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 the Q&A video for Idea #14, "Symmetry." A mixture of abstract thoughts about the integers, what it means for dimensions to be complex, and how we know if a theory has topological defects. 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 by Sylvia Cordedda at DeviantArt: https://www.deviantart.com/c-91/art/Naive-341640491 #science #physics #ideas #universe #learning #cosmology #philosophy #math #grouptheory #symmetry