And thank you for adding your voice, Ross. Great comments. I really like your concept of the relationship between solid and emptiness. Aikido as smoke! The inherent resistance of a structure is interesting too. I wonder how we can fit the surface tension of a liquid into this model. By the way the system wouldn't let me message you.
Surface tension? Reason #4
Smoke, air, water... I do think aikido and fluid dynamics have a lot in common. But fluids often are bounded by, and directed by channels and surfaces. To me, aikido is not about being either solid or empty, but about understanding the intercourse between them. We can be either, or both, in varying degrees as need and opportunity arise.
Not sure about the PM. Feel free to contact me directly any time at <firstname.lastname@example.org