He was born in November 1, 1896 at Barneveld-Netherlands. His parents are also educators. He spent a difficult life. He was the student of KAPTEYN and got his PhD in 1923. He become professor in astronomy at Amsterdam. He spent most of his life as the educator in developing countries (Indonesia, Liberia, Turkey). He became the ministry of education of Indonesia. Later in 1954 came to Turkey and became the director of the Astronomy Institute. He continued his job untill his death on August 16th, 1964.