The following is an excerpt from The Little Book Of Aliens by Adam Frank.

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The Little Book Of Aliens

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Everybody loves aliens. I know this because everybody tells me they love aliens. Life in the universe is the first thing people ask me about when they hear I’m an astrophysicist. “Do aliens exist?” is one of those special questions, kind of like “What happens after you die?” Lots of opinions, no real answers, and, most important, actually knowing the answer would change the world.

The thing is: I love aliens too. In fact, I have been obsessed with them since I was a kid. I first got hooked when I found my dad’s pulp science-fiction magazines as a five-year-old. On the cover of every issue were images of spaceships, barren moons, and bug-eyed alien monsters. From that moment on, I was on a mission to learn everything I could about the stars and alien life. This obsession made me a pretty annoying kid (apparently, I liked to quote the speed of light to four decimal places), but it also drove me to watch all the documentaries, bad sci-fi movies, and Star Trek reruns in existence. Any depiction of an alien was good enough for me as I dreamed of possibilities out there waiting to be discovered.

Back in the 1970s, at the height of my childhood obsession, the scientific search for life in the cosmos had barely begun. There were only a few very brave and determined pioneers carrying out the search for extraterrestrial intelligence (SETI), and most of them faced the scorn of their colleagues. SETI was considered a little “out there,” marginal at best in the scientific community. A big part of that dismissal was just bias. There just weren’t many astronomers who thought about the problem of life in its cosmic context back then. And it’s true, we really didn’t have much to go on in those days in terms of setting up a true scientific search for life among the stars, smart or otherwise.

Most of all, we didn’t know if there were any planets in the galaxy other than the eight that orbited our Sun. This was a killer point, since scientists expect planets to be necessary to get even simple life started. So not having a single example of an extrasolar planet (an exoplanet) meant we literally didn’t know where to look. We also didn’t know much about how planets and life evolve together in ways that might keep a world habitable for billions of years, long
enough for “higher” animals and even technological civilizations to appear. In short, when it came to searching for alien life in the universe, we were pretty much in the dark.

Not anymore.

As you read these words, the human species is poised at the edge of its greatest and most important journey. Over the past three decades, the scientific search for life in the universe—a field called astrobiology—has exploded. We’ve discovered planets everywhere in the galaxy, and we’ve figured out how and where to look for signs of alien life in the atmospheres of these new worlds. We’ve also looked deep into Earth’s almost four-billion-year history as an inhabited
world. From this view, we’ve gained new and powerful insights into how planets and life evolve together. Seeing the way life hijacked Earth’s evolution over the eons gives us clues about what to look for on distant planets (like oxygen, which generally can exist in an atmosphere only if life puts it there). We’ve also sent robot emissaries to every planet in our solar system. With their wheels or landing pads on the ground, we’ve begun searching these neighbor worlds for evidence of life existing now or perhaps deep in their past. Most important, we have launched and are building insanely powerful, next-generation telescopes. With these tools, we’ll finally go beyond just yelling our opinions about life in the universe at each other. Instead, we will get what matters most—a true scientific view of if, where, and when extraterrestrial life exists.

All these new discoveries, from exoplanets to Earth’s deep history, are transforming what we think of as SETI. A new research field is rising that scientists are calling technosignatures,* which embraces the “classic” efforts of SETI while taking the search for intelligent life into new forms and directions. Knowing that the galaxy is awash in planets means we now know exactly where and how to look for alien civilizations. Rather than hoping for someone to set a beacon announcing their presence (one premise of the first generation of SETI), we can now look directly at the planets where those civilizations might be just going about their “civilization-ing.” By searching for signatures of an alien society’s day-to-day activities (a technosignature), we’re building entirely new toolkits to find intelligent, civilization-building life. These toolkits will also allow us to find the kind of life that doesn’t build civilizations. Using our telescopes to find a signature of a planet covered in alien microbes or alien forests (a biosignature) would also be a game changer in terms of how humanity sees its place in the cosmos.

So now, finally, we are on the road to finding those aliens I was so obsessed with as a kid. Or we’re on the road to finding out we really are alone in the cosmos. Either answer would be stunning. It’s a pretty damn exciting moment.

