The Life and Death of Planet Earth -- Book Review
The Life and Death of Planet Earth: How the New Science of Astrobiology charts the Ultimate Fate of our World.
By Peter D. Ward and Donald Brownlee
Henry Holt: New York. 2002
We are a fortunate generation in that we are the first people in human history who really understand in the broad outline where it all came from, how we got here, and ultimately where it is all going. No other people that have ever lived have known this. People have always wondered. They have dreamed; they have imagined; they made up stories; but no one really knew. Today we know. Not in all the details and there is much that is still mysterious and puzzling, and more surprising discoveries certainly await us. But over the last forty to fifty years especially, the big picture of the story of life is becoming increasingly clear and vivid.
The Life and Death of Planet Earth gives a sweeping panorama of that knowledge with an emphasis on the future, on the destiny of the earth and all living things that inhabit it. The story is bleak and is told in counterpoint to the story of the death of Peter Ward’s own mother. The poignant description of the decline and death of his own mother serves as a metaphor for the ultimate decline and death of our planet. All things must pass: our mothers, ourselves, even the earth itself will ultimately disappear and vanish. The Age of Life on earth is already past its prime. The planet is already in decline in terms of its habitability for complex life. In another 500 million years or so, all that will be left is bacteria. Bacteria could last quite a while longer, perhaps several billion years. But ultimately as the earth’s temperature heats up due to the sun’s gradual brightening, they too will finally succumb. The sun is about 30% brighter now than it was at the time of the earth’s formation. In a billion years it will be another 10% brighter than it is now. This will very slowly but steadily increase the surface temperature of the earth. In perhaps a billion years, maybe even sooner, the oceans will evaporate and be lost into space.
There is some uncertainty about how long this will take. It could be as quickly as 100 million years, or more likely several billion years. But once the oceans are gone the time of life on earth is over. A few primitive bacteria could persist several billion years longer depending on how hot it gets on the earth’s surface. But the earth as a haven for evolving life will be over. Once all life is extinguished, the earth will still continue as a hellish shell for perhaps another several billion years until the sun reaches the end of its life as we know it, and expands into a red giant. This will most likely engulf the earth into the body of the sun; the interior temperatures of the sun will dissolve all chemical bonds between atoms and the earth and everything in it will be vaporized. That will be the final chapter in the history of the earth, ladies and gentlemen. Have a nice day. But it won’t happen for another 6 or 8 billion years, so you don’t need to worry about it too much. You’d better be worried about ice and glaciers. But I’ll let them tell you about that. They pointedly avoid discussing the ultimate fate of humanity. But our fate is complicated by a number of possibilities that are not easily estimated: not only our response to climate change, but also the possibilities of infectious diseases, and warfare.
The authors do an excellent job of explaining the workings of the carbon cycle, plate tectonics and the biosphere in regulating the earth’s temperature and how these huge forces interact and evolve over long periods of time. Life can only exist within a rather narrow temperature range and the relative stability of earth’s temperature over hundreds of millions of years has enabled life to evolve into the complex forms that we see today. Powerful natural forces are at work to keep the earth’s temperature fairly stable, but those forces also evolve and change over time, they are subject to fluctuations that can have profound effects on living things, and eventually it will be temperature that finally spells the demise of life. The authors do an excellent job of explaining this and making these relationships clear. You have to read this book carefully. There is a lot to absorb, but they have put it all down with clear explanations, and you can really put the story together from a careful reading of this book. They also consider scenarios such as a comet striking the earth or a gamma ray burst from a supernova. These are both highly unlikely, but were either to occur it could bring a very abrupt catastrophic end to life on planet earth. In lieu of sudden catastrophe, evolution will do its inexorable work and ultimately close the curtain down on life and this is their main emphasis. Altogether Ward and Brownlee have written a beautiful, readable account of the timeline of the earth and its future. It is a rich, stimulating overview that avoids the technical calculations. It deals with the big questions, the simple questions, the most profound and searching questions that people wonder about as children, and it answers them. Anyone interested in our ultimate destiny should find it a sober, provocative, and interesting summary.