New Scientist: YOU'VE done it half a dozen times today without giving it a second thought. If it was chilly in the morning, you may have turned up the heating or put on another layer. As the day got warmer perhaps you opened a window to cool things down. We are adept at controlling our immediate environment. What about the living planet as a whole? Can the biosphere regulate the environment to suit itself, preventing the planet from freezing or boiling? This is the essence of the Gaia hypothesis proposed in the...