A. E. Ringwood believes that many of the major problems we face in understanding the nature of the earth's interior and of the moon's interior and of the origin of the earth-moon system can be solved in his lifetime. It is just possible that he is correct, and reasons for such optimism are not hard to find. Progress in understanding the earth and the moon has been immense in the eighteen years that have elapsed since Ted Ringwood received his Ph.D. from the University of Melbourne. He has played a major role in the development of this understanding through his personal research. Moreover, he has stimulated and inspired colleagues in Canberra and throughout the world to work with him in seeking solutions to these problems that will meet the tests that geophysics and petrology can supply.