5.0 out of 5 stars Easy read about scientific facts and speculations.
In this easy-to-read and sometimes entertaining book, Gabrielle Walker tells the story of the discovery of the massive glaciations of pre-Cambrian Earth that have come to be known as "Snowball Earth". The fact that "Snowball Earth" really happened is not controversial, despite what some reviewers have suggested. The basic reason is the well-known fact that the Sun is...
Published on Nov. 9 2003 by Filippo Neri
3.0 out of 5 stars A Biography and Detective Story, Plus a Little Science
I will start with a brief synopsis of the science. In the last six years, many scientists have come to think that an ice age of incredible severity gripped the Earth for a few million years, ending about 590 million years ago. The ocean surface apparently froze all the way to the equator, although the ice may have been thin and patchy near the equator. The Earth's...
Published on May 17 2004 by Dennis Evans
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3.0 out of 5 stars A Biography and Detective Story, Plus a Little Science,
Ce commentaire est de: Snowball Earth: The Story of a Maverick Scientist and His Theory of the Global Catastrophe That Spawned Life As We Know It (Paperback)
I will start with a brief synopsis of the science. In the last six years, many scientists have come to think that an ice age of incredible severity gripped the Earth for a few million years, ending about 590 million years ago. The ocean surface apparently froze all the way to the equator, although the ice may have been thin and patchy near the equator. The Earth's average temperature was about -40 degrees Fahrenheit. Volcanoes belched out greenhouse gases for a few million years, and the atmospheric CO2 levels rose to many times what we have today. The ice receded from the tropics, and the greenhouse effect accelerated, driving the average planetary temperature above 100 degrees Fahrenheit (compared to about 60 today) within a few thousand years or less. This super ice age was the last of 4 to 6 such ice ages, with the first one occurring about 2.4 billion years ago, and the others between 750 and 590 million years ago. These ice ages may have occurred when all of the continents were strung around the equator. (The book presents a theory on why this might be so.) Finally, complex multi-cellular life forms first appeared in the Ediacaran period, shortly after the last super ice age. The book suggests that the last super ice age somehow spurred the appearance of complex life, but does not provide a good explanation of why this might be. (Maybe there is an assumption that "right after X" must mean "because of X.") Finally, the book asserts that such a calamity may occur again about 250 million years in the future.
The book is oddly written: part biography and part detective story, with some science scattered throughout. At no point does the book lay out a comprehensive exposition on the snowball hypothesis. Rather, the scientific theory comes through in bits and pieces as the book goes along. The book is, in large part, a biography of the four men who invented the snowball Earth theory: Paul Hoffman, Brian Harland, Joe Kirschvink, and Dan Schrag. It presents lots of extraneous information about these four guys, especially Hoffman (e.g., his exploits in running marathons). The book hops back and forth between the lives of the fantastic four, all the while letting the scientific mystery play itself out. This is something like a detective story. Many readers will probably like this approach, but I would have preferred that the first chapter explain the "snowball Earth" theory in detail. The rest of the book could then have dealt with how the theory came about, and the people who invented it. Moreover, the book is too narrowly oriented towards geology. Additional emphasis on atmospheric sciences, biology, and astrophysics would have been welcome. (For example, the sun's luminosity has increased about 1% every 200 million years for the last 3 billion years. During the various snowball epochs, the sun's brightness was about 88% to 97% of today's value. At what point is the sun too hot to allow a snowball epoch?)
The book also contains some errors. For example, it states that bacteria survived a trip to the Moon on an Apollo mission in 1967. The first Apollo moon landing was in 1969. Also, the book fails to consider the possibility that complex life may have provided an additional feedback mechanism for regulating CO2 levels in the air. In other words, it may have been that complex life caused an end to the snowball epochs, more so than the snowball epochs stimulating the appearance of complex life.
Finally, the book should, but does not, have pictures, illustrations, and maps.
