After his degree in 1966, he was post-doctoral fellow at the Mainz Academy of Sciences working with Pascual Jordan, in Germany. Then, he was post-doctoral fellow with John Archibald Wheeler and Member of the Institute for Advanced Study in Princeton and later became instructor and assistant professor at Princeton University. In 1975, he was visiting Professor at the Universities of Kyoto (Japan) and of Western Australia, Perth. In the years 1975-78, he cooperated with NASA being member of the task force on the scientific use of space stations. In 1976 he became Professor of Theoretical Physics at the University of Catania and in 1978 he was appointed Professor at the University “Sapienza”. In 1985, he was elected President of the International Center for Relativistic Astrophysics (ICRA). In 1984 he was cofounder, with Abdus Salam, of the Marcel Grossmann Meetings. In 1987, he became co-chairman of the Italian-Korean Meetings on Relativistic Astrophysics. In the years 1989-93, he was President of the Scientific Committee of the Italian Space Agency. He is Editor of a variety of Scientific Journals. He is married to Anna Imponente and has a son, Iacopo.