x l I N T R O D U C T I O N T O V O L U M E 1 5 Much of Einstein’s correspondence in this volume engages with Dayton C. Miller’s interferometric experiments in which he claimed to have detected an ether drift, overturning the null result of the Michelson-Morley experiment and generat- ing renewed interest in experiments of this type in both Europe and the United States. As in the past, relativity remained a contested topic among right-wing circles in Germany and abroad.[1] In March 1927, Einstein learned that a high school teacher in Virginia had been charged with blasphemy for teaching relativity. In his sarcastic retort, Einstein lampooned the school’s directors, pointing out that they were so lacking in confidence that they needed God’s help to assist them in their campaign against relativity (Doc. 493). The current volume encompasses a wealth of documents, ranging over several significant scientific topics, as well as politics, Zionism, and myriad family con- cerns. We present 535 documents as full text and more than 900 documents in the Calendar of Abstracts. Among the former are 99 writings, of which only 56 have previously been published. They include two dozen scientific papers, drafts, and calculations, as well as poems, aphorisms, homages to Isaac Newton and Hendrik A. Lorentz, more than three dozen appeals and writings on political matters and Jewish affairs, and several patents. Among the 440 letters presented as full text, 270 were written by Einstein. This massive personal and professional correspon- dence of more than 1,300 letters, and the almost 100 writings show that Einstein’s immense productivity and hectic pace of life were more intense during the twenty- four months covered by this volume than in the previous two years.[2] He undertook several unsuccessful attempts to reduce his involvement in vari- ous spheres of activity and to balance private life, work, and public roles. In mid- June 1925, Einstein informed Mileva Mariü that he felt well after his South American trip because the return voyage had been “so restful” (Doc. 7). However, merely eight days later, he wrote to Paul Ehrenfest and others that he did not intend to travel either to Pasadena or to Petrograd, as he needed to be “more frugal with his nerves” (Docs. 10, 20, and Abs. 95). During 1926, Einstein attempted to lighten the burden of responsibilities. In January, he offered his resignation from the board of the German League of Human Rights (Doc. 149), but eventually decided to re- main on it. He also informed the Marxist-Zionist party Poale Zion that he would no longer support multiple individual Jewish causes since the overuse of his name would lead to its devaluation (Doc. 150). In this spirit, he also let the World Union of Jewish Students know that he had “resigned [his] honorary position as king of the schnorrers for good” (Doc. 196). The 1925 Locarno Treaties renewed Einstein’s optimism in the prospects for Eu- ropean reconciliation. He continued to participate in the League of Nations’ International Committee on Intellectual Cooperation and efforts to end the boycott