This non fiction book is about the long term fate of life on
planet Earth. The early chapters are very good. They describe the conditions on earth
that allow life to thrive (the carbon cycle, plate tectonics, etc). Then the authors
describe how current conditions will change in the future. They argue that earth is
already into its middle age, that the natural future of our planet will be less diversity
and less ideal conditions for earth.
Long ago, the sun was much cooler, and thus appeared smaller in the sky.
But there was much greater quantities of carbon dioxide in the atmosphere, so the green house
effect efficiently trapped the heat and allowed dinosaurs and jungles to thrive. As the sun
ages, it slowly expands and heats up. The earth has correspondingly been removing carbon dioxide
from the atmosphere, so temperatures remain optimal for life. (However, the mechanisms for
temperature are slow to adjust, and will overcorrect, and thus ice ages or
warmer/wetter Earth environments will result. Currently, the Earth is in a period of ice ages,
all of humans record history has sprung up in a 10,000 year interval between ice ages. The ice
should be returning soon if only natural causes had an effect on global temperatures.) Eventually,
the sun will continue to heat the earth, but there will be no more carbon dioxide to remove from
the atmosphere as compensation - already the percentage of CO2 in the air is quite low. Once that
happens, the Earth has no way to counteract the warmer sun, and surface temperatures will begin
to rise. Eventually, land animals will perish, and, much later, the sea will boil away and nothing
will remain but hardy bacteria. Much later, the Earth will be sterilized by increasingly higher temperatures
when the sun swells to its red giant phase. Thus the end of life of earth is a "rewind" of how life started -
a long period where nothing but single celled organisms existed, followed by multicellular sea life,
and then plants and animals conquer land.
Unfortunately, the book runs out of material. It seems like the authors are padding
the last few chapters. One chapter seems like a summary of Rare Earth, which is their previous book
that describes why they believe intelligent life in the galaxy is rare. Rare Earth is very good book,
well worth reading, but there is no need for the summary in this book. Of course, the reader wants to
know what chance humans have to prevent the end of life on planet earth. The authors are surprisingly
negative about the fate of humanity. They don't even seem to believe we would be successful at sending
men to Mars, believing that the period of weightlessness and the bombardment of cosmic rays
endured during transit would be too much of obstacle. But if we build big, shielded ships and spin them
for artifical gravity, of course we can go to Mars. Maybe not with today's technology, but perhaps with
technology hundred or 200 years from now. (They say there is no source of power on Mars - too far
from the sun for solar, no fossil fuels, no geothermal or hydropower on Mars, and air is too thin for
wind power. But then they dismiss nuclear power as an option, because nuclear power is so out of favor
here on Earth. But nuclear power is only out of favor here in the US, France and Japan have lots of
nuclear plants, and China is rapidly adding more. And why do they assume we will never solve question
of fusion power? Give humans another 100 years, lots of technology will become available.) They do
describe a clever scheme where the earth orbit is adjusted outward by repeated flying a massive asteroid
past the Earth, and dragging Earth out to orbit of Mars to nullify effect of increasingly hot earth.
But then they say: But unfortunately, Mars already occupies that orbit. To which I say - if you can move
Earth out to orbit of Mars, can't you also move Mars out of the way, stick it halfway between old Mars
orbit and Jupiter?
This is an interesting book, and a quick read. But if you haven't read Rare Earth, that
is probably a better book, in my opinion.