I spent some time at play this weekend. On Friday night, I ate with Winnie at Nizza La Bella, a little French/Italian restaurant on San Pablo Ave, near the intersection with Solano. We had an excellent meal, which cost roughly the same amount that admission to the spring ball would have cost. I visited Barnes and Noble briefly on Saturday afternoon, and walked in the sun to Solano Avenue for brunch late this morning. Dave invited Patxi, Esther, and I over for dinner this evening, too. There is something very satisfying about sharing a meal with friends; even on the days when I'm feeling hermit-like, I usually feel better after meal shared (though perhaps in companionable silence).

The rest of the time, I worked on the fluids class paper. I finished around 11 this evening. I managed to fit what I wanted to say into five pages, but I had not a centimeter of space left over. Of course, it took me longer to figure out what I wanted to say than it did to write. It seems as though for every sentence I write, I erase at least two sentences -- and that's when I construct a first draft! Of course, for each sentence I speak, there are usually two or three that I decide are best left unspoken. Any edged tool deserves to be used with care; words are no different.

I'm glad I was able to spend the weekend with this work, though. I needed to teach myself something about this topic, and the class deadline was a good excuse to do it now. The ideal is simple enough: time runs in one direction, but the wave equations of mathematical physics allow solutions which go either forward or backward in time. For computer simulations, as for analytical calculations, there needs to be some way to pick out the solution that goes in the right direction. The details, of course, are more complicated. At this point in my career, though, they are manageably more complicated, and I was able to set up the theory, numerically and analytically solve several test problems to illustrate the point, and write everything up in the course of about three days.

And now I will read iaijutsu for half an hour before I sleep.