What is light? That is something that has plagued scientists for centuries. It behaves like a wave... and a particle... what? Is it both? In this episode of Crash Course Physics, Shini introduces the idea of quantum mechanics and how it helps us understand light. Also, there's this thing called the ULTRAVIOLET CATASTROPHE! -- Produced in collaboration with PBS Digital Studios: null -- Want to find Crash Course elsewhere on the internet? Facebook - http://www.facebook.com/YouTubeCrashC... Twitter - http://www.twitter.com/TheCrashCourse Tumblr - http://thecrashcourse.tumblr.com/ Support CrashCourse on Patreon: http://www.patreon.com/crashcourse CC Kids: null