Plücker, Julius (1801-1868)

German mathematician and physicist. He made fundamental contributions to the field of analytical geometry and was a pioneer in the investigations of cathode rays that led eventually to the discovery of the electron.

Plücker was born in Elberfeld, Wuppertal, and studied at Bonn, Heidelberg, Berlin, and Paris. He was professor of mathematics at Bonn 1828-33 and again 1836-47, when he became professor of physics there.

Plücker introduced six equations of higher plane curves which have been named Plücker's coordinates. His work led to the foundation of line geometry.

He was one of the first to recognize the potential of gas spectroscopy in analysis, and found the first three hydrogen lines.

Experimenting with electrical discharge in gases at high pressures, Plücker found in 1858 that the discharge caused a fluorescent glow to form on the glass walls of the vacuum tube, and that the glow could be made to shift by applying an electromagnet to the tube, thus creating a magnetic field. It was left to one of his students to show that the glow was produced by cathode rays.