On 4 June 1924, a relatively unknown Satyendra Nath Bose from Dacca University in East Bengal, India, sent a short article to Albert Einstein with an accompanying letter (see figure 1), which begins 1
Bose goes on:
Einstein’s reply came in a postcard dated 2 July 1924 (figure 2) on which he wrote, “I have translated your paper and given it to Zeitscrift für Physik for publication. It signifies an important step forward and pleases me very much.” In a note appended to his translation and published with the paper, 2 Einstein says that Bose’s derivation “appears to me an important step forward. The method used here also yields the quantum theory of an ideal gas, as I shall show elsewhere.” In fact, Bose’s concern was radiation, for which the number of photons was not conserved; Einstein’s generalization was to massive particles whose numbers were fixed.