Cosmic rays coming from exploded stars help to make clouds that cool our planet, but when the sun is in a vigorous mood it blows many cosmic rays away and allows the world to grow warmer. This amazing discovery by Danish scientists smashes the 'greenhouse' theory, which says that the cause of the recent global warming is carbon dioxide and other gases added to the air by human carelessness. Instead the ever-changing sun, which also varies its output of light, accounts for most or all changes of climate over past centuries and our own. Here, in plain language, is the story of the battle between the solar theory and the greenhouse theory.