I'm out in Leiden for the next three days for the AMUSE Workshop. AMUSE is an evolution of MUSE, a software framework for integrating various different modules of stellar modeling together. So-called "N-body models" model the orbits of lots ("N" being a large number) of stars orbiting around each other as a result of their mutual gravity. They're great as far as they go, but they aren't all of the physics. If the timescale of your simulation goes on long enough, eventually you're going to have to take into account stellar evolution-- the fact that more massive stars live shorter lives and go supernova, spewing most of their mass out into interstellar gas. If you're dealing with dense systems (think the Galactic core, or globular clusters), you have to take into account "strong interactions" between stars, which most N-body codes don't handle by themselves. And, if the systems are really dense, you may have to take into account mergers of stars, which involves hydrodynamics. Additionally, there is gas in galaxies, which also involves hydrodynamics.
Traditionally, all of these different areas are modeled separately. Sure, there is definitely some overlap between N-body codes and few-body strong-interaction codes. However, the goal of MUSE was to make it possible for people who write disparate simulations to link them together for a more realistic simulation that needs to take into account multiple systems.
All of which is why I'm here. But the real reason I want to write this is to just dump my first impressions of Leiden:
- This is a very bike friendly city! There are paths for bikes and motorized scooters, bike lanes, and massive bike parking lots all over the place. And you see huge numbers of bikers riding around. But very few of them are wearing helmets.
- The Dutch language is much more mystifying to me as an American than either French or Spanish. Now, yes, I did study French all the way through junior high and high school, so I'm not coming at French as a complete ignorant. But I certainly find Spanish names easier to wrap my brain around than Dutch names. However, it's not as hard as Sweden, where the collection of letters that form street names just would not stick in my brain with the linguistic substructure I've built in there all my life.
- Trash! There is litter, and there are piles of trash, all over the streets.
Update 2009/10/06: It turns out that the trash was a transient thing. October 3 is an annual festival that Leiden celebrates for its liberation from Spain a few hundred years ago. That festival can go on for days and culminates on October 3. I was seeing the aftermath of Saturday night's festivities when I arrived on Sunday, October 4. I happened to arrive on exactly the worst day for trash in the streets...!