Critical Mass

"Critical Mass looks at human behavior from the perspective of physics. It’s one of these analogies that I found very impressive and convincing. He basically asks, ‘Can some of the patterns of human society, like markets or traffic or social media, be understood using physics and complexity theory?’ This is what’s called ‘social physics,’ the idea that while individual human beings are complex and unpredictable, the way groups interact can follow mathematical laws. He claims that in some cases, groups act like particles do in physics. Sometimes you get a ‘phase transition,’—like when a liquid turns into a gas—when a traffic jam suddenly develops, or a market suddenly crashes. He suggests similar patterns of movement occur. That’s the ‘critical mass,’ and when you reach it, you end up with a transition to a completely different human behavior in society. He connects up the way birds flock together to the way stock markets work, and talks about attempts to understand human society through physics and chemistry. He also says there are limits to doing this, because humans are reflective in a way that particles aren’t. We think about our behavior, and we have the capacity to understand what’s going on, to an extent. So you can explain human behavior as operating like particles in a dynamic system and that gets you some of the way—but it can be misleading. The metaphor has a limit. I found that a really sensible and helpful way of thinking about things, because too many popular science books try to just sell the metaphor completely. Yes. It’s helpful in understanding how cities work, for example, and how effects in one part of a city can affect another part of the city. In my own work, I’ve looked at how a lot of our assumptions around policy fall down because we assume we’re dealing with a straightforward linear system where we go from A to B. Work like this shows that when you’re dealing with societies, those assumptions do not hold true, so you do have to think differently. It gives you a different lens for thinking about behavior at scale. What if it was acting like a phase transition or like social physics? So it’s not the whole answer, but I’ve found it really helpful for understanding how you manage a system that you can’t always influence directly, or that may behave in surprising ways."