by Nathan Collins

  Karl Weierstrass was born in Ostenfelde Westphalia on October 31, 1815.  He came from a more or less, average family.  His father was well educated but worked as a tax collector.  Karl was good at math and enjoyed it when he attended the Gymnasium, but when he went away to college at the University of Bonn he was expected by his father to study finance. He wanted to pursue mathematics, but worried about what his father might think so instead he studied nothing.  He spent his time at Bonn fencing and drinking until dropping out after four years.  He had, during his time at Bonn, decided that he should study mathematics and did do some reading on his own there.  He was encouraged by a friend to pursue a teaching certificate at the Academy of Muenster after returning from Bonn.  He went to Bonn and studied mathematics under Gudermann who  was impressed by his abilities.  After Karl passed his teachers examination Gudermann recommended him for a university position, but no one listened. 
He taught at various German Gymnasiums for the next 13 years.  During this time he made major mathematical discoveries, but having no professional contacts and because he did not publish, many of them were never seen until much later.  Finally, in 1854, Weierstrass submitted a paper to Crelle's Journal, a respected and wide read mathematical periodical at the time.  His paper received major recognition and came as a huge surprise to the mathematical community; it was after all, as it is today, uncommon for unknown high school teachers to publish groundbreaking mathematics.  He received an honorary doctorate, and after publishing his full theory of inversion of hyperelliptic integrals a few years later in the same journal, he was offered numerous university positions.  He eventually took a chair at the University of Berlin where he became a very popular lecturer.  He is sometimes called the father of modern analysis and it was during his time at Berlin that he expounded his rigorous theory of

calculus.  Much of the way analysis is taught today is due to Weierstrass.
He had many great students while at Berlin, but one of particular note is Sofia Kovalevskaya.  This was still a time when sexist policies barred woman from attending university, but seeing great spirit and promise in Kovalevskaya, Weierstrass gave her private lessons.  Sofia went on to receive recognition as a mathematician.  She was bestowed an honorary doctorate and eventually held a position at university in Stockholm.
Weierstrass had many important results, including the first proof that the complex numbers were the only commutative algebraic extension of the real numbers.  Students who took Math 263 might recall the continuous everywhere differentiable nowhere function given as an absolutely convergent power series.  That function, along with much of the fundamental work on power series and convergence (much more significantly over the complex numbers), is due to Weierstrass.  His p-function is a common example of an elliptic function given in complex analysis.  He published less in volume than many of his ability, but he spent much of his time rebuilding what he saw as shaky theories from the ground up in his characteristic rigorous fashion, so it is understandable.  No one would argue that he did not have a profound impact on mathematics. Weierstrass died in 1897.