The Life and Death of Planet Earth: How the New Science of Astrobiology Charts the Ultimate Fate of Our World
Science has worked hard to piece together the story of the evolution of our world up to this point, but only recently have we developed the understanding and the tools to describe the entire life cycle of our planet. Peter D. Ward and Donald Brownlee, a geologist and an astronomer respectively, are in the vanguard of the new field of astrobiology. Combining their knowledge of how the critical sustaining systems of our planet evolve through time with their understanding of how stars and solar systems grow and change throughout their own life cycles, the authors tell the story of the second half of Earth’s life. In this masterful melding of groundbreaking research and captivating, eloquent science writing, Ward and Brownlee provide a comprehensive portrait of Earth’s life cycle that allows us to understand and appreciate how the planet sustains itself today, and offers us a glimpse of our place in the cosmic order.
About the Author(s)
Peter D. Ward and Donald Brownlee are the co-authors of the acclaimed and bestselling Rare Earth. Ward is a professor of geological science and zoology at the University of Washington and the author of nine other books, including Future Evolution, The Call of Distant Mammoths, and The End of Evolution, which was a finalist for the Los Angeles Times Book Prize. Brownlee is a professor of astronomy at the University of Washington.
Bleak but fascinating, May 31, 2003
It might be that professors Ward and Brownlee are working on a new genre: non-fiction science fiction. Instead of speculations embedded in story form they speculate about the future in a narrative without plot or characterization or other elements of the story form. Of course they are not the only writers doing this, but they are among the best in a growing industry.
Well, what about it? I gave up reading most science fiction years ago because either the story elements were wooden or the science was ridiculous (or both). It is not easy to be simultaneously a master story teller and a polymath of science. We know that (e.g.) Asimov, Clarke and Sagan were exceptions and were able to combine both tale and cutting edge knowledge very well, and in some cases spectacularly well. But their world is gone. Today’s science is much more complex. To write convincingly about the future it is not enough to be a world expert in one’s chosen field. The future is influenced by science of all kinds; consequently it is requisite that one be an expert in a number of scientific disciplines just to avoid naive projections.
So it is natural that Peter Ward, who is a geologist and zoologist, (and, by the way, a sometimes poetic prose stylist, witness his expositions in Future Evolution ), and Brownlee, who is an astronomer and NASA scientist, might join forces to augment their individual expertise; and that they might eschew the story form in writing about the future.
At any rate, this is an excellent book of speculation about the future of our planet aimed at a general readership. It is a fine follow-up to their Rare Earth: Why Complex Life Is Uncommon in the Universe (2000). As in that book their conclusions are pessimistic. They concluded in Rare Earth that we are probably alone in the galaxy; here they conclude that we will go extinct without getting beyond our solar system. This bleak prognosis should not unduly trouble us however since our demise by their calculation is at least millions of years in the future, possibly hundreds of millions of years. In fact their scenario reverses the biological experience of the planet: things will get hotter and drier until life necessarily retreats back into the ocean, and then as the oceans evaporate, life forms regress from the complex to the simple until the only life left on the planet is single-celled, as it was three billion years ago. And then of course the sun expands into a red giant and the earth is burned to a crisp.
Is there any escape? Not according to Ward and Brownlee who argue effectively that it is unlikely that we will acquire the ability and the will to even terra form Mars or other places in the Solar System. The idea that we might become interstellar travelers is also quashed as being impractical in the extreme. They conclude "Interstellar travel will likely never happen, meaning we are stranded in this solar system forever." (p. 207)
While I tend to agree with Ward and Brownlee for the most part, as I did with their conclusions in Rare Earth, I think we should realize that their argument in part is a bit beside the point since in millions of years (at most)–not tens of millions, not hundreds of millions and certainly not billions of years–we will no longer be human anyway. The average life span of a species is something like a million years. Because of the incredibly rapid pace of cultural evolution it is highly unlikely that humans as presently constituted will be around in even a thousand years. Some people think we will be part software and part machine before this century is out. Also as science fiction writers have pointed out, the constraints on our species as presently constituted (in terms of our ability to travel in space and to influence cosmic processes) may not apply to the creatures we are becoming.
Ward and Brownlee do not consider this point of view, most likely because it would be extraneous to the scope of their book. So some of their ideas should be considered as stimulative and consciousness-raising, not definitive. As they acknowledge in the epilogue, "Prophecy is a risky business…" (p. 210) Furthermore, most of their material is on the purely physical changes that will take place on planet earth as it evolves toward its ultimate fate, and I have no doubt that the picture that Ward and Brownlee present is as accurate as present knowledge allows.
I was especially intrigued by their discussion of the return of the once and future supercontinent, Gondwanaland, and how its reconfiguration will affect earth’s climate. Their exposition on the carbon dioxide cycle and the end of plant life when the amount of CO2 in the atmosphere falls below 10 ppm was also fascinating. The chapter asking the question, "What Trace Will We Leave?" really gives the lie to human vanity, reminding me of the sentiments in Shelley’s poem "Ozymandias." If anything, Ward and Brownlee are even more pessimistic than the poet, pointing out that our proud "messages in a bottle" sent into interstellar space are not likely to impact "a planet within a trillion years," by which time there won’t be any planets. (p. 186)
While most of the book is very well written and edited, some of the sentences in the later chapters are less carefully constructed. There are even some gaffs. For example on page 192 they repeat an error from their previous book, stating that there are "between 200 million and 300 million" stars in our galaxy, when the number is more like 100 billion plus. Also on page 194 they give the Drake Equation enhanced with new terms they think appropriate, but in fact the equation is without explanation shorter than Drake’s Equation given on page 192.