This book has a number of good features --
(1) References: over twenty-five pages that mainly consist of recent journal articles written by respected scientists.
(2) Two 2-page introductions that summarize the entire book. These are entitled "Dead Zones of the Universe" (where Life As We Know It, LAWKI, is postulated not to exist) and "Rare Earth Factors" (18 factors that may be unique to Earth and that permit LAWKI). These provide a kind of roadmap for the first ten chapters of the book.
(3) The first ten chapters are very detailed and build-up (using both historical theories and data as well as recent new theories and data) the summary information mentioned in (2) above.
(4) The last three chapters are particularly interesting. Here we get more aquainted with the authors' Rare Earh Hypothesis (microbial life is common in the universe, but multicellular animal life is rare) and introduced to the Rare Earth Equation (which challenges the assumptions of the famous Drake equation).
(5) The honesty of the book. The authors state, "Perhaps Earth is not rare after all but is simply one variant in a nearly infinite assemblage of planets with life." In other words, they acknowledge that life as we DON'T know it may possibly exist.
In conclusion, for those thinkers who want to read a book on the cutting edge of modern scientific investigation, this book is for you!
on August 22, 2003
I both hate & love this book. I think it is a must read. Like all reviewers here, I am one of those who hopes that it's a "Star Trek" universe out there but unlike other reviewers on this board, I do not think that this book will get outdated anytime soon.
This book without trying, seems to partially reconcile the 'Creation' & 'Evolution' hypothesis. It does this by sticking to the 'Evolution' script but listing powerful arguments as to why 'Life' as we know it may be unique or at least rare. In the face of mounting evidence, perhaps the church could support this hypothesis without losing legitimacy.
The hypothesis is not built on one single argument & therein lies its strength. The book starts by making a clear distinction between microbial & animal life and concedes quickly that the former may be quite common around the universe. Animal life on the other hand, requires a fortuitous alignment of the stars and planets :)
The first concept explored in this regard is that of a 'Habitable Zone'(HZ). Off the 3 types of galaxies, only large spiral galaxies are likely to host life. The other two types are either too dense (globular galaxies) or too old (elliptical galaxies & small clusters), lacking the heavy elements necessary to sustain habitable conditions. The former is a problem of overcrowding, too much sun (literally), gravity, harmful radiation & frequent cataclysmic events (supernovae, black holes etc.). The latter would mean a world without a heated core, mostly composed of hydrogen & helium. Think of the Sun & Jupiter, what are the odds of life in these two places.
After eliminating all but spiral galaxies, the hypothesis also does the same to systems within spiral galaxies. Too close to the core and you have the same problems faced within globular galaxies, too far & you have the environment similar to an elliptical galaxy, i.e., too few heavy metals. That leaves only the arms of spiral galaxies as likely habitats for complex life.
Within the HZ of galaxies, planets also have to be formed within the HZ of their star. Too close & they're toast (all water evaporates and escapes into space), too far and they are too cold to sustain anything but microbial life. Additionally it requires a star with certain properties, a certain size (only 5% of stars are the required size, most stars in the universe unlike our Sun are too small) and a high percentage of heavy metals (again a rare combination).
Finally, the roles played by the Moon & Jupiter in supporting life on earth. The Moon stabilizes the rotation of the Earth. Imagine a basketball rolling on a floor rotating in varying directions as opposed to a top, rotating on a fixed axis. Without the Moon, the poles & equator would be constantly shifting. Our planet would be covered by water, temperatures & seasons would be unpredictable. Without Jupiter (because of its size & gravitational pull) attracting and capturing most celestial objects on a collision course with Earth, there would be many more large bodies crashing on earth and threatening life. You know what happened the last time this happened, ask Mr. T-Rex.
Even assuming all these factors are duplicated, there is the additional factor of a time period. This ranges from the time the solar system has cooled down & the planets settled into stable orbits to the end when the star runs out of fuel & dies. Complex life has this time span to evolve, live & likely perish.
