"Of all the planets in our universe,there is only one we know can support life. Just the right distance from its sun with a perfect climate. lt's been called the lucky planet. About five billion years ago,a huge asteroid crashed into Earth tilting it at an angle of exactly 23 and a half degrees to the sun. This cataclysmic accident turned out to be nothing short of a miracle. Without that crucial tilt,everything would have been different. For it created the seasons,the extremes of climate, hot and cold,and landscapes of spectacular beauty. The perfect conditions for life on Earth. All life on Earth is built on chance and powered by the sun. But the delicate balances of our world are faltering,as the planet struggles to support our growing demands. This is the time to take stock of what we have and what we stand to lose."