Leonhard EulerLeonhard Euler, (born April 15, 1707, died September 18, 1783), was the most prolific mathematician in history. His 866 books and articles represent about a third of the entire body of research on mathematics, theoretical physics, and mechanical engineering published between 1726 and 1800. In pure mathematics, he integrated Leibniz's differential calculus and Newton's method of fluxions into mathematical analysis; the concept of function was refined; made many mathematical notations common, including e, i, the pi symbol, and the sigma symbol; and laid the foundations for the theory of special functions, introducing the transcendent beta and gamma functions. He also worked on the origins of the calculus of variations, but withdrew his work out of respect for JL Lagrange. He was a pioneer in the field of topology and made number theory a science, enunciating the prime number theorem and the law of biquadratic reciprocity. In physics he articulated Newtonian dynamics and laid the foundations of analytical mechanics, especially in his Theory of the Motions of Rigid Bodies (1765). Like his teacher Johann Bernoulli, he developed continuum mechanics, but he also developed the kinetic theory of gases with the molecular model. With Alexis Clairaut he studied lunar theory. He also did fundamental research on elasticity, acoustics, the wave theory of light, and the hydromechanics of ships. Euler was born in Basel, Switzerland. His father, a pastor, wanted his son to follow in his footsteps and sent him to the University of Basel to prepare for the ministry, but geometry soon became his favorite subject. Through Bernoulli's intercession, Euler obtained his father's consent to change his major to mathematics. After failing to obtain a physics position in Basel in 1726, he joined the St. Petersburg Academy of Sciences in 1727. When funds were withheld from the academy, he served as a medical lieutenant in the Russian navy from 1727 to 1730. St. Petersburg boarded at the home of Bernoulli's son Daniele. He became professor of physics at the Academy in 1730 and professor of mathematics in 1733, when he married and left the house of Bernoulli. His reputation grew after the publication of numerous articles and his book Mechanica (1736-37), which for the first time extensively presented Newtonian dynamics in the form of mathematical analysis. In 1741, Euler joined the Berlin Academy of Sciences, where he remained for 25 years. In 1744 he became director of the mathematical section of the Academy. During his stay in Berlin he wrote over 200 articles, three books on mathematical analysis and a scientific popularization, Letters to a Princess of Germany (3 vols.., 1768-72).