The Big Splat, or how our Moon came to be by Dana Mackenzie

The moon has long fascinated humanity, and over the millennia, many explanations have been given as to what it was, what it was composed of, and how it came to be. This book details the many views of the moon, from ancient tribes to the modern day, and how it took a trip to the moon to begin to understand exactly how the moon came to be.

The book begins by looking at the ancient view of the moon. Many cultures considered the moon to be a God or divine being, just as they considered the sun to be also. It took the Greeks to divorce the idea of the moon being a divine being from humanity, but what they came up with to replace it wasn't much better. Some considered the moon to be nothing but a tremendous fire. Others thought it a mirror, perhaps a cloudy one. Many thought the moon made its own light, since at times it dimmed and grew red and smoky (lunar eclipse). But only one Greek Thinker actually got it right. The moon was made of matter, and orbited the earth, since a meteor had crashed in greece and was found soon after it landed. Anaxigoras probably came the closest to a modern understanding of the moon.

Next it was Kepler who became entranced with the moon and worked out how it moved... or so he thought, anyway. And so the moon was studied by a whole host of scientists, until the modern day, and the first Apollo mission to the moon. By then, there were three competing theories of how the moon came to be: 1) The Capture Hypothesis- in which the moon was an extrasolar or other body that passed by the Earth and was somehow caught by Earth's Gravitational Field and ended up orbiting the earth. 2) Simultaneous formation- That the earth and moon formed together out of the same nebula, but somehow didn't end up joined together. and 3) That the moon formed out of a piece of the earth that had broken off somehow while the earth was forming.

All three hypotheses had their adopters and detractors, but it remained until the Apollo mission to actually find definitive proof for one of the three. Instead, what they found on the moon stunned the scientists. None of the three theories was correct. If the moon had been a wandering planetoid captured by the Earth's gravity, why were the rocks on the moon formed in exactly the same way and in many of the same concentrations as the Earth's rocks? If they formed together, how did they stay separate when bombarded by planetesimals? In other words, why didn't the earth absorb the moon? And if the Moon formed out of a piece of the earth, why didn't it have as much iron as the earth? Where did the missing iron go?

While there was no hypothesis that explained how the moon had formed after the Apollo Missions, soon afterwards, Four scientists independently came up with a hypothesis that fit the facts as discovered on the moon: that of The Big Crash, or as the author likes to call it, the Big Splat: that soon after the earth had formed, another cosmic body, 1/10th to 1/8th the size of the Earth slammed into it in a vast cosmic collision. The Earth was partially destroyed, and a vast cloud of molten rock and pieces of stone formed around what remained of the earth. While much of this cloud, mostly the heavier iron ores, fell back into the earth, the lighter parts, mostly stone, coalesced to form the moon. This not only explains where the moon's iron went (it became part of the Earth, which has more iron in its composition than all the other planets in the inner part of the solar system- coincidentally, the moon has the least) and how the moon was made, according to the rocks found on its surface, including a massive boulder composed mostly of Olivine that shot up from the moon's inner core during a meteor strike.

This is still a Theory in formation, but most of the kinks have been worked out of it, and it was near-unanimously adopted after the Kona Conference, a meeting of Selenologists that took place in Hawaii. When the four scientists presented their conclusions, no one in the conference stood up to refute them or propose a different method of the moon's formation. But few people heard of it, because it was adopted so quickly and universally that there was no controversy, and nothing to interest the public. Research into the conditions during and immediately after the formation of the moon continue today, and the planetoid that slammed into the proto-Earth, even has a name: Theia, also known as the mother of the greek woman Selune, one of the names for the moon.

This was a fascinating book, tracing the moon's history through the history of human thought, philosophy and science, and as it gets closer and closer to the modern day, it steadily becomes more and more fascinating. So few people know about how scientists think the moon was formed, but this book makes it interesting instead of dull and boring, as it is as much about the scientists who led the research into the moon, their egos, fueds and ideas as it is about dry facts.

Far from being boring, the book is extremely interesting. It's clean, concise and clearly written. For those who need to know what all thosw words mean, there is a glossary at the back of the book, and a hefty section with references and an index. Reading this book gave me a greater appreciation for both the science behind our understanding of the moon, and the moon itself. Anyone interested in the moon, the science behind understanding it, our solar system, our universe, or even anyone who likes science and wants a fascinating read would greatly enjoy this book.