The Greek mathematician Euclid imagined an ordered and methodical universe, but his vision struggled to catch on for centuries, until Renaissance painters and French monarchs found a way connect the ancient science of geometry to the real world. Science historian Amir Alexander joins Ira to share the story of geometry’s rising global influence in his new book Proof!: How The World Became Geometrical. Plus, a million years ago, the black hole at the center of our galaxy burped. Now, scientists are exploring what the resulting bubbles might say about our kinship with other galaxies. And here on Earth, neuroscientists say they can learn a lot by observing brains at play—particularly those of rats playing hide and seek.