The calculation of the Sun's surface temperature at 5,430 degrees Celsius stands as one of the definitive achievements of physicist Josef Stefan. Born in Sentpeter in 1835, he spent his professional life at the University of Vienna, where he established a career that bridged experimental measurement and theoretical mathematics, ultimately shaping the foundations of modern thermodynamics and electromagnetism.
Academic Foundation and Career
Stefan attended the Europagymnasium Klagenfurt from 1846 to 1853 before moving to the University of Vienna. He completed his studies there between 1853 and 1858, beginning a long tenure at the institution that lasted until his death in 1893. Throughout his time in Vienna, he served in various academic capacities, including as rector during the 1876-1877 academic year, and earned recognition for his contributions, most notably the Lieben Prize in 1865.
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In 1879, Stefan formulated the physical law now known as the Stefan-Boltzmann law, which dictates that total radiation from a black body is proportional to the fourth power of its thermodynamic temperature. He derived this from the measurements provided by Dulong and Petit. His student, Ludwig Boltzmann, later extended the application of this law to grey-body emissions. This research remains a primary reference for calculating thermal output in ideal bodies.
Fluid Dynamics and Electromagnetism
Beyond thermodynamics, Stefan produced significant work in fluid dynamics and electricity. He provided early measurements of gas thermal conductivity and studied evaporation rates, leading to the designation of the Stefan flow. In electromagnetism, he calculated the inductivity of coils with quadratic cross-sections and researched the skin effect. His mathematical work on movable boundaries, known as the Stefan problem, specifically addressed the growth rate of ice layers.
Professional Recognition
Stefan was a prominent figure within the scientific community of the Austrian Empire and abroad. He held memberships in the Austrian Academy of Sciences, the Göttingen Academy of Sciences and Humanities in Lower Saxony, and the Bavarian Academy of Sciences and Humanities. His output, which included nearly 80 articles published in the Bulletins of the Vienna Academy of Sciences, cemented his role in European physics.
Fast facts
- Born: 1835, Sentpeter
- Died: 1893, Vienna
- Citizenship: Austrian Empire
- Education: University of Vienna (1853-1858)
- Positions: Rector of University of Vienna (1876-1877)
- Award: Lieben Prize (1865)
- Languages: German, Slovene
- Burial: Vienna Central Cemetery
Questions readers ask
What is the Stefan-Boltzmann law?
It is a physical law stating that total radiation from a black body is proportional to the fourth power of its thermodynamic temperature.
What was Stefan's contribution to astronomy?
He used his radiation law to provide the first sensible calculation of the Sun's surface temperature, estimating it at 5,430 degrees Celsius.
Achievements
- Notable work: Maxwell–Stefan diffusion
- Notable work: Stefan Adhesion
- Notable work: Stefan flow
- Notable work: Stefan number
- Held posts at University of Vienna
- Educated at Europagymnasium Klagenfurt and University of Vienna
- Fields of research: physics
