|Hans Bethe in his young days|
Hans Bethe has long been a big hero of mine, not only because he was one of the greatest scientists of the twentieth century but also because he was one of its most conscientious. The sheer body of work he produced beggars belief, but so does his rocklike, steadfast determination on which others could rely in the most trying of times – and there was no dearth of such times during Bethe’s lifetime (1906-2005).
Bethe’s diversity of contributions to virtually every branch of physics was probably rivaled only by Enrico Fermi in the 20th century. The seminal body of work that he produced encompasses every decade of his unusually long life, beginning with his twenties as a student of Arnold Sommerfeld in Munich and ending only a few months before his death at age 99. It ranges across almost every imaginable field of theoretical and applied physics: quantum mechanics, nuclear physics, quantum electrodynamics, astrophysics, solid state physics, nuclear weapons and nuclear reactor design, missile engineering. In addition there is the vast trove of documents featuring his key contributions to government policy over six decades. The sum total of this oeuvre is so large that it led one of Bethe's distinguished colleagues to joke that it must have been the result of a conspiracy crafted by many people who all decided to publish under the name "Hans Bethe".
What made Bethe so successful? Intelligence, certainly, but the twentieth century had no dearth of off-scale intelligent scientists, especially in physics. Coupled with very high intelligence were some other qualities that his fellow scientists noted: supreme powers of concentration and an indefatigable stamina (he could churn out hundreds of pages filled with equations sitting at one place from dawn to dusk with almost no mistakes), a facility with almost every mathematical tool and trick used in physics, and a remarkable versatility of talent that could combine mathematical rigor (which he learnt from Sommerfeld) with simplicity and physical intuition (which he learnt from a postdoctoral stint with Enrico Fermi).
To some extent many of these qualities are intrinsic and cannot be acquired, but others definitely can. Among the latter is a quality that’s best encapsulated in my favorite Bethe quote: “Always work on problems for which you possess an unfair advantage”. Since so many of modern physics’ ansatzs, rules and equations are named after Bethe, I will call this piece of advice ‘Bethe’s Dictum’.
I believe that Bethe’s Dictum was largely what allowed Bethe to achieve everything that he did, and I think it’s a profoundly useful dictum for the rest of us. How did Bethe himself apply this dictum? Here’s what I wrote in a review of Bethe’s recent biography written by his longtime friend and biographer Silvan Schweber:
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. He could not sit in a chair and divine the deep secrets of the universe by pure thought. 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.
The ability to pick problems for which you possess an unfair advantage, to selectively apply your strengths and minimize your weaknesses, is important in all walks of life. And yet it is easy to overlook this match between abilities and problems because too often we choose to study what’s fashionable, what’s “cool” or the "in thing", or what seems to attract the most funding rather than what our intellect and personality is best suited for. I got a minor taste of Bethe’s Dictum myself when I was in college. I was intensely interested in physics then and had almost made up my mind to major in it. And yet my father who clearly knew Bethe’s Dictum without knowing anything about Bethe wisely counseled me to seriously consider chemistry, since he thought that my abilities would be more suited to that field. In retrospect I think he was absolutely right. I am sure I would have enjoyed studying physics and might have even become a passable physicist, but I have little doubt that my tendency to think more broadly than deeply is better suited to chemistry and biology, where one cannot derive most facts from first principles and where memory and connections between various sub-fields can play a more important role than raw mathematical ability and intelligence. I suspect many fields of experimental physics are similar.
Bethe’s Dictum is especially important in a world which suffers from an extravaganza of choices for professional and interdisciplinary study. The dictum is also important when deciding whether to learn something new or maximize the use of something old; it hints at achieving a balance of these activities. And it’s especially important advice for young people who are just starting out in your career. It’s perfectly fine to try to study something which you are passionate about, but passion can only take you so far. The hard fact is that talents and interests may not always overlap, and down the road on which lies interest without talent also lies frustration. In the long term it might be far better to study something which may not be your absolute top interest but for which you possess an unfair advantage in terms of your temperament and skill set. It’s probably the most important lesson we can learn from Hans Bethe’s extraordinary, long and satisfyingly lived life.