Max Planck (1858-1947)

Max began his elementary schooling in Kiel. In the Spring of 1867 his family moved to Munich when his father was appointed Professor there. This city provided a stimulating environment for the young boy who enjoyed its culture, particularly the music, and loved walking and climbing in the mountains when the family took excursions to Upper Bavaria.

He did well at school, but not brilliantly. One might have expected him to excel in mathematics and science but, in his early school years, there was no sign of outstanding talent in these subjects. Music was perhaps his best subject, and he played piano and organ extremely well.

He entered the University of Munich on 21 October 1874. After taking mostly mathematics classes at the start of his course, he enquired about the prospects of research in physics, and was told that physics was essentially a complete science with little prospect of further developments. Fortunately, Planck decided to study physics, despite the bleak future for research that was presented to him.  
 
It was customary for German students to move between universities at this time and indeed Planck moved to study at the University of Berlin from October 1877 where his teachers included Helmholtz and Kirchhoff. Planck returned to Munich and received his doctorate in July 1879 at the age of 21 with a thesis on the second law of thermodynamics.

In 1885 Planck was appointed ‘Extraordinary Professor of Theoretical Physics’ in Kiel and held this chair for four years. at the same time became director of the Institute for Theoretical Physics. This made him financially secure so he could now marry Marie Merck whom he had known for many years.

He now worked on thermodynamics, publishing three papers on applications to physical chemistry and thermoelectricity. He was promoted to Ordinary Professor in 1892 and held the chair until he retired in 1927. He continued to indulge his passion for music, having a special harmonium built and holding concerts in his own home.

After the death of Kirchhoff in October 1887, the University of Berlin looked for a physicist to replace him and to work with Helmholtz. They approached Ludwig Boltzmann but he was not interested, and the same proved true for Heinrich Hertz. In 1888, the appointment of Planck was proposed by the Faculty of Philosophy at the University of Berlin, strongly recommended by Helmholtz.
 
 
While in Berlin, he studied thermodynamics, in particular examining the distribution of energy according to wavelength. By combining the formulae of Wien and Rayleigh, Planck announced in October 1900 a formula now known as Planck's radiation formula.

Within two months, Planck made a complete explanation of his formula, renouncing classical physics and introducing ‘quanta’ of energy. In December 1900 he presented his theoretical explanation involving 'quanta of energy' at a meeting of the Physikalische Gesellschaft in Berlin. In doing so, he had to reject his belief that the Second Law of Thermodynamics was an absolute law of nature, and accept Boltzmann's interpretation that it was a statistical law.

At first the theory met resistance but, due to the successful work of Niels Bohr in 1913 calculating positions of spectral lines using the theory, it became generally accepted. Planck himself said that, despite having invented quantum theory, he did not understand it himself at first. Planck received the Nobel Prize for Physics in 1918 for his achievement.

Planck was 42 years old when he made his historic quantum announcement, but took only a minor part in the further development of quantum theory. This was left to Einstein, Poincaré, Bohr, Dirac and others.
 
 
Sadly his life was filled with tragedy in the years of his work on quantum mechanics. His wife Marie died in 1909. One of his sons from his first marriage was killed in 1916 during World War I. Both his daughters died in childbirth.

His home in Berlin was destroyed by fire after an air raid in February 1944, and he lost most of his possessions including his irreplaceable scientific notebooks. His second son was suspected of being involved in the plot to assassinate Hitler and was executed in 1945.

Planck was 87 years old at the end of World War II but, remarkably, he was able to put effort into reconstructing German science and he again became president of the Kaiser Wilhelm Gesellschaft in 1945.

Named in his honour, ESA’s Planck mission is analysing the CMB radiation from near the time of the Big Bang for clues about how clusters of galaxies and even individual galaxies formed.