor formula devised by astronomer Frank Drake in 1961 that estimates whether extraterrestrial civilizations are vanishingly rare—or common as dirt.
In the new book Cloudy with a Chance of Starships, Seven Rasmussen, an astrobiologist and devoted Star Trek fan, acts as a tour guide to the astrocurious, showcasing how the Drake equation is more than the sum of its parts—it’s not just a tool for quantifying our chances of first contact but also a tracker of astrobiology’s ever changing frontiers.
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Scientific American spoke with Rasmussen about what the latest values for the Drake equation are, how the definition of “intelligent life” is slippery and how our unending search for alien neighbors is like gazing in a cosmic mirror.
In 1961 Frank Drake had a problem. He had just performed the first-ever search for extraterrestrial intelligence (SETI) by pointing a radio telescope at some nearby stars and was hosting a conference to discuss the project. He wanted to start the discussion with something cool, so he came up with a seven-[term] equation that can tell us how many civilizations we could talk to in the galaxy right now. I love the way the Drake equation is organized so much because it starts off with things that we know pretty well, such as the rate of star formation in the galaxy, and then it wades into thornier things, such as how many planets there are per star. And then it gets into really wild things, such as: What are the odds that a planet hosts intelligent life? And finally, it ends with the average lifetime of a civilization, which is something absolutely unknowable to us at present.
You say at one point in the book that astrobiology is “20 sciences in a trench coat,” which I thought was funny. So what is astrobiology, and what’s in this trench coat?
It really is, though. Astrobiology is the study of life in the universe—both as it occurs here on Earth and as it could occur elsewhere. The reason I love to say it’s 20 sciences in a trench coat is because it really draws upon every single science that we can imagine.
It has astronomy and biology in the name, but astronomy is physics, and biology is chemistry. And a lot of the things that we know about all of these different sciences come from the fossil record, and that’s all geology. And, of course, at the foundation of all these things is math. But there’s also network science in there, and if we’re talking about technological civilizations, then there’s engineering and a whole lot more. It’s really the science that encompasses all other sciences.
Another memorable bit from the book is that the most common phrase uttered by exoplanet scientists is probably a curse word, and after that it’s got to be “oops.” I think that’s an observation that says just as much about the researchers themselves as it does about their field. I’m fascinated by these sorts of peeks into the personalities of the people who are drawn to this kind of science, which is so full of big, unanswered questions. So is there anything else you can tell me about the sort of nerds that choose to become astrobiologists?
Well, it’s definitely a very specific type of nerd. You know, it’s somebody who’s adventurous and curious and, most importantly, okay with studying something for which they may never get an answer. And that’s why I first got into astronomy and astrophysics—I loved it because it was just so big. Astrobiology is this bizarre fabric that pulls and weaves together all the threads of physics and biology and intelligence and philosophy. It’s really beautiful, and it’s all about embracing the unknown.
Yeah, these are folks who are seriously, actually looking for aliens all the time—which is like every kid’s dream of what a scientist does. But the reality, I imagine, is different from the dream: What are we actually looking for when we search for alien life? In the book, you talk about “biosignatures” and “technosignatures,” for instance, but what do those actually look like?
Well, biosignatures are basically any evidence that a living creature, past or present, has interacted with whatever environment or material you’re looking at—like if a rover rolling around Mars finds a fossil. Another example would be gases produced by living creatures that leak out into the air—so-called atmospheric biosignatures, a topic I’ve studied in-depth in my research. Earth’s atmosphere, for example, has lots of free oxygen—but it also has methane, which is a gas emitted by some types of microbes that isn’t thermodynamically stable in the oxygen’s presence. I talk a lot more about this in the book, with the upshot being how, if you see a whole lot of methane on a somewhat Earth-like planet, that could be evidence that Earth-like life is there, too.
Source: Read the original article on www.scientificamerican.com
