"What it is and what it is not." This might be an appropriate subtitle to Prof. Harrie Massey’s lecture, delivered at CERN on 30 November 1960. This was during the intergovernmental conference on space research and the lecture was intended to brief CERN staff on the whys and hows of space research. It drew the largest crowd ever gathered in the big audi¬torium, including many journalists and persons from outside CERN.