5.0 out of 5 stars Easy read about scientific facts and speculations.,
Ce commentaire est de: Snowball Earth: The Story of the Great Global Catastrophe That Spawned Life as We Know It (Hardcover)
In this easy-to-read and sometimes entertaining book, Gabrielle Walker tells the story of the discovery of the massive glaciations of pre-Cambrian Earth that have come to be known as "Snowball Earth". The fact that "Snowball Earth" really happened is not controversial, despite what some reviewers have suggested. The basic reason is the well-known fact that the Sun is slowly getting hotter and was significantly less bright a billion years ago. Also not very controversial anymore are other assertions like the fact that the dinosaur extinction was indeed caused by the collision with Earth of one (or more) comets or asteroids. Walker is not uncritical about these facts, just well informed. There are some small misstatements in the book, like the assertion that magnetic pole inversion have happened regularly through geologic time, while, in fact, there was no inversion for an extended period (tens of millions of years) in the Mesozoic. More controversial, is the idea that "Snowball Earth" somehow "caused" the Cambrian animal radiation. This is the subject of just chapter 9. In many ways this is, for me, the most interesting chapter of the book, and also the most problematical. I assume that most of the experts don't doubt a relationship between the end of "Snowball Earth" and the "Big Bang" of animal life. But most would just assume that the big glaciations prevented the radiation of animals, that otherwise were ready to go, with Hox genes and all. Still chapter 9 is very interesting. Many of the discoveries discussed in it, like the finds of trace fossils of known Ediacaran "animals" have not been published in refereed journals. If it were true, Fedonkin's find of slug-like trails left by Kimberellas, would be extremely important. It would prove that this "animal" is indeed an animal, probably related to the common ancestors of mollusks and annelids. It is very strange that the Fedonkin has chosen to use Walker's book to announce such an epochal discovery. I think the explanation is in Gabrielle's picture, in the back of the book: she is so charming and enthusiastic that nobody can avoid bragging to her about their latest finds! My biggest complaint is that this book really needs graphs and pictures.
4.0 out of 5 stars Snowfights,
By A Customer
Ce commentaire est de: Snowball Earth: The Story of the Great Global Catastrophe That Spawned Life as We Know It (Hardcover)
It is always exciting to learn about new ideas on the cutting edge of any science. The idea of a Snowball Earth has sparked many debates and arguments. Snowball Earth, by Gabrielle Walker does more than defend the theory in face of academic scrutiny. She manages to introduce the reader to the man behind the theory, and in effect, write a story that resembles, the relationship between the man and his theoretical construct. This is what makes Snowball Earth, such a fascinating work. We are allowed to witness the man at his best, and at his worst. We are given an honest and open-minded view of the individual and his sometimes-sour relationships with others (generally those who do not follow his ideas). His arrogant and egotistical nature is not excused in any way, more fittingly it is used as a reason for his genius. The capacity to strongly trust what he believes in, makes Dr Paul Hoffman such a champion of his Snowball Earth Crusade, and more of the protagonist in the tale, than the theory itself.
The book opens with a chapter that accurately describes the manner in which Dr Hoffman approaches both life and his work. When still a young Postgraduate student with a passion for distance running, and on his very first attempt at the Boston Marathon, managed to come in a very respectable 9th place. His conviction to the cause, and self-will were the fuels which drove him on in the race, and remain to this day the fuels which drive his ambitions to prove to the world that the world has been through periods of massive freezing, the entire globe has been entirely frozen over, including the equatorial regions. This theory has been contested many times since it was first proposed to the Geological community, due to the fact that perhaps the most fundamental principle in Geology - Uniformitarianism, states that everything in the world behaves today as it always has. Processes, which are occurring today, have been occurring throughout Geological time. This means that we have the capacity to interpret past events through direct observation of present day functions. The idea of a Snowball Earth, then flies in the face of uniformitarianism.
Gabrielle Walker accurately describes the manner in which this affects the relationships between Dr Hoffman and his critics and compatriots. His driven belief in his own abilities (as proven by his Boston Marathon performance) often causes him to bash heads with those around him, not winning him many personal friends in support of his outlandish theory.
