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5.0 out of 5 stars As gripping as a murder mystery
Of all the books I have read about climate change, "Snowball Earth", by Gabrielle Walker, is definitely one of the best ' and it's not even about the current climate change.

Part of what makes it so good is the style of writing. As the Los Angeles Times said about her later book, An Ocean of Air, 'Walker has a Ph.D. in chemistry, but she writes like a poet.'...
Published on Jan. 15 2012 by climatesight

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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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5.0 out of 5 stars As gripping as a murder mystery, Jan. 15 2012
This review is from: Snowball Earth: The Story of a Maverick Scientist and His Theory of the Global Catastrophe That Spawned Life As We Know It (Paperback)
Of all the books I have read about climate change, "Snowball Earth", by Gabrielle Walker, is definitely one of the best ' and it's not even about the current climate change.

Part of what makes it so good is the style of writing. As the Los Angeles Times said about her later book, An Ocean of Air, 'Walker has a Ph.D. in chemistry, but she writes like a poet.' And, indeed, after an education at Cambridge, Walker has spent most of her career as a science journalist. It's sort of sad that this doesn't happen more often. Usually, those who understand a subject best are not the ones who communicate it. Walker is the exception to this rule.

Take, for example, this passage about the history of life on Earth: "Stretch your arms out wide to encompass all the time on Earth. Let's say that time runs from left to right, so Earth was born at the tip of the middle finger on your left hand. Slime arose just before your left elbow and ruled for the remaining length of your left arm, across to the right, past your right shoulder, your right elbow, on down your forearm, and eventually ceded somewhere around your right wrist. For sheer Earth-gripping longevity, nothing else comes close. The dinosaurs reigned for barely a finger's length. And a judicious swipe of a nail file on the middle finger of your right hand would wipe out the whole of human history."

Another impressive aspect of Walker's writing is her characterization. Wacky, stubborn, and exuberant scientists are brought to life. Instead of just hearing about their work and accomplishments, you feel like you're getting to know them as people. She writes about arguing scientists particularly well. Arguing scientists are so much fun to read about ' that's one reason I loved The Lost World by Arthur Conan Doyle.

However, the best part of this book, by far, is the subject matter. The theory of Snowball Earth is possibly the most awesome thing I have ever heard about. Here's how the story goes:

From what paleontologists can see preserved in fossils, complex life arose at a very specific point in prehistory: the end of the Precambrian. For several billion years before that, the only thing that lived on Earth was unicellular goop. But then, suddenly, all at once, complex organisms burst onto the evolutionary stage.

Something must have caused this dramatic appearance, and a series of scientists from the 1940s on ' most prominently, Paul Hoffman ' likely have discovered what. At the end of the Precambrian, there are signs of ice in rocks all over the world ' scratches, rock deposits, everything that led Agassiz to discover the ice ages.

Because plate tectonics moves everything around so much, though, rocks were not necessarily formed at the location they sit today. Their magnetic field is what discloses their birthplace. Tiny bits of magnetic material, such as iron, line their field up with the Earth's. The Earth's magnetic field is perpendicular to the surface at the poles and parallel to the surface at the Equator. So, if a rock's magnetic field is vertical, it was formed at the poles. If it is horizontal, it was formed at the equator.

Incredibly, scientists found Precambrian rocks, with signs of ice, with horizontal magnetic fields. During that period of prehistory, the equator was covered in ice ' and, therefore, the whole planet, because it's not really possible to freeze the equator without freezing all the other latitudes too.

The scientists determined that, for several instances on the Precambrian, the continents were arranged in a way that was very conducive to ice-albedo feedback. With the smallest trigger, ice from the poles would creep across the temperature zones and meet at the equator. Frozen oceans, frozen land, the whole bit.

And now CO2 comes into the story. Volcanic eruptions naturally release carbon dioxide, but the amount is so small that the oceans have no trouble soaking them up ' unless they're frozen on the surface and cut off from the air. CO2 would gradually build up, in that case, and millions of years later, the greenhouse effect would be so strong that all the ice would melt and the planet would plunge into a state referred to as Hothouse Earth. Then the oceans would start absorbing all the extra CO2, and ice would reappear at the poles, and the cycle would begin again.

