Beyond UFOs: The Search for Extraterrestrial Life and Its Astonishing Implications for Our Future - Brossura

Bennett, Jeffrey

Brossura

ISBN 10: 0691149887 ISBN 13: 9780691149882

Casa editrice: Princeton Univ Pr, 2011

Riassunto

The quest for extraterrestrial life doesn't happen only in science fiction. This book describes the startling discoveries being made in the very real science of astrobiology, an intriguing new field that blends astronomy, biology, and geology to explore the possibility of life on other planets. Jeffrey Bennett takes readers beyond UFOs to discuss some of the tantalizing questions astrobiologists grapple with every day: What is life and how does it begin? What makes a planet or moon habitable? Is there life on Mars or elsewhere in the solar system? How can life be recognized on distant worlds? Is it likely to be microbial, more biologically complex--or even intelligent? What would such a discovery mean for life here on Earth?


Come along on this scientific adventure and learn the astonishing implications of discoveries made in this field for the future of the human race. Bennett, who believes that "science is a way of helping people come to agreement," explains how the search for extraterrestrial life can help bridge the divide that sometimes exists between science and religion, defuse public rancor over the teaching of evolution, and quiet the debate over global warming. He likens humanity today to a troubled adolescent teetering on the edge between self-destruction and a future of virtually limitless possibilities. Beyond UFOs shows why the very quest to find alien life can help us to grow up as a species and chart a course for the stars. In a new afterword, Bennett shares the most recent developments in extrasolar research, and discusses how they might further our quest to find alien life.

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Informazioni sull?autore

Jeffrey Bennett is an astrophysicist, author, and educator. His books include leading college-level textbooks in astrobiology, astronomy, mathematics, and statistics, as well as the award-winning children's book Max Goes to the Moon.

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"With the possible exception of the God question, I can think of no subject that has inspired such wide-eyed wonder and speculation as the matter of whether or not we are alone in the cosmos. The search for extraterrestrial intelligence today has almost theological status in terms of its implications, and yet it is a rigorous science conducted by world-class scientists. Jeffrey Bennett's book is one of the finest primers on this burgeoning new field. And even though this can be a technically daunting science, Bennett's highly readable prose invites everyone into the dome to gaze through the telescope to have a look for themselves, for this is a journey we are all on together."--Michael Shermer, publisher of Skeptic and columnist for Scientific American

"Bennett describes the search for life beyond the Earth in terms that are accessible to the nonscientist and yet reveal a broad understanding of the evolution of stars, planets, and organisms. The author's optimism is contagious. May it help inspire us to actually accomplish these lofty goals."--James F. Kasting, Pennsylvania State University

"Precise, accurate, lucid, and engaging. This is popular-science writing at its best. I enjoyed reading this book."--Christopher McKay, NASA Ames Research Center

"This is a fascinating book about the living universe, well-written and timely."--David Morrison, coauthor of The Planetary System and Voyages to the Planets

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BEYOND UFOS

The Search for Extraterrestrial Life and Its Astonishing Implications for Our FutureBy Jeffrey Bennett

PRINCETON UNIVERSITY PRESS

Copyright © 2008 Jeffrey Bennett
All right reserved.
ISBN: 978-0-691-14988-2

Contents

PREFACE Alien Dreams...............................................xiACKNOWLEDGMENTS....................................................xv1 Worlds beyond Imagination........................................12 What Makes It Science?...........................................223 What I Know about Aliens.........................................414 What Is Life?....................................................625 Getting Life Started.............................................876 The Makings of a Truly Great Planet..............................1117 Life in the Solar System.........................................1378 Life among the Stars.............................................1619 The Search for Extraterrestrial Intelligence.....................18410 Where Is Everybody?.............................................197TO LEARN MORE......................................................207AFTERWORD TO THE PAPERBACK EDITION.................................209INDEX..............................................................221

Chapter One

WORLDS BEYOND IMAGINATION Do there exist many worlds, or is there but a single world? This is one of the most noble and exalted questions in the study of Nature.

