Taken from the January 2020 issue of Physics World. The fact that pairs of moving pendulums can become synchronized was first observed by the great Dutch scientist Christiaan Huygens back in the 17th century. But as Jonatan Pena Ramirez and Henk Nijmeijer explain, synchronized pendulums still have today’s researchers scratching their heads (Courtesy: Frederique Swist/IOP Publishing) Ballet dancers moving in harmony to the rhythm of ...