Critics of the snowball model (such as Nick Christie-Blick, Hoffman's chief adversary) insist that if at any time the entire surface of the earth was frozen over, the amount of insolation absorbed within the atmosphere, would greatly decrease, due to the nature of ice. The reflection of this radiation back into space would mean that ice depths would increase, and the earth would remain locked in a state of ice indefinitely. Dr Hoffman's Snowball Earth theory entails the periodic covering of the entire surface of the earth, under a layer of ice around 20km thick. This ice would then be thawed eventually after around 100 000 years or so due the combined action of volcanoes, and the releasing of gases such as CO2. These gases are released in the atmosphere, and they, along with the surface of the earth, absorb the incoming solar radiation and re-radiate it back down to the earth's surface. The net effect of this, is that enough internal heat is stored within the atmosphere to raise global temperatures, and in doing so, begin the melting process, which relieve the earth of its frozen blanket, to more closely resemble those conditions we know of today. The way, in which Walker describes complicated scientific processes, is simple and easy to follow, which is the mark of a good scientific biography.
Walker is giftedly able to place the reader in the company of Hoffman and his colleagues as they scour parts of the globe looking for evidence for rocks that would prove the earth had indeed frozen over entirely. We are taken from places as diverse as Svalbard Norway, to closer to home, Namibia. The signs and signatures of rocks that had been frozen are searched for. In order for Hoffman to prove the entire surface had indeed frozen, he needed evidence that showed that the rocks at the equator had frozen too. To do this he needed to identify the mark of rocks that had been frozen, then place them at the equator through the study of palaeomagnetism. When newly formed rock solidifies, it holds with it the magnetic signature of the Earth's magnetic field. By knowing the alignment of that field, you can work out the approximate latitude of that rock at formation. The work of Joe Kirschvink, enabled Hoffman to show that there had indeed been equator rock which at some stage had been frozen. The specific time period searched for by Hoffman was between 750-590 million years ago, the time before the Cambrian explosion. The reasons for this are made very clear by Walker, and explain the draw and attraction of the theory to the layman. Before this time, all life that existed on earth was in the form of a primordial sludge of single celled organisms. After the Cambrian explosion, the world entered a period of massive diversification, in which single celled organisms became multicellular life. We saw the birth of shells, and scales, and spines. Teeth and external and internal skeletal structures. The ancestors of life on earth as we know it today. This is why Dr Hoffman is so interested in finding these specifically aged rocks, with these specific palaeomagnetic signatures. Snowball Earth may then prove to be the catalyst that sparked the emergence of complex life on earth. The cooling and rapid warming of the earth may have created an environment stressful enough to cause single cells organisms to huddle together for survival. Creating specific functions for each cell, and uniting them to form a single complex entity.
The way in which Gabrielle Walker approaches the tropic is informed and passionate. Her capacity to convince the reader of the validity of the theory may even rival that of Dr Paul Hoffman himself. Snowball earth is a fascinating read, with massive contemporary appeal in the wake of modern existential reasoning. We may have found the source of complex life, floating in a glass of cool drink.
3.0 out of 5 stars A Snow job or a revelation?,
Ce commentaire est de: Snowball Earth: The Story of the Great Global Catastrophe That Spawned Life as We Know It (Hardcover)
Gabrielle Walker's first book portrays the struggle of a renegade scientist to establish a theory of evolution's progress. Charles Lyell's established "uniformitarianism" in geology, followed by Charles Darwin's application of it in his theory of evolution by natural selection. The concept of gradual change in life as reflected in the fossil evidence is being challenged by some scientist. Paul Hoffman's research in Namibia indicated that Earth was subjected to an intense Ice Age prior to the Cambrian, severely interrupting life's progress. Walker introduces us to Hoffman and other major contestants in this game of reading the rocks. She presents him and the arguments with dynamic style, giving the book a certain panache.
Even under Walker's admiring scrutiny, Hoffman doesn't appear as an endearing figure. Yet, the very characteristics some find irritating are the same drives that kept the theory of Snowball Earth alive. Walker shows how combative science can be, with contenders sniping and quarreling like feuding families. They all have fossils, climate mechanisms and glacial processes on show. Walker attempts to give them all a hearing, but the opponents make but cameo appearances. She gathered her evidence by extensive journeys - her travel budget must have been prodigious. Walker reveals their peccadilloes and their strengths. When you are done, you feel a sense of identity, even intimacy with them.
