No CrossRef data available.
Published online by Cambridge University Press: 14 August 2015
There are two important questions in which the physics of radio sources impinges upon cosmology. The first is whether the large apparent expansion velocities of certain compact sources can be explained satisfactorily within the hypothesis that their red-shifts are due to the Hubble expansion. The second is the whole broad question of the evolution of the radio source population with epoch. I do not have a new and convincing answer to the first, and the second is pretty nebulous, since we do not even understand radio sources at the present epoch very well. So I shall not present a general survey: instead, I shall use my allotted time to discuss a smaller question to which one can now give a fairly definite answer.