Fifth Miracle : The Search For The Origin And Meaning Of Life - 99 edition

Davies, Paul :

Paul Davies is a theoretical physicist and the bestselling author of more than twenty books. He is the recipient of the 1995 Templeton Prize for his work on the philosophical meaning of science. His books include About Time, The Mind of God, God and the New Physics, The Cosmic Blueprint, and Other Worlds.

CHAPTER 1: The Meaning of Life Imagine boarding a time machine and being transported back four billion years. What will await you when you step out? No green hills or sandy shores. No white cliffs or dense forests. The young planet bears little resemblance to its equable appearance today. Indeed, the name ''Earth'' seems a serious misnomer. ''Ocean'' would suit better, for the whole world is almost completely submerged beneath a deep layer of hot water. No continents divide the scalding seas. Here and there the peak of a mighty volcano thrusts above the surface of the water and belches forth immense clouds of noxious gas. The atmosphere is crushingly dense and completely unbreathable. The sky, when free of cloud, is lit by a sun as deadly as a nuclear reactor, drenching the planet in ultraviolet rays. At night, bright meteors flash across the heavens. Occasionally a large meteorite penetrates the atmosphere and plunges into the ocean, raising gigantic tsunamis, kilometers high, which crash around the globe.The seabed at the base of the global ocean is unlike the familiar rock of today. A Hadean furnace lies just beneath, still aglow with primeval heat. In places the thin crust ruptures, producing vast fissures from which molten lava erupts to invade the ocean depths. The seawater, prevented from boiling by the enormous pressure of the overlying layers, infuses the labyrinthine fumaroles, creating a tumultuous chemical imbroglio that reaches deep into the heaving crust. And somewhere in those torrid depths, in the dark recesses of the seabed, something extraordinary is happening, something that is destined to reshape the planet and, eventually perhaps, the universe. Life is being born.The foregoing description is undeniably a speculative reconstruction. It is but one of many possible scenarios offered by scientists for the origin of life, but increasingly it seems the most plausible. Twenty years ago, it would have been heresy to suggest that life on Earth began in the torrid volcanic depths, far from air and sunlight. Yet the evidence is mounting that our oldest ancestors did not crawl out of the slime so much as ascend from the sulfurous underworld. It may even be that we surface dwellers are something of an aberration, an eccentric adaptation that arose only because of the rather special circumstances of Earth. If there is life elsewhere in the universe, it may well be almost entirely subterranean, and only rarely manifested on a planetary surface.Although there is now a measure of agreement that Earth's earliest bioforms were deep-living microbes, opinion remains divided over whether life actually began way down in the Earth's crust, or merely took up residence there early on. For, in spite of spectacular progress over the past few decades in molecular biology and biochemistry, scientists still don't know for sure how life began. The outline of a theory is available, but we are a long way from having a blow-by-blow account of the processes that transformed matter into life. Even the exact location of the incubator remains a frustrating mystery. It could be that life didn't originate on Earth at all; it may have come here from space.The challenge facing scientists struggling to explain the origin of life is the need to piece together a narrative of events that happened billions of years ago and have left little or no trace. The task is a daunting one. Fortunately, during the last few years some remarkable discoveries have been made about the likely nature of Earth's most primitive organisms. There have also been great strides in laboratory procedures, and a growing understanding of conditions in the early solar system. The recent revival of interest in the possibility of life on Mars has also served to broaden the thinking about the conditions necessary for life. Together, these developments have elevated the subject from a speculative backwater of science to a mainstream research proj

''Paul Davies has been writing excellent books about science for so long that it is hard to believe that he is still getting better. But on this evidence, he is.... Delightful.''-- John Gribbin, author ofIn Search of SchrOdinger's Cat

Preface

Chapter 1: The Meaning of Life

Life's mysterious origin
What is life?
The life force and other discredited notions
The tale of the ancient molecule
Microbes and the search for Eden

Chapter 2: Against the Tide

The degeneration principle
Where does biological information come from?
The entropy gap: gravity as the fountainhead of order

Chapter 3: Out of the Slime

The tree of life
The three domains of life
The earliest rock fossils
Spontaneous generation
Re-creating the primordial soup
Chance and the origin of life

Chapter 4: The Message in the Machine

Replicate, replicate!
Making a living
The genetic code
Getting the message
A code within the code?

Chapter 5: The Chicken-and-Egg Paradox

RNA first
RNA last
Self-organization: something for nothing?

Chapter 6: The Cosmic Connection

The stardust in your eyes
Cosmic chemistry
Genesis from space
Impact
The Sisyphus effect

Chapter 7: Superbugs

Some like it hot
Life in the underworld
Ascent from Hades
Let them eat rock
The rest is history

Chapter 8: Mars: Red and Dead?

A bad place for a vacation
Flood
The Martian greenhouse
Was there life on Mars?
Is there still life on Mars?
Meteorites from Mars
Traces of life?
Killer plague from the red planet!

Chapter 9: Panspermia

Survival in space
Did life come to Earth in a meteorite?
Did Earthlife come from Mars?
Did Earthlife go to Mars?

Chapter 10: A Bio-Friendly Universe?

Did life ever begin?
Are the laws of nature rigged in law favor of life?
Is it Darwinism all the way down?
A ladder of progress?
Is mind predestined?

Notes

Index