by R. Hanbury Brown, F.R.S., Professor of Radio Astronomy, University of Manchester
Second hearings of the talks arranged to mark the tercentenary of the Royal Society

Radio techniques have developed into a valuable observational method in astronomy. They provide information inaccessible to optical telescopes; conversely, the precision of conventional methods supplements radio data. The problems raised by the stability of spiral galaxies are among those that may be solved by this new approach.
(BBC recording: second broadcast)