Even if the luminosity of Daisyworld’s sun increases substantially, Daisyworld itself maintains a constant temperature-until the environmental conditions caused by the solar warming become just too extreme for the biota to regulate. If the temperature is high on Daisyworld, the white daisies flourish and reflect heat back off into space. If the temperature is low on Daisyworld, the black daisies flourish because they absorb more heat. Daisyworld contains two types of daisies, white and black, that naturally live in a certain temperature range and absorb different levels of heat. When critics complained that Lovelock’s theory smacked of teleology or design, he created a simple computer model called Daisyworld. But the Gaian superorganism has successfully maintained a steady temperature through its metabolic processes. Moreover, Lovelock and Margulis claimed that Gaia was a testable, scientific hypothesis.ĭuring the past 4.5 billion years, solar luminosity has increased by at least 10–30%. Lovelock proposed that “the evolution of the species and the evolution of their environment are tightly coupled together as a single and inseparable process,” a claim that was supported by his colleague, the microbiologist Lynn Margulis. While other planetary scientists had supported a “Goldilocks theory”-assuming that the temperature and atmospheric composition of the Earth had been “just right” for the emergence of life by chance-Lovelock showed that life itself had altered the planetary environment. The atmosphere so composed was an atmosphere friendly to life, both in terms of its content and its stable, hospitable temperature. Over immense periods of time, the biosphere transformed the atmosphere into its present composition. This planetary-wide crisis provided a window of opportunity, however, when a new type of blue-green bacteria finally learned to synthesize oxygen into life-energy. Oxygen itself was highly toxic to the first bacteria. But around two billion years ago, the process gave rise to a planetary crisis-an “oxygen holocaust”-when too much oxygen had accumulated. These first blue-green bacteria removed carbon from the atmosphere, which cooled down the planet, and gave off oxygen as a waste product. The metabolic activity of the first bacteria started to give birth to a planetary-wide physiology. In the alchemy of Earth’s primordial oceans, the living metabolism of bacteria transmuted carbon dioxide and other elements into an expanding tapestry of life. But with the emergence of blue-green bacteria and photosynthesis, carbon dioxide became a life-giving food. When the Earth was formed billions of years ago, the atmosphere was almost entirely made out of carbon dioxide, just like Mars and Venus. Table of Planetary Atmospheres, after Lovelock, The Ages of Gaia. Without the presence of life, the climate of the Earth would be incredibly inhospitable. But without the presence of life on Earth, carbon dioxide would make up 98% of the atmosphere and the average surface temperature of the planet would be somewhere between 464 and 644˚ Fahrenheit. The average surface temperature on the earth is 55˚ Fahrenheit, because the carbon dioxide level is so low. By contrast, the atmosphere of the Earth contains 21% oxygen with only a trace amount of carbon dioxide. The atmospheres of Venus and Mars contained over 95% carbon dioxide with only trace amounts of oxygen. What Lovelock saw was straightforward but startling (see figure below). Lovelock looked at the atmospheres of Venus, the Earth, and Mars, and concluded that the presence of life on any planet would be reflected by chemical changes in the atmosphere of that planet. In 1961, atmospheric scientist James Lovelock was hired by NASA to study the detection of life on Mars. According to Gaia theory, life is a planetary-wide phenomenon that alters the environment on a planetary scale. One of the most unpredicted outcomes of the space program was the Gaia hypothesis, the theory the biosphere itself works to regulate the temperature and chemical content of the Earth’s atmosphere.
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