Christian Goldbach

Goldbach is notable for his work on number theory. On a decade-and-a-half journey around Europe, he met Moivre in London, Leibniz in Leipzig (they continued to correspond), and Nicolaus Bernoulli in Venice, who suggested Goldbach contact his brother Daniel — they corresponded for 7 years. Euler became a colleague in St Petersburg; they started a 35-year correspondence. In one of his letters, Goldbach outlined the conjecture now famously named after him; characteristically, Euler tested its validity substantially further than Goldbach, who tended to be more interested in the ideas than the hard work.