A simple explanation of the theory of relativity by the great Austrian physicists, Hans Thirring, one of the earliest popular expositions on the subject.
About Thirring (from Wikipedia):
Hans Thirring (March 23, 1888 in Vienna, Austria-Hungary – March 22, 1976 in Vienna, Austria) was an Austrian theoretical physicist, professor, and father of the physicist Walter Thirring. He won the Haitinger Prize of the Austrian Academy of Sciences in 1920.
Together with the mathematician Josef Lense, he is known for the prediction of the Lense-Thirring frame dragging effect of general relativity in 1918.
He received a deferment during World War I because he had broken one of his feet while skiing. He was a leading pacifist before the Anschluss and after World War II. But he could not save his older son, who was declared missing in action during the final two months of World War II. His body was never located.
Hans Thirring served as assistant, professor, and head of the institute for theoretical physics of the University of Vienna until his forced retirement in 1938 after the Anschluss, the annexation of Austria by Nazi Germany. After the end of World War II, he was reinstated and became dean of the philosophical faculty in the years 1946-1947. He was also active in the Socialist Party of Austria and served as member of the Federal Council of Austria during 1957-1963.