Albert Einstein, one of the greatest thinkers of the twentieth century, was born in 1879 in Ulm, Germany, to German-Jewish parents. As a young adult, he moved to Switzerland, where he be-came a citizen and where he published his first great theories in the early 1900s, while working as a patent clerk. It was as a professor at the University of Berlin that he finished the general theory of relativity in 1915–17. Later, Einstein left Germany and came to the United States to join the Institute for Advanced Study at Princeton. In his later years he became more interested in social is-sues and penned several books, including About Zionism, on the state of Israel. He died in 1955 at the age of seventy-six.