Whether you are convinced of the thesis remains problematic. Walker's own sketchy knowledge forces a pause, wondering about the validity of her presentation. Her admission of being a "Snowball Earth groupie" erodes credibility. She offers many assertions as givens, such as the asteroid dinosaur extinction thesis. Theory popularity is good journalism, but sketchy science. Her journalist role leads her to overuse of buzzwords - "Slimeworld", the habit of bacteria to form mats - achieves fatiguing redundancy.
The predominant question, which Walker addresses only superficially, examines what process life underwent under these conditions. There was life before the Cambrian - clearly multi-cellular. How complex was it, and how resistant to the environmental crisis evoked by the Snowball Earth hypothesis? Ediacaran life was shallow sea bottom or surface dwelling. An ice blanket a kilometre or more thick would have been devastating to this population. Walker and her "group" are unable to form a coherent thesis of how life achieved complexity after the Snowball's meltdown, only that it must have happened - otherwise "we wouldn't be here". A valid statement, but one needing further support for how it might have occurred.
Walker's personalised account makes engaging reading, presenting a new idea needing more attention. While various modifications of the Snowball Earth notion have been offered, final judgment remains deferred. This is a good, but limited, overview of the debate and the participants. At some point, someone qualified will enlighten us further. [stephen a. haines - Ottawa, Canada]
5.0 out of 5 stars An Argumentative Champion for a Revolutionary Theory,
Geologists since the eighteenth century have advocated "uniformitarianism," the concept that what is going on to the Earth now is essentially the same as what has gone on before. It is a good rule of thumb, but like most rules of thumb, it requires intelligent neglect or violation, and working geologists do so to form an accurate picture of Earth history. There has sometimes been resistance to violation of the rule; the wipeout of the dinosaurs by an asteroid hit 65 million years ago is now generally accepted, but was not when it was proposed. But even without extraordinary outside forces, our globe used to be a very different place. Between 750 and 590 million years ago, there were sudden lurches in climate that froze even lands at the equator. Or so goes the Snowball Earth Theory. _Snowball Earth: The Story of the Great Global Catastrophe that Spawned Life as We Know It_ (Crown Publishers) by Gabrielle Walker describes the theory and its importance, but the current importance may not be merely its scientific significance. What makes the theory particularly interesting right now is that it is being championed by a colorful Harvard geologist who is attempting to make it accepted geological thought. Walker's surprisingly exciting book is thus not just a summary of ancient geology, but also an entertaining examination of personalities involved.
The snowball Earth theory is not entirely new, but the book is largely the story of Paul Hoffman, a brilliant, driven geologist who was eager to make some sort of difference in his field. Argumentative, energetic, and brilliant, he has a strong reputation as a geologist and as a difficult character. Disputes by him are not objective quibbles published in obscure journals, but stand-up, screaming fights. Partially because Hoffman has taken up a sort of gladiatorial grandstanding for the theory (he has made his own contributions and confirmations), there are equally adamant anti-snowballers. The combative nature of science is on display here; Walker writes, "Science works at its best when somebody puts forward a theory and everyone else tries to pull it down." She is good at describing the pains of field work (something at which Hoffman is adept), but academic battles are the emphasis in her book. Of course Hoffman hopes his ideas share the same fate as those of Alfred Wegener, whose ideas about Plate Tectonics were originally ridiculed; so far, they have survived the challenges about which Walker reports.
Particularly valuable in the theory is the light it might throw on the bloom of life into complex multicellular creatures. Of course a deep freeze would have been disastrous for all the simple slimes that were found all over the Earth when the freeze came. There might have escaped, however, pockets of cells that, according to the theory, were the precursors for the famous Cambrian explosion in the trilobite times. Perhaps the snowball produced the complexity, although this is far from clear. It is one of the many details that is going to have to be argued over. Walker winds up with a description of the Earth's future; if we are still around in a few hundred million years, we might well have to deal with a return of the snowball. It is too hard to think about time lengths of such spans, but geologists routinely do so, although the spans are back in the past. Walker's book is a good introduction to serious thought about such times, and to the very human way such science is done.
