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If the Universe Is Teeming with Aliens... Where Is Everybody? Fifty Solutions to Fermi's Paradox and the Problem of Extraterrestrial Life

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This is the most up-to-date and thorough discussion of the Fermi Paradox that I have read. Stephen Webb examines all the popular solutions as well as some esoteric ones, giving us considerable background on each along with the benefit of his knowledge on a wide range of relevant subjects including microbiology, plate tectonics, evolution, intelligence, language, philosophy, as well as astronomy and cosmology. And then he gives his solution: we are alone.

That was Fermi's solution of course, and it is a popular one; however I don't think that Webb comes anywhere near to making a convincing case; and at any rate he is somewhat equivocal about whether his answer applies to the entire universe or to just the galaxy. It is clear that his answer applies only to life as we know it, having a carbon based biochemistry and a cellular structure. My feeling is that intelligent life forms may evolve from some other chemical basis or even from some use of energy and matter we know nothing about.

On pages 237 to 239 Webb presents his argument that we are the only extraterrestrial civilization (ETC) in the galaxy by a process of elimination, i.e., life must be on a planet within both a galactic habitable zone (GHZ) and a solar continuously habitable zone (CHZ) around the right kind of star; must avoid cosmic disasters like supernovae; must have the right kind of moon, Jupiter, and plate tectonics; must evolve beyond single cells; must develop tool use and language, etc. He ends up sifting out everything except us, and the only reason he doesn't sift us out is that he has set us aside since we actually exist!

This is close to sophistry, perhaps, but it has been argued before. I might call it the Fallacy of Elimination by Unknown Probabilities about Matters that May or May Not Be Essential. Putting that aside, consider this: If we extrapolate from what we know (as opposed to any speculation) about the existence of life in just our own galaxy, we should expect on average--at the very least--one ETC per galaxy. Wow. Far from being alone, this suggests more than 100 billion other ETCs are out there, although we are not likely to ever communicate with them.

One of the things this book demonstrates, as others have before (see especially, Peter D. Ward and Donald Brownlee's Rare Earth: Why Complex Life Is Uncommon in the Universe [2000], which Webb acknowledges as influential), is that when you're dealing with so little concrete information in such a vastness, it is impossible to be entirely convincing one way or the other. The conclusion in Rare Earth, with which Webb concurs, is that life is common in the universe, but intelligent life is rare. I agree substantially with this, but my "rare" is perhaps larger than their "rare."

Some of the familiar but crucial questions considered here were addressed in the excellent Extraterrestrials: Where Are They? (1995) edited by Ben Zuckerman and Michael H. Hart. For example, How long do ETCs exist before they go extinct? Is space travel enormously difficult and expensive or is it just very difficult? Do ETCs have a psychology similar enough to ours to make them want to communicate? How would they communicate, using what sort of medium?--even: would we recognize a communication from an ETC if we received one?

The answer to these questions and many others is, we don't know. But it's fun to speculate; and in speculating at least we can eliminate many conceptual and logical errors that might crop up. Furthermore such speculations expand the mind and allow the imagination a greater range. In direct contrast to Webb I think there's only the smallest chance that we are alone. Amazing how people can come to such divergent conclusions from the same evidence!

For such answers as, They are so advanced that they have no interest in communicating with us, and They are so into their own self-constructed pleasure-enhancing virtual existence that they care not to look outward, etc., Webb has a ready response. For such answers to solve the Fermi paradox, he says, they have to apply to every single ETC. Surely, he posits, not all ETCs would have such a psychology. But, by taking all such solutions and playing an elimination game similar to the one Webb plays on pages 237-239, we can reverse his conclusion and eliminate all existing ETCs as non-communicative for one reason or another, arriving at the grand conclusion that we are not alone and that there are indeed a whole bunch of ETCs out there.

I wish I had the space to address some other Stephen Webb arguments that I think are faulty, but perhaps just one more will be suggestive. On page 229, while arguing that only humans have symbolic language, he relates an experiment in which a dolphin learns to operate an apparatus to release food. The dolphin is timed. Then the scientists close that dolphin off and release a second dolphin into the pool with the apparatus. The first dolphin can send signals to the second dolphin. The scientists then time how long it takes for the second dolphin to learn to work the apparatus. They discover that it takes the second dolphin on average just as long as it did the first. Webb writes: "We can conclude from this that the first dolphin was unable to tell the second dolphin how the apparatus worked."

