| Abstract: | The striking morphologies of spiral galaxies have long captured the imagination of both the general public and professional astrophysicists. Yet even basic questions about their diversity of dynamical structures — how they form, how they evolve, and why they appear in some disk galaxies but not others — remain largely unresolved. Our own Milky Way, with its central rotating bar and spiral arms, offers a unique window into the dynamical underpinnings of these features. As the only galaxy where we can trace the motions of individual stars in detail, it holds the key to understanding spiral structure and bar dynamics more broadly. But our vantage point within the disk complicates the picture: even with Gaia’s extraordinary six-dimensional stellar data, our view is limited to a local patch, and much of the global dynamical structure remains obscured. Still, that local patch is rich with dynamical clues and hints. Armed with new theoretical tools — adapted from fields ranging from plasma physics to cosmology — our ability to extract global information from local measurements has made significant progress. In this talk, I will show how new projections of the Gaia data, guided by a deeper theoretical understanding of galactic dynamics, are allowing us to reveal the transient nature of the Milky Way’s spiral arms, and to constrain the mass, pattern speed, and slowdown rate of its central bar. |