Atmospheric Tension is essential to life

Stated briefly, the Gaia hypothesis is that life as an aggregate interacts with the physical environment in such a way that it not only keeps the Earth habitable but continually improves the conditions for life. It does this through a series of feedback systems similar to biological homeostasis, the mechanism by which living organisms maintain a stable internal environment. Those aspects that most affect the habitability of the planet - temperature, the chemical composition of the oceans and fresh water, and the make-up of the atmosphere - are not just influenced by life, they are controlled by it.

"The entire range of living matter... from whales to viruses and from oaks to algae could be regarded as constituting a single living entity capable of maintaining the Earth's atmosphere to suit its overall needs and endowed with faculties and powers far beyond those of its constituent parts," he wrote in his 1979 book Gaia: A new look at life on Earth. In other words, the Earth is not simply a planet that harbours life, it is itself alive.

SHOOT: Fascinating.

clipped from www.newscientist.com Sarah Howell)" /> If we were to choose a mythical mother figure to characterise the biosphere, it would more accurately be Medea, the murderous wife of Jason of the Argonauts. She was a sorceress, a princess - and a killer of her own children. The Gaia story starts in the 1960s, when Lovelock and Hitchcock showed that the Martian atmosphere was in a state of chemical equilibrium - a stagnant pool of carbon dioxide with a dash of nitrogen but very little oxygen, methane or hydrogen. They contrasted it with our own, which they recognised as being in chemical disequilibrium, with CO2 and oxygen levels in constant flux. The key driver of this flux is life: photosynthesis exchanges CO2 for oxygen, and aerobic metabolism does the opposite. Without life, our atmosphere would radically change from the oxygen-rich and life-sustaining gaseous mix we breathe to one in chemical equilibrium - one that, like the Martian atmosphere, would be inimical to life.