Abstract

70 years after Al Hiltner used the McDonald Observatory 82” telescope to discover interstellar polarization, we finally understand the physics of the underlying grain alignment.   Over the last three decades the “Radiative Alignment Torque” (RAT) paradigm has been developed and successfully tested.  Because of the quantitative nature of the theory, it can be used to better probe the magnetic fields of the ISM, and to constrain the characteristics of the dust, radiation fields and other environmental factors.   I will discuss the basics of RAT alignment, describe some recent results testing and utilizing the process and some remaining challenges in interstellar grain alignment and polarization studies.