The Rare Earth hypothesis is exactly that, it is not a law. Ward & Brownlee make a strong case, one whose implications I don't like but are nevertheless persuasive. If you are students of science, the origin and future of mankind, I would strongly recommend you read this book.
on February 15, 2004
Peter Ward and Donald Brownlee have written a very thought-provoking book in "Rare Earth." They have, in fact, given voice to some thoughts that had occurred to me and to a lot of others quite some time ago - namely "Where is everybody?" Flying saucer enthusiasts and alien abduction aficionados aside, most of us who think about such things have wondered why no alien civilization's radio transmissions have not obviously reached planet earth by now if alien civilizations were so common. Also we are starting to wonder where life exists in our solar system outside of Earth.
When I was in my teens I eagerly kept track of every launch of a spacecraft. I dreamed of even becoming an astronomer specializing in planetary geology. But my true love was biology and the thought of a possible alien biological system was fascinating. I was soon disillusioned. First the veil of Venus was lifted and where swamps and dinosaur-like creatures roamed in science fiction was a barren acid and heat scorched version of Dante's Inferno. Mars was also found to be a volcanic version of the earth's moon, except with weather (dust storms mostly), pole caps of carbon dioxide and water ice, and a very thin atmosphere. The temperature of close to 100 degrees F. below zero did not seem promising and still does not. Thus the civilizations of Mars envisioned by Lowell disappeared into the Martian dust (as they had started to even before the first space probes). Then the moons Titan (Saturn) and Europa (Jupiter) were proposed as abodes of life, however weird, and a Martian meteorite with strange "nano-bacteria" was brought out. The latter "nano-bacteria" have become dubious at best and the moons are looking less promising by the day. Titan may have such a smoggy atmosphere and be so cold as to be certainly questionable as an abode for life. In addition to this, recent reports indicate that Europa is covered with a layer of concentrated sulfuric acid (possibly from the neighboring moon Io, which has sulfur volcanoes on its surface) and hydrogen peroxide- not exactly a good place for living things! To top it off some scientists think that the ice on Europa may actually cover a sea of sulfuric acid with a pH close to 0!
If we cannot find even primitive living things (bacteria, lichens, fungi) on other planets in our system we may have to face the fact that life, while it may exist on numerous planets, is not nearly as common and as accessible as some would have it and that "civilizations" are even less common.
Why is this? Ward and Brownlee have provided detailed answers, which, even if their formulae are somewhat flawed (as one reviewer suggested), are persuasive. We have to keep in mind that we do not know how long civilizations last or how often they occur but do not develop our type of technology. We are up against billion of years of time and trillions of cubic light years of space. Star Trek aside, we are not even sure that interstellar travel will ever be possible, so we may never know for sure what is out there.
As Ward and Brownlee point out, to even have a planet with the possibility of life we have to have several conditions met. First planets revolving around multiple stars probably do not last long because of tidal effects and if they do life might have to cope with radical changes in surface temperature. Given that, we still have a number of candidate stars and have even found a number of such stars with planets (most of which are huge, some even by Jupiter standards). We also need planets within a star's habitable zone (assuming the star is not unstable and lasts long enough for the development of life). Then contingency has to allow for the development of living forms sometime during the life of the planet. To get more complex life than bacteria we need several billion years and perhaps a large moon. It gets even dicier if we want intelligent life, and even then we may have intelligent ocean-dwelling creatures who never develop radio and thus may not be detectable. Even if radio waves are produced by a civilization, we need to exist ourselves within that civilization's survival time frame (or actually light years later).
Ward and Brownlee have provided, I think, some very good reasons why we are unlikely to find multicellular life on nearby planets or advanced technologies on planets even around distant stars. Even if life is fairly abundant in the universe (and I think it probably may be), planets with life (even at the bacterial level) may not be anywhere near as abundant as lifeless ones. This is not a reason to embrace creationism, as some would have it, but is simply a property of our universe. While I wish it were not so, I fear we cannot argue with the logic of this- especially with the little evidence we now possess. Of course one cannot completely rule out the possibility that Ward and Brownlee have missed something, but that is a present a meager hope.