—Saint Albertus Magnus (c. 1206–1280)

This is a book about possibilities. It is about the possibility that, within a decade or two, robotic or human explorers will drill into the Martian surface and discover microscopic life in subterranean pockets of liquid water. It is about the possibility of landing spaceborne submarines on Jupiter's moon Europa, where they might melt their way through miles of ice and observe life swimming in a volcanically heated ocean. It is about the possibility of strange, cold-adapted life forms on Saturn's moon Titan, a world on which we have already landed a robotic emissary, despite its being located nearly a billion miles away. It is about the possibility of SETI researchers detecting an unmistakable signal coming to us from a civilization that has grown up around a faraway star. It is about the possibility that we may already be surrounded by a galactic civilization, populated by beings who surpassed our own current level of development millions or even billions of years ago. Most of all, it is about the possibilities that await us, if and when we learn that we are not alone in the universe.

It doesn't take long to begin to appreciate these and other possibilities, but you have to be in the right frame of mind. If you're reading at night and you happen to live in a place with clear, dark skies, take a moment to put the book down and go out and look at the stars. If you live in a city or it is cloudy or daytime, close your eyes and picture yourself at a favorite vacation spot on a perfect night. Personally, I like the mountain lakes not far from my home in Colorado, where the stars sometimes shine so brightly that I can make out the constellations by their reflections in the still water. As you look out into the seemingly infinite heavens, you should feel a change in your mental state as your thoughts shift from the daily trials of life to questions of who we are, how we got here, why we exist, and whether we have companionship among the planets and stars.

The mere sight of the myriad stars may seem enough to answer the last question. After all, when you consider the fact that each star is a sun, possibly orbited by planets of its own, it may seem inevitable that others are out there, looking at us as a dot of light in their own skies. But possibilities are not certainties, and despite everything we know about the universe today, we still have no proof that even the tiniest microbes live beyond the confines of our small world. We may have good reason to be entranced by the possibilities for life beyond Earth, but it is also possible that such life exists nowhere except in our own minds.

That is where science comes in. Science is a way of distinguishing possibilities from realities. We can imagine all the possibilities that we want, but science asks us to put them to the test. If we find confirming evidence for our possibilities, then we have at least some reason to think they reflect reality. If our possibilities conflict with reality, then we know they were figments of our imagination. Of course, oftentimes we have no clear evidence either way, as is the current case for the possibility of extraterrestrial life. In such cases, the job of science is to help us keep looking and learning, until we someday acquire the evidence we seek.

Today, many hundreds of scientists around the world are engaged in the scientific search for life in the universe, a topic of study that is often called astrobiology or exobiology. In the United States, NASA has established an Astrobiology Institute, which functions as a collaborative effort between scientists at NASA research centers and at more than a hundred universities and independent research laboratories. The European Union has a similar collaborative effort with its European Exo/Astrobiology Network. Australia, Great Britain, Spain, France, and Russia also have formal astrobiology centers, and almost every other nation on Earth has at least a few scientists whose research bears on the question of life in the universe.

Given that we don't yet know of any life beyond Earth, you might wonder how so many scientists can be gainfully employed in its study. The answer, like this book, is about possibilities. Only a few scientists—those involved in the search for extraterrestrial intelligence, or SETI for short—are currently engaged in a direct effort to detect alien life. For all the others, current efforts focus on learning about the possibility of life existing elsewhere. For example, planetary scientists explore other worlds in our solar system either telescopically or by sending out robotic spacecraft. While their efforts could in principle turn up direct evidence of life, for the time being they are more focused on helping us understand the conditions found on different worlds, thereby allowing us to evaluate whether those conditions might be conducive to life. Many scientists working in astrobiology study the basic chemistry and nature of life, which should help us recognize alien life if we happen to come across it. Others seek to understand the origin of life on Earth; after all, an understanding of how life arose on our own planet ought to make it easier for us to determine the likelihood that life might arise somewhere else. Still others study Earth itself, which teaches us about how the geological nature of Earth helps make it home to abundant life. Even astronomers get in the game, seeking stars that could make good suns, looking for planets around those stars, and developing technologies that may someday help us detect life even on worlds that we can study only through telescopes.

