Scientists agree that over the last century the earth has become warmer. But do we really know why this has happened? A deftly written and enjoyable read, ''The Chilling Stars'' outlines a brilliant, daring and undoubtedly controversial new theory that will provoke fresh thinking about global warming. As prize-winning science writer, Nigel Calder and climate physicist Henrik Svensmark explain, an interplay of the clouds, the Sun and cosmic rays - sub-atomic particles from exploded stars - seems to have more effect on the climate than manmade carbon dioxide. This conclusion stems from Svensmark's research at the Danish National Space Center which has recently shown that cosmic rays play an unsuspected role in making our everyday clouds. And during the last 100 years cosmic rays became scarcer because unusually vigorous action by the Sun batted many of them away. Fewer cosmic rays meant fewer clouds and a warmer world. The theory, simply put here but explained in fascinating detail in the book, emerges at a time of intense public and political concern about climate change.Motivated only by their concern that science must be trustworthy, Svensmark and Calder invite their readers to put aside their preconceptions about manmade global warming and look afresh at the role of Nature in this hottest of world issues.