Read this book if you are interested in why complex life may be uncommon in the universe.
on September 13, 2000
_Rare Earth_ is a polemic for the view that complex life, both animals and higher planets, is rare in the Milky Way Galaxy and perhaps even in the Universe. Unfortunately, it fails to provide convincing evidence for this view, is often marked by sloppy writing, and in places borders on being wrong.
As an example of the latter, the authors seem to imply that the Sun has little or no interaction with the Galaxy's spiral arms and that the inter-arm regions of a spiral galaxy have a lower stellar density than inside the spiral arms. Neither is correct. It is true that the Sun is not now located in a spiral arm. However, the Sun orbits the Galactic center, taking about 250 million years to do so. The Galaxy's spiral arms do not rotate with the stars. The Sun therefore probably passes through at least one spiral arm every orbit. Over its lifetime the Sun has made approximately 20 orbits, plenty of time to pass through multiple spiral arms. Indeed the authors seem to be unaware of a proposal that massive extinctions in the Earth's past were caused by passage of the Sun through a spiral arm.
In many places the presentation also seems muddled. If we are told that Jupiter is more than 300 times the mass of the Earth (p. 235), do we really need to be told less than three pages later that Jupiter's mass is 318 Earth masses (p. 238)?
While reading it, I kept finding myself saying, That's not right, or, But what about ....? It's truly disappointing because the title is so provocative and because we are learning so much about the formation of planets and the origin of life on the Earth. However, having read the book, I certainly would not have purchased it initially.
on March 12, 2000
Professors Ward and Brownlee come to the right conclusion - that we have an incredibly unique planet, and the chance that there is complex life elsewhere in the universe is just about zero - but they don't always use the best evidence to get there. They rely on evolution and all the things that have to fall into place for evolution to happen. They talk about the many catastrophic extinctions that have happened during earth's history, but still there was supposedly enough time for evolution to happen. They even spend a whole chapter trying to explain the away the Cambrian Explosion and it's bad implications for evolution, but to no avail. All this, even though there is no scientific proof - from the fossil record to biochemistry - that evolution could be the process by which life formed and then diversified in the first place. Another thing abou this book that is intriguing is how they talk so often about all the 'amazing coincidences' that had to happen in order for Earth to be able to support complex life. Earth "just happened" to be in the habitable zone in the solar system, plate tectonics "just happened" to develop, the atmosphere "just happened" to be just the right composition, the moon "just happened" to be just the right size, and so on. There are actually currently 118 factors that have to be fine tuned - some cannot vary by more than one part in 10^37 - in order for life to exist at all. As scientists, one would think the authors could see that they should take all those factors into consideration, and then they might come to the realization that the likelihood of all those factors coming together at just the right places and times by chance alone is absolutely zero. However, maybe they don't like the implications. As other people have already pointed out, Hugh Ross has been making this point for years in his books "The Creator and the Cosmos" and "The Genesis Question." Maybe now that secular scientists have finally realized what Christian scientists have been saying for a long time, people will listen.
Other than that, there is some great information in this book. The chapters on habitable zones, plate tectonics, and the importance of the moon and Jupiter to life are fantastic, and contain a lot of good information written in a way that a no scientist can understand. Overall, a very interesting read, and a real eye-opener for those who have always assumed that there is life elsewhere in the universe.
on February 21, 2000
The body of evidence drawn upon by this book is well known by now and was no surprise to me. What is a surprise to me is how these two writers could come up with such dramatic claims based on this evidence.
Folks, the fact is that we have barely even begun to explore the habitablility of our Universe beyond planet Earth. Don't be mislead into thinking the task is finished. Despite much self-lauding on how much we've discovered, we've only been at it for 50 years! We know very little even of the other planets in our own solar system, and we are NOT sure that none of them harbor complex life.
Outside our own Solar System our knowledge is even less complete. The best we can do at this point is look for fluffy, hot giant planets. While the technology to detect Earths around other stars is certainly coming along, it is not here yet. Ergo, we know nothing about the frequency of Earths orbiting other stars, let alone whether they are habitable.
