| Abstract: Fluid dynamics set exoplanetary system architectures. The gravity from planetary and binary companions sculpts the natal disk, and tidal interactions between planets and their host star affect spins, eccentricities, and inclinations. Hot Jupiters, in particular, are strongly influenced by tidal dissipation. These planet orbits are often misaligned with their host star equators due to their tumultuous past, but only for hot hosts: cool hosts are predominantly aligned. Prior attempts to explain this correlation between stellar obliquity and effective temperature have proven problematic. We discuss how resonance locking – the coupling of the planet's orbit to a stellar gravity mode (g-mode) – can preferentially damp the obliquities of cool stars. The radiative cores of cool stars support internal gravity waves, that drive strong tidal dissipation and damp obliquities. Future avenues of investigation for tides in stars, and seismic oscillations in planets, are discussed. |