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 #15, "Gauge Theory." Here is where the last couple of ideas come together, and we see how geometry and symmetry underlie the fundamental forces of nature as they are currently understood. 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: http://www.desktopwallpaperhd.net/blue-fractal-mirror-nice-background-wallpapers-84056.html #science #physics #ideas #universe #learning #cosmology #philosophy #math #gaugetheory #symmetry