丹麦人,天文学家,生于1644年2月25日,死于1710年9月19日。但从1671年到1681年在巴黎当法国皇太子的教师并为科学院的成员,后来做过数学教授并担任丹麦哥本哈根天文台台长及哥本哈根市市长之职。他利用木星的卫星蚀或早或迟的视现象来测定光速。他首先建造了子午线观测用的通过仪器(Durchgangsinstrument),并用一个分度圆盘进 Dane, astronomer, born February 25, 1644, died September 19, 1710. But from 1671 to 1681, he was a teacher and a member of the Academy of Sciences in Paris, France. Later he was a mathematics professor and served as director of the Danish Copenhagen Observatory and the mayor of Copenhagen. He uses Jupiter’s satellite eclipse as soon as possible or later to determine the speed of light. He first built the instrument for meridian observation and used a graduation disc