Noted for modernizing Swedish physics, Karl M. G. Siegbahn contributed significantly to the field of X-ray spectroscopy begun in Germany and England. His design and application of equipment and techniques in this field vastly improved the accuracy of existing methods by which X-ray wavelengths were distinguished, and led to important discoveries about the nature of X rays (electromagnetic radiation invisible to the unaided human eye) and atomic structure.

Karl Manne Georg Siegbahn was born in Örebro, Sweden, on December 3, 1886 to Nils Reinhold Georg Siegbahn and Emma Sofia Mathilda Zetterberg. Siegbahn entered the University of Lund in 1906. He studied astronomy, chemistry, mathematics, and physics there, eventually receiving his bachelor's degree in 1908, and his licentiate degree (comparable to a master's degree) in 1910. Studying electromagnetism as a research assistant to Johannes Rydberg, Siegbahn was awarded a doctorate in physics in 1911 for his dissertation on the measurement of magnetic fields. He...