Book excerpt: This selection from the author's famous Physics for the Inquiring Mind is a book for readers who want to grow in scientific wisdom, who want to know the fundamentals of the history and theory of basic astronomy. Originally published in 1982. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.