Well, maybe. But replace the dolphins with humans, and the reward of food with hundred dollar bills, and perhaps we might conclude that humans are also unable to communicate how the apparatus worked!

Bottom line: for SETI enthusiasts and anyone interested in the prospect of extraterrestrial life, this is a book, despite its flaws, not to be missed.

Four guys walk into the caf at Los Alamos for lunch and start discussing extraterrestrial intelligence. They decide that life, intelligence, and conquering the galaxy shouldn't be that hard. Then one of them asks, "where is everybody?" Far from being the beginning of a bad nerd joke, this lunchtime discussion actually took place in the summer of 1950 and Enrico Fermi really did ask the now famous Fermi Question. The discussion and question led to the Fermi Paradox: if the universe is as old as it is, and if the Earth isn't the oldest planet with intelligent life, and conquering the galaxy is as easy as it seems, then where the heck are they?

Physicist Stephen Webb does an admirable job of discussing some possible answers to the Fermi Paradox in If The Universe Is Teeming With Aliens...Where Is Everybody?: Fifty Solutions To The Fermi Paradox And The Problem Of Extraterrestrial Life. It's a tough job, even for a fan of the Fermi Paradox like Webb, since it means being well versed in a wide range of subjects AND it means thinking like an alien intelligence. Webb describes and critiques 49 of his favorite solutions, starting with They Are Here And They Call Themselves Hungarians, and then throws in a fiftieth solution of his own design. The solutions are subdivided into three sections: 1) They Are Here, 2) They Exist But Have Not Yet Communicated, and 3)They Do Not Exist. The book is set up so that after reading Chapters 1 and 2, a person can read the solutions as they wish. Some basic math and science skills are required, but the book should be accessible to a wide reading audience. Albeit not a perfect book, I enjoyed reading Where Is Everybody?, especially since it made me think A LOT! This is NOT a book about flying saucers, alien abductions, and forced interspecific sex, so if that's what you're looking for, STAY AWAY from this book. Besides appealing to folks interested in the question of life elsewhere, it should appeal to any person with wide-ranging interests [both the natural sciences and the social sciences] who wants to exercise the full range of their brain power. For serial readers like me, read this one in combination with Rare Earth by Ward and Brownlee and What Does A Martian Look Like? by Cohen and Stewart for a mind expanding [and exploding] experience.

The answer to the question "is there life elsewhere?" is profound no matter which way it is answered. I continue to run my SETI@home screensaver and hope. It would be terrible if there were billions of channels and nothing is on.

In "If the Universe is Teeming with Aliens ... WHERE IS EVERYBODY?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life," Stephen Webb has written a clever exposition of 50 hypothetical solutions to Fermi's famous paradox. Webb organizes these solutions into three categories: (1) they (the aliens) are here, (2) they exist but have not yet communicated, and (3) they do not exist. The appropriateness of these categories and the specific selection of solutions are arguable, but I will not address this in this review. The fiftieth solution, Webb's personal view, is a refinement of the view that intelligent, communicating extraterrestrial civilizations (ETCs), do not exist. He believes we are alone. Some of his arguments are persuasive, but only superficially so. They are reminiscent of the ancient argument that the earth is at the center of the universe because it looks that way, or because this view conformed to one or another philosophical dogma. But now, in Webb's view, it is intelligent life on earth that is "alone" and consequently the earth is its lonely center.

Webb makes several assumptions that underlie the solutions he presents and his own conclusions. He does not directly explain them nor even explicitly refer to them. Four assumptions merit particular attention: (1) ETC populations increase without bound, (2) ETCs maintain biological and cultural cohesiveness and continuity over millions of years and tens of thousands of light years, (3) The Kardashev model is the measure of how advanced an ETC is, and (4) At least some ETCs use communication technologies we would recognize. These assumptions are questionable. (Some are discussed later in this review.)

Using these assumptions, Webb presents most of the forty-nine solutions in ways that ultimately support the fiftieth. Moreover, in most solutions he concludes that if ETCs have ever existed, then surely at least one will have beat the odds, and would have long ago established a permanent presence throughout the galaxy. But this apparently hasn't happened, which to Webb means that no ETCs have arisen in the past, and which thus solves Fermi's paradox. Webb's repetition of this reasoning becomes more than a little irritating long before his last solution is offered. Webb does a good job of inviting the reader to think (irritations aside). To his credit, he frequently reminds the reader of the absence of real evidence for or against ETCs. And, although some readers have pointed out computational errors, in the end they are not central to his conclusions.

