Beginning in 1924, Proceedings are incorporated into the Apr. number.

Where did we come from? Before there was life there had to be something to live on - a planet, a solar system. During the past 200 years, astronomers and geologists have developed and tested several different theories about the origin of the solar system and the nature of the Earth. Together, the three volumes that make up A History of Modern Planetary Physics present a survey of these theories. The early twentieth century saw the replacement of the Nebular Hypothesis with the Chamberlain-Moulton theory that the solar system resulted from the encounter of the Sun with a passing star. Fruitful Encounters follows the eventual refutation of the encounter theory and the subsequent revival of a modernised Nebular Hypothesis. Professor Brush also discusses the role of findings from the Apollo space programme, especially the analysis of lunar samples, culminating in the establishment, in the 1980s, of the 'giant impact' theory of the Moon's origin.