The head of the Los Angeles County Natural History Museum explores the way in which three geologic revolutions have forever changed the way we see ourselves and our place in the universe. Everyone knows what geology is, but few people realise that almost everything we know about the planet Earth is barely a hundred years old. Here, James Powell unearths a wholly new perspective on the history, and human impact, of an oft underestimated science. Beginning the the 'revolution of time', Powell reveals how we came to know how long the earth has existed and helps readers begin to fathom an astounding fact: if all of the 4.5 billion years of geologic time were compressed into 24 hours, Homo Sapiens would have arrived only in the last second. Next, the 'revolution of drift' the discovery of plate tectonics, explained how the ground we walk on came to be and how it will change in the future. Lastly, the 'revolution of chance' followed from the recognition that the earth, indeed the entire solar system, has been bombarded from the beginning by innumerable meteorites, some of them as large as moons. And if the tape were layed again, the history of the solar system would unfold differently: it might never again provide for conditions under which humankind could evolve. This revolution transformed our understanding of how lucky we are to be here at all.