Christian Christiansen (physicist)

Christian Christiansen (1843 to 1917) was a Danish physicist who first taught at the local polytechnical school and in 1886 was appointed to a chair of physics at the University of Copenhagen. He mainly studied radiant heat and optical dispersion, discovering the Christiansen effect and the Christiansen filter, and around 1917 he found the anomalous dispersion of numerous dyes, including aniline red, by recording absorption spectra. In 1884 he confirmed the Stefan-Boltzmann law. He was elected a member of the Royal Swedish Academy of Sciences in 1902 and was the doctoral advisor of Niels Bohr; when he retired in 1912, Martin Knudsen became professor.