《研究生英语精读教程》(第三版下)Unit 4课文The Man Who Discovered Mother NatureJames Lovelock's bold new theory may forever change the way we look at life on our planet.Lowell PonteAMID GREEN ROLLING HILLS in southwest England, themud-and-straw cottage seems unchanged since Shakespeare's time. Peacocks strut in the surrounding meadow. But a new adjoining building houses a laboratory filled with computers, chromatographs, chemical and electronic equipment.The owner, James Lovelock, is an anachronism. In an age when almost all scientists are specialists working in large organizations, Lovelock, now 72, is an independent researcher and inventor, freely pursuing his curiosity across many fields. Credited with more than 40 patents, he resembles a modern Ben Franklin, who would study the Gulf Stream one day and the next fly his kite to catch the secrets of lightning bolts. And from his small laboratory, Lovelock has proposed a theory that is changing the way scientists think about life on our planet.It all began more than three decades ago when Lovelock devised the electron capture detector. Still widely used, this electronic nose is able to sniff out a few parts per trillion of chemicals found in the soil,water or air. Aware of Lovelock's skills, NASA asked him in 1961 to help devise ways of detecting life on Mars.Lovelock studied the chemistry of Mars, using analyses provided by NASA's infrared telescopes, and found that no chemical changes were going on. Such stability was a clear gravestone marking a lifeless planet. Later, two Viking robot landers on Mars confirmed his grim analysis. But now notice this. If one simply withholds treatment, it may take the patient longer to die, and so he may suffer more than he would if more direct action were taken and lethal injection given. This fact provides strong reason for thinking that, once the initial decision not to prolong his agony has been made, active euthanasia is actually preferable to passive euthanasia, rather than the reverse.But while searching for signs of life on Mars, Lovelock became fascinated with the "Goldilocks Problem", a puzzle that has long intrigued scientists: Why is Venus too hot for life, Mars too cold and Earth just right?Researchers used to assume that Earth simply had the good luck to be at precisely the right distance from the Sun so that water remained in a liquid state, at temperatures between boiling and freezing. But our sun has burned hotter as it ages; the best estimate is that it shines with 25 to 30 percent more light and heat than when life first appeared on Earth about 3.8 billion years ago. Earth's average temperature then isestimated to have been around 73 degrees Fahrenheit. Today it's cooler, about 59 degrees F. How could this be?Lovelock wondered whether some powerful, self regulating system was at work. He came up with a provocative thesis: our planet acts like a giant living organism, in which all living things interact to maintain stability.Individuals and species unknowingly play a part, much as the red blood cells in your body have a life of their own, but unwittingly work in concert to maintain your life.Nobel Prize winning author William Golding, Lovelock's neighbor, suggestedcalling the theory Gaia(GUY-ah)after the ancient Greek Earth goddess, Lovelock embraced the name. Since he first propounded it in 1969, the Gaia Hypothesis has become the center of a major storm of scientific debate.Simple as it sounds, the Gaia Hypothesis is a revolutionary idea. It argues that living things are not passive victims of their environment but can alter it. The theory could transform scientific thinking much as did Sir Isaac Newton's image of the universe as a clockwork mechanism. Gaia challenges the scientific establishment - whose experts jealously rule narrow specialties-to see a bigger picture: the world as one system in which sea and sky and life transform one another. As Lovelock, whoearned his doctorate in medicine, has said, "We need to study Earth as doctors diagnose and treat patients, not as an isolated leg or ear but as a whole, living being. We need scientists to think in a new way, to be geophysicians."To understand how Gaia works, turn the clock back to when life was first emerging. Evidence suggests that Earth's atmosphere then contained up to 98 percent carbon dioxide. This produced a "super greenhouse effect“ that kept our world warm. But as the Sun gradually burned hotter, what prevented Earth from becoming overheated? Just such a runaway greenhouse effect turned Venus, a planet very similar to ours in size and primordial chemistry, into a hellish place with surface temperatures above 800 F. Lovelock's answer is that on Earth living things made the difference. The first bacteria, for instance, consumed carbon dioxide, removing it from the atmosphere and limiting the effect of this greenhouse gas.Then around 3.7 billion years ago, early forms of blue green algae began to use sunlight to make food. But they also produced what was in their world a poisonous gas-oxygen. When this eventually began to accumulate in the atmosphere, 2.5 billion years ago, it cooled the planet and killed some life forms. Other organisms learned to live with oxygen, and that set the scene for the life we now know.Today oxygen makes up 21 percent of Earth's atmosphere.Carbon dioxide comprises only 3/100ths of one percent of the air around us. On Venus, it is 98 percent. Gaia has many feedback systems. For instance, Lovelock once mentioned his measurements ofplankton-produced dimethylsulfide gas in the atmosphere to University of Washington scientist Robert Charlson. Charlson had been puzzling over what unknown particles provide the nuclei on which moisture condenses, forming clouds. As a result, Lovelock, Charlson and two other colleague hypothesized another Gaian feedback mechanism. If weather warmed, plankton might emit more dimethylsulfide; the resulting sulfur particles in the air might produce more abundant droplets and reflective clouds, thereby shading the world beneath and reflecting more sunlight back into space. Earth, according to this still debated theory, would be responding to hotter conditions with action to cool the environment.In the 22 years since Lovelock propounded it, the Gaia Hypothesis has attracted an odd assortment of enthusiasts. Some industrialists like Gaia because it seems to suggest that Mother Earth could survive even vast amounts of industrial pollution. Lovelock would agree, but he would add that the survival might include replacement of humans by more pollution resistant species. Many activists in Europe’s environmentalist “Green” parties have embraced their own notions of Gaia. But Lovelock has criticized environmental politics as a “lush pasture for demagogues".Gaia was heretical to many scientists because it seemed to suggest that life on Earth consciously controlled its environment. But Lovelock believes that Mother Nature acts in accord with Darwinian evolution, with no conscious plan or intelligence. It’s just that, with 30 million species in the world, life has enormous resilience.“Whether you agree with Gaia or not, it’s a brilliant organizing principle,” says Stephen Schneider, a climatologist with the U.S. National Center for Atmospheric Research. “It brings together scientists who normally don’t talk to one another, such as biologists, geochemists and atmospheric scientists, to ask profound questions about how living things and the planet interact."One critic of the Gaia Hypothesis, British biologist Richard Dawkins, has argued that Earth cannot be regarded as a giant living organism, because, among other things, it doesn't reproduce. Lovelock's later work has suggested an intriguing answer to this challenge.Recent research shows that Mars receives just enough sunshine to sustain life. Lovelock and a collaborator, science journalist Michael Allaby, have proposed a bold futuristic scheme: unleashing the power of Gaia to bring life to Mars. To warm the planet and get water flowing again, they suggest flooding the Martian atmosphere with chlorofluorocarbon gases that would begin a greenhouse effect. Then tough microorganisms from the dry valleys of Antarctica would be implanted. By photosynthesis thewee creatures would begin turning carbon dioxide and water into oxygen. Unimpeded by predators or competitors, they could quickly reproduce and cover the surface ofthe planet. Human colonies could follow.Earth would thus have its first offspring, seeded by spaceship.。
