Explore the fascinating connection between classical and quantum physics in this 29-minute video from the World Science Festival's "Your Daily Equation" series. Delve into Paul Ehrenfest's groundbreaking 1927 theorem, which demonstrates how Newton's equation can be derived from Schrödinger's, establishing a profound continuity in our understanding of the physical universe. Follow along as Brian Greene provides a concise explanation of Ehrenfest's essential idea and the mathematical manipulations required to realize it. Gain insights into quantum mechanics, integration by parts, and the fundamental principles that bridge these two seemingly disparate realms of physics. Even with limited mathematical background, engage with pivotal equations and exciting stories about nature and numbers, offering a fresh perspective on the universe.