Author clarifies credit for H-bomb calculations

I am pleased by Cameron Reed’s excellent and insightful review of my book Building the H Bomb: A Personal History (Physics Today, July 2015, page 46 ). Let me add a couple of minor clarifications.

Reed reports that we used “card-fed and plug-board computers” for the thermonuclear calculations. Indeed, we used such computers in 1950 and 1951, but the final calculations that led to the 7-MT predicted yield of the “Mike” device were carried out on the SEAC (Standards Eastern Automatic Computer) at the National Bureau of Standards in Washington, DC. SEAC was a stored-program computer that, in 1952, was probably the best computer in the world, with its 3 kB of memory and its 1-MHz clock speed.

Reed refers, overgenerously, to “Ford’s calculations.” They were mine only in the sense that I was the person who shepherded the calculations night after night for several months on the graveyard shift. The coupled differential equations that we were solving numerically were devised principally by John Wheeler, with my assistance and that of John Toll and other young theorists at Princeton University’s Project Matterhorn and in the theoretical division at Los Alamos. I wrote the code, with Toll’s help.