We are very special here--anyone who has walked in the rain, sung a song or been in love will agree. But whether we are ALONE is a whole other matter, one that neither Ward nor Brownlee is prepared to answer given the current body of knowledge. Therefore I find the argument of this book quite misleading to the general public and mildly insulting to the authors' colleagues.
on July 9, 2000
Rare Earth is an overview of the complexities of, what we consider, life. Unfortunately, the book can easily be summarized in one sentence: life may be rare because Planet Earth may be rare. This simple statement may seem flippant, but the authors really offer no more conclusive information than this simple statement.
The book does have some nice summaries of astrobiology, evolution, plate tectonics, snowball earth events, etc. If you are in the simple sciences (physics, astronomy, biology etc.), this book may provide a good read because there is a lot of theory but little real information. If you are looking for analysis and solid conclusions, this book will be a clear disappointment.
on June 14, 2000
This is a fascinating topic and the authors did a good job of explaining their thesis. For the lay reader, however, some parts may be a bit technical and explained in too much detail. I almost think this could have been better presented to the non-scientist reader as a long magazine article rather than a full book.
However, that is minor criticism; there were many intriguing ideas presented in this book. And I should really give it 5 stars -- the extra star awarded to the authors for debunking the ideas of that pompous populist, Carl Sagan (I can just hear him saying..."Only one civilization in the galaxy? NO! Billions and billions and billions...").
on February 20, 2003
The only reason I give this book a 3-star rating is that it is already becoming dated by the blinding speed at which exoplanetary science is developing. When this book was written (remember that books typically take at least a year to see the light of day from the time they're written), the science that was discovering exoplanets (planets outside our own solar system) was fairly recent and the number of planets discovered was very low, and they were all "super-Jupiters".
However, the methods used have improved greatly and the number of known exoplanets is now over 100. More recent discoveries of terrestrial plannets in addition to gas giants makes it increasingly likely that planetary systems are the rule, not the exception.
The other criteria the authors state as necessary: large moon, Jupiter-type planet, etc., are also turning out to be common. This is not to slight their work; given the available information at the time they wrote the book, it was solid research. However, just as early mariners had to continuously redraw their maps as the world's oceans were explored, so will our self-important ideas uniquemess have to be abandoned.
Simply put, the numbers are mounting to a simple but profound conclusion: It is very likely that we are not alone, which is no surprise given that there are 200 billion stars in our galaxy alone and there are over 400 quadrillon known galaxies, each with hundreds of millions of stars. Put in perspective, our galaxy is like a grain of sand among all the beaches of Earth. Statistically, uniqueness is a statistical impossibility.
on December 7, 2002
While I think that it would be fascinating if we do someday discover evidence of an inhabited planet around a distant star, I think that the authors Peter Ward and Donald Brownlee raise important questions about what makes Earth a habitable planet. They bring up many considerations of habitability that one often doesn't think of (for example, the presence of a large moon, of Jupiter, of plate tectonics, and also the metal content of the Sun compared to other stars). Of course, I think we know too little about other solar systems to be able to say whether or not these factors are truly rare (even the book at times acknowledges this), so it is premature to draw any firm conclusions about whether there are other habitable planets. But I do think that, if we wish to do an honest assessment of whether extraterrestrial life is likely to exist, we need to at least ask these questions. I still fully support searching for signs of other habitable planets, since there still could be interesting surprises in store for us. It is also very interesting to read about the factors making Earth habitable, whether or not you agree with the conclusion
Although this is a scientific (not a theological) book, I will also mention that I am a believing Catholic. So I believe that it is up to God whether Earth is the only inhabited world, or whether there are others (the Church takes no official position on extraterrestrials). I believe that is providential that the conditions on Earth are so favorable for life, and that the same would be true of other habitable planets (if they exist).
I recommend this book for helping to understand the factors that make a habitable planet, and also one can learn a lot of astronomy, biology, and geology in the process.