When a system fails, how do you think about cause and effect? One way to consider this in complex systems is to imagine a pile of sand, and dropping one grain of sand at a time in random positions onto the pile. As time passes, you'll start to form little hills. Eventually, a grain of sand will hit one of these hills, and you get an avalanche. Do you believe that the avalanche was caused by the last grain of sand falling onto it, or do you believe that the avalanche happened due to the shape of the hill itself? To explore this sand pile model, we are joined today by Neil Johnson, Professor of Physics and Head of the Dynamic Online Networks Lab at George Washington University.   Connect: Simplifying Complexity on Twitter Sean Brady on Twitter Sean Brady on LinkedIn Brady Heywood website This show is produced in collaboration with Wavelength Creative. Visit wavelengthcreative.com for more information.