EMAIL LOST to HISTORIANS

Until quite recently, letters were the most common way – and often the only way – for scientists to communicate informally with each other. It is not surprising therefore that science historians have long relied on letters as invaluable sources of information.

A dramatic illustration concerns the now-famous meeting between Werner Heisenberg and Niels Bohr in Nazi-occupied Denmark in September 1941 during which the two physicists, talking in private, sought to eke out the other's view on progress towards a nuclear bomb. At first, the principal account of the mysterious visit came from a letter that Heisenberg sent in 1955 to the German science writer Robert Jungk. But among Bohr's papers were several drafts of letters that Bohr wrote but never sent to Heisenberg after reading the latter's account of the meeting. In 2002, when the Bohr family made the drafts public, the letters served as a corrective to Heisenberg's version, showing it to be deceitful and self-serving.

Now that e-mail has replaced letter writing as the principal means of informal communication, one has to feel sorry for future science historians, who will be unable to use letters and telegrams to establish facts and gauge reactions to events. In addition to the Copenhagen episode, another example of the role of letters is Stillman Drake's startling conclusion, based on a careful reading of Galileo's correspondence, that the Leaning Tower event actually happened. And of all the reactions to the discovery of parity violation in 1957, the simplest and most direct expression of shock came from Robert Oppenheimer. After receiving a telegram from Chen Ning Yang with the news, Oppenheimer cabled back: "Walked through door