Stefan Meyer (27.04.1872-29.12.1949) was an Austrian physicist and a member of the Austrian Academy of Sciences. He was born in Vienna. He received (1896) the degree of Doctor of Philosophy at the University of Vienna and in 1902 began to head the department of physics there (professor in 1920-38), and in 1910-20 he was also director of the Radium Institute.
His research concerned mainly radioactivity and nuclear physics. Together with E. von Schweidler he determined the half-life of polonium (140 days), established its transformation into lead, and found (1899) the deflection of radium rays in a magnetic field. His work was also in the field of the precise determination of the heat produced by the radiation of radium, the study of the absorption of alpha rays, the radioactivity of springs, minerals and the products of radioactive decay in the atmosphere, and the determination of mass defects.