Of course, all this effort is predicated on the idea that the possibility of extraterrestrial life is worthy of scientific study. Here, we must distinguish between an idea that is philosophically reasonable and one that is scientifically testable. The fact of our own existence makes it philosophically reasonable to wonder if life exists beyond Earth, but until quite recently there was no way in which we could actually test out the idea. In most of the rest of this chapter, I will try to explain why, in just the past couple of decades, the search for life in the universe has suddenly become a topic of intense scientific interest. First, however, it's worth developing a bit of historical perspective on the philosophical question that drives us to wonder if we are alone.

THE ANCIENT QUESTION OF WORLDS BEYOND EARTH

Even aliens need a place to call home. No matter whether we consider the tiny intelligent beings who I once imagined visiting my bedroom or the most primitive single-celled slime, all life must have gotten its start somewhere. Thus, the question of life beyond Earth makes sense only if we have reason to think that there are other worlds upon which life could live.

Those of us who would like to meet aliens generally take it for granted that the universe is indeed full of hospitable planets on which life and civilizations might have arisen. We cannot yet be certain that this is the case, because our technology is not quite yet up to the task of discovering such planets around other stars. Nevertheless, as I'll discuss in more detail shortly, the idea seems reasonable today because we know that other stars have at least some planets, and our understanding of planetary formation makes it plausible to imagine that planets with life could turn out to be common. But if we go back just a few centuries, the context for considering life beyond Earth was quite different.

Consider the quotation from Saint Albertus Magnus that opens this chapter, which begins: "Do there exist many worlds, or is there but a single world?" If you read Magnus's quotation with a modern eye, you might think he's using the term world in the sense of an Earth-like world with life. But he was actually using it in a much more basic way. Before the time of Copernicus, Kepler, and Galileo, all of whom lived less than 500 years ago, scholars generally assumed that Earth held a central place in the universe. Our solid home—which, by the way, had been known to be spherical since the time of the ancient Greeks—was assumed to be surrounded by a great sphere of stars, and between Earth and the stars lay additional spheres that carried the Sun, the Moon, and the five planets known at the time. Thirteenth-century philosophers and theologians had no more reason to think of any of these objects as "worlds" than to think of them as gods—an idea that had long since been rejected as ancient mythology.

In fact, pre-Copernican scholars did not even consider Earth to be a planet. The word planet comes from the Greek for "wanderer," and it originally referred only to objects that appear to wander among the stars in our sky. The idea will be clear if you think about the universe as it appears to the naked eye. We live on our seemingly central and unmoving home, while the stars appear to circle around us with each passing day, always staying in the fixed patterns of the constellations. The Sun also makes a daily circle around us, but not quite at the same rate as the stars. That is why the Sun gradually makes its way through all the constellations of the zodiac over the course of a year. The Moon follows this same basic pattern of motion, but moves more quickly through the constellations than the Sun, completing a full circuit and cycle of phases in about a month (think "moonth"). Before the era of airplane lights and aside from an occasional comet, the only other objects that ever seemed to move against the background of the stars were the five bright points of light known as Mercury, Venus, Mars, Jupiter, and Saturn. Thus, from the perspective of people living more than 500 years ago, there were seven objects that appeared to wander among the stars and hence qualified as "planets": the Sun, the Moon, and the five innermost planets besides Earth. The planetary status of these seven objects is enshrined in the names of the seven days of the week. In English, only Sunday, Moonday, and Saturnday are obvious, but if you know a romance language like Spanish you'll be able to figure out the rest: Tuesday is Mars day (martes), Wednesday is Mercury day (miércoles), Thursday is Jupiter day (jueves), and Friday is Venus day (viernes).

Because the Earth-centered belief system implied that our world should be fundamentally different from any of the lights in the sky, you might wonder how Saint Albertus Magnus could even have conceived of other worlds. The answer is that, following a line of thought dating back to ancient Greece, he was considering the possibility of other worlds that were more like what we might think of as separate universes—each world the center of its own cosmos, circled by its own sun, planets, and stars. The question he asked also dated back to the ancient Greeks, inspired by his reading of Aristotle, which at the time had recently been translated into Latin.

