Following a brief, undesired career in medicine, in 1798 Simeon Denis Poisson began to study mathematics at Ecole Polytechnique, where he later in life would end up teaching.   It was a good thing that Poisson made this career change because he went on to become one of the greatest mathematicians in the area of applied math.  In recognition of his contributions, he was elected to the royal Society of London in 1818, and in 1832, he was awarded the Copley Medal of the Royal Society.  Long before these awards, his talent was recognized by Laplace and Lagrange, his teachers, and later his friends, at Ecole Plytechnique.  This French mathematician was once quoted as saying, "Life is good for only two things, discovery of mathematics and teaching mathematics."  Although he was an excellent teacher of mathematics, it is a good thing that was not all he was good at because he was able to do some excellent work in the 300-400 pieces of math work that he published in his lifetime.  The authors of the Mac Tutor web sight said that his most important works of his life from 1781-1840, were his papers on definite integrals and advances of the Fourier series.
 
The Fourier Series states that any function can be represented by a trigonometric series in the interval (-pi, pi) by the equation a⁰/2  +  the summation from n=1 to infinity of (aⁿcosx + bⁿsinx), where a and b are real numbers.  Poisson's advances on this Fourier series provided the basis for the work of Direchlet, as he generalized the series on the bases of the convergence, and for the work of Riemann.

The Poisson distribution first appeared in 1837 in "Recherches sur la probabilite des jugements…".  This distribution describes the problem that a random event will occur in a time or space interval under conditions that the probability of that event occurring is very small but the number of trials is very large so that the event actually occurs a few times.
 
As if his mathematical contributions were not enough, Poisson would be remembered because there is a crater on the moon named after him, and he is recognized on the Eiffel Tower in Paris with other great French mathematicians.

Author: Maggie Cooper

References:
Eves, Howard, "An Introduction to the History of Mathematics, 6th ed," Saunders College Publishing, San Diego, 1990, p485-9,494-5.

O'Conor, John J. and Robertson, Edmond F., <<http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Poisson.html>>, Mac Tutor History of Mathematics archive, Dec.1996.