Many scientists believe that these Precambrian cycles of extreme heat and extreme cold provided such a strong pressure on organisms that natural selection was pushed to new boundaries. Complex life had an advantage in these extreme conditions, and it flourished. The most catastrophic climatic event our planet has ever experienced, in our knowledge, was what led to the evolution of multicellular organisms, and eventually, us.

It makes me feel very small, the same way that attempting to comprehend the vastness of the universe makes me feel very small. The life we see all around us only exists because of a series of coincidences. Human beings, one of the youngest of the millions of animal species that have ever existed, are alive because of continental drift lining things up in the right way. And who knows what would have happened if things had been slightly different?

Please visit my blog, [...], for more articles about climate change, including many book reviews.
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3.0 out of 5 stars A Biography and Detective Story, Plus a Little Science, May 17 2004
By 
Dennis Evans (Alexandria, VA United States) - See all my reviews
(REAL NAME)   
This review is from: 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.
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5.0 out of 5 stars Earth's History and How Science Is Trying to Read It, May 8 2004
By 
Andrew Wyllie "History Buff" (Roslindale, MA United States) - See all my reviews
This review is from: Snowball Earth: The Story of a Maverick Scientist and His Theory of the Global Catastrophe That Spawned Life As We Know It (Paperback)
This book offers a fascinating look at a possible explanation of how life went from single cell organisms to multicellular organisms. Also shows how different scientists can view and interpret the same data in different ways to support their different views. I have a lot of respect for Ms. Walker. Not only does she interview the main scientists that are involved in this debate, she has gone to some pretty remote areas of the world to see the very rocks that these scientists are basing their views on. That is alot more than most people would expect from someone just relating a story.
If you are interested in early life on Earth, you should read this book. If you are interested in how science tries to determine what has gone before, you should read this book. In short, if you are curious about life/science/the earth , "read this book."
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4.0 out of 5 stars Snowballs and egos on the loose, April 29 2004
By 
James Safranek "Holocene Meltwater" (Steinbeck Country) - See all my reviews
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Great writing for the layperson interested in pre-quaternary climate change theory, but some of the geoscientists researching the 'snowball earth' appear to have personalities verging on the psychotic. Would make an excellent case study for psychiatrists studying the obsessions of the geoscientific research community. Some of these geologists should've had their egotistical butts coldly rocked when they were being raised. I feel sorry for their students.
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4.0 out of 5 stars Up close and personal. Theories and Controversy., April 21 2004
By 
Robert C. Martin "unclebob@objectmentor.com" (Green Oaks, IL United States) - See all my reviews
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This book provides wonderful insight into both an interesting and controversial theory, and the personal and professional struggles of those who debate it. The author pulls no punches in describing the egos, strenghts and foibles of the various protagonists. They are sometimes seen as heroic, other times as petulant.
The author comes down a little too strongly in favor of the Snowball Earth theory, but so well exposes the controversy that her particular opinions are not given undue weight. The reader is left juggling many of the same balls that the scientific community is currently dealing with.
A quick but delightful read. Certainly worth the investment.
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5.0 out of 5 stars Easy read about scientific facts and speculations., Nov. 10 2003
By 
Filippo Neri (Los Alamos, NM) - See all my reviews
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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.
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4.0 out of 5 stars Snowfights, Oct. 13 2003
By A Customer
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.
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3.0 out of 5 stars A Snow job or a revelation?, Sept. 9 2003
By 
Stephen A. Haines (Ottawa, Ontario Canada) - See all my reviews
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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]
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5.0 out of 5 stars An Argumentative Champion for a Revolutionary Theory, July 30 2003
By 
R. Hardy "Rob Hardy" (Columbus, Mississippi USA) - See all my reviews
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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.
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3.0 out of 5 stars Icy personalities clash over Big Chill while frostily-SLAP!!, July 6 2003
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...
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