On January 12, 1665, French lawyer and amateur mathematician Pierre de Fermat, famous for his research in number theory, analytical geometry and probability theory, passed away. He is best known for Fermat's Last Theorem, which he described in a note at the margin of a copy of Diophantus' Arithmetica.
On the 7th of June in the year of our Lord 1742, Prussian mathematician Christian Goldbach wrote a letter to his famous colleague Leonard Euler, which should make history. Well, at least in the mathematical world. In this letter Christian Goldbach refined an already previously stated conjecture from number theory concerning primes to his friend Euler, which by today is known as the famous Goldbach conjecture.