Background
Paul Ehrenfest was born in Vienna (in what was then Austria-Hungary), on January 18, 1880. His parents— Sigmund Ehrenfest and the former Johanna Jellinek— had moved to Vienna in the 1860s from the small village of Loschwitz in Moravia. Although very poor at the time of this move, the Ehrenfests had used Johanna’s dowry to establish a grocery store in Vienna. By the time Paul (the youngest of five sons) was born, the business had become a successful enterprise and the family was living comfortably. The loss of Ehrenfest’s mother, when he was ten, and his father, when he was sixteen, contributed to his sense of depression and a lack of confidence which would plague him throughout his life.