What Webb and many others fail to recognize is the simple fact that Fermi's paradox is also contingent on social and cultural factors ... our own. The 30s, 40s, and 50s were decades in which science fiction flourished, with tales of interstellar conquest, galaxy-wide colonization, and empire building by ETCs. This leitmotif reached its zenith with Asimov's Foundation series and, of course, Lucas's Star Wars double trilogy. These elements have their roots in real-world history of previous centuries: from the age of exploration, soon followed by conquest and colonization, through the empire building that (may have) ended in the 20th century. Empire building and its precursor forces operated for only a small part of human history, long after hunter-gathers became farmers and then city dwellers. However, during that historical outburst of energy, and powered by it, human population exploded.
Now the third millennium has arrived and with it a hint that the world's population may ultimately stabilize and even decline. Several first-world nations are already experiencing this (Italy, Japan, and Sweden, for example). There are many reasons for this: wealth, leisure, longevity, and reproductive choice. It is simplistic to believe that an advanced ETC would be interested in propagating itself throughout even small regions of the galaxy. There is no advantage to an ETC, whose individuals probably enjoy almost unlimited resources and life spans, to promote an exponentially growing population. Any ETC with the technology to reach its neighboring star systems will also have the technology to understand and control its genetic destiny.

The "first law" of understanding ETCs is that natural selection applies to all life in the universe, intelligent and otherwise. The "second law" is that all ETCs are comprised of social animals. These two laws imply cooperation (reciprocal altruism). Advanced civilizations whose members are extremely long-lived individuals ultimately become extremely conservative in the sense of being risk averse. Preservation of both the individual and the supporting social structure becomes a central factor in their behavior. Risky exploration and riskier colonization are out. Robotic surrogates are in. Both communication and exploration (robotic or otherwise) would range from being cautious to stealthy or secretive. Exposure is dangerous. This is another solution to Fermi's paradox.

Here is the "third law" of understanding the nature of advanced ETCs: any ETC advanced enough to communicate or travel over interstellar distances must understand atomic and nuclear physics, which implies that it understands the chemical/molecular basis of life, which means that it not only has reproductive choice but also that it can control its genetic destiny.

The earth has an almost four billion-year history of life, from the earliest prokaryotes (and for most of the time the only form of life) and eukaryotes, to the dinosaur, and finally to Homo sapiens. Sixty five million years ago very large animals populated the earth. The age of dinosaurs lasted millions of years ... and hundreds of millions of individuals lived and died. Yet, of their fossilized remains we find only a very small (and certainly incomplete) sample of their once global and epoch-spanning reign. It is likely that we have identified only a very small fraction of the species of dinosaurs that once roamed the earth. Interestingly, this hints that it is at least possible that the earth might have been explored by ETCs and that they might have established temporary outposts many times... and yet it is likely that we will find no trace of this occupation. Continental drift, subduction associated with plate tectonics, volcanism, glaciations, weathering, and other natural forces all act to obliterate any evidence. Thus, to claim that no evidence of this means no ETC contact ever occurred is a weak and unsupportable argument.

Every year one or two supernovas explode in our galaxy. Gamma-ray bursters and other energetic events add to the violence and destruction. This means that any expanding "wave-front" of exploration and colonization would be rapidly reduced to Swiss cheese, with more holes than cheese ... disintegrating into isolated outposts totally cut-off from any putative galaxy-wide integrated civilization. If the speed of light is an insurmountable limit to any form of communication, then beyond a very few hundred light-years, the ability to maintain communication, command, and control breaks down. An ETC's attempt to form an integrated galactic empire ETC would fail ... natural selection, and catastrophic events make such dreams impossible. Consider also that since galaxies are so energetic and violent, the safest place for really advanced ETCs is in the depths of intergalactic space. Command, control, and communication cannot be maintained over tens of thousands, let alone millions, of years required for galactic colonization and rule. An ETC's original species will "mutate", or evolve, from natural or self-imposed causes into hundreds of new species and cultures over that time. To assume otherwise is to assume a culture that has stagnated into a uniformity that defies imagination. For example, could the British have maintained their colonies, say India, if it took 500 years or more to communicate the latest edict or to respond to a problem already 500 years old at its reporting to London?

Speaking of violent places to colonize and thrive, here is another solution to the Fermi paradox. And it is a very ominous one. An ETC that might otherwise be in our neighborhood may have forecast an unacceptably high probability of, say, supernova activity around these parts, or some other impending violent events that we cannot even guess. Should we call this the "Doug Adams" solution to the Fermi paradox ("Goodbye, and thanks for all the fish.")?

