Human Dynamics The Correspondence Patterns of Darwin and Einstein.pdfVIP

Human Dynamics: The Correspondence Patterns of Darwin and Einstein While living in different historical era, Charles Darwin (1809–1882) and Albert Einstein (1879–1955) were both prolific correspondents: Darwin sent (received) at least 7,591 (6,530) letters during his lifetime while Einstein sent (received) over 14,500 (16,200). Before email scientists were part of an extensive university of letters, the main venue for exchanging new ideas and results. But were the communication patterns of the pre-email times any different from the current era of instant access? Here we show that while the means have changed, the communication dynamics has not: Darwin’s and Einstein’s pattern of correspondence and today’s electronic exchanges follow the same scaling laws. Their communication belongs, however, to a different universality class from email communication, providing evidence for a new class of phenomena capturing human dynamics. We start from a record containing the sender, recipient and the date of each letter1,2 sent or received by the two scientists. As Fig 1a indicates, their correspondence exploded after their raise to fame, and reached a highly fluctuating yet relatively steady pattern afterwards. While on average they write 0.59 (D) and 1.02 (E) letters per day during the last 30 years of their life, these averages hide significant daily fluctuations. For example Darwin writes 12 letters on 1874-1-1 and Einstein receives 120 letters on 1949-3-14, for his 70th birthday. The response time,  , represents the time interval between the date of a letter received from a given person, and the date of the next letter from Darwin or Einstein to him or her. As shown in Fig. 1b and c, the probability that a letter will be replied to in  days is well approximated by a power law