  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.
