Hans Bethe was one of the greatest and most versatile scientists of the twentieth century. The sheer magnitude of his scientific accomplishments ranging across almost every field of theoretical physics almost defies belief; he was probably the last "universalist", a man who could solve virtually any physics problem that came his way. The sum total of his work in science and government is so vast and diverse that it led the astrophysicist John Bahcall to joke that a conspiracy of several people must have published all those papers under the name Hans Bethe. But Bethe also had the rare distinction of being an even greater human being, a man with rock-solid integrity, strength of mind, character and equanimity. After building the atomic bomb, he worked ceaselessly until the age of 98 for nuclear disarmament and became known as the conscience of the scientific community, a Rock of Gibraltar on whom others could rely for sound and courageous advice even during the most trying of times. In every sense as both a scientist and human being, he was a role model for all of us. In this volume, his biographer Silvan Schweber tells us how Bethe became who he did. Schweber is supremely qualified to write about Bethe, having been his postdoc in the 50s and already having penned an outstanding contrasting study of Bethe and Oppenheimer as well as a superb history of quantum electrodynamics. Through many interviews and a friendship going back fifty years, Schweber gives us a rare glimpse into the personal and professional life of this great man. The biography achieves the rare goal of being both scholarly and engaging. The few technical sections can easily be skipped by non-specialists.
The account is really of the years 1906-1940, beginning with Bethe's birth and ending with his participation at the highest ranks in the Manhattan Project. Bethe grew up in Germany during the tumultuous years between the two great wars so his life is also a microcosm of German and American history during the early twentieth century. Schweber does an outstanding job in tying Bethe's background to the German scholarly and cultural tradition. His father was a noted biologist and inspired Bethe's interest in science. His remarkable mathematical talents manifested themselves at an early age. After finishing high school, his qualities were noticed by Arnold Sommerfeld, then Europe's leading teacher of physics who had already trained some of the twentieth century's most prominent theorists. Studying with Sommerfeld provided Bethe with a rigorous mathematical foundation which he then powerfully extended into new realms. It was under Sommerfeld that Bethe blossomed as a physicist. Another profound influence on him was that of Enrico Fermi with whom Bethe spent a year as a postdoctoral fellow. Fermi's dazzling simplicity of thought, mastery of all of physics and remarkable ability to get to the heart of a problem combined with Sommerfeld's rigor made Bethe uniquely positioned to apply the newly developed quantum theory to novel problems. During the twenties Bethe made key contributions to solid-state physics, quantum mechanics and nuclear physics. And his thorough grasp of the mathematical machinery of physics allowed him to instantly contribute to the new science of nuclear physics in the 30s. Throughout this time he formed lasting friendships and collaborations with outstanding theorists like Fermi, Peierls, Teller, Mott, Blackett and Oppenheimer.
Schweber has a sure grasp of Bethe's development and his achievements during the 30s. It was during this time that Bethe's professional and personal lives were profoundly changed. After Hitler came to power in 1933, Bethe whose mother was Jewish was dismissed from his academic position. After spending a year in England, he had the good fortune to be invited to Cornell University which became his home until the end of his life. Bethe's arrival at Cornell heralded a new era of physics in the United States, an era of which he became one of the leading statesmen. It was Bethe along with other famous European emigres like Fermi, Teller, Einstein and Szilard who was responsible for the ascendancy of the US in physics, a trend which has continued up to the present day. Schweber tells us how Bethe readily embraced his new country with its freedom and informality. He established a world-class center of physics at Cornell, mentored many influential physicists (both Freeman Dyson and Richard Feynman were later proteges of his), contributed an authoritative set of articles to nuclear physics (called the "Bethe Bible") and most importantly, married Rose Bethe who was the daughter of his old teacher Paul Ewald. Throughout his life Rose was a major and steadfast influence on Bethe, and he consulted her on the moral consequences of working on nuclear weapons. A separate chapter on Rose makes her importance in Hans's life clear.
It was his scientific achievements and the propitious developments in his personal life that led Bethe to call the 30s the "happy 30s". It was at the end of this decade that he made his most lasting contribution - an explanation of the origin of the sun's energy generated through nuclear fusion. As Schweber tells us, Bethe was inspired to solve this problem during a conference and, helped by his incomparable knowledge of nuclear physics, worked out the essential details in short order. This was one of those puzzles that scientists had grappled with for more than a hundred years, and Bethe solved it in a characteristically direct way. Its solution addressed an elemental aspect of human curiosity, one that manifested itself when our hominid ancestors looked up at the sky and wondered what was out there. For this achievement Bethe was unsurprisingly awarded the Nobel Prize, although the Nobel committee themselves acknowledged that he could have gotten the award for half a dozen other major discoveries. Working until the end of his long life, Bethe continued to contribute to fields as wide-ranging as particle physics, astrophysics and cosmology.
For me the most important part of this book was an appreciation of Bethe's qualities which Schweber communicates with much sensitivity and insight. It is not possible for us to mirror the extraordinary mental faculties of minds like Bethe and Einstein. But we can very much try to emulate their personal qualities which are more accessible if we persevere. In case of Bethe, one of his most important traits was an uncanny ability to sense his own strengths and limitations, to work on problems for which he "possessed an unfair advantage". Bethe knew he was not a genius like Dirac or Heisenberg. Rather, his particular strength was in applying a dazzling array of mathematical techniques and physical insight to concrete problems for which results could be compared with hard numbers from experiment. He could write down the problem and then go straight for the solution; this earned him the nickname "the battleship". Another important thing to learn from Bethe was that just like Fermi, he was willing to do whatever it took to get the solution. If it meant tedious calculations filling reams of paper, he would do it. If it meant borrowing mathematical tricks from another field he would do it. Of course, all this was possible because of his great intellect, formidable memory and extraordinary powers of concentration, but there is certainly much to learn from this attitude toward problem solving. The same approach helped him in other aspects of his life. He became extremely successful as a government consultant and scientific statesman partly because he knew when to compromise and when to push ahead. This wisdom of being diplomatic at the right time is another lesson that Bethe imparts to the rest of us. Taken together, Bethe's science and life provide ample inspiration for future scientists, policy makers and teachers. And Schweber does a wonderful job telling us how all these scientific and personal qualities manifested themselves and contributed to twentieth-century science during the tumultuous 20s and 30s.
My only regret about the book is that Schweber stops at the end of the 30s. Bethe's life during World War 2 and later is at least as interesting as his earlier years. I do hope that Schweber can write an equally insightful volume about this second phase, giving us another memorable portrait of a great scientist and citizen.