But it’s also a confusing moment. Just as the scientific search for alien life is gaining steam, there’s also been an explosion of interest in aliens that are supposedly visiting Earth right now. Over the last few years, a handful of videos taken by US fighter pilots have cropped up online showing fuzzy blobs appearing to fly in ways that would be impossible for normal aircraft. The videos have brought unidentified aerial phenomena (UAPs) into the spotlight, raising the stakes on the alien debate. But the UAP furor also confuses the issue about the giant leap science is taking as it begins looking for aliens in the most likely place (i.e., alien planets).

UAPs are the US government’s new name for unidentified flying objects (UFOs), a subject that’s been around for years, holding modern culture in thrall. UFOs as alien visitors make for great science fiction (everything from The X-Files to Independence Day to Nope). The possibility of their actual existence has mostly been dismissed by scientists. The overwhelming majority of astronomers see UFOs as natural phenomena that get misidentified, objects related to national defense, or just purposeful hoaxes. In 2021, however, the US government revealed more than a hundred UAP sightings for which it had no obvious explanation. The media tornado over the UAP videos was unrelenting, even as most scientists emphasized that unexplained can mean there simply isn’t enough data, or good enough data, to even begin formulating an explanation. Still, in the wake of the new government interest, I am left wondering, “Do these things really have anything to do with aliens?”

Between the remarkable progress in astrobiology and technosignatures on the one hand, and the blizzard of coverage about UAPs on the other, aliens are big news. More than ever, we want to know: Is anyone out there? I wrote this book to help people understand that question as scientists see it, the definitive answers scientists are working to find, and, most amazing of all, how close we are to getting some of those answers.

For a chunk of my career as an astrophysicist, I studied less freakydeaky stuff. At the University of Rochester, I ran a “computational astrophysics” research group in which my students and I used the world’s most powerful computers to explore how stars form from giant clouds of interstellar gas and how they die by tearing themselves apart in titanic stellar winds. These were very cool projects, and I loved the vistas they opened for me. But I never lost my little kid interest in cosmic life. So, about a decade ago, I started a research program in astrobiology, doing work on exoplanets and their atmospheres. Then I started thinking about climate change from the perspective of astrobiology, positing that maybe every civilization triggers its own version of global warming.

My life really changed, however, in 2019 when a group of colleagues and I were awarded NASA’s first grant to study exoplanet technosignatures. That is, NASA began funding us to think about the best ways to look for alien civilizations. We applied for the grant because, over dinners (and beers) at international meetings, we all got way too excited (it was the beers) about those exoplanet discoveries and how they could rewire the search for intelligent life. But NASA had never funded a project like the one we were thinking of. In fact, after years of getting burned by Congress for funding SETI research as a waste of taxpayer dollars, the space agency had barely funded any work on intelligent life in the cosmos.

So when we put in our proposal, we kept our hopes low. But then to our surprise, amazement, and joy (and more beers), it was accepted. The frontier was opening. We’d been given a chance to help shape the most exciting quest humanity had ever taken on. It was a milestone for the field and a recognition of how much had changed in the scientific thinking about life in the universe. Since then, we and other researchers have been pushing into new terrain. We’re all preparing for a truly systematic, scientific search for alien life and alien civilizations. That search is just getting started now.

It’s from this vantage point that I see, and understand in my bones, why everyone wants to know about aliens. But if you’re interested in the science—from SETI to astrobiology to technosignatures—where do you begin? There is a mess of history, concepts, and terminology floating around that you need to know to understand what’s about to happen. What, for example, is the Drake equation, and why does it matter so much? What’s the Fermi paradox, and how much SETI searching has actually been done to resolve the paradox? How many exoplanets are there, and which of them matter? What is a technosignature (or a biosignature), and how is anyone going to find one? And what about the UFOs/UAPs? Should we take them seriously? If we do, what are the questions we should ask, and how should we ask them?

The aim of this book is to give you a good ten-thousand-foot overview of what’s happening now, what’s going to happen soon, and why it matters so much. My biggest goal in writing it was to give you a fast, fun path into all the amazing questions and issues swirling around that mother of all questions:

Are we alone?

So, suit up. It’s time to get started on our journey. We have a lot of ground to cover. By the time we’re done, though, you’ll have everything you need to know about everything there is to know (for now, at least) about aliens. From that point on, you’ll be ready to join this great voyage of discovery, and you’ll be ready when someone says we’ve found “them.” Because in the end, we don’t want to just believe; we have to know.

Excerpted from The Little Book Of Aliens. Copyright © 2023 by Adam Frank. Excerpted by permission of Harper Collins.