In Sync How Fireflies, Heartbeats and Human Brains Fall into Rhythm

On June 10th, 2000, a new footbridge opened across the River Thames in London, and within minutes of the crowds stepping onto it, it began to sway — not because of a storm, not because of a flaw anyone had foreseen, not because anyone planned it that way. It happened because people walked across it. Specifically, it happened because people walked across it together, their footsteps gradually, imperceptibly, unconsciously falling into the same rhythm. The bridge began to sway. And as it swayed, even more walkers adjusted their stride to keep their balance — which made the swaying worse — which synchronized more walkers — which amplified the oscillation further. Two days later, the Millennium Bridge was closed, and it stayed closed for almost two years while engineers worked out how to stop it. The bridge was teaching anyone willing to listen one of the deepest lessons in all of science: when things are coupled together, they synchronize. And synchrony, once it begins, can be almost impossible to stop.

This is not a metaphor. It is mathematics. It is biology. It is the same principle that makes fireflies flash in unison across a dark forest, that keeps the sixty trillion cells of a beating heart locked in perfect time, that causes audiences at concerts to begin clapping together without any conductor, any signal, any agreement. It is a principle so fundamental that physicists, biologists, neuroscientists, and psychologists have all stumbled toward it independently, each arriving at the same startling conclusion from a different direction: synchrony is not a coincidence. It is a law.

What does it mean that human beings are, at some level, oscillators — coupled to one another, continuously adjusting our internal rhythms to match the people around us?