March 15, 1984
I enclose the last six chapters of The Universe of Motion, together with the first few pages of the “References.”
One matter that we left unfinished is the question of how the index is to be prepared. I agree that a selective index is more useful than a comprehensive one. In fact, the computer I am using is set up exactly for this, and it seems to me that we should make use of it. It will save time and labor. What I have to do is to insert a certain control word (in this case “.ix”) in front of each entry to be indexed. There can be up to three levels for each entry (in Nothing But Motion you use mostly two levels, but in the case of “Compounds,” three). If you decide to use the computer for indexing, you would indicate each word that is to be indexed (perhaps by underlining it with a red pencil), and in the margin write down the subheading, if any. This would allow me to produce the index exactly as you want it, while saving you some work.
On March 6 I went to a lecture by Vera Rubin of the Carnegie Institution of Washington on “Systematic Dynamical Properties of Spiral Galaxies.” The main topic were the rotational velocities of Sa, Sb and Sc galaxies. If plotted on a curve with distance from the galactic nucleus on the x-axis and the velocity on the y-axis, the curves for the various spirals always reach a maximum at a short distance from the nucleus, and thereafter remain almost totally flat. This fact was realized only in 1972. The graph, if I interpret it correctly, illustrates the evolution of the spiral structure. In order to “keep up” with the rotation of the nucleus, the galactic arms would have to move at a constantly increasing velocity as one travels outward. Since in fact they maintain the same speed as the outer edges of the nucleus, they are lagging behind, and wrapping themselves around the central region. The transition from the rotation of the central region, which moves together as a solid body, to the rotation of the arms is quite abrupt, as is evident from the rough sketch that is attached. I wonder if the sharp angle on the graph is related to the transition from the region of faster-than-light speeds in the nucleus to the below-unity speeds of the rest of the galactic structure. If this information is of interest to you, I will try to locate some printed discussion.
I have been nagging Eden Muir about the illustrations, and he’s promised to get to work very soon.