The Life and Death of Planet Earth

by Peter Ward and Donald Brownlee
hardback - 240 pages
from Times Books, Henry Holt & Co

Time is a constant befuddler of our human perceptions. It surprises us how fast, in retrospect, our children have grown up, even though we have lived with them underfoot every day. Weeds and toadstools spring up seemingly overnight, rather like new buildings seem to have when we return to an old neighborhood. We tend to assume that the world always has been and always will be as we see it now. Even in the natural realm we speak of the "forest primeval" and the "ageless mountains." Yet all of these are "passing fancies" of a world in constant flux. Flowering plants and grasses are recent additions to Earth's botanical repertoire, towering mountains are temporary wrinkles in our planet's shifting crust, and even the oxygen that we breathe is a passing belch from the billion year old rise of algae in our oceans.

In their previous book, Rare Earth, authors Ward and Brownlee detailed the complex and interrelated set of astronomical, geological, and biological processes and coincidences that produced the world as we know it today. Their theme was the rarity of a planet like Earth, not just in our galaxy but our universe, and the resultant unlikeliness of nearby alien neighbors a la TV science fiction. In this follow up work they focus on Earth's habitable period and the forces that set limits to the atypically benign climate and environment we currently enjoy. In the past, asteroid/comet impacts, ice ages, climate changes, etc. have periodically stressed the ecosystem and produced mass extinctions. But even glossing over these transient events, life on Earth is ultimately doomed.

Stars, like people, change as they age and our Sun is gradually, imperceptibly on the human time scale, brightening. In a billion years or so (regardless of how we deal with global warming) Earth's oceans will boil, producing a runaway greenhouse effect and a climate similar to hellish Venus. Earth's age of life will be only a memory. A few billion years later our planet itself may be vaporized as the Sun expands into a bloated red giant star at the end of its life. Will we forestall the ultimate end by moving the Earth into a more distant and cooler orbit or vacate the rundown neighborhood for greener pastures via interstellar migration? Ward and Brownlee speculate on these possibilities, and the more ominous threat that, long before any cosmic curtain call, we could produce our own homegrown catastrophe via nuclear, biological, or ecological mishap.

The Life and Death of Planet Earth mixes dollops of geology, planetology, and astronomy into a surprisingly enjoyable concoction considering its rather somber topic. You will end up with a better appreciation for the fleeting joy of life on a temporary planet called Earth.