There was a time when an iron curtain would descend after a performance between the stage and the audience, which would clap rhythmically to induce the conductor or actors to appear in front of the curtain, through a little door at its center. The reason, Vicsek and his colleagues in the United States and Romania believe, has as much to do with mathematics as it does with aesthetics and psychology. According to Steven Strogatz, a mathematician at Cornell University who has studied synchronization for 20 years, the same set of mathematical principles governs the phenomenon wherever it occurs - be it among applauding people, flashing fireflies, or roomfuls of grandfather clocks. Strogatz has been fascinated by synchronization since he experimented with pendulums in his first science class. Now he seems to see it wherever he looks.
Asian fireflies flash together each night in the mangrove trees along a riverbank.
Crickets chirp in unison, and cicadas emerge from the ground at the same moment every 17 years. The moon rotates around its own axis at exactly the same rate as it orbits around Earth, which is why one side of the moon is never seen. Pacemaker cells in the heart oscillate in harmony. There is even the curious case of menstrual synchrony among women who live together. To understand the mechanics of synchrony, Strogatz suggests, imagine several athletes running around a circular track.