When the Nobel Prizes started to be given at the beginning of the 20th Century, there were a number of procedural questions still open. One of the questions generated considerable discussion within the Royal Swedish Academy of Sciences, namely the question if discoveries or inventions in astronomy could be rewarded with the Nobel Prize in physics. The outcome of the discussions was a working rule saying that this could be the case only if the discoveries or inventions were important for physics. The prize to Hewish and Ryle in 1974 was the first one to be given in astronomy and it is interesting to note that the Academy uses the term “radio astrophysics” instead of “radio astronomy”. In his talk at Lindau, which was also his first, Hewish picks up this physics thread and stresses the fact that observations of the Universe may give insight into physics under extreme conditions that could never be obtained in the laboratory. In particular, the gravitational forces in space may compress matter to extreme densities, thus forming strange objects such as the “bubbles in space-time” that we today call black holes. The discovery in which Hewish played a decisive role was made in 1967 and consisted in the finding of a new kind of stellar object, later given the name pulsar. The observation finger-print consists of a regular and rapid succession of very short radio signals. The discovery eventually led to the understanding that matter may be compressed to such an extent that the electrons and protons of the ordinary atoms recombine to form neutrons. This may happen as the result of a supernova explosion and leaves a rapidly spinning neutron star behind, acting as a light-house. If the Earth happens to be swept over by the light-house beam, the pulsar may be registered and studied. It is a sad fact that the PhD student who made the actual discovery was not given a shared part of the prize. But is is positive that 20 year later, when a similar discovery was rewarded in 1993, the professor and the PhD student shared the prize.