1962 Guthrie Lecture: The Physical Basis of the Research Programmes at Jodrell Bank

This paper, which is the written version of the 1962 Guthrie Lecture, describes the physics underlying the radio astronomical researches at Jodrell Bank. The following topics are covered: (i) the physical theory of the scattering of radio waves from the ionized columns of meteor trails based on the classical expression for the scattering cross section of a free electron; the effects of resonance and polarization, the manifestation of the diffraction pattern, the measurement of velocities, and the application to the measurement of certain physical parameters in the high atmosphere; (ii) the possible alternative processes occurring in the scattering of radio waves from auroral formations; (iii) the lunar scattering of radio waves, the effects of libration which give rise to the short period fading and the Faraday rotation in the ionosphere which is responsible for the long period variations in signal strength; (iv) the origin of radio waves from the galaxy and their explanation in terms of synchrotron emission from relativistic electrons in the interstellar field, and thermal emission from ionized hydrogen clouds; (v) the problem of the energy requirements in the localized galactic supernova sources and in the radio sources which are extragalactic at great distances; (vi) the line emission from neutral hydrogen on 21 cm as it affects the work at Jodrell Bank, particularly the attempt to measure the interstellar field by observation of the Zeeman effect which has recently given a positive result. The paper ends by reference to the evolution by Hanbury Brown of the intensity interferometer at Jodrell Bank and to the problem of the scintillation of the radio stars.