It can be tempting to think that people who lived more than 2,000 years ago were more primitive or simpleminded than we are, but in fact many ancient civilizations were remarkably sophisticated. The ancient Greeks, geographically positioned at a crossroads that gave them access to ideas and inventions from cultures throughout Eurasia and northern Africa, developed philosophies that still resonate today. On the question of other worlds and extraterrestrial life, the Greeks split into two distinct camps.

On one side were the atomists, Greek philosophers who held that everything is made of tiny, indivisible atoms of four basic elements: fire, water, earth, and air. The atomist doctrine was developed largely by Democritus (c. 470–380 B.C.), who argued that the world—both Earth and the heavens—had been created by the random motions of infinite atoms. For example, he imagined atoms of earth to be rough and jagged, like tiny pieces of a three-dimensional jigsaw puzzle, so that they could stick together when they collided and thereby explain how our world had formed in the first place. Because the atomists believed the total number of atoms to be infinite, they assumed that the same processes that created our world should also have created others. This inevitably led them to conclude that other worlds and other life must exist, an idea summarized in the following quotation from the atomist philosopher Epicurus in about 300 B.C.: "There are infinite worlds both like and unlike this world of ours.... we must believe that in all worlds there are living creatures and plants and other things we see in this world."

Although it's difficult to ascribe modern sentiments to ancient beliefs, the atomists seem to have been essentially atheistic. They did not see the need for any hand of God in creation, instead just seeing random events in infinite time and space. However, in the pre-Christian era it was not the question of God that bothered their detractors so much as the question of infinity.

Aristotle (384–322 B.C.) represented the opposing camp. Like the atomists, Aristotle assumed the world to be made of the four elements, fire, water, earth, and air. But he did not necessarily accept that these elements could be broken down into indivisible atoms, and he certainly didn't agree that they floated randomly in an infinite space. Instead, Aristotle held that all elements had their own natural motion and place. For example, he believed that the element earth moved naturally toward the center of the universe, an idea that offered an explanation for the Greek assumption that Earth resides in a central place. Water, being lighter, settled on top of earth, thus explaining oceans, while air settled above that to explain the atmosphere. The element fire, he claimed, naturally rose away from the center, which is why flames jut upward into the sky. These incorrect ideas about physics, which were not disproved until the time of Galileo and Newton almost 2,000 years later, caused Aristotle to reject the atomist idea of many worlds. If there were more than one world, there would be more than one natural place for the elements to go, which would be a logical contradiction. Aristotle concluded: "The world must be unique.... There cannot be several worlds."

Aristotle also came to a very different conclusion than the atomists about the nature of the sky. Because he had natural places for all four elements to go, he concluded that the heavens must be made of something else, which he called the ether (literally, "upper air"). That's how the word ethereal came to mean "heavenly." You may also recognize that the ether was in a sense a fifth element after fire, water, earth, and air, thus explaining how the word quintessence—which literally means "fifth element"—came to be associated with heavenly perfection.

Interestingly, Aristotle's philosophies were not particularly influential until many centuries after his death, when his books were finally translated into Latin and came to the attention of people like Saint Albertus Magnus and one of his students, Saint Thomas Aquinas (1225–1274). Aquinas found Aristotle's philosophy particularly appealing and integrated it into Christian theology. The contradiction between the Aristotelian notion of a single world surrounded by heavens and the atomist notion of many worlds in an infinite universe became a subject of great concern to Christian theologians. Many even argued that extraterrestrial life could not be possible because it would contradict the Aristotelian notions of Earth and heaven. While a few biblical fundamentalists still take this position, it's fairly clear that the Bible itself does not weigh in on the question of life beyond Earth. As a result, today you can find fundamentalist Christians who also believe in UFOs.

(Continues...)

Excerpted from BEYOND UFOSby Jeffrey Bennett Copyright © 2008 by Jeffrey Bennett. Excerpted by permission of PRINCETON UNIVERSITY PRESS. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Dettagli dell?edizione

• Editore: Princeton Univ Pr
• Data di pubblicazione: 2011
• ISBN 10: 0691149887
• ISBN 13: 9780691149882
• Rilegatura: Copertina flessibile
• Lingua: Inglese
• Numero di pagine: 223
• Contatto del produttore: non disponibile