3.0 out of 5 stars Icy personalities clash over Big Chill while frostily-SLAP!!,
Sorry, couldn't help it!
This is a fun, fascinating layman's account of the controversial theory of cryptozoic global glaciation, how it may have been the trigger behind the rise of complex life, and the fieldwork and theorizing that led to it. Another book, _Great Feuds in Science_, detailed how great science really gets done, not just with experimentation and evidence collection, but with clashes of personalities and battling reputations. This is in the same vein, as we follow Paul Hoffman and his allies and opponents through a decade of geological work, in pursuit of evidence supporting or disproving the Snowball theory.
Ms. Walker's intimate style is a bit off-putting, if you're used to the more nuts-n-bolts science writing of an Isaac Asimov or Timothy Ferris. And this book really could have used some portraits, diagrams, and other illustrations. Portraits, especially, given the up-close-and-personal rendering of the principals. But it will keep your interest to the end, and give the reader a sense of discovery, as the bits of the puzzle fall into place. The last chapter is a prognostication on the possibility of a future snowball. Chilling...
5.0 out of 5 stars Splendid Look At A New Controversial Theory of Geology,
Gabrielle Walker's "Snowball Earth" reads like a gripping detective tale and spellbinding memoir. Her relatively terse epic primarily tells the tale of arrogant, maverick Canadian geologist Paul Hoffman, and how his study of Precambrian geological formations in Namibia, Africa lead inexorably to a new, controversial theory in the geological sciences; "Snowball Earth". Possessed by a zeal equalled only by a religious fanatic, Hoffman, a professor of geology at Harvard University, gradually builds up an impressive theory explaining how the Earth was encased in ice, not once, but probably at least four times, over the course of two hundred million years (He believes it began around eight hundred million years ago.). Furthermore Hoffman has suggested that this was the event which triggered the evolution of metazoan life and the subsequent Cambrian explosion of metazoan phyla. Walker also introduces us to Caltech geologist Joe Kirschvink whose work in magnetostratigraphy supplied important clues that aided Hoffman in shaping his theory. But to her credit, she also spends considerable time discussing important critics such as Columbia University's Nicholas Christie-Blick and University of California, Riverside's Martin Kennedy and noting their substantial objections without sounding dismissive. Told in engaging lyrical prose, Walker's book will interest anyone fascinated with research done by field as well as laboratory geologists. Her book is a splendid little ode to exciting state-of-the-art geology and some of its most fascinating scholars, most notably Hoffman, himself. Without question, this is among the finest popular books on geology that I've come across.
4.0 out of 5 stars A great overview of a current controversy,
This is an excellent read, for scientists and non-scientists alike. How often do we get snapshots of scientific controversies as they evolve? I can't think of any. And it is an accessible and fascinating controversy for the literate public. Ms. Walker has bent over backwards to keep the geojargon out, and I applaud this. She has done a great job of presenting the scientific problem and the psychological drama implicit in resolving this within the scientific community. Her vignettes of the personalities are great and she pulls no punches. All are presented as humans, with incisive assessments of strengths and weaknesses. She does a great job presenting how they interact, and this for me was the best part of the book. The footnotes are unusually useful and entertaining; would that all footnotes were as readable. I like the way that she uses footnotes to steer the interested reader to other papers and books. The decision not to have photos or maps is strange, this was a mistake that I hope she does not repeat in her future efforts. We may be witnessing the beginnings of a great career in writing science here.
2.0 out of 5 stars Snowball Earth, A Review,
There is no doubt left to the reader where Gabrielle Walker, author of the new book Snowball Earth: The Story of the Great Global Catastrophe that Spawned Life as We Know It, stands in the scientific debate over the Snowball Earth Theory. The first line in the acknowledgements of the book reads, "For the past two years or so, I have been a Snowball Earth groupie."
