Hello everyone, welcome to the Mindscape Podcast. I'm your host Sean Carroll.

One of our longstanding interests here at Mindscape is in the idea of complexity.

Not just the simple systems that particle physicists or cosmologists like myself like to study,

but the interesting phenomena that come into existence when things have many, many,

moving parts. And you can find emergent behavior that might not have been

immediately obvious just from thinking about the component parts.

Now we've talked about complexity. We talked about it recently with Scott Aronson,

but that was in the sense of computational complexity. How difficult is it to solve a certain

well-posed puzzle? Here we're going to be talking about complex systems. So either physical

systems that you could build up, like a robot or for that matter a human being, but also

social systems, information systems, the internet itself is a complex system. So Neil Johnson is

one of the experts in this area, an incredibly prolific physicist who heads up a new initiative

at George Washington University in complexity and data science. And our conversation has two

different focuses. The first part of the talk will be about what is a complex system? What

makes something complex? How do you know? How do you characterize it? So various words that you might

have heard before, like power law behavior will appear. And Neil explains very, very clearly how

power laws are different than bell curves or other things that you might run across in the natural

world. But then we turn our attention to the specific idea of information systems and how people

get information in the real world. A lot of Neil's recent research interests are on how

extremism or conflict or various forms of bad behavior spread through complex networks. How do

extremist groups recruit their volunteers? How does disinformation promulgate through social

networks or through official news channels? So this is, as you might guess, scarily relevant stuff

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