My subject is a topic in astrophysical fluid dynamics; specifically, the behavior of the supersonic jets that are observed to squirt out of the nuclei of active galaxies, compact stellar objects, and proto-stars. Some years ago, I had the good fortune to discuss this topic with Hans Liepmann, who quickly recognized that astrophysical jets pose some fascinating problems in fluid mechanics. However, he did not seem completely confident about the ability of astronomers to solve them (apparently some of my colleagues had been publishing papers on turbulence). Both of these insights turned out to be correct, as I hope to demonstrate in this talk. ; © 1988 Springer-Verlag.