520 Everyone loves to see the beauty of the star-studded night sky, but how many of us understand what makes stars shine, where Saturn's rings come from, or why galaxies have their distinctive shapes. Observational astronomy excels at cataloging celestial objects, but it takes a more rigorous discipline to come up with physical explanations for them. That field is astrophysics, which uses the laws of physics to investigate everything beyond Earth. In these 24 visually rich half-hour lectures, Professor Joshua Winn of Princeton University gives a hands-on demonstration of the formulas of astrophysics. Assuming a first-year college background in physics and math, he walks you step by step through calculations that reveal the inner-workings of planets, stars, and galaxies. You discover Isaac Newton's path to his theory of gravity, calculate the event horizons for different black holes, investigate the optics of telescopes, determine the ignition temperature for a star, and much more. Throughout the course, Dr. Winn uses custom-designed graphics and animations to help you visualize what's happening. Even if you don't follow every step, you will marvel at how astrophysicists wrestle with unwieldy problems to reach new insights about the cosmos. Introduction to Astrophysics is an inside look like no other at the tools and techniques that have unlocked the secrets of the universe.