Born on June 16, 1801, Julius Plücker was a German physicist and mathematician who made significant contributions to both fields during the early part of the 19th century. He was educated at the Universities of Heidelberg, Berlin, and Paris. Shortly thereafter, he went to the University of Bonn and, after four years of unpaid lecturing, was hired as a professor in 1829. One year later, at the age of thirty, he proposed that the fundamental geometrical unit could be a line, rather than a point. This marked the beginning of a lifetime of innovative discoveries.
Over the next several years, he studied spatial geometry, curves, singularities, and other geometrical concepts. When he became a professor of physics in 1847, he began making some of his most significant and lasting contributions. Plücker started his work in the field of physics focusing primarily on cathode ray tubes and gas spectroscopy. While experimenting with cathode ray tubes, he noticed that he could cause the ray (which is made of electrons) to bend using magnets. This prompted further research into magnetism as it reflects on atomic physics and served as a precursor to the discoveries of Sir Joseph John Thomson. In the field of spectroscopy, Plücker speculated that chemicals have characteristic spectral patterns (which is basically true). According to one of his contemporaries, he was the first to see the Hydrogen spectrum; unfortunately, he died a few months before this spectrum was officially recognized in the sun. He also dabbled in magnetism theory, making several minor contributions that are rather widely applied today.
At the urging of several friends and colleagues, he was eventually persuaded to return geometry, his original field of expertise. He was quick to resume his work with line-based spatial geometry, rapidly making significant progress with his theories. Though he died before these theories were ready for publication, his pupil and assistant, Felix Klein, completed and published Plücker's final work.
Julius Plücker died on May 22, 1868. On an irrelevant but interesting note, when Plücker's name is romanized, it is generally left as "Plucker", rather than the more logical "Pluecker" (the German character 'ü' is the equivalent of 'ue').