The Biggest Ideas in the Universe is a series of videos where I talk informally about some of the fundamental concepts that help us understand our natural world. Exceedingly casual, not overly polished, and meant for absolutely everybody. This is Idea #16, "Gravity." By which we mean Einstein's theory of General Relativity, according to which gravity is the curvature of spacetime. Since we've already learned about spacetime and about curvature (geometry), this one is a breeze. My web page: http://www.preposterousuniverse.com/ My YouTube channel: https://www.youtube.com/c/seancarroll Mindscape podcast: http://www.preposterousuniverse.com/podcast The Biggest Ideas playlist: https://www.youtube.com/playlist?list=PLrxfgDEc2NxZJcWcrxH3jyjUUrJlnoyzX Blog posts for the series: http://www.preposterousuniverse.com/blog/category/biggest-ideas-in-the-universe/ Background image: Astronaut Bruce McCandless floating in space, NASA. https://www.nasa.gov/astronautprofiles/mccandless #science #physics #ideas #universe #learning #cosmology #philosophy #gravity #generalrelativity #einstein #spacetime