What are we and what guides our behavior? Each of our groups around the planet have a set of leaders, attitudes, faiths, ethics, and so forth, and it’s common to think that those largely determine what any group can and can’t do. So if one of our groups grows rich or powerful through building something complex—for example, a city of a million or more of us—it must be because of that group’s leaders, attitudes, and such.

No doubt such things matter, but there might be another set of organizing forces, too, for we aren’t the only species that builds complex things which then affect how they live. For instance, some termite species build giant nests that sport fungus farms, nurseries, and air, humidity, and heat ducts. And multiple millions of them might live in a single nest. But they don’t do that because their queen tells them what to do. Her pinhead brain is no bigger than that of any other termite. Even killing her may not trouble the nest much, since it might just grow a new queen. As far as we know, termites don’t have clever leaders—or leaders of any kind. Nor, as far as we know, do they have attitudes, faiths, and so on. None of them plan the outcomes of their actions, yet those actions, in aggregate, are coherent, not random. Together they form a network that acts so as to persist the nest in which it exists, so in that sense it’s a self-perpetuating network.

Could we be something like termites? Of course, we’re smarter, and we build bigger and more complex things, but that needn’t therefore mean that everything we end up doing is always something that we intend. Nor is that a new idea. In 1714 Bernard Mandeville argued in The Fable of the Bees that we often do things as a network, but not for the moral, religious, or political reasons that we so often espouse. His idea enraged a lot of readers, who saw it as immoral, sinful, and degrading, and several authors rushed to refute it. But in 1776 Adam Smith argued in The Wealth of Nations that, at least for our free-market economies, there seems to be a hidden order to how we network economically, and it needn’t be one that we intend. For him, such economies often appear to be guided—but not by us, rather by an invisible hand.

Today we know of other sorts of unintended but non-random networks. Consider a highway full of fast-moving cars. On the highway we often enter a traffic jam but on leaving it we don’t see anything that may have caused it. Why? Any traffic incident—a major accident, a temporary merging lane, even just someone braking a little too hard—can trigger a clot of slow-moving cars. Fast-moving cars entering that clot from behind will slow down and slow-moving cars exiting its front will speed up. But while a driver reaching its front can speed up, the driver right behind that driver won’t speed up as much—or else they might collide. So even after the incident clears up, the clot can back away from the point of that incident, against the flow of traffic.

So a traffic jam may have started miles ahead and hours before we become engulfed in it. Various cars will enter it and leave it, but it itself can persist for some time—often for hours. Similarly, various termites live and die, yet their network of interactions results in a nest that can persist for some time—often for decades. A termite nest is far more complex than a traffic clot, but both are a bit like living things. Both can be born and both can die, and, in a sense, both can act so as to persist. A traffic clot persists when it can engulf more fast-moving cars at its rear than it poops slow-moving cars out its front—rather as if it were a simple cell that lives on roads.

Just as termite nests are made by termite actions without needing termite intentions, a traffic clot is made by our actions but not via our intentions. Do any of the other things that we do and build arise in the same sorts of unintended but non-random ways? If they do, perhaps we, like termites, may be parts of a giant, life-like, complex system—a human swarm. Such a swarm may obey its own internal, self-organizing network forces, regardless of what we intend, desire, believe, or even notice.

If there could indeed be organization without an organizer, what might that suggest about us and our possible future? What might make such a network ‘life-like?’ And what might we be able to say about its ‘physics?’ That’s what this book is about. Call it swarm physics.