Snowball Earth traces the latest theory to send shockwaves through the geological community. Controversial theories in geology are not new (plate tectonics, and the extinction of the dinosaurs are two that come to mind), and a thorough understanding of the different sides in the debate of these new theories is needed to make sure the theory stands the tests of time and scientific scrutiny. The debates over new theories take place in the scientific journals, at scientific conferences, on field trips, and in the press. A good book about a theory presented for the lay-people can help educate the masses on the various points, pro and con, for the new theory. Unfortunately, Gabrielle Walkers book falls short on this ideal.
Snowball Earth is a semi-biography of the men that have postulated the 'Snowball Earth' theory, who have championed it in the scientific community and who have weathered the storm of debates and controversy over the various parts of the theory. The book opens, and mostly follows, the work of Paul Hoffman who put the many pieces of the puzzle together into the theory that became 'Snowball Earth'. Subsequent chapters focus on other players in the Snowball Earth drama. Brian Harland whose work in Svalbard, Norway leads Walker to dub him "the grandfather of the Snowball" and Joe Kirschvink whose skill with magnets and paleomagnetism helped prove the position of the continents in the tropics at the time of the Snowball. All played a role in bringing life to the Snowball Earth theory and Walker holds each high for the reader to esteem and praise.
Opponents of the Snowball Earth theory are given their due, but each is treated like a cameo character in a movie whose sole role is to come and challenge the hero in the white hat and fall away under the truth of the hero's cause. Scientists like Nick Christie-Blick of the Lamont Doherty Earth Observatory at Columbia University and Martin Kennedy of the University of California, Riverside, are each paraded before the reader to give their opposition to the Snowball Earth theory. The data and counter-evidence collected by these and other geologists has sparked the heated debate over the Snowball Earth theory almost from its inception. In the end though, each is somehow shown to actually provide evidence that supports the Snowball Earth theory.
Walker's treatment of the theory and its proponents is not completely biased. Her skilled writing shows the arrogant and egotistical side of Paul Hoffman and the personality conflicts that all too often arise between strong willed people. The reader can feel the passion each of the players feel for their side of the debate. Walker does an excellent job of putting the reader in her shoes so you feel you are walking the hills of Namibia to see Paul Hoffman's field sites, or are scouring the rocks of Australia with Jim Gehling in search for rare Ediacarian fossils. In the end though Walker's skilled writing and easy-to-read style are not enough. Unless you are already a firm believer in the Snowball Earth theory the reader is left feeling incomplete. The time, effort, and attention to detail Walker gives to Hoffman, Kirschvink and the other proponents of the Snowball Earth theory are not given to those who oppose the theory. The alternate models, such as the 'Slushball Earth', are skimmed over, and in general the reader is left with the impression that the Snowball Earth is the only plausible explanation because that's how Walker presents it. In a way the reader feels patronized, that we are not capable of deciding for ourselves the merits of the theory based on the evidence from all sides of the debate.
4.0 out of 5 stars Science History in the Making,
It is fascinating to watch the unfolding of new scientific theories, particularly after having lived through some of them. For example, when I first began studying geology, continental drift was just beginning to be accepted. This book advances some interesting ideas in Earth history that seem to have good evidence for them. It's also well written and entertaining (although, I agree with the other reviewer who called it too "dumbed down").
The book really, really needs illustrations (there are NONE), and it's astonishing that it does not have them, given the opportunities. There are the stunning landscapes of Namibia and Svalbard that could appear. There really should be photos of the Hamelin Pool, of Stromatolite fossils, of the minerals and rock formations, and of the geologist protagonists. I'd recommend fifty color photos, and I might just buy another copy if a new edition is produced that way.
Minor gripe: There's only one place in the world one can have an "intercontinental train" -- and it's not Canada. Proofreader, hello?
All in all, a very worthwhile read.
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Snowball Earth: The Story of a Maverick Scientist and His Theory of the Global Catastrophe That Spawned Life As We Know It by Gabrielle Walker (Paperback - Feb. 24 2004)
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