How hard is Sudoku? Searching for the answer leads us to questions about the nature of space and time.
How do extraordinarily complex emergent phenomena — like ants assembling themselves into living bridges, or tiny water and air molecules forming into swirling hurricanes — spontaneously arise from systems of much simpler elements?
Our planet is made up of millions of networks from microscopic ecosystems to global migration. Here's how we may better understand when those networks are in danger of collapse.