Radio and the birth of the universe

The radiation which mediated the processes of nucleosynthesis at the birth of the universe and controlled the helium/hydrogen radio prevailing ever since is that, cooled by adiabatic expansion, now described as the 3K cosmic microwave background. This article reviews the growth of radio astronomy until 1964 when Penzias and Wilson discovered this background. Also it deals with measurements to determine the degree of anisotropy in the radio background and how the antenna temperature variation led to a determination of the 'peculiar' velocity of the galaxy. The theory of the 'hot big bang' is touched upon and there is a summary of the modern state of the theory which has been able to build upon the essential fact supplied by the temperature measurement of 3K of the noise background - the ratio of the number of photons to the number of nucleons. (author)