Finally, the Kardashev measure of technological advancement dependents on how much energy a civilization controls: all the energy resources of a planet (K1), all the energy output of a star (K2), or all the energy output of a galaxy (K3). We are almost at the K1 stage. Obviously, this criterion predates the information age. Today, we would choose information processing capability as a measure of advancement. This makes a big difference in how we search for SETI and is itself a subject worthy of a deep analysis (too much to go into in this review).

It is very likely that most of our galaxy's worlds, whether dead or teeming with life, intelligent or otherwise, will remain forever untouched and even unobserved by others. There is no Fermi paradox to solve. Today, Fermi himself would recognize that galactic empires are simply dreams of childhood. Over time, and within less than galaxy-spanning groups of stars and worlds, some ETCs will interact, either through communication or, more rarely, through "close encounters of the third kind."

How exciting that will be!

This is a well-researched book that discusses 50 solutions to a paradox posed by Enrico Fermi: if there is intelligent life out there why hasn't it found us yet? Readers interested in this topic should find this book informative and interesting. However, early in his analysis of the solutions it becomes apparent that the author is not only presenting the solutions but trying to discredit each, so that his anwer, which he presents at the end, will be seen as the only reasonable one. To this end he engages in tactics ranging from the straw man fallacy to outright demagoguery.

Two examples: he describes an option called the "singularity" solution, which basically says that technological societies eventually reach a point of almost god-like power. At that point the population literally abandons the flesh and takes on new lives as wholly artificial super intelligences. With their new god-like perspective they simply have no interest in creatures as mundane as humans.

Sounds plausible to me, but what does Webb say? "Surely not all of the individuals would opt for this super existence, preferring to remain mortal and flesh and blood. Those individuals would explore space till they found us."

Talk about a stretch - Webb "debunks" this position by asserting that some sentient creatures would forego eternal life, unlimited power and limitless possibilities to exist a century or so in shells of meat until their inevitable and irreversible deaths. He then says that these technology-shy individuals would proceed to build starships and explore the galaxy, risking their fragile and limited existences in the process. Better not blow too hard on that house of cards, it'll collapse in a heartbeat.

He does similiar injustices to the view I favor: the "strange universe" solution. According to this proposal societies that explore space eventually discover not only how to travel faster than light but also how to build wormholes to distant galaxies and even parallel universes. Thus, with an eternity of different worlds to explore they simply haven't had time to get to us yet.

Webb derides this view, saying it is the preferred solution of UFO and alien abduction enthusiasts. Excuse me, Dr. Webb, but I think that alien abductions are pure baloney and that 99.9 percent of UFO sightings are easily explained (the remaining ones are, in my non-humble opinion, probably sightings of classified military craft). He also says that concepts like parallel universes aren't necessary to explain the universe and thus should be ignored.

Apparently the good doctor has been in isolation for the past couple of decades. Else he might have read some of the numerous articles by his colleagues that posit parallel universes as inevitable consequences of both an inflationary big bang as well as string theory. In addition a good many scientists believe that the many universes theory is the only non-theistic way to answer the Strong Anthropic Principle.

There is one huge problem with Webb's argumentation that I frankly feel reveals him to be a scholar of at best middling abilities. That problem is this: in his efforts to debunk all positions but his own he consistently says (I paraphrase here) "the problem with this solution is that, while it may apply to some extra terrestrial beings it surely cannot apply to all, thus it fails as a solution to Fermi's paradox."

I was so astounded by this blunder that I reread the book to make sure I didn't misunderstand him.

The obvious response to this line of reasoning it that there may very well be multiple answers to the paradox.
Some of the aliens may have blown themselves up, others may have escaped into another dimension, still others may have no desire to explore space, yet others may be signaling us now but on a level we cannot yet understand, and so on and so on.

In the end I recommend this book, but with strong reservations. In my opinion it would have been much better if written by, say, Michio Kaku, a scientist whose popular works are among the best available. I recommend all of his books very highly, especially one I'm sure Dr. Webb would love, "Parallel Worlds." Comments? wordsmiththreetwooneathotmail.com.

+++++

As the author, physicist Stephen Webb states, "The purpose of this book is to present and discuss 50 proposed solutions to Fermi's [Paradox]." Webb also states Enrico Fermi's (1901 to 1954) paradox (which he uttered in 1950) more eloquently as "the contradiction between the apparent absence of aliens, and the common expectation that we should see evidence of their existence...[in the form of] their craft or their probes or their signals [or even their artifacts]. We should not have to wait for evidence of their existence--the evidence should already be here."

This contradiction has a greater significance when the famous Drake equation is used to calculate the possible number of advanced civilizations in our Galaxy. Webb does a calculation based on this equation (before he delves into the solutions to Fermi's paradox) and gets a number of one million. (The late Dr. Carl Sagan did the same thing in his book "Cosmos" (1980) and came up with a number of ten million.) Thus:

"The Galaxy should be swarming with extraterrestrial civilizations. Yet we see no sign of them. We should already know of their existence, but we do not. Where is everybody? Where are they? This is the Fermi Paradox."

This book (that has many black-and-white pictures as well as diagrams) is for the general, educated reader. "One of the beauties of the Fermi Paradox is that it can be appreciated without the need for any [science or] mathematics beyond an understanding of exponential notation."

Forty-nine (specific) solutions (which are not intended to be exhaustive) are presented in chapters three, four, and five of this eight chapter book. These solutions come from scientists in several different scientific fields and even science fiction authors. As the author says,

"[These are] my favorite [specific] solutions to the paradox; not all of them are independent, and sometimes I revisit a solution in another guise...In the discussion [of each solution] I will try to be as even-handed as possible, even if I disagree with the solution (which I often do)."

The way these specific solutions are organized is around three general categorical answers. These general answers that are for optimists, SETI (Search for ExtraTerrestrial Intelligence) enthusiasts, and pessimists respectively are as follows:

(1) Chapter three contains 8 specific solutions based on the general answer that THEY ARE HERE
(2) Chapter four contains 22 specific solutions based on the general answer that THEY EXIST BUT HAVE NOT YET COMMUNICATED
(3) Chapter five contains 19 specific solutions based on the general answer that THEY DO NOT EXIST.

For example, someone might ask Fermi's question of "Where is everybody?" Picking one of the three general categorical answers presented above, a general answer might be "They exist but have not yet communicated." One of the 22 specific solutions presented in this book based on this general answer is that "We have not listened [for their signals] long enough." (This is the favorite solution of Dr. Frank Drake, co-founder of the SETI Institute).

Chapter six contains the fiftieth solution to the paradox that is the author's "own view of the resolution of the paradox." Actually, what is presented is a numerical solution to the paradox that is based on some of the qualitative solutions presented in chapters three to five.

Chapter one presents a general introduction to the topic and outlines the entire book. The second chapter gives a brief biography of Fermi, discusses the notion of a paradox, and presents a brief discussion of the history of the Fermi Paradox (and, as well, gives a good discussion of the Drake equation). Chapter seven presents as notes all the footnotes used in the book (that make for interesting reading in themselves). The final chapter cites all the references that were used.

I did find some minor errors but listing these would be nit-picking as they do not distract the reader from the main message of the book. For example, the math error that occurs in step five of the author's solution (chapter six) does not really matter to the author's overall result.

I was, however, surprised by two things:

First, the Fermi Paradox implies two obvious ideas: the aliens must be intelligent (if they are to build special craft that travel vast distances or to build sophisticated equipment to signal others of their presence) and they must have some kind of appendages that enable them to manipulate tools (used to build craft or equipment). It would have thus been instructive to have a general discussion of both these topics near the beginning of the book instead of at its end.

Second, after giving a good discussion of the Drake equation and praising the book "Rare Earth" which has the Rare Earth equation, the author chooses to ignore these equations and perform his own numerical calculation (which has elements of both the stated equations). I feel, with the added insight gained from the previous 49 solutions, that he could have plugged in values into these two equations first before performing his own calculation. A comparison of the final numerical answers would have been interesting and, I think, instructive.

Finally, I recommend these two books after reading this one: (1) "Is Anyone Out There?" (paperback, 1994) by Frank Drake (2) "Rare Earth" (paperback, 2003) by Ward and Brownlee.

In conclusion, this is a unique book that presents the best discussion of the Fermi Paradox that I have encountered. Be sure to read this book to enjoy the sheer pleasure of speculative thinking!!

+++++

This is a terrific, fun book to read. The author discusses 50 solutions to the Fermi paradox (you know the one: "if advanced alien civilizations exist, then why don't we see them?"), and does so very wittily. I didn't agree with all the arguments given in the book, but it many ways that's the whole point: this is the kind of topic you can have great fun arguing about. It captured my imagination, and it made me think - which is what I look for in books.

My only criticism of the book is the awkward referencing system it uses. Numbers in the main text point to a "Notes and Further Reading" chapter (these notes are themselves fun to read!), but then numbers in this chapter point to a "References" chapter. It got confusing for a while.

Fermi's Paradox can be stated in this way: If we humans are nothing special in the Universe, it must be teeming with intelligent life. If the Universe is teeming with intelligent life, we ought to see the evidence. We haven't seen the evidence. Why haven't we seen the evidence?

Webb examines and rejects forty nine proposed solutions to the problem. Each of the forty nine solutions leads to one of three conclusions: 1. They're here and we don't know it. 2. They're out there and we cannot communicate with them. 3. We're all alone.

After discussing the strong and weak points of each of the forty nine explanations and giving his reasons for rejecting them, Webb then gives a fiftieth explanation which he calls the "Sieve of Fermi." Beginning with a generous estimate of the vast number of planets in the Milky Way, he uses the "Sieve of Fermi" to winnow out all the possible planets which do not contain intelligent life. Only one planet makes it through the sieve--Earth. We are alone.

Webb's conclusion is strongly argued, but I don't think it carries the day. There's an old saw in forensic science to the effect that "negative evidence proves nothing." In other words, the lack of evidence of extraterrestrial intelligence doesn't prove that it doesn't exist.

The "Sieve of Fermi" does invalidate one of the presuppositions of Fermi's Paradox--the Universe is not teeming with intelligent life. Intelligent life in the Universe is extremely rare. Conclusion 2, they're out there but we can't communicate with them, is the likeliest scenario.

A well-researched, well-argued book which brings home to the reader what a low-probability occurrence human life is. Maybe we are special after all.

This book is fabulous. It is well written and engaging. It is geared to the non-scientist, but not watered down too much. There was only one scientific aspect that I felt needed more description (prokaryotic cells vs. eukaryotic cells). At the end of the book, I was sad because of the conclusion, but also sad because the book was done. I couldn't put it down. I have read perhaps a dozen books on this topic in the past two years. If I had to do it over, I would start with this one and read it more than once. Really impressive work!

Are there any civilizations in the Galaxy that are sending out radio signals besides us?

If so, why haven't we detected them? Why hasn't such a civilization visited us? After all, our Galaxy has been around for billions of years, but it would take only a few million years to populate it.

Webb is thorough in covering possible answers to these questions. Perhaps they are already here! Maybe they call themselves Hungarians. Or perhaps they exist but haven't communicated with us. The author discusses this all at great length. And next, he gets into the most obvious possibility: maybe they don't exist. Maybe we're the only ones. Or maybe we're just the first of many.

Webb discusses the possibility that there are several difficult steps (say, 12) on the path from abiotic material to intelligent life. Maybe we'd be the only lucky ones who made it through all twelve! Actually, I think this argument is mildly garbled by Webb, and that the best way for us to be the only ones is for there to be exactly one very unlikely step that could happen at any time (like winning a lottery).

There are other reasons why we might be the only ones. Perhaps there are unusual properties of our part of the Galaxy or of our planet that make our odds much better. There is a discussion of "habitable zones," both of the Galaxy and of stellar systems. And there is a discussion of hazards to life: another area where we humans may have been luckier than we might imagine. Webb also writes about how life may have originated on Earth in the first place.

At the end of the book, the author gives his own "solution" to the problem. Basically, it is that roughly one planet in the Galaxy has communicating life. Actually, that looks like a very interesting and plausible guess. But he also estimates that there are 10,000 planets in the Galaxy with complex life. Or is it 4,000,000? You see, he sloppily made three arithmetic mistakes in his calculation: factors of 10, 10, and 4. Who proofread this book?

Nevertheless, I enjoyed this book and recommend it.

"Where Is Everybody" is a very readable and enjoyable book that offers 50 possible answers to the question "are we alone in the universe?". The answers offered range from incredibly absurd to extremely thought-provoking. The book does not offer any unique insights or ideas which have not been suggested before. Its value lies in the collection of all of these ideas in a single volume. I found the book enjoyable and easy to read (most of the time).

I do have two complaints, however: (1) the book is somewhat repetitive, and I frequently got the sense that the same solution was offered multiple times for the sole purpose of reaching a total of 50 solutions; (2) portions of the book are poorly structured and needlessly use scientific concepts which are not adequately explained in the book. This is most notable in the sections of the book that discuss the biochemistry of life on earth.

Bottom line, I really enjoyed "Where Is Everybody?" and I warmly recommend it to anyone interested in the subject.