Every morning dozens of people get up early to participate in communal tai chi and qigong classes in Washington Square Park. Some of the larger groups have more than 50 people; many individuals, wary of appearing too interested, follow along at a distance, across the grass field, perhaps behind a tree, giving a disorienting synchronicity to the many swaying motions. Tai chi sword is also popular: Its practitioners swing 3-foot blades in graceful, slow-motion arcs, as if choreographing a fight scene. And tai chi fan is beginning to take hold, with participants snapping Chinese fans open with a crack that echoes through the morning air. How do you join? Just show up and take your place, or grab someone else's after he's done. After all, it's not like they're moving too fast for you.