The following is an exception The Little Book of Aliens By Adam Frank.

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The Little Book of Aliens

Everyone loves foreigners. I know this because everyone 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?” It's one of those special questions, like, “What happens after you die?” There are a lot of opinions, no real answers, and most importantly, actually knowing the answer will change the world.

The thing is: I like foreigners too. In fact, I've been obsessed with them since I was a kid. I was first impressed when I came across my father's science fiction magazines when I was five years old. On the cover of each 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 stars and alien life. This obsession made me a very annoying kid (apparently, I liked to put the speed of light to four decimal places), but it also drove me to watch every documentaries, bad sci-fi movies, and Star Trek reruns out there. Any depiction of an alien was good enough for me as I dreamed of possibilities waiting to be discovered.

In the 1970s, at the height of my childhood obsession, the scientific search for life in the universe had barely begun. There have been only a few very brave and determined pioneers undertaking the Search for Extraterrestrial Intelligence (SETI), and most have faced the disdain of their colleagues. The SETI project was considered somewhat “existent” and fringe at best in the scientific community. Much of this dismissal was just bias. There were not many astronomers who thought about the problem of life in its cosmic context at that time. And it's true, we didn't have much to do in those days in terms of conducting real scientific research into interstellar life, intelligent or otherwise.

Most important of all, we did not know whether there were any planets in the galaxy other than the eight planets orbiting our sun. This was a crucial point, because scientists expected planets to be necessary for simple life to begin. So not having a single example of an exoplanet means we literally don't know where to look. We also didn't know much about how planets and life co-evolved in ways that might keep the world habitable for trillions of years, for a long time
Enough for the emergence of “higher” animals and even technological civilizations. In short, when it comes to searching for alien life in the universe, we've been largely in the dark.

Not anymore.

As you read these words, the human race stands on the precipice 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 discovered how and where to look for signs of alien life in the atmospheres of these new worlds. We also delved deeply into Earth's nearly four-billion-year history as inhabited
world. From this perspective, we have gained powerful new insights into how planets and life co-evolved. Seeing the way life has hijacked Earth's evolution over the eons gives us clues about what to look for on distant planets (such as oxygen, which generally can't exist in the atmosphere unless life puts it there). We have also sent robotic emissaries to every planet in our solar system. With their wheels or landing pads on Earth, we began searching these neighboring worlds for evidence of life existing now or perhaps deep in their past. Most importantly, we have launched and are building extremely powerful next-generation telescopes. With these tools, we will finally go beyond just screaming Views About life in the universe and in each other. Instead, we'll get what's most important: real scientific insight into whether, where and when extraterrestrial life exists.

All of these new discoveries, from exoplanets to the deep history of Earth, are changing what we call SETI. A new field of research is emerging that scientists call “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 full of planets means we now know exactly where and how to look for alien civilizations. Instead of hoping that someone will set up a beacon announcing their presence (one of the hypotheses of first-generation SETI), we can now look directly at planets where those civilizations might just be a “civilization.” By searching for signatures of an alien society's daily activities (the technological signature), we are building an entirely new toolkit for finding intelligent, civilization-building life. These toolkits will also allow us to find the kind of life that does not build civilizations. Using our telescopes to find the signature of a planet covered in alien microbes or alien forests (a biosignature) would also be a game-changer in terms of how humanity views its place in the universe.

Relevant part

How close are we to answers about aliens?

And now, finally, we're going to find those aliens you obsessed over as a kid. Or we are on our way to discovering that we are alone in the universe. Either answer would be amazing. It's a very exciting moment.

But it's also a disorienting moment. While the scientific search for alien life is gaining momentum, there has also been a growing interest in aliens that are supposedly visiting Earth right now. Over the past few years, a collection of videos taken by American fighter pilots have appeared online showing mysterious dots that appear to fly in ways impossible for regular aircraft. The videos highlighted unidentified aerial phenomena (UAPs), raising the stakes of the alien controversy. But the UAP buzz also confounds the issue of the giant leap science takes when it starts looking for aliens in the most unlikely place (i.e. alien planets).

UAPs are the US government's new name for unidentified flying objects (UFOs), a topic that has been around for years, enslaving modern culture. UFOs as alien visitors make for great science fiction (everything from The X-Files to Independence Day to Nope). The possibility of its actual existence has been mostly rejected by scholars. The vast majority of astronomers view UFOs as misidentified natural phenomena, objects of national defense, or simply intentional hoaxes. However, in 2021, the US government uncovered over a hundred UAP sightings for which it had no clear explanation. The media hurricane around the UAP videos has been relentless, with most scientists even emphasizing that the lack of an explanation could simply mean that there is not enough data, or good enough data, to even begin to formulate an explanation. However, in the wake of new government interest, I wonder: “Do these things really have anything to do with aliens?”

Between remarkable advances in astrobiology and technological signatures on the one hand, and the whirlwind coverage around UAPs on the other, aliens are big news. We want to know more than ever: Is there anyone out there? I wrote this book to help people understand this question as scientists see it, the definitive answers scientists are working to find, and, most surprising of all, how close we are to getting some of those answers.

During a period of my career as an astrophysicist, I studied less exotic things. At the University of Rochester, I ran a research group in the field of “computational astrophysics,” where 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 giant stellar winds. . These were very exciting projects, and I loved the horizons they opened up for me. But I never lost my little boy's 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 an astrobiology perspective, hypothesizing that perhaps each civilization would lead to its own version of global warming.

However, my life really changed in 2019 when a group of my colleagues and I received our first NASA grant to study the technosignatures of exoplanets. That is, NASA began funding us to think about the best ways to search for alien civilizations. We applied for the grant because, over dinners (and beers) at international meetings, we were all very excited (it was beer) about exoplanetary discoveries and how they might restart the search for intelligent life. But NASA has never funded a project like the one we were thinking about. In fact, after years of Congress criticizing funding for SETI research as a waste of taxpayer money, the space agency has barely funded any work on intelligent life in the universe.

So when we submitted our proposal, we kept our hopes low. But then, to our amazement, astonishment, and delight (and more beer), it was accepted. The borders were open. We have the opportunity to help shape the most exciting mission humanity has ever undertaken. This was a milestone in the field and an acknowledgment of how much scientific thinking about life in the universe had changed. Since then, we and other researchers have pushed into new areas. We are all preparing for truly systematic scientific research into alien life and alien civilizations. This research is just beginning now.

From this perspective I see, and understand in my bones, why everyone wants to know about aliens. But if you're interested in science — from SETI to astrobiology to technosignatures — where do you start? There is a mess of history, concepts and terminology that you need to know to understand what is going to happen. For example, what is the Drake Equation, and why is it so important? What is the Fermi Paradox, and how much research has been done at SETI to solve the paradox? How many exoplanets are there, and which ones matter? What is a technical signature (or biosignature), and how can anyone find it? What about UFOs/UAPs? Should we take them seriously? If we do, what questions should we ask, and how should we ask them?

The goal of this book is to give you a good, ten-thousand-foot-deep overview of what's happening now, what's coming soon, and why it's so important. My biggest goal in writing it was to give you a quick and fun path to all the amazing questions and issues surrounding that mother of all questions:

Are we alone?

So, follow up. It's time to start our journey. We have a lot of ground to cover. However, by the time we finish, 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 expedition, and you'll be ready when someone says we've found “them.” Because in the end, we don't just want to believe; We have to know.

Adapted from The Little Book of Aliens. Copyright © 2023 by Adam Frank. Excluded by permission of HarperCollins.