(August 6, 1667 – January 1, 1748)
Johann Bernoulli is Jacob’s younger brother; as well as father to Daniel, Nicolaus (II), and Johann (II): all of whom were acclaimed mathematicians. He was tutored by Jacob, and also learned from Gottfried Leibniz. On his part, Johann nurtured the greatest of all mathematicians, Leonhard Euler. He discovered Leonhard’s unprecedented mathematical prowess; and persuaded his father (Paul Euler who was a local pastor as well as a family friend to the Bernoullis) to let him study mathematics in lieu of theology. A grateful Leonhard venerated his mentor, and maintained lifelong friendships with his sons. Like his brother Jacob, Johann was revered across Europe for his brilliance. He founded the Calculus of Variations which Joseph-Louis Lagrange would later revolutionize. He also made lasting contributions to Differential Geometry, Optics, Oscillation and Elasticity. Indeed, most of the works which made Guillaume de l’Hôpital famous are actually Johann Bernoulli’s. The underlying secret arrangement could be summarized thus: L’Hôpital, who was a wealthy aristocrat furtively pledged steady income to Bernoulli, provided that Bernoulli will correspond with him in details regarding all his new maths discoveries which must not be shown to other people, and which he (L’Hôpital) may use as he prefers. Agreed, the two sealed the deal. But as L’Hôpital gained fame by publishing those works, a jealous Bernoulli sulked. L’Hôpital’s untimely death in 1704 allowed Bernoulli to expose their secret deal. He formally complained to Gottfried Leibniz. Several letters, manuscripts, notes, and bills discovered in 1921 (in Basel, Switzerland) supported Bernoulli’s authorship claims.