The attempt to understand the physics of the structure of stars and their change in time - their evolution - has been bothering many physicists and astronomers ever since the last century. This long chain of successful research is well documented not only by numerous papers in the corresponding journals but also by a series of books. Some of them are so excellently written that despite their age they can still be recommended, and not only as documents of the state of the art at that time. A few outstanding examples are the books of R. Emden (1907), A. S. Eddington (1926), S. Chandrasekhar...

Although this book has been available for some time, it is only now appearing in an English edition. This gives me the opportunity of adding a few explanations. I have not struggled to include the very latest, tentative results. I have, instead, concentrated on presenting cosmological ideas to interested non experts. They often encounter considerable difficulties when attempts are made to explain even long-established results in this field, so the aim of this book is to provide them with help. Naturally, I have also tried to include modern findings. To help with the explanation I have made...