The Navier-Stokes equations are enormously successful at predicting how fluids flow and swirl. But they fail to account for the microscopic bits that make up matter. But now math based on symmetries offers a new conception of fluids and why they behave the way that they do. On this episode of The Quanta Podcast, host Samir Patel speaks with writer Charlie Wood on the longstanding effort to rebuild the theory of fluids from the bottom up, including a strange connection to black holes and models that simultaneously run time forward and backward. This topic was covered in a recent story [https://www.quantamagazine.org/theory-of-fluids-enters-the-21st-century-20260817/] for Quanta Magazine.   Each week on The Quanta Podcast, Quanta Magazine editor in chief Samir Patel and Senior Editor Hannah Waters speak with the people behind the award-winning publication to navigate through some of the most